Chilli Spice Production in Australia

Chilli Spice Production in Australia A report for the Rural Industries Research and Development Corporation by Andreas Klieber University of Adelaide...
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Chilli Spice Production in Australia

A report for the Rural Industries Research and Development Corporation by Andreas Klieber University of Adelaide

April 2000 RIRDC Publication No 00/33 RIRDC Project No UA-38A

© 2000 Rural Industries Research and Development Corporation. All rights reserved. ISBN 0 642 58063 4 ISSN 1440-6845 "Chilli Spice Production in Australia” Publication No 00/33 Project No. UA-38A The views expressed and the conclusions reached in this publication are those of the author and not necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any person who relies in whole or in part on the contents of this report. This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the Publications Manager on phone 02 6272 3186. Researcher Contact Details Dr. Andreas Klieber Department of Horticulture, Viticulture & Oenology University of Adelaide Waite Campus PMB 1 Glen Osmond SA 5064 Phone: Fax: Email: Website:

(08) 8303 6653 (08) 8303 7116 andreas.klieber@ adelaide.edu.au http://www.waite.adelaide.edu.au/~aklieber

RIRDC Contact Details Rural Industries Research and Development Corporation Level 1, AMA House 42 Macquarie Street BARTON ACT 2600 PO Box 4776 KINGSTON ACT 2604 Phone: Fax: Email: Website:

02 6272 4539 02 6272 5877 [email protected] http://www.rirdc.gov.au

Published in April 2000 Printed on environmentally friendly paper by Canprint

Foreword

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Australian diets are changing rapidly, with a broad-based acceptance of spicy foods. Chillies are an essential ingredient in Asian and Central American based foods that are becoming ever more popular. It is estimated that $30 million could be added to the Australian economy by replacing importation of chilli spice. However, there are a number of impediments to the successful commercialisation of chillies for spice production in Australia. This project was designed to make the chilli spice production system economically feasible by addressing production, harvesting and processing constraints. This report presents the results from these investigations and highlights a number of improvements to the chilli production system that reduce the production costs of chilli spice, improve the quality of the final product and make the industry internationally more competitive. This project was funded from RIRDC Core Funds which are provided by the Federal Government. This report, a new addition to RIRDC’s diverse range of over 450 research publications, forms part of our Asian Foods R&D program, which aims foster the development of a viable Asian Foods Industry in Australia. Most of our publications are available for viewing, downloading or purchasing online through our website: • •

downloads at www.rirdc.gov.au/reports/Index.htm purchases at www.rirdc.gov.au/pub/cat/contents.html

Peter Core Managing Director Rural Industries Research and Development Corporation

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Acknowledgements This research on chillies arose from industry need, but also from my own personal interest in chillies. Therefore my initial thanks need to go to my wife Julia who, through her love for this spice, first introduced me to the enjoyment of chillies. Also I would like to thank two students who worked very hard on this project, Mayuree Krajayklang who undertook a PhD project on most of the research aspects reported here, and Nancy Bagnato who undertook her honours research studying the colour stability of chilli powder. In addition the cooperation and support from John Peninger and John Small of the Hunter Valley Herb Farm are gratefully acknowledged; without them this project would not have gotten off the ground and run its course. Peter Dry, a senior lecturer in my Department, also contributed much in the area of the splitroot irrigation trials and as cosupervisor of Mayuree. We also received support by a whole host of other people at the Waite campus of the University of Adelaide and the University of Newcastle.

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Contents Foreword ..................................................................................................................... ii Acknowledgements .................................................................................................... iv Executive Summary.................................................................................................... vi 1. History and Economic Significance ........................................................................ 1 2.1. The chilli spice production system .................................................................................2 2.1.1. Seed and site selection ...........................................................................................2 2.1.2. Managing production factors...................................................................................3 2.1.3. Harvesting ...............................................................................................................6 2.1.4. Processing ..............................................................................................................7 2.1.5. Storage of powder...................................................................................................9 2.2. Defining quality ..............................................................................................................9 2.3. Gaining competitiveness..............................................................................................11 2.4. Research Goals ...........................................................................................................12

3. Research Findings and Conclusions .................................................................... 13 3.2. Harvesting....................................................................................................................15 3.3. Postharvest ripening ....................................................................................................18 3.4. Drying ..........................................................................................................................19 3.5. Storage of dried powder ..............................................................................................21 3.6. Aflatoxins .....................................................................................................................23

4. Industry Outlook and Further Research Needs .................................................... 25 5. References ........................................................................................................... 26 6. Colour Plates ........................................................................................................ 31

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Executive Summary Capsicum species are grown worldwide for fresh fruit and spice production. The main types of spice are powders that are derived from hot, red-coloured chilli fruit or from mild, red-coloured paprika fruit. The resulting spice is referred to as chilli or paprika spice. The main quality characteristics therefore are the colour and the heat level (pungency). Genetics, that is the cultivar selected, and the environment influence the heat level. For example growing chillies under cool conditions reduces their hotness. Colour is influenced by stage of ripeness of a fruit at harvest, processing and storage of the final spice powder. In addition an important quality aspect is the absence of aflatoxins in the spice powder. Chilli and paprika spice is vulnerable to contamination from mould toxins, the most potent carcinogens and toxins of which are the aflatoxins. We set out to examine the whole chilli spice production system to maximise yields and quality of the final product. The specific aspects we examined were growing practices, harvesting, ripening of insufficiently ripe fruit before processing, drying of fruit and storage of spice powder. In addition we tested commercial chilli products for aflatoxin content. The need for this work arose from the lack of detailed information for Australian conditions, as most previous work had been carried out overseas and as recommendations were not always clear. To allow for cost-effective machine harvesting, plant spacing and cultivar habits need to be considered. Cultivars with large, pendulous fruit are preferred as they are easier to harvest and process. Machine harvesters can detach larger fruit more easily and they are easier to cut for drying. Site selection needs to take into account soil, temperature and water requirements. A hot climate, as for example found in Mediterranean climates of South Australia and subtropical to tropical areas of Queensland is preferred and growing best occurs from about September to March. Cooler months or climates result in slower plant and fruit growth and reduce heat levels dramatically. Another critical cultural factor for chilli production is irrigation. If insufficient rain is expected during flowering, fruit set and development, as in many parts of Australia, supplemental irrigation is essential. Drip irrigation is very effective and prevents fruit from dropping. Fruit drop would otherwise reduce yields below half of normal. Normally recommended levels of fertiliser application gave satisfactory results. Chilli fruit are of widely ranging ripeness at harvest due to the plant’s architecture. Fruit at the lower nodes ripen first compared to fruit at higher positions on the bush. This results in reduced yields for machine harvesting, during which all fruit are stripped off the plant at once. Application of the ripening hormone ethylene, in the form of ethephon, was examined to synchronise ripening on the bush. However, ethephon reduced yield dramatically as it caused fruit drop. Overall the best strategy to ensure maximum yield of red coloured fruit is to leave fruit on the bush until most fruit have achieved a suitable colour. Separating insufficiently ripe fruit after harvest and ripening them is practised for a number of crops. This would increase yields as under-ripe chilli fruit could be ripened to sufficient levels for processing. However, chilli fruit that are not of a deep red colour at harvest do not colour up sufficiently. Only fruit that are deep red or deep red and slightly shrivelled on the bush produce a spice powder with a good colour quality. Exposing fruit to ethylene, as is practised to ripen many other fruit, does not influence ripening rate or the final quality of the spice. Chillies have a thick waxy skin that prevents rapid drying. Energy efficient heat pump dryers are well suited to drying fruit, as they operate at low temperatures. This is essential for chilli drying as the spice otherwise becomes brown instead of a bright red colour. The drying temperature should be below 60°C; appropriate drying regimes would be 40°C at 20% relative humidity for heat pump dryers or 60°C for 6h followed by 40°C for hot air dryers. The initially high temperature does not cause browning, as the moisture content of the fruit is still too high at this early stage of the drying cycle to allow browning reaction to occur.

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To accelerate drying, fruit should be cut into small, regular segments. This allows water to move out of the tissues without interference from the waxy skin. Using a drying oil, as for sultanas, also increased drying rates. However, this was not as effective as cutting fruit and high rates of oil were needed due to the tough nature of the waxes. A final moisture content of about 8% is ideal, as a moisture content above 11% allows mould growth and below 4% causes excessive colour loss. To slow colour loss, which occurs naturally during storage, it is important to keep the spice powder cool and out of light. In addition packing powder under nitrogen stops colour loss, as it excludes oxygen that is needed for the colour loss reactions. Different grinding techniques do not alter powder quality as long as they produce the same particle size. Keeping seed in the fruit during grinding results in the best yield and least cost, but dilutes colour. Potentially this could reduce shelf life as the lower limit of colour intensity is more quickly reached, even though the rate of colour loss is slower. Therefore, it is advisable to include seeds, but to use additional methods as described above to prevent colour loss. Seeds of different cultivars have varying effects on the rate of colour loss. This is most likely due to varying antioxidant content in the seed. Vitamin E, a fat-soluble antioxidant, has a similar effect on reducing colour loss. Selecting cultivars with high seed antioxidant levels is therefore necessary to produce a colour stable spice powder. Adding seed oil, to increase gloss, should be discontinued as a commercial practice as it results in rancid off-odours. Also colour is not protected from degradation, as antioxidants that are present in the oil are quickly degraded as the powder becomes rancid. Currently virtually all chilli spice is imported into Australia. A survey of 90 chilli products sold in Australia showed extensive contamination with aflatoxins. Overall only 9% of samples complied with the 5µg/kg maximum level as set out by Australian standards. Another 12% were considered marginal. On the whole spice powders performed worst, with minced and sauce samples having higher passing rates. Whole and crushed fruit also performed better than ground samples. The mean level of aflatoxins recorded was 19µg/kg with a maximum of 89µg/kg. This survey indicates that there are considerable improvements that need to be made in order to produce a safe food product for consumers. In order to avoid damage to this spice market, importers need to insist on better quality assurance and testing by the producers. However, also a significant opportunity exists for local producers to produce a safe product that will replace imported product with an unknown safety history. Aflatoxins are best controlled using an integrated strategy and by developing a HACCP (hazard analysis of critical control points) system, as commonly used in the food industry. Initially disease access to fruit in the field needs to be controlled by preventing insect damage to fruit. At harvest obviously diseased fruit need to be discarded to minimise potential sources of aflatoxin producing moulds. Fruit should be processed immediately after harvest or stored at refrigerated temperatures below 13°C to prevent potential aflatoxin production. During processing conditions need to be controlled so that mould cannot grow and produce aflatoxins. Either fruit have to be dried quickly at low relative humidity to reduce surface moisture content, or the temperature needs to be above 37°C as long as fruit have a high moisture content during initial drying. After drying fruit are ground into powder. This powder rapidly attracts moisture. To maintain a moisture content below 11%, powder should be packed immediately under low humidity conditions into packages with good moisture barrier properties. Suitable packages would be sealed plastic bags or glass containers. Storage below 13°C further reduces the risk of aflatoxin production. As a final step all batches should be tested to comply with relevant legal limits, which are 5µg/kg in Australia

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1. History and Economic Significance The Capsicum family belongs to the Solanaceae and is related to eggplants, potatoes and tomatoes (Bosland et al., 1996). They most probably originated in Bolivia and Peru (Purseglove et al., 1981, Bosland et al., 1996) and were distributed after the discovery of America to other parts of the world. They now grow in all parts of the world (Somos, 1984) and are part of many cuisines. Capsicum spp. can be divided into groups based on fruit characteristics ranging from pungency (hotness) and colour to shape, intended use and genetics. Capsicum fruit are berries, even though they are considered vegetables by consumers, and are either consumed as sweet types or hot types. Sweet nonpungent types are generally capsicums, also called bell pepper, and some other types such as pimiento (Bosland et al., 1996). Paprika is in some cases classified as non-pungent (Bosland et al., 1996), even though it may contain low or high levels of pungent compounds. The main differences in classification of paprika around the world arise from the fact that in the U.S. paprika refers to red non-pungent dried powder, whereas in Europe, especially Hungary, it refers to Capsicum in general and therefore may be pungent or non-pungent (Bosland et al., 1996). In this review paprika will refer to cultivars that produce non-pungent red spice powder. There are many hot pungent types that vary in pungency; for example New Mexico, Jalapeno, Cayenne, Thai and Habanero types increase in pungency in this order. Chillies are generally smaller and lower in red colour than non-pungent fruit (Purseglove et al., 1981). The main uses of Capsicums vary according to their pungency and colour. Uses range from salads, using capsicum to add flavour, to cooked dishes, using fresh green and red chillies to add pungency, to using dried powder spice of paprika and chilli to add red colour and pungency (Biacs et al., 1989), to pickles, using for example Jalapeno chillies, and to sauces, using for example Tabasco and Habanero chillies. Fruit colour can be green, yellow or red; for dried spice production red fruit are used which have ripened from their green unripe form. The most common species for dried spice production is C. annuum. It is generally agronomically the easiest species to grow and also produces large fruit that are easier to harvest and process. Examples are paprika and Cayenne chilli. Species for fresh fruit production also include smaller fruited types such as C. chinense, e.g. Habanero, C. frutescens, e.g. Tabasco, C. pubescense, e.g. Manzano, and C. baccatum, e.g. Aji (Bosland et al., 1996). Fresh Capsicum production grew worldwide from 11 in 1990 to 16 million tonnes in 1997 (FAO, 1999). Of that 9.5 million tonnes are produced in Asia (FAO, 1999) with pungent chillies contributing 5.5 million tonnes in this region (Vinning, 1995). Of the world production of fresh Capsicum 1.1 million tonnes, or US$ 1,400 million, were traded internationally (FAO, 1999); pungent chilli contributed 0.1 million tonnes, with a value of US$ 340 million, to international trade with 50% traded in Asia alone (FAO, 1987). Australia produces 30,398 tonnes of fresh Capsicum and imports have declined from 1,000 tonnes, with a value of A$4 million, (FAO, 1987) to 10 tonnes (FAO, 1999) and now exports 798 tonnes with a value of A$ 1.3 million (FAO, 1999). Australian production of chillies was about 1,000 tonnes fresh weight (Miles, 1994) and due to changing eating patterns the Australian market is expected to grow to A$30 million in the near future (Miles, 1994). Most of the following report will consider production and processing of red chillies, and closely related paprika, for dried spice production. While dried spice production was the main focus of this study, production, harvesting and postharvest findings will be relevant for fresh product as well as chillies produced for processing into, for example, puree or sauces.

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2. Chilli Spice Production System An extensive review of capsicum, or bell pepper, has been conducted by Wien (1997) who summarised production from seed to vegetative growth to fruit development especially in regard to glasshouse production. While some aspects are relevant and the review should be referred to, chilli for spice production is field produced and different considerations for production, harvesting and processing apply.

2.1. The chilli spice production system Chilli, and paprika, spice powder is produced in many locations around the world. The system generally consists of a progression from: • determination of a market for the product; • seed and site selection; • managing production factors such as fertiliser and water application and pest and disease control; • determining harvest maturity and harvesting the crop; • drying and grinding the fruit; • and then storing the powder until consumption or incorporation into a food product. Research into individual parts of this system has been carried out, with the majority of research relating to general growing practices in the field (Indira et al., 1985; Grattidge, 1990; Meena-Nair et al., 1990) and glasshouses (van Uffelen and Elgersma, 1990) and varietal improvements (Tewari, 1987; Fuentes and Mora, 1988; Wright and Walker, 1991; Hibberd et al., 1992). The following summarises previous findings in each of the above production system areas. 2.1.1. Seed and site selection When selecting seed for chilli spice production a number of factors need to be considered. C. annuum spp. are considered to be more easily cultivated. They also tend to produce larger fruit that are easier to harvest and process. Pendulous fruit are preferred, as they are easily harvested by mechanical harvesters. The desired hotness level needs to be taken into account (Table 1). Different types have widely varying heat levels, but even within one group different cultivars can be quite different. It is generally advisable to test specific cultivars under local conditions, as the environment can also influence expression of heat levels as discussed later. Table 1 Relative heat levels of some Capsicum types (0=mildest, 10=hottest). Heat level 10 9 8 7 6 5 4 3 2 1 0

Type Habanero Chile Piquin Tabasco Thai, Jalapeno, Cayenne Serrano, Jalapeno, Cayenne Wax, Cherry Bell (Romanian Hot) New Mexican New Mexican Mew Mexican Bell pepper (capsicum), Wax

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Scoville Heat Units 100-325,000 100-250,000 100-200,000 50-100,000 20-40,000 5,000-10,000 3,000-5,000 2,500 1,000 500 0

The site chosen for producing chilli has a large influence on quality. It is a warm season crop that does not thrive below 15°C and is susceptible to frost (Matta and Cotter, 1994). Seed emergence is significantly slowed down by low temperatures and seed emergence from soil may be prevented altogether by temperatures below 15°C (Lorenz and Maynard, 1980). Rapid emergence is desirable for production of good stands and yields (Matta and Cotter, 1994). Light frost will kill the plants and temperatures between 4-16°C will stop the plants from thriving (Bosland et al., 1994). Fruit set is also prevented by temperatures below 16°C and above 32°C. Chillies prefer a well drained, moisture holding loam or sandy loam containing some organic matter (Bosland et al., 1994; Matta and Cotter, 1994). A pH of 7.0-8.5 is suitable and the land should be levelled to 0.01-0.03% to allow adequate drainage and prevent root diseases. Adequate water supply is essential. Water stress can cause abscission of fruit and flowers, especially when it occurs during flowering (Matta and Cotter, 1994) and reduces yield through reduced pollination (Haigh et al., 1996). Chillies should be rotated to reduce disease problems; it should be only planted every 3-4 years in the same soil (Bosland et al., 1994). Stress during growth may increase heat levels. Low growth temperatures reduce the level of pungency in chilli fruit (Cotter, 1980), and poorer soil types and water stress are believed to produce lower yields of hotter fruit (Collins and Bosland, 1994; Miles, 1994; Lindsey and Bosland, 1995). Follow-up work to quantify this effect and to determine suitable stresses that induce hotness while minimising yield sacrifices is needed. 2.1.2. Managing production factors As chillis are sensitive to frost, and maturity is delayed by low soil temperatures, chillies are best established in the field in mid-spring; harvest of fruit occurs in late summer (Bosland et al., 1994). This period results in the best overall quality. Repeat harvests may be possible if there is no risk of frost, but our experience is that quality, especially heat level, is reduced when growing temperatures become too low. Chilli plants can be established by transplanting or direct seeding (Carter, 1994). For transplanting, seeds are germinated and grown in glasshouses for about 5-6 weeks, before the 15-20cm tall seedlings are transplanted into the field. Spacings of 30cm within rows 90-100cm between rows have been recommended (Carter, 1994), but higher densities of 18cm within row spacing in double rows 65cm apart are also feasible (Small J., pers. comm. 1998, Plate 1 & 2). As many roots as possible need to be retained and phosphorus solutions may aid in root establishment. Transplanted plants tend to be shorter and have more nodes (Bosland et al., 1994). Transplanting, together with row covers and plastic mulches, can result in production of earlier crops (Matta and Cotter, 1994), but results are variable (Bosland et al., 1994). Overall the higher planting and establishment costs need to be weighed up against the reduced costs of seeds and cultivation compared to direct seeding. For establishment from seed, dry seeds are generally direct seeded into the soil. When the soil temperature is low this can result in slow and non-uniform germination. This may be overcome by several techniques whose success is variable though. These include moisturising the seed to 10-25% and seed priming in polyethylene glycol for 3-7 days before drying to the original moisture content before the seed is planted (Carter, 1994). Seeds are generally sown to a depth of 1.9-2.5 cm (Bosland et al., 1994; Carter, 1994); crusting of the soil due to wet-dry cycles during seedling emergence has to be avoided, as chilli seedlings are relatively weak. Sprinkler irrigation can be used where soils tend to crust (Carter, 1994). Seeding rates of 2.2-4.4kg/ ha can be used for single rows on flattened beds that are spaced 90-100cm apart; plants are then thinned to 30cm apart when they are 10-15cm tall (Matta and Cotter, 1994). To reduce thinning costs, high-density plantings can also be used. In this case seeds are direct-drilled 2.5 to 5cm apart in double rows that are 65cm apart (Small J., pers. comm. 1998). Each plant is reduced in size and individual yield, but overall

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due to the high density excellent yields can be obtained. As stated previously, chillies require a good supply of water, as yield will be dramatically reduced by water stress. Underwatering results in flower and small-fruit drop and blossom end rot of fruit, while overwatering results in increased risk of root diseases (Dickerson, 1994). Irrigation will vary with plant size, wind, sunlight, temperature and relative humidity. As the chilli plant takes most moisture out of the top 30cm of soil, irrigation can be scheduled with moisture sensors within that zone. Visually irrigation should be scheduled when plants show wilting in the early afternoon (Bosland et al., 1994). After emergence, as roots grow into wet soil, irrigation may not be necessary for 3 weeks, then irrigation may be applied every 5-7 days, with longer periods during rain episodes and towards the end of the season to improve quality (Bosland et al., 1994). Drip irrigation is commonly practiced and is more efficient than sprinkler or furrow irrigation. However, chilli plants are sensitive to salinity and therefore the salinity of the irrigation water is critical. Soil salinity before planting should be less than 1920ppm (Carter, 1994). Salt injury is expressed as stunted and dead seedlings, burned root tips, necrosis on leaf margins and wilting. For drip irrigation plants should be planted in the centre of beds as salt moves to the outside of beds with the water front and sufficient water needs to be applied to leach salt below the root zone (Goldberg, 1995). Fertiliser regimes should be based on soil analysis. Especially nitrogen and phosphorus are important nutrients for chillies. A preplant nitrogen application can aid the establishment of vigorous seedlings if the soil nitrogen is below 20ppm nitrate; 2.2-5.7kg nitrogen/ha should be banded 7-10cm below the seed (Bosland et al., 1994). Also 34kg/ ha of P2O5 is banded before seeding if levels are low in the soil. Phosphorus results in better yields and more red coloured fruit (Matta and Cotter, 1994). During growth further nitrogen may be applied to achieve better yields; however excess nitrogen will result in lowyielding, large plants, delayed maturity and increased risk of disease development (Bosland et al., 1994). A side dressing of 22-34kg/ ha of nitrogen should be applied when the first flower buds appear and again when the first fruit set (Bosland et al., 1994). Foliar sprays for micronutrients and phosphorus side dressings may also be necessary based on soil conditions. A minimum of 60kg/ ha nitrogen, potassium and phosphorus may be necessary on phosphorus poor soils (Small J., pers. comm. 1998). Deficiencies and toxicity of minerals is best determined by tissue analysis (Goldberg, 1995). Wind exposure may reduce yields, increase bacterial diseases and reduce plant size and leaf area (Hodges et al., 1996). Appropriate windbreaks are therefore necessary. A number of pests can cause problems for chilli production. These include spider mites, thrips, leafhoppers, aphids, fruitflies, weevils and Heliothis among others (Swaine et al., 1991). Chilli yields and quality can be reduced by direct pest damage as well as from indirect damage as pests can also act as vectors for virus diseases. Appropriate biocides may be used to control these pests. In addition to conventional insecticides and miticides, integrated pest management with BT toxin (Bacillus thuringiensis) and natural extracts from, for example, neem is becoming more common place (Walter, 1996). It should be noted that ‘stung’ fruit will rapidly develop disease infections that make the fruit unmarketable as discussed below. To fully discuss pest management including integrated pest management is beyond the scope of this publication, but the reader may refer to standard texts. Weed control is exercised using mechanical means, such as hand hoeing, or chemical means using registered pre-emergence and post-emergence herbicides (Lee and Schroeder, 1995). Weed control can be important in controlling insect populations as well as viruses that can use some weeds as alternative hosts. Chillies are prone to a range of diseases that are described, with pictures, by Goldberg (1995) and Persley et al. (1989); the descriptions below are largely taken from the former reference. These include root rots, viruses, bacterial leaf spot, fruit rots and nematodes (Bosland et al., 1994). Root-knot nematodes are a common problem in sandy, warm soils (Goldberg, 1995). Soil temperatures between 15 and 27°C in sandy areas in the field are associated with yield loss; seedlings are more easily damaged than mature plants. Symptoms are primarily the formation of knots on the root system. Nematodes are easily spread with soil on equipment, transplants and through irrigation water. Control is achieved through sterilising potting

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mixes and soil fumigation. Breeding for nematode resistant cultivars is also being carried out. The three main soil borne diseases of chilli are Phytophthora root rot (Phytophthora capsici), Verticillium wilt (Verticillium dahliae) and Rhizoctonia root rot (Rhizoctonia solani) (Goldberg, 1995). Phytophthora root rot mainly causes problems in excessively wet fields from over-irrigation or excessive rains; heavy soils, slow draining low spots in the field and shading of plants due to buildings and windbreaks exacerbate the problem. Good field drainage is therefore important. There are no truly resistant cultivars and chemicals have a limited effect; 3-4 year crop rotation with for example lettuce, brassicas, onions and small grains can reduce residual Phytophthora populations. Symptoms are the death of the plant due to the death of the root system; roots become discoloured and die, the stem’s bark sheds easily and the plant becomes straw coloured and often shows sign of defoliation. Verticillium wilt symptoms are variable, but most commonly results in yellowing and stunted plants. Eventually defoliation may occur. The disease can be identified by the discolouration of the vascular tissues in the stem as they become plugged by the fungus, causing the plant to die. This disease tends to be a problem in more temperate climates and is difficult to control once it enters a field. Fumigation may give control and crop rotation as above will help; no resistant cultivars exist. Rhizoctonia root rot affects the plant on the stem near the soil; from this it moves into the stem and the taproot causing reddish-brown lesions and leading to the death of the plant. Some plants may recover somewhat by forming secondary roots above the lesions and good watering may prolong their life; however, yields are much reduced. Control is best achieved with seed fungicidal treatments as for damping off and no resistant cultivars exist. Damping off is a seed or seedling disease that can be caused by a number of organisms such as Rhizoctonia solani, Phytophthora capsici, Pythium spp. and Fusarium spp. (Goldberg, 1995). Seeds fail to germinate and seedlings die rapidly due to the destruction of the roots or due to stem collapse. Fungicidal or hot water seed treatments, well drained fields and seed beds and the use of good quality seeds help to control this problem. Bacterial leaf spot (Xanthomonas campestris pv. vesicatoria), Cercospora leaf spot (Cercospora capsici) and powdery mildew (Leveillula taurica) are common leaf diseases (Goldberg, 1995). Bacterial leaf spot and Cercospora leaf spot occur in wet, humid conditions and cause crop losses. The former causes circular water-soaked lesions that turn purplish-grey with a yellow halo; the latter causes circular lesions that turn grey or white and then dark brown with a reddish edge. Both diseases are best controlled with copper based chemicals, even though some resistant fungal strains exist; these compounds need to be applied before wet weather to be effective. Weed control is important as these diseases can be harboured on many weed spp. Powdery mildew prefers warm weather (18-35°C) and can occur at low or high humidity. A powdery white fungal mass covers the lower side of leaves and some discolouration on the top of leaves occurs as this disease develops. Field sanitation and sulphur containing fungicides are the best control options; sprays need to be applied early and thoroughly to achieve control. A number of fruit diseases occur that reduce yield, but also have important safety implications for the final spice product. This latter aspect will be further expanded upon in the quality section below. Phytophthora fruit rot results in shrivelled fruit with a white mycelium on the inside infecting the fruit and seeds. Control is achieved as for the Phytophthora leaf spot. Anthracnose (Colletotrichum spp.) initially establishes itself in the field during wet conditions; it then lies latent and appears when the fruit ripens as water soaked lesions that are coloured dark red to black. It is therefore often considered a postharvest problem. Clean seed and crop rotation are the best control methods, and some fungicides may assist in its control. Bacterial soft rot is mainly caused by Erwinia carotovora pv. carotovora in rainy weather where soil is splashed onto fruit. The bacteria enter fruit through any minute damage, which is often caused by insect damage, and liquefies the tissue at the infection site. Fruit often turn into water filled bags and for fresh market fruit the disease spreads rapidly to neighbouring fruit in a box. Control is best achieved by insect control in the field and chlorination of wash water after harvest.

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The most serious field infection of fruit, however, comes from the black mould caused by Alternaria spp. (Goldberg, 1995). Alternaria spp. occurs with excessive moisture late in the season and can be primary causes of disease or secondary agents. As a secondary agent it infects fruit that have already been affected by other disease agents. Black mould can be controlled by preventing other diseases and insect problems, by reducing irrigation and fertilisation in the late season, and by harvesting red fruit as soon as possible. After harvest chillies must be kept dry and processing techniques also need to be correct to minimise problems. In addition to Alternaria spp., other moulds may be present as secondary disease agents (Goldberg, 1995). This may be of concern as some of these fungi, given the right conditions produce mycotoxins, including aflatoxins, the most potent liver carcinogen known. The implications of this problem are discussed in the quality section below. Paprika plants are affected by beet curly top virus, tomato spotted wilt virus, pepper mottle virus, alfalfa (lucerne), cucumber and tobacco mosaic viruses and pepper geminiviruses among others (Goldberg, 1995). Leafhoppers transmit beet curly top virus from susceptible plants resulting in seedling death, plants stunting and curled, twisted and dimpled leaves with clear veins. Thrips are the vector of tomato spotted wilt virus that causes off-coloured spots and distortion of fruit, and leaf distortion and mosaic and chlorotic ring spots. Aphids transmit pepper mottled virus resulting in misshapen, mottled and puckered leaves. Aphids also spread cucumber mosaic virus and it causes narrowing, stunting and light coloured spots of leaves, and may cause small, distorted fruit. Alfalfa mosaic virus spreads through close proximity of alfalfa (lucerne) plants and causes distorted fruit. Tobacco mosaic virus causes light and dark green bumps on leaves and small, unevenly coloured fruit; it is transmitted mechanically on tools and hands, and on seeds. Pepper geminiviruses cause stunting, yellow mosaic patterns on curled or twisted leaves and distort fruit; they are transmitted by whitefly. Virus control varies with the vector; insect or aphid transmission is controlled by controlling the vector and of weeds that are alternate host. Tobacco mosaic virus is difficult to control and prevention depends on good hygiene practices and clean seed. Alfalfa (lucerne) should not be planted nearby and resistant cultivars are available for tomato spotted wilt virus and tobacco mosaic virus. A number of non-microbial disorders can also affect chilli fruit (Goldberg, 1995). These include nutrient deficiencies and toxicities, salt, wind, hail and herbicide damage, and blossom end rot and sunburn. Blossom end rot is related to poor irrigation practices that lead to calcium deficiency (Bosland, 1994). Fruit develop brown/ black spots on the lower portion and ripen prematurely in response to insufficient water, and therefore calcium, being supplied to rapidly developing fruit. Sunburn occurs when fruit are exposed to direct sunlight for extended periods due to wilting or defoliation from underwatering or diseases. The affected tissue turns tan in colour, becomes papery and is often affected by secondary fungal infections (Goldberg, 1995). 2.1.3. Harvesting The harvest maturity of chilli for spice production is normally determined by the colour stage, that is the ripeness stage, that the fruit have reached. As fruit ripen they turn from green to green with some light red colour showing, to all light red, to deep red (blood colour), to deep red with partial drying of fruit. Commercially fruit of deep red colour that are or are not partially dried can be used for spice production (Deli et al., 1996; Worku et al., 1975). Partial drying of fruit on the plant does not reduce quality, as fruit will be dried during processing. Additionally, colour stability of red chilli spice was best when harvest was delayed (Isidoro et al., 1995). On the other hand light red fruit have too low a colour content and reduce the quality of the final spice powder. Chilli fruit on the bush have a wide range of ripeness due to the growth habit of the chilli plant (Figure 1).

6

Node 4 Node 3 Node 2 Node 1

Figure 1 Schematic representation of a chilli plant. As the plant grows it repeatedly branches and flowers at the thus created node. Node 1 flowers first, node 2 second and so on. Therefore the ripeness of the fruit also decreases from node 1 to the top node. It is not uncommon for fruit to be harvested from 6-7 nodes. As most fruit will be harvested from the top nodes, it is essential for a good yield that the fruit from the top nodes are allowed to ripen. This can be done by either harvesting mature fruit repeatedly or by leaving fruit on the plant for a once-over harvest. The latter is necessary for machine harvesting. Heat levels of fruit from top nodes may also be lower than from lower nodes due to increased competition for pungency precursors (Zewdie and Bosland, 1996). Due to the relatively high proportion of fruit from top nodes the average pungency levels will be more similar to that of fruit from top nodes than the maximum heat level. The different ripeness stages also contribute to differences in colour and pungency levels of fruit within and between bushes (Miles, 1994). Plant hormone sprays are used widely in the horticultural industry. One that has been used for synchronising chilli ripening is ethylene, a natural ripening hormone, in the form of ethephon sprays (Indira et al., 1985). Kader (1992) reports that ethephon is registered for preharvest ripening sprays in chillies in the US and has been reported to successfully accelerate (Batal and Granberry 1982; Worku et al., 1975) or concentrate (Sims et al., 1970) Capsicum fruit ripeness. The effectiveness of ethephon, when applied to chilli plants before harvest, varies with factors such as rate, number of application, temperature, cultivar (Beaudry and Kays, 1988; Rylski, 1986) or even the type (Batal and Granberry, 1982; Sims et al., 1970). Most previous work (Sims et al., 1970; Worku et al., 1975) found that ethephon had the greatest effect, if any, at application rates in the concentration range of 1000 to 5000 µL/L. Due to economic considerations, mechanical harvesting of chilli for processing is essential in Australia (Miles 1994). While the use of a single destructive harvest is efficient (Palevitch, 1978), a uniform ripeness at harvest is needed. The possibility of using ethephon to synchronise fruit ripeness of cultivars grown in Australia therefore needed to be investigated. 2.1.4. Processing After harvest, chilli fruit are normally directly dried and ground into powder. However, fruit that are not fully red may continue to ripen after harvest. This may provide an opportunity of separating dark red from other fruit at harvest, and allowing the other fruit to ripen to increase overall yield. Fresh chillies are often classified as non-climacteric (Saltveit, 1977; Kader, 1992), that is, they do not show an increase in metabolism or ethylene production as they ripen. However, other reports suggest that some chillies produce increased ethylene levels during colour changes (Gross et al., 1986). This suggests that chillies are sensitive to accelerated ripening using ethylene after harvest. Suitable ripening conditions would be similar to tomatoes with a temperature of about 20°C, a high relative humidity (RH) of 90-95% to reduce water loss and about 100ppm ethylene (Kader, 1992). However, it is not known whether the quality of fruit ripened after harvest will be comparable to fruit harvested ripe. Also it is not clear what the

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minimum maturity for postharvest ripening is for chillies; as an indication immature green tomatoes, where the gel has not started to soften, will never ripen after harvest. Chilli fruit, as indicated above, are generally washed to remove debris, dirt and residues and then dried. To accelerate drying fruit may be cut into segments. At this stage diseased fruit must be removed to prevent health risks from mycotoxin production as discussed below. Dried chilli powder is widely used as a food ingredient for its hotness and colour. Most dried chilli powder used is red; however, in many cases powder becomes brown during drying and this reduces quality (Miles, 1994). The browning reactions that mask the red colour of chillies (Bosland, 1993) are due to enzymic activity (Mayer and Harel, 1979) and, more importantly during drying, due to non-enzymic Maillard reactions. The latter reactions increase in rate at higher temperatures (Roos and Himberg, 1994) and at intermediate levels of moisture content in the fruit (Wedzicha, 1984). Therefore drying at high temperatures or drying slowly will result in a browner powder of poorer quality. Traditionally chillies are sun dried in major production areas in the world (Shirvastava et al., 1990) and solar driers have improved drying efficiency (Shirvastava et al., 1990, Tiris et al., 1995). However, these techniques, similarly to hot air driers, utilise high temperatures and chillies remain for long periods at intermediate moisture levels resulting in brown discolouration of the product. Industrial driers result in a better quality, more uniform product (Minguez-Mosquera et al., 1994b). These driers often use a higher temperature, about 60°C, early during drying while the moisture content of the chillies is high. Then the temperature is reduced to about 45°C to prevent browning reactions during the final stages of drying. Drying of chillies is a slow process due to the very slow movement of water through the waxy cuticle of the fruit. To accelerate drying fruit are often cut into segments. Some workers have claimed that chillies can be dried in less then 20 hours (Zapata et al., 1992 cited in Minguez-Mosquera et al., 1994a), but longer periods are common in commercial practice. The drying time and conditions also have implications for the microbial safety of the resulting powder as discussed in the quality section below. Fruit are generally dried to a moisture content of about 8%, as 4% or below results in accelerated colour degradation and 11% or above induces fungal growth (Wall and Bosland, 1993). The final moisture of the powder is as important as that of the dried un-ground fruit, as the powder is hygroscopic (i.e. it attracts water) and may rapidly pick up moisture in humid environments. Re-drying after grinding and packaging with moisture proof plastic liners may be necessary. It is important to dry chillies faster than is currently possible to make the drying process more economical and to produce a better quality powder. The faster the drying process is, the smaller the capacity of the dryer has to be to dry the same quantity of product in a given season. This has a major effect on capital outlay needed to produce chilli powder. One way in which drying is accelerated for dried fruit like sultanas, is to use a drying oil that contains mostly ethyl ester of fatty acids (C14/C16/C18) and potassium carbonate (K2CO3) as active constituents. Whether this technology or cutting of fruit results in faster drying and which process results in better quality powder needs to be evaluated. After drying, chilli fruit need to be ground to produce the spice powder. A number of different considerations are important for the final quality of the powder. The red colour intensity will vary depending on whether the whole fruit or only the flesh without seed is used for manufacturing. Seeds are colourless and therefore will dilute the colour of the powder (Purseglove et al., 1981; Almela et al., 1991). However, the omission of the seed and of the associated placental tissue will reduce the hotness of the powder, as the pungent compounds mainly reside in these. Seeds also seem to have colour protectant qualities that stop the loss of red colour during storage (Biacs et al., 1992). The ratio of flesh to seed used may also be varied, by separating both after drying and adding them together in a defined ratio during grinding. In Hungary two types of paprika powder are traded, Delicacy Sweet Noble, which has a flesh to seed ratio of 100:45, and the lower quality Sweet Noble, with a flesh to seed ratio of 100:75 (Small J., pers. comm. 1998). Commercially two types of mills may be employed for grinding chilli fruit. For example in Hungary traditional stone mills are used, whereas for industrial manufacturing hammer mills are common. The two

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methods of grinding vary in their action, as stone milling is thought to crush the seeds so that their contents mix more thoroughly with the powder. This may result in increased gloss and reduced colour loss during storage (Biacs et al., 1992; Minguez-Mosquera et al., 1993), due to natural antioxidants present in the seed oil. This supposed benefit, however, needs to be quantified more carefully. 2.1.5. Storage of powder The storage of the resultant chilli spice powder has important implications for its quality. The carotenoid colour pigments responsible for the red colour are readily oxidised and the spice powder becomes less intensely coloured, developing an orange rather than a red hue. Researchers have tried new cultivars, different drying and storing methods to reduce the instability of the carotenoids (Okos et al., 1990; Biacs et al., 1992; Minguez-Mosquera et al., 1993; Biacs et al., 1994; Minguez-Mosquera et al., 1994b; OsunaGarcia and Wall, 1996). Natural antioxidants, such as α-tocopherol (Vitamin E) and ascorbic acid (Vitamin C) reduce colour loss, even though α-tocopherol is more effective (Biacs et al., 1992). A synthetic antioxidant, ethoxyquin, also reduced colour loss of paprika spice powder during storage (OsunaGarcia and Wall, 1996). However, the addition of natural or synthetic antioxidants to spices is not permitted in Australia (Australian and New Zealand Food Authority, 1996). Okos et al. (1990) found that the mixing of ground seeds from chilli fruit with their fruit flesh reduced colour degradation during storage. Light, air and temperature during storage also have a profound effect on colour retention in chilli spice powders (Malchev et al., 1982). Exclusion of light and oxygen and storage at low temperatures all reduce the rate of colour loss. Oxygen could be excluded by nitrogen storage (Bunnell and Bauernfeind, 1962). However, little is known about relative effects of different colour stabilising treatments and therefore which treatment would be most applicable for the spice industry.

2.2. Defining quality The final quality of chilli spice powder is assessed by a number of different parameters. Colour and pungency levels are the most obvious parameters assessed, but sweetness and flavour of non-pungent paprika powders are also important. In addition the spice trade may specify limits of impurity, levels of microbial counts of, for example, fungi, yeasts, Salmonella and coliforms, particle size and moisture content among others. The main characters discussed here will be colour, pungency and mycotoxins in relation to their biochemistry, assessment and desired levels. Other microbiological tests are standard throughout the food industry and can be performed by any registered microbiological laboratory. The colour of chilli spice powder is due to the presence of red-pigmented carotenoids. The main pigments are capsanthin, capsorubin, zeaxanthin and cryptoxanthin (Lease & Lease, 1956). Carotenoids are very stable in intact plant tissue. However, when chillies are processed by drying and grinding into spice powder, the carotenoids easily autoxidise due to effects of heat, light and oxygen as discussed above (Bunnell and Bauernfeind, 1962; Simpson et al., 1976 study cited in Britton and Hornero-Mendez, 1997). This leads to a more orange and less intense colouration that devalues the spice powder. In addition carotenoids have provitamin A activity (Somos, 1984; Minguez-Mosquera and Hornero-Mendez, 1993) and vitamin A is essential for the human diet; in fact the daily vitamin A requirement can be met by daily consuming 3-4g of capsicum powder (Somos, 1984). Carotenoids also have antioxidative properties that may prevent cancer (Hertog et al., 1997). Colour of chilli powder can be measured either as extractable red colour or surface colour. Extractable colour is the official method used by the American Spice Trade Association (ASTA, 1985) and in international trade (Woodbury, 1990). Generally in trade the lower limit allowable for chilli powder is 120 ASTA units and for non-pungent paprika 160-180 ASTA units. However, the higher the colour level is the better the quality of the spice is; also the loss of red colouration during storage needs to be considered to allow the spice to be of acceptable colour when it reaches the consumer. Surface colour measurements will give some indication of how the chilli powder will look to the eye. The lightness (L) value can give some indication of colour differences, as powder of higher colour intensity

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will have a lower ‘L’ value. However, powder that is dried at too high a temperature or that has other quality defects, for example fungal development, may be dark and brownish and the ‘L’ value may therefore be artificially low. For chilli powder a hue angle (h°) of 0º is red and 90º is yellow; therefore the closer the value to 90° is the more orange a powder will appear (Wall, 1994). However, as it is difficult to interpret complex ‘L’ and ‘h°’ data, the standard technique used by the spice industry is to measure extractable colour and to observe the powder visually for defects. Heat, or pungency, in chillies is caused by a group of compounds called capsaicinoids (Collins and Bosland, 1994), which are amino amides of vanillylamine and C9-C11 branched fatty acids (QuinonesSeglie et al., 1989). The two major capsaicinoids are capsaicin and dihydrocapsaicin, accounting for about 90% of total capsaicinoids. The minor capsaicinoids are nordihydrocapsaicin, norcapsaicin, homocapsaicin, nornorcapsaicin and homodihydrocapsaicin. Capsaicinoids are controlled by a range of factors from genetics, position of fruit on the plant and the environment as discussed previously. Therefore to achieve the heat potential determined by the genetics (see Table 1), the environment has to be conducive. For example cool growing conditions dramatically reduce heat levels. Capsaicinoids are mainly synthesised in the placenta (Iwai et al., 1977; Fujiwake et al., 1982) and are also found in the seed (Purseglove et al., 1981). Heat is perceived due to the interaction of the capsaicinoids with nerve cells of the skin and mucous membranes that trigger responses similar to ones caused by thermal heat (Clapham, 1997). For trade it is important to adequately measure heat levels. This allows standardisation of products. On a very subjective level, chilli fruit are often rated on a scale similar to the one shown in Table 1. However, responses are very subjective. This is due to tasters getting used to capsaicinoids over time, showing reduced responses to similar heat stimuli. The commercial method of determining heat levels in chillies is to measure pungency as Scoville Heat Units (SHU). These are named after the inventor of the Scoville Organoleptic Test to determine pungency by dilution series (Collins and Bosland, 1994). For the analysis a representative ground spice sample is used, which allows the analysis of the average heat level of a batch, rather than the very variable level found in different chilli fruit. The most reliable method of analysis is high-performance liquid chromatography (HPLC), but near infrared spectrophotometry methods (Asian Vegetable Research and Development Centre, 1993) are also being developed. The level of SHU desired for a product varies, depending on the market. However, U.S. style paprika generally only has traces of pungency, while commercial chillies for spice production can vary with some specifications being around 60,000 SHU. Capsicum products are known to be susceptible to contamination with mycotoxins (Scott and Kennedy, 1973; Seenappa, Stobbs and Kempton, 1980; Udagawa, 1982; Putzka, 1994). In particular aflatoxins are of concern, as they are the most common mycotoxin found in chilli products around the world and are possibly the most potent liver carcinogen known. Health effects include acute toxicity and long-term development of cancers, for example of the liver. Aflatoxins are produced by specific fungal strains of Aspergillus flavus and Aspergillus parasiticus under suitable conditions. Aflatoxin B1, B2, G1 and G2 exist, and all have been found in chilli powder or paste. In addition occasionally ochratoxin A, produced by Aspergillus ochraceus or Aspergillus carbonarius, may occur in chillies (Patel et al., 1996; Heenan et al., 1998). Fumonisins, produced by Fusarium spp., are unlikely to be found in chillies (Patel et al., 1996). Alternaria alternata, a common fungus in chilli, may also produce mycotoxins (Wall and Biles, 1994), but levels and toxicity are likely to be low (Pitt, J., pers. comm. 2000). What is of particular concern for public health is that aflatoxin contamination of chilli products is widespread and high levels can be found. For example significant levels of aflatoxins were found in commercial samples of 10/17 American cayenne pepper samples, of 6/6 Indian chilli powders and of 1/1 crushed, dried chillies samples (Scott and Kennedy, 1973). In a Japanese study 2/12 chilli and 5/12 paprika samples (Tabata et al., 1993), and in a German study 55% of chilli/ paprika samples (Putzka, 1994) contained levels of aflatoxins above legal limits. The permissible level of aflatoxin in Australia (Australian and New Zealand Food Authority, 1996) is 5µg/kg, 2µg/kg in Germany (Putzka, 1994) and 20µg/kg in the U.S (Food and Drug Administration, 1999). The permissible level implies that defective spice must be destroyed; it cannot be blended with a powder of lower aflatoxin content to produce a spice that passes the requirement. However, in chilli samples levels of up to 525µg/kg were reported in Ethiopia (Fufa and

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Urga, 1996), up to 48µg/kg in India (Jaffar et al., 1994), 51µg/kg in the UK (Macdonald and Castle, 1996) and 234µg/kg in Italy (Finoli and Ferrari, 1994). As referred to above, aflatoxins will only be produced if the right fungal strain meets the correct environmental conditions. For example, 16/44 of soil isolates of A. flavus (Saito et al., 1976), 28% of strains of A. flavus from spices (Udagawa, 1982) and 25% of strains of A. flavus from chilli spice (Ath-Har et al., 1988) produced aflatoxins. Conditions that inhibit aflatoxin production on whole fruit are a relative humidity (RH) of 80% or below and temperatures above 37°C (Pitt and Hocking, 1997). For dried powder the moisture content needs to be below 14% and/or the storage temperature below 13°C to prevent potential aflatoxin production (Anon., 1994; Pitt and Hocking, 1997). Therefore, holding, drying and storage conditions for chillies and chilli spice should fall within these parameters to minimise fungal growth and aflatoxin contamination. To this end diseased fruit from the field need to be excluded through sorting as they potentially contain aflatoxin-producing moulds. Drying should occur quickly at low humidity or at temperatures above 37°C. Powder should be packaged to maintain its low moisture content, and sanitation needs to minimise the level of contamination of the environment with fungal spores. If fruit are stored before drying, they must be kept cool, 7°C being optimal for chilli fruit. This minimises microbial growth that may otherwise occur rapidly due to fruit injury sustained during mechanical harvesting. However, it is not possible to reduce levels of aflatoxins by processing or cooking once contamination has occurred, as aflatoxins are chemically very stable (Macdonald and Castle, 1996). Aflatoxins, and other mycotoxins, can be measured in samples using HPLC methods, but new enzymelinked immunoabsorbent assays (ELISA) can be performed without sophisticated equipment (Adachi et al., 1991). Routine testing of batches for aflatoxins therefore can, and indeed should, be carried out to minimise public health risks. No data is publicly available on levels of aflatoxin contamination in chilli products in Australia, and therefore a survey of chilli products available in supermarkets and ethnic food outlets was conducted.

2.3. Gaining competitiveness Considering the description of the chilli spice production system above, and current industry practice in Australia a number of research issues have evolved to make Australian chilli spice production competitive. As labour costs are low in many competitor countries, repeated hand harvesting at the optimum ripeness of fruit is feasible there. To minimise this cost-disadvantage, Australia needs to adopt machine harvesting. It is estimated that machine harvesting in Australia is only 20% of the cost of hand harvesting (Small J., pers. comm. 1998). Ready-made equipment is available for large fruited cultivars with a hanging fruit habit, contrary to standing-up fruit. However, machine harvesting relies on once-over harvesting as all fruit are stripped of the plant. If the ripeness is not right, or varies a lot between fruit, a large number of unmarketable fruit will need to be culled leading to increased costs and reduced yields. Strategies to minimise losses due to varying maturities include the use of ethephon sprays, as discussed above, letting fruit from top nodes catch up with lower nodes before harvest, and the ripening up of culls after harvest to a marketable stage before processing. As responses to ethephon vary with different cultivars and growing conditions, all three avenues of yield and quality maximisation need to be investigated for commercially grown cultivars in Australia. In a previous RIRDC sponsored study by Miles (1994) the main obstacles for Australian chilli development were identified as using appropriate growing conditions to produce internationally competitive hotness, lack of synchronous crop development resulting in non-uniform quality, and poor colour retention during drying. While non-synchronous development was addressed above, appropriate growing conditions need to be established. While, as discussed previously, hotness is determined by the genetics of the cultivar, growing conditions seem to have a large influence over this quality aspect. Therefore water, temperature and nutrition have to be right to achieve good quality. However, potentially conflicts exist between quality and yield considerations. For example some water stress may limit yield but maximise hotness. Ranges of in-field parameters that allow the production of good yields of good quality fruit need therefore to be established under Australian growing conditions.

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The issue of colour retention after drying, alluded to above, needs to be tackled on two levels. On the one hand it is known that the wrong drying parameters will cause browning of the powder. This necessitates the selection of a proper drying technique as well as the right conditions. In addition, the long drying periods observed in industry potentially increase the potential of quality problems. Slow rates are linked to the inherent water barrier (cuticle) of chilli skins, low temperatures that may be used to reduce browning of pigments, or running dryers above capacity. Overall the industry would save significant costs, if fruit could be dried more efficiently; these savings would be derived from lower capital outlays for smaller driers if drying cycles are shortened and some energy savings. On the other hand the chilli spice powder quality is influenced by processing factors, such as the presence of seeds, and by storage factors, as the red carotenoid pigments are susceptible to breakdown. Therefore, to overcome the problems cited by Miles (1994), more work is needed on drying and storage methodology to produce a well-coloured and stable powder.

2.4. Research Goals The main research goal, as discussed above, was to increase the competitiveness of Australian chilli spice production. This involved an integrated approach tackling the various weaknesses of the existing chilli spice production system from field production, harvesting to processing and storage. In particular the aims were: •

to optimise in-field parameters for production of good quality fruit and yield;



to synchronise ripeness at harvest to allow machine harvesting with minimal culling of immature and unripe fruit;



to evaluate post-harvest ripening to reduce culls of fruit due to non-uniformity of ripeness at harvest;



to increase drying efficiency and quality of the dry powder;



to investigate processing and storage techniques to improve chilli spice powder quality;



to determine the extent of aflatoxin contamination of commercial samples in Australia.

Research was carried out in controlled environmental conditions and laboratory as well as on-farm to maximise the transferability of results to commercial operations.

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3. Research Findings and Conclusions Detailed methods are given in a separate document that can be obtained from RIRDC. For the tables shown, treatment means for a cultivar followed by different letters are significantly different at P