26) SELECTED TECHNOLOGIES FOR FRUITS AND VEGETABLES The oldest method of preservation method for fruits and vegetables is sun-drying. Figs, grapes, and dates grown in ancient Canaan and Egypt were among the first fruits and vegetables dried, requiring no peeling or special treatment. Formation of moulds, fermentation, and insect attacks were among the problems associated with man's initial efforts to preserve fruits. It's likely that wine and vinegar were by-products formed during fermentation that accompa nied early attempts to preserve grapes and grape juice for sacramental purposes. Yeast were naturally present on the skins of the fruit, and the rate and extent of fermentation were controlled by the addition of honey .The temperature was varied by storing containers in caves, and exposure to air (oxygen) was reduced by use of special ceramic containers. For the past seven centuries fermentation has been an important area of research and development. Even today, viticulture, enology , and microbiology continue to produce more and better wines, brandy , and related beverages. Spices have also been used as a fruit preservative from the time of antiquity. They contain alkaloids, which act as antioxidants, and add flavour, colour and bouquet. When added to fruit along with vinegar and honey (sugar), they provide the foundation for spiced fruits and fruit pickles. Chemical preservation of fruit, by the use of vinegar , wine, and sugars also was practised before biblical times. Pickles and even fruit preserves are partially or wholly preserved by chemicals. In pickles the preservative may be sugar , salt, vinegar (acetic acid), alcohol (wine or liquors), and by- products. Chemicals preserve foods in several ways. The chemical may be a poison to the micrograms tha t causes spoilage; it may provide an environment in which the micrograms cannot grow , even though it is not killed; or it may react with the fruit to form a new product. A high sugar content also serves another purpose: it ties up moisture, which is then not available to micro-organisms. Many procedures have been improved and products bettered as the use of undesirable chemicals have been eliminated, and others have been developed that are effective n preserving food without harmful side effects to people. Among these are ascorbic acid, which is added to frozen fruits and canned apple juice to preserve a light colour, and benzoic acid and sorbic acid, which are used to prevent mould and yeast growth. Calcium chloride is added to canned fruits for firmness. The greatest breakthrough in fruit processing, however , was development of thermal processing, the technique of preserving foods by heat. Nicholas Appert, who perfected thermal processing of fruits, vegetables, and meat and published his methods in 1810 (Goldblith 1972), received a prize of 12,000 francs from the French government for his work. Appert's process consisted of four steps: 1. Enclosing the food to be preserved in bottles 2. Corking the bottles carefully 3. Submerging the bottles of food in boiling water for a time, depending upon the nature of the food 4. Removing the bottles and cooling them

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Since Appert's early work, the technology of thermal processing has advanced and become quite sophisticated. The several significant developments are: A. Tin, aluminium, steel, or containers that can be hermetically sealed can be used instead of bottles. B. Some fruits and vegetables retain their colour, flavour, and texture better in containers of special metals; and containers of certain metals require a protectiv e lacquer to prevent colour or flavour reactions between the food and container. C. Some fruit and vegetable products may be aseptically packed by heat-sterilising the product and conveying it aseptically into containers that have been pre-sterilised, followed by aseptic closure of the containers. D. High-temperature short -time (HTST) processing can reduce treatment time for many fruit and vegetable products and is especially suited for purees, juices, and other products with heat-sensitive colour and flavours. E. Most fruit and vegetable products with pH 5.5-6.0 can be processed in boiling water and retain acceptable colour, flavour, and texture, but some products with a pH ~ 7 .0 require such a long treatment time to kill micro- organisms that the texture of the fruit is destroyed. F. Because high-temperature short-time heat-sterilising reduces the extent of products denaturisation, high-speed heat exchangers and turn-over containers are being developed, resulting in constantly improved processed fruit and vegetable products. MAJOR TECHNIQUES IN FRUIT and VEGETABLES PRESERVATION The 10 major techniques used in commercial fruit processing, in their approximate order of importance, are 1. Canning at high temperatures 2. Freezing at low temperatures 3. Dehydration (such as air dying, osmosis, microwave, electric/magnetic field, ect.) 4. Preserving with high sugar concentrations (e.g., preserves, syrups) 5. Preserving with chemicals such as sulphur dioxide, sorbic acid, sodium benzoate, ascorbic acid, acetic acid, citric acid, and alcohol 6. 7 .Fermentation with yeast and bacteria 7. Pickling with sugar , spices, and vinegar 8. Reduction of oxidation by the use of vacuum, antioxidants, and reducing agents 9. Reduction of visible light by the use of opaque containers and dark storage Often, a combination of the two or more of these techniques is used in processing a particular product. Other materials may be added to achieve specific effects: calcium salts to improve texture; ascorbic acid to retain red colours; sugars to enhance flavours; spices to add pungency; tannins and caffeine as stimulants and to add bitterness. Practically every major fruit and vegetable processing operation such as a canning, freezing, drying, or juice extraction plant can be adapted for the manufacture of minor or speciality products from fruit/vegetable that is overripe, hail damaged, irregularly formed, bruised by mechanical handling, from a little known cultivar , off-season, or produced to meet a special Paper 26 – PAGE 2 / 5

market. Sometimes the manufacture of speciality products provides substantial revenue and furnishes employment in out-of-season months. It also provides a way to utilise agricultural products more completely. As more fruits/vegetables are mechanically harvested, graded, and sorted, bruising is increased, and a smaller percentage of choice product results. This increases the need for developing by-products to help finance a commercial processing operation. In many instances manufacture of speciality products is economically attractive even if the operation only breaks even because it eliminates the cost of disposing of otherwise waste materials such as peels, seed, cores, and windfall, immature, or overripe fruit. The leading methods of processing fruits have shifted continuously during the centuries from sun-drying, sugar preserving, and chemical preserving to canning, artificial dehydration, concentrating, radiation, and freezing, and combinations of one or more of these methods; but as long as records have been kept, the percentage of fruits and vegetables pr ocessed, compared with that eaten fresh, has steadily increased. This general trend has been due to one or more improvements in the cultivators used for processing; horticultural practices and production of fruits especially suitable for processing; mechanical harvesting of fruits for processing; techniques for processing large volumes of fruits/vegetables; containers that extend the shelf-life of processed fruits; the standards and nutritional value of processed fruits; and the marketing of processed fruits, especially imported ones. Fruits and vegetables provide an abundant, cheap source of fibre and several vitamins and minerals. In general, they have the highest nutritional value when eaten fresh, although an exception may be fermented foods, in which the process of fermentation can nacres the content of B-vitamins. The extent to which nutrients are lost during processing varies according to both the type of fruit or vegetable and the process that s used. A summary of losses of selected nutrients is show n in Table 1.

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Table 1. Summary of nutrient losses in different types of fruit/vegetable processing

% Loss

Process/Product

Carotene Thiamin Riboflavin Niacin

Vit. C

Pantothenic Vit.B 6 acid

Fermentation: Grapes/wine

66

66

Cabbagelpickled

43

33

Soybean/Ternpeh

41

(+817)

(+488)

Soybean/soysauce

(+400)

(+616)

(+667)

73

57

19 (+437)

Blanching: Peas

25

Broccoli

30

Green beans

20

Canning/bottling : Carrots

0-9

67

38-60

32

75

54

80

Peas

0-30

75

47

71

67

80

69

Tomatoes

0

17

25

0

26

30

10

Peaches

65

49

39

39

56

71

21

Pears

-

45

45

0

73

69

18

Pineapple

25

7

30

0

57

12

-

Fruits (average for apple, apricot, peach and grape)

6

55

0

10

56

Vegetables (average for peas maize, cabbage and beans)

5