The Impact of Kilning on Enzymatic Activity of Buckwheat Malt

The Impact of Kilning on Enzymatic Activity of Buckwheat Malt Blaise Patricia Nic Phiarais 1,2, Hilde Henny Wijngaard 1,2 and Elke Karin Arendt 1,3 AB...
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The Impact of Kilning on Enzymatic Activity of Buckwheat Malt Blaise Patricia Nic Phiarais 1,2, Hilde Henny Wijngaard 1,2 and Elke Karin Arendt 1,3 ABSTRACT

J. Inst. Brew. 111(3), 290–298, 2005 This study investigated the impact of kilning on ␣-amylase, ␤amylase (total and soluble), ␤-glucanase and protease activities in buckwheat malt. Common buckwheat (Fagopyrum esculentum) was steeped at 10°C for 12 h, germinated at 15°C for 4 days and kilned at 40°C for 48 h. Moisture content and enzymatic activities were determined throughout the kilning period. Results showed moisture content was reduced from 44% to 5% after 48 h of kilning at 40°C. ␤-Amylase was found to exist in a soluble and latent form in buckwheat. Maximum activity of (a) ␣-amylase, (b) total ␤-amylase, (c) soluble ␤-amylase, (d) ␤glucanase and (e) protease activity occurred after (a) 8, (b) 7, (c) 30, (d) 0, and (e) 8 h of kilning, respectively. The final malt exhibited very little ␤-glucanase and cellulase activity. Proteolytic activity was low in buckwheat malt when compared to the barley malt control. All enzymatic activities were found to decrease during the kilning stage. Results indicated that after prolonged kilning at 40°C, inactivation of hydrolytic enzymes occurred; two-stage kilning for shorter periods is recommended. Although, amylolytic activity was low in malted buckwheat, buckwheat malt shows potential as an ingredient for the brewing and cereal industry. Key words: Buckwheat, enzyme activity, free amino nitrogen (FAN), kilning, malting, total nitrogen (TN), total soluble nitrogen (TSN).

INTRODUCTION Buckwheat is classed as a pseudocereal because it forms an integral part of the Polygonaceae family, while barley is classed as a cereal as it belongs to the Poaceae family. Seeds of pseudocereals resemble cereals in structure, chemistry and edibility 3. Buckwheat has the potential to be used as a raw material for the production of gluten free beer 26. Since there are no glutein-like proteins in buckwheat, it is considered gluten free and can be consumed by those who suffer from coeliac disease 2,13. Coeliac disease is a food induced immunological disease of the upper small intestine and results from gluten ingestion in genetically susceptible individuals 2,38. The true incidence of coeliac sufferers worldwide will increase in future because of a heightened awareness of coeliac disease 1 Department

of Food and Nutritional Sciences, National University of Ireland, University College Cork, College Road, Cork, Ireland. 2 Bio Transfer Unit, National University of Ireland, University College Cork, College Road, Cork, Ireland. 3 Corresponding author. E-mail: [email protected] Publication no. G-2005-1108-310 © 2005 The Institute of Brewing & Distilling

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and more advanced serological tests 12. Buckwheat contains compounds, that are claimed to have a positive effect on health such as antioxidants, which have an antihypertensive effect 37,38. It contains large amounts of soluble and insoluble dietary fibre(s) which have a positive effect on constipation and obesity conditions 24. Buckwheat protein has a high biological value as it contains one of the highest amino acid scores of protein and plant stuffs37. There are three types of buckwheat: cymosum (wild), tartaricum (tartary) and esculentum (common) 3. Fagopyrum esculentum is the most economically important species, making up approximately 90% of the world production of buckwheat 28. Almost all of the buckwheat plant can be utilized for a variety of applications. The buckwheat flower is used as an excellent honey source, the hull is used for the filling of pillows and the grain is used as a basic material for a wide range of products e.g. pancakes and pasta 6. Buckwheat can also be used to make malt 39. Barley is a monocotyledonic plant and buckwheat is a dicotyledonic plant. This leads to a different location of reserve compounds in the kernels 20. Due to this botanical difference, enzyme production and therefore the malting process may differ between buckwheat and barley. In a recent study, the effect of germination temperature on ␣amylase, ␤-amylase and protease activity in buckwheat was determined 39. It was found that both ␣-amylase and ␤-amylase activities were low in malted buckwheat in comparison to malted barley. The maximum activity level of ␣-amylase was 47.8 units g–1 (wet wt) in buckwheat without hull, which was germinated at 16.5°C. In addition, maximum apparent fermentability (56%) was reached when buckwheat was germinated at 20.2°C. This study analyses the impact of kilning on moisture content and enzymatic activity, specifically ␣-amylase, ␤-amylase (total and soluble), ␤-glucanase and protease activity during the malting of buckwheat. Enzyme levels of buckwheat were compared to those of barley and sorghum.

MATERIALS AND METHODS Unmalted buckwheat Common buckwheat (Fagopyrum esculentum) was used in the malting trials. The buckwheat samples were obtained from Trouw B. V. (Rotterdam, The Netherlands). Malting procedure The malting trials were carried out in duplicate (n = 2). In every trial 4 × 2 kg buckwheat was malted in a micro malting machine (Joe White Malting Systems, Perth, Aus-

Fig. 1. Means of moisture percentages (%) of buckwheat against kilning time (h).

Fig. 2. Rate of drying (%) in buckwheat against kilning time (h).

tralia). In every trial steeping, germination and kilning conditions were kept constant: steeping (12 h /10°C), germination (96 h /15°C) and kilning (48 h /40°C). For all enzyme analysis, rootlets were removed. Analytical procedures Analytical procedures were carried out in duplicate (n = 2) and the means of all results were calculated. All concentrations were based on dry weight, unless mentioned otherwise. Freeze-drying Throughout the kilning period, samples were collected and immediately frozen in a –80°C freezer for a minimum

of 24 h. Freeze-drying (AMSCO, Finn Aqua, Lyvovac GT2, Germany) was carried out at

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