Changes in contents of proteins, antinutritive substances and fatty acids in soya bean grain and full-fat meal under storage conditions

Abstract

The effects of storage conditions of soya bean grain and full-fat meal on total and water soluble proteins, available lysine, total oil, fatty acids, as well as, antinutritive substances - enzymes lipoxygenase 1, urease and trypsin inhibitor, were observed in this study. Grain and meal of the cultivars Goyou Kurakake and L93-7290 were analysed after five-month storage in PVC bags at the temperatures of 25oC and -20oC. The statistically significant decrease in contents of water soluble proteins, available lysine, trypsin inhibitor and activities of urease and lipoxygenase occurred five months after storage. The lowest content of the albumin fraction was recorded after grain storage at 25oC. This content was reduced by 18.5%, i.e. 21.1% in grain of cultivars Goyou Kurakake, i.e. L93-7290, respectively. In relation to trypsin inhibitor, storage conditions much more affected changes in urease activities in soya bean meal. The lipoxygenase 1 activity amounted to 6.89 µmol ml-1min-1 in the grain of the cultivar Goyou Kurakake and this activity was reduced by 28.2% during the storage period. On the other hand, this activity amounted to 11.89 µmol ml-1min-1 in the grain of the cultivar L93-7290, while the activity drop was 26.6%. After storage of full-fat meal of both cultivars, the lipoxygenase 1 activity was also statistically significantly reduced. During the five-month storage of soya bean oil, primarily of the cultivar L93-7290, a high stability to atmospheric oxidation was observed in oil. This oxidation was much more pronounced than in soya bean meal. The linolenic acid content in L93-7290 cultivar meal was lower by 27.3% than in the control after storage at 25oC.

U ovom radu proučavan je uticaj uslova čuvanja sojinog zrna i punomasnog brašna na promene sadržaja ukupnih i u vodi rastvorljivih proteina, iskoristivog lizina, ukupnog ulja, masnih kiselina, kao i antihranljivih materija - enzima lipoksigenaze 1, ureaze i tripsin inhibitora. Analizirano je zrno i brašno sorti Goyou Kurakake i L93-7290 nakon čuvanja pet meseci u PVC vrećicama na temperaturi od 25oC i -20oC. Nakon pet meseci čuvanja došlo je do statistički značajnog smanjenja sadržaja u vodi rastvorljivih proteina, iskoristivog lizina, tripsin inhibitora i aktivnosti ureaze i lipoksigenaze. Najniži sadržaj albiminske frakcije utvrđen je nakon čuvanja zrna na 25oC. U zrnu sorte Goyou Kurakake sadržaj je smanjen za 18,5%, a u zrnu sorte L93-7290 za 21,1%. U odnosu na tripsin inhibitor, uslovi čuvanja imali su daleko veći uticaj na promene aktivnosti ureaze u sojinom brašnu. U zrnu sorte Goyou Kurakake u kojem je aktivnost lipoksigenaze 1 bila 6,89 µmol ml-1min-1, tokom čuvanja došlo je do pada aktivnosti za 28,2%, dok je u zrnu sorte L93-7290 u kojem je aktivnost lipoksigenaze 1 bila 11,89 µmol ml-1min-1 pad aktivnosti izvosio 26,6%. Nakon čuvanja punomasnog brašna obe sorte, aktivnost lipoksigenaze 1 je takođe statistički značajno opala. Tokom pet meseci čuvanja, ulje sojinog zrna, prvenstveno sorte L93-7290, pokazalo je visoku stabilnost na atmosfersku oksidaciju, dok je oksidacija ulja bila daleko izraženija u sojinom brašnu. Sadržaj linolenske kiseline nakon čuvanja brašna sorte L93-7290 na 25oC bio je za 23,7% niži u odnosu na sadržaj u kontrolnom uzorku.