Lipase Activity and Lipid Metabolism During Oat Malting

Abstract

Cereal Chem. 76(1):159-163Experiments were conducted to determine the relationship, if any, between lipase activity and the metabolism of lipids during malting (germination) of oat (Avena sativa L.) seed. During the course of malting, concentration of the free fatty acid fraction increased markedly at the expense of the neutral lipid fraction (predominantly triacylglycerides), while the initially high lipase activity (most of which is located in the surface layers of the grains) decreased by ≈40%. The fatty acid compositions of total and neutral lipid fractions were stable during malting, but there were marked changes in the free fatty acid and phospholipid fractions. In a comparison among 12 hulled and hull-less genotypes, there were no significant regressions between the quantitative changes in lipid fractions and lipase activities. Brief treatments with chemicals or hot H 2 O that partially or completely inhibited lipase activity had various effects on subsequent quantitative changes in lipid fractions, but these changes were not consistent with the inhibitions in lipase activity observed. It was concluded that the degradation in triacylglycerides and increase in free fatty acids observed during oat malting were not controlled by the level of total lipase activity. Rather, it was suggested that oat may have another lipase present in the cells where the oil bodies are located that hydrolyzes triacylglycerides from the oil bodies during germination. Further research is needed to substantiate this hypothesis.

The combined use of triacylglycerols containing medium-chain fatty acids and exogenous lipolytic enzymes as an alternative to in-feed antibiotics in piglets: concept, possibilities and limitations. An overview

“…However, the total microbial count on the feeds and feedstuffs used in all our experiments (Dierick et al 2002a,b) was about 1000 colony forming units/g. A simple calculation indicates that such populations are much too small to contribute significantly to lipolytic activity, which is in line with the results of Petersen (1999).…”

Germination: a means to improve the functionality of oat

“…On the other hand, the formation of free fatty acids during germination was more intense in hulled samples than in hull-less ones indicating the occurrence of both formation and degradation of lipids during germination. Peterson (1999) studied further the relationship between lipase activity and the lipid metabolism during germination. He found that the…”

Role of lipid reactions in quality of oat products

“…Cereal seeds contain apparently only 1 or up to 3 different isoenzymes of lipases acting on storage lipids (Baxter 1984, O'Connor et al 1989, Peterson 1999, Edlin et al 2002. On the other hand, the hydrolysis of phospholipids in plant membranes is a far more controlled process involving the induction of plant defense system, and multiple isoenzymes of each phospholipase classified in Figure 1 (Wang 2001).…”

“…In nongerminated oat these activities are, however, not detected consistently with lipase activity. Also the fact that neither lipid hydrolysis nor an increase in lipase activity is observed during early germination, suggests that the lipase activity present in mature oat grain is not related to the germination process (Peterson 1999, Outinen 1999. More likely, the activity represents either a residual activity originating from the lipid synthesis upon the seed development or is related to some other biological function such as defense systems (Urquhart et al 1983).…”