Effect of flaxseed oil-cake addition on the nutritional value of grass pea tempeh

Abstract

Cold-pressed flaxseed oil-cake is rich in nutrients and bioactive compounds. The aim of the study was to examine to what extent the inclusion of this by-product as a fermentation co-substrate can influence the nutritional value of tempeh obtained from grass pea seeds. Flaxseed oil-cake introduction to grass pea seeds (5 - 35% w/w) resulted both in increasing fat content in tempeh products, from 50 to 190%, and in changing the fatty acids profile. n-3 Linolenic acid share in total fatty acids was from 3.6 to over 10 times higher in tempeh with oil-cake addition, dependently on the dose. Furthermore, these products had more advantageous n-6/ n-3 fatty acids ratio (2.5/1 to 0.5/1) than grass pea tempeh (11/1). Grass pea tempeh contained about 300 g/kg protein, of which almost 70% was available in vitro. The introduction of oil-cake to fermentation substrate neither decreased the protein level in tempeh, nor lowered its in vitro availability. Protein of products enriched in oil-cake had lower Lys content by 6 - 12% but higher sulphur amino acids level by 10 - 46% than that of grass pea tempeh.