| Abstract [eng] |
Press-cakes are by-products of vegetable drink production, usually discarded as bio-waste or used as animal feed. These press-cakes are rich in nutritious compounds like proteins, carbohydrates and minerals, which can be utilised to enhance the nutritional value and functionality of various plant- based food products giving rise to development of a circularity in the production processess. Along with nutrients, press-cakes also contain some anti-nutritional compounds like trypsin inhibitors, phytates and tannins. They usually descrease the biological value and assesibility of nutrients in the products, therefore need to be reduced. This thesis report aimed to carry out the extrusion process for soy and oat press-cakes and determine their impact on the chemical, functional and sensory properties when used in meat analogue matrix. The raw materials used in the project included soy and oat press- cakes received as a by-product from tofu (Soy t) and soy and oat (Soy d and Oat d) drink manufacturing. A low moisture extrusion process with four designed moistures and temperatures models were carried out to attain the aim. The extrusion process made the Soy d and Oat d press-cakes darker, while extruded Soy t press-cakes became lighter in colour. The chemical analysis of untreated press-cakes and extruded press-cakes were performed and compared. The results showed a reduction in protein content due to degradation during the extrusion process. To study the effect of extrusion on the anti-nutrients, the biogenic amines, acrylamide, free fatty acids and trypsin inhibitor activity was analysed. The amount of biogenic amounts were within the limit safety limits. The amount of trypsin inhibited after extrusion showed a reasonable inhibition rate. The analysis of functional properties showed that the water- holding capacity and oil-binding capacity of extruded press-cake samples increased with elevated temperatures and humidity. These extruded press-cakes were further analysed by adding them in 3% and 6% in amounts to the meat analogue matrix containing texturised soy protein as the base. The chemical analysis of meat analogues containing extruded plant origin press-cakes showed a high presence of proteins and unsaturated fatty acids but a lower amount of saturated fatty acids and sugars when compared with control samples (without addition of extruded press-cakes). The anti-nutrient analysis showed that the addition of different amounts of press-cakes extruded at different humidity and temperature lowered the biogenic amines, free fatty acids and trypsin inhibitor activity but increased the acrylamide content. The analysis of functional properties revealed that the meat analogue containing 6% press-cakes extruded at a temperature of 120 °C and humidity of 45% or 60% showed the best functional technological properties when compared to that of control sample. The texture profile analysis depicted that the addition of extruded press-cakes to the matrix improved its hardness, springiness, and gumminess compared to the control meat analogue without extruded press-cakes. The colour measurements and sensory analysis scores had high acceptability of meat analogues with extruded press-cakes, making it an excellent product to be developed further for market launch. |
