Effect on protein digestibility of different processing conditions in the production of fish meal and fish feed

Abstract

The effect of processing conditions on protein digestibility and fluorodinitrobenzene (FDNB)-reactive (available) lysine in the production of fish meal and extruded fish feed has been studied under pilot and commercial conditions using mink as model animals. Fish meal produced under pilot-plant conditions at processing temperatures below 70-80 • C (FM1) had protein digestibility of 929 (grams of protein digested per 1000 g protein consumed) compared with 905 when processed at temperatures above 100 • C (FM2). A low-temperature-processed commercial fish meal (CFM1) had protein digestibility of 940 compared with 888 for a standard commercial fish meal (CFM2). Pilot-produced extruded fish feed had protein digestibility of 913 when based on FM1 as the main protein source (95% of total protein) compared with 892 when based on FM2. Commercial extruded fish feed had protein digestibility of 912 when based on CFM1 compared with 871 when based on CFM2. Varying extrusion conditions at the pilot scale, ie temperatures from 100 to 126 • C and moisture contents from 21 to 12%, did not affect protein digestibility. Similarly, under commercial conditions, variation in temperature from 89 to 110 • C and moisture from 24.5 to 19.5% did not affect FDNB-reactive lysine and protein digestibility. The FDNBreactive lysine content and protein digestibility of the extruded feed were less than the values calculated from the ingredient mixture before extrusion. Thus, despite different extrusion conditions not giving different FDNB-reactive lysine and protein digestibility, the total process, ie extrusion, drying and oil coating, caused a reduction.

Effect of Processing Methods on the In Vitro Protein Digestibility and Vitamin Content of Edible Winged Termite (Macrotermes subhylanus) and Grasshopper (Ruspolia differens)

“…Exposure to denaturation temperatures may increase digestibility of native proteins by unfolding the polypeptide chain and rendering the protein more susceptible to digestive enzymes (Opstvedt et al 2003). On the other hand, when proteins are exposed to some heat treatments, digestibility may be reduced due to formation of disulphide bonds in the protein (Stanley 1998;Oria et al 1995).…”

A Comprehensive Look at the Possibilities of Edible Insects as Food in Europe – A Review

“…Insect processing methods affected their nutrient potential, as evidenced by the changes in the protein digestibility and the vitamin content. Depending on the processing conditions, heat processing may reduce (when proteins are exposed to some heat treatments due to the formation of disulphide bonds in the protein [Stanley, 1989]) or increase (by unfolding the polypeptide chain and rendering the protein more susceptible to digestive enzymes [Opstvedt et al, 2003]) protein digestibility [Kinyuru et al, 2010]. Solar drying at 30°C of the toasted sample led to a much higher loss (64%) in the ribofl avin content as compared to the fresh dried sample (46%).…”

Fishmeal Production and Sustainability

“…Other spoilage mechanisms are autolysis by the release of native (proteolytic) enzymes and microbial spoilage. Cooking and drying at temperatures below 90°C improve digestibility (Opstvedt et al, 2003) and give rise to less protein degradation chemistry, for example through Maillard reactions (non-enzymic browning). Lipid stability entails prevention of oxidation, which can be helped by the inclusion of antioxidants such as ethoxyquin (200-1000 ppm).…”