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Evaluation of protein utilisation of vacuum microwave, air, and freeze-dried Euphausia pacifica in a rat model Landymore, Corrie Lorraine


Euphausia pacifica was dried using vacuum microwave blanching at a high temperature followed by air-drying (VH), vacuum microwave dehydrating (VMD) at a low temperature (VL), freeze-drying (FD), and hydrolysis plus freeze-drying (HZ). The effect of the drying method on the protein utilisation by young rats was evaluated. Five groups of fats were each fed an isocaloric diet containing 25.9 ± 0.2 % protein from one of five sources. The protein sources were casein (CA) as the control protein, and the four dehydrated krill samples (VH, VL, FD, and HZ). The results showed that the inclusion of the dehydrated Euphausia pacifica as the only source of protein in the feeds resulted in significantly reduced (p ≤ 0.05) body weight gains, feed intakes, protein efficiency ratios (P.E.R.), and nitrogen balances as compared to the CA control group. The nitrogen balance of the HZ group was significantly higher (p ≤ 0.05) than those of the VL and FD groups. There were no significant differences (p ≤ 0.05) in the apparent digestibilities of the CA, VL, FD, and HZ feeds. The VH feed had an apparent digestibility that was significantly lower (p ≤ 0.05) than the other experimental feeds. No significant differences (p ≥ 0.05) amongst the experimental groups were noted for apparent biological values (B.V.), apparent net protein utilisations (N.P.U.), or apparent urinary nitrogen losses. The available lysine content of the VH feed was significantly lower (p ≤ 0.05) than the other feeds. Only the FD group had a plasma α-amino nitrogen level significantly lower (p ≤ 0.05) than the CA control group; however, it was not statistically different (p ≥ 0.05) from the other krill meal fed groups. The rates of proteolysis of the VL, FD, and HZ feeds with added chitinase were all significantly faster (p ≤ 0.05), and the VH feed showed a trend towards being faster, than the rates of proteolysis of these feeds without the added chitinase. Fluoride levels in the VH, VL, FD, and HZ feeds were correlated with a reduction (p ≤ 0.05) the rats' feed intakes and weight gains. Drying Euphausiapacifica significantly reduced (p ≤ 0.05) or destroyed protease activity. Overall, fluoride present in the krill meals was correlated to a decrease (p ≤ 0.05) in the rats' feed intake, which affected the values of the biological methods used for assessing protein quality and utilisation. The method used to dehydrate Euphausia pacifica did not statistically (p ≥ 0.05) affect protein utilisation in the rat model.

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