Production Of An Aquatic Protein Powder By Solid-state Fermentation

Anchovy, as one of the harvest single catches fish species in the world, has a large number resource. It contained abundant protein and the composition of amino acids was reasonable. While the high-value development and application of anchovy have not taken more attention due to anchovy is easy perishable after away from water. Soybean meal, a by-product of soybean oil extraction, contains abundant protein resource. The popular application of it has been restricted by the anti-nutritional factors. In this study, water-soluble protein powder with high protein content was obtained by two-stage processes from anchovy and soybean meal, including (Stage 1) anchovy endogenous enzymatic hydrolysis and (stage 2) solid-state fermentation of anchovy hydrolysis residue and soybean meal. The anti-nutritional factors in soybean meal were eliminated by solid-state fermentation. The hydrolysis protein solution for decoloratiomn and deodorization, then obtained the powder by spray drying the protein solution.The results of the nutrition contents of anchovy and soybean indicates that moisture, protein, fat and ash contents in anchovy were 73.27%,17.05%,4.95% and 2.69%, in soybean meal were 12.56%,48.76%,2.08% and 5.94%, respectively. Both materials contain abundant amino acids, especially the essential amino acids, and some elements which were benefit to animal or human body.The optimum conditions for anchovy endogenous enzymatic hydrolyze were determined by single factor experiment and orthogonal experiment. The optimal hydrolysis conditions were pH 6.5,60 ℃ for 4 h with one portion water. In those conditions, the recovery of protein (RP) and the recovery of acid soluble protein (R-ASP) of anchovy were 57.08% and 35.08%, respectively.The result indicated that the anchovy protein can be hydrolyzed by endogenous enzymes.Four portions of anchovy hydrolysis residue and one portion soybean meal were thoroughly mixed and then solid-state fermentation by Bacillus subtilis N-2. Both RP and R-ASP were higher than solid-state fermentation with pure anchovy hydrolysis residue. This indicates that soybean meal make contribute to protein recovery from anchovy hydrolysis residue. The optimum conditions for solid-state fermentation were determined by factorial experiment design and response surface experiment design. The results shown that moisture content, initial pH of fermentation substance, fermentation temperature and fermentation days were the four factors to solid-state fermentation among the six factors. And the optimum conditions for solid-state fermentation were 60% moisture content,7.0 initial pH,32 ℃ and fermentation 6 days. In those conditions, the recovery of protein (RP) and the recovery of acid soluble protein (R-ASP) of fermentation substance were 74.332% and 48.905%.Macroporous resin static absorption method was adopted to decolourize the protein solution. The results of orthogonal experiment shows that the best decoloring conditions for static adsorption were 2 h, resin content of 5%, adsorption temperature 35 ℃ and the pH value of protein solution was 5.0. Under those conditions, the decolorization rate of protein solution was 77.89% and the loss rate of protein was 27.87%. By comparing different fishy smell elimination methods, the result shows that the yeast fermentation method was best among those method. The results of orthogonal test shows that the best conditions for yeast fermentation were 1% yeast amount,90 min at 35 ℃. In those conditions, the protein solution has under the no fishy smell and with the aroma of yeast. In order to increase the stability of the protein solution, different kinds of stabilizers were added. The results show that xanthan gum, sodium alginate and CMC had influence on the stability of the protein solution. The best addition amount of xanthan gum, sodium alginate and CMC were 0.1%,0.075% and 0.05%, respectively.According to the characteristics of this produce process, this study analyzes the necessary instrument and equipment for industrialization. The protein powder was light yellow powder and had good solubility after dried by spray drying. The results of chemical composition analysis of the protein powder shows that the protein powder belongs to high-protein and low-fat diet products, had abundant amino acids and the composition of amino acids was reasonable. The contents of various metal elements in protein powder in the permitted range by the world health organization (WHO). The antigen protein soybean meal and bad oligosaccharides were all eliminated. The result of molecular weight distribution shows that most protein in the protein powder was 4 to 6 peptides. All results proved that this protein powder was high safety and high nutritional value, can be used as food additives and feed additives.