A new rapid enzyme digestion method for predicting in Vitro protein quality (PDD index)

Recovery and utilization of useful by-products from egg processing wastewater by electrocoagulation

The efficacy of a laboratory electrocoagulation (EC) system for treating egg processing plant waste-water (WW) is reported. For simulated and industrial egg processing WW, chemical oxygen demand, turbidity, and total suspended solids (TSS) were reduced 92 to 97%, 97%, and 99%, respectively, after treatment with EC. The final TSS concentration and turbidity values were 30 mg/L and 5 formazin turbidity units (FTU), respectively, similar to that of potable water standards. The recovered by-product solids had a similar pattern of essential amino acids compared to that of liquid whole egg and were comparable to the Food Agriculture Organization's essential amino acid profile for an ideal protein. The relative protein digestibilities of the recovered solids and a commercial corn meal averaged 130 and 56%, respectively, compared to liquid whole egg (set at 100%). An economic analysis of EC indicated that this treatment is economically feasible in that a savings of approximately $425,000 per year is possible in addition to recovering the capital equipment costs after about 14 mo of operation. These findings demonstrate that EC can be successfully applied to treat egg processing plant WW, yielding a high quality water suitable for recycling and valuable by-products having a highly digestible protein and fat value.

Recovery and characterization of by-products from egg processing plant wastewater using coagulants

The effectiveness of precipitation or coagulation technology to treat commercial egg processing plant wastewater, using such coagulants as lignosulfonate, bentonite, carboxymethylcellulose, and ferric chloride, was evaluated. For simulated and industrial waste-water, chemical oxygen demand, turbidity, and total solids were reduced over 90, 97, and 95%, respectively, for all coagulants tested. Protein and fat recoveries were over 95% for all coagulants. The optimal coagulant concentration for maximum by-product recovery depended on initial wastewater concentrations of protein, total solids, and fat. The dried by-products contained high concentrations of protein (30 to 50%) and fat (30 to 40%) and had similar essential amino acid profiles as standard proteins from the United Nations Food and Agricultural Organization (FAO). The relative protein digestibilities of each recovered solid (carboxymethycellulose, lignosulfonate, bentonite, and ferric chloride) and corn meal relative to a liquid whole egg standard were approximately 80, 90, 60, 30, and 56%, respectively. These compositional and in vitro digestibility studies suggest that the recovered by-products could be useful as livestock feed ingredients or for other applications.