The production of higher value food ingredients from white mustard seed via aqueous extraction

Abstract

A sequential two-pH process increased protein and oil extractions to 95% and 90%, improved oil recovery and used 60% less water than previous processes (Xu et al. 2003). Keywords. Mustard, Processing, Mucilage, Aqueous Extraction, Protein Isolation, Isoelectric Precipitation, Oilseeds, Sinapis alba, Brassica alba, Brassica hirta. Aqueous extraction of oil and protein from full-fat white mustard seed (Sinapis alba) was investigated in relation to the production of food-quality protein products. Conventional technology requires defatting using hazardous organic solvents prior to protein isolation. The final process involved multi-stage extraction and precipitation, incorporated ultrafiltration and bleaching, and produced a high quality protein product while recovering a substantial amount of oil as an emulsion. The protein product was 10% oil and better than 80% protein, with a yield of 15 g/100 g of starting mustard flour. It had a light colour, bland flavour, good binding ability and was comparable to commercial soy protein isolate when used in meat products. Mucilage on Sinapis alba seeds complicates aqueous processing. A rapid, efficient mucilage removal process was developed on 1 L and 5 L scales. Two-stage extraction using 8 parts 45°C water to one part seed removed over 90% of the mucilage in three hours. A three-parameter extraction model was developed using kinetic data from 4 different water to seed ratios. Mucilage removal improved with low water-to-seed ratios, vigourous mixing, increased temperature and pH. Removal eased separation when wet grinding the seed, lowering the emulsion and residual solids water contents. Oil and protein extraction from mustard flour was investigated using a commercial blender and batch centrifuge. Full-factorial design examination of extraction temperature, pH, period, and water-to-flour ratio showed pH was the most significant factor at both 25°C and 60°C. Room temperature protein and oil extraction efficiencies were up to 50% at pH 4.8, low near pH 7 and greater than 90% and 80% at pH> 11. Two 20 minute extraction stages were sufficient for maximum extraction. Lower contact ratios improved oil extraction. Salt greatly increased native pH extraction while significantly lowering pH 10 extraction. Oil recovery was near quantitative at pH 4.8. The project demonstrated that a high quality protein isolate can be prepared from mustard seed using solely aqueous processing.