99% pure protein isolate may lead to functional cottonseed protein derivates, composites.
Cotton is an important crop. It's a major source of oil for human consumption and cotton meal for feeding livestock. Cottonseed (Gossypium hirsutum) meal is a natural source of protein, fiber and energy. It is the most abundant plant protein available in the United States after soybean meal. Glandless cottonseed is a concentrated source of protein for human nutrition.
The aim of scientists at New Mexico State University was to develop a protein concentrate and a technique for extracting isolate from glandless cottonseed meal. They found that using the spray-drying process to isolate protein from glandless cottonseed meal allows for a clean alternate plant-based protein.
Different extraction solvents--water, sodium chloride, water and potassium hydroxide, and sodium chloride and potassium hydroxide--at temperatures of 5 C or 55 C, were studied by the researchers on glandless cottonseed meal samples, which had 6%, 12% and 19% fat content. The protein extracts were neutralized and spray-dried or acidified with 0.1 N (normal) solution of hydrochloric acid to its isoelectric point, and then spray-dried.
More protein was extracted using the potassium hydroxide solution than with the other tested solvents. The scientists were able to extract 64% of the total protein present in cottonseed meal. Protein solubility increased when the extraction temperature increased from 5 C to 55 C, depending on the extraction solvent used.
The researchers observed the highest protein solubility increase when using water and sodium chloride. Protein purity was greater when applying potassium hydroxide extraction at 55 C. They also found that lipid content and pH have an effect on the purity of the protein. The interaction between fat content and protein purity depends on hydrophilic and hydrophobic residues. Also affecting protein purity is the amino acid group charge in acid or basic solution. The highest purity non-defatted glandless cottonseed meal was 41.5[+ or -]0.9% at 4.5 pH.
The highest protein purity was achieved using cottonseed meal that had a 6% fat content, compared to 12% and 19% fat content. A chloride acid prewash had a negative effect on protein concentration for cottonseed meal with 6% lipid content. But the wash increased the protein purity from cottonseed meal with 19% lipid content concentrates.
The researchers obtained a concentrate with 90% protein content and protein isolate with 99% purity that may be used to develop different functional cottonseed protein derivate or composite materials.
Further information. Nancy Flores, Food Technology, New Mexico State University, PO Box 30003, MSC 3AE, Las Cruces, NM 88003; phone: 575-646-1179; fax: 575-646-1889; email: firstname.lastname@example.org.