Research On Protein Extraction From Chili Residues And Its Preliminary Functional Properties

Chili residues, left behind after the extraction of capsanthin and capsaicin from red chili,is commonly sold to farmers at a low price or discarded by factories ultimately. However, the abundant nutrients existing in these residuals including protein, fat, fiber, saccharide, mineral, vitamin B1, niacin, etc might be neglected or could not be thoroughly utilized.In fact, the proportion of protein, containing a great deal of essential amino acid, accounts for about 16%, much higher than other components. In this study, the techniques of extraction and purification of chili protein were focused on and the functional properties of chili protein were analyzed by imitating the processing circumstances. The results were listed below.1. Essential chemical components were determined. The fiber constituted 44.09%; protein 15.67% within which essential amino-acid presented in complete types and took up to 30%; P 323mg/100g; Ca 271mg/100g; K 179mg/100g; Mg 75.9mg/100g. Heavy metal such as As, Pb and Cd were within international restrictions.2. Single alkali method and the ultrasound-assisted alkali method were conducted respectively to extract the protein from chili residues. According to the single-factor experiments results, the latter indicated a higher extraction rate. From the experimental design of response surface analysis, it could be concluded that the maximum protein extraction by ultrasound-assisted alkali method was 86.81%.The best conditions were acquired by ultrasonic treatment for 102min with the temperature 56℃, alkali concentration of 0.3 mol/L and 1:27（m:V） of the material-liquid ratio while the isoelectric point of chili protein was 3.6. The purity of chili residues protein（CRP） was 60.09% after freeze-drying. When classifying CRP, albumin was the highest in amount by 61.66% with purity of 92.26%.3. When the main components of CRP were tested, fiber accounted for 10.17%. If CRP was treated by cellulase, in single-factor and orthogonal experimental design, the purity could rise up to 70.21% in conditions of hydrolysis temperature 50℃, enzyme treatment 80min and 1.25% cellulase concentration. Comparing the essential amino-acid consisting in CRP and purified chili residues protein（PCRP）, they accounted for 41% and 42% of total amino acids respectively with complete types. When these CRP and PCRP were analyzed by score of ratio of coefficient （SRC） of amino acid recommended by FAO/WHO, the PCRP was more nutritive than CRP, with SRC at 75.62 higher than 74.33.4. Studied the functional poperty of chili protein, some functional properties of CRP and PCRP were assessed by several factors. The properties were solubility, water binding capacity, oil holding capacity, foamability, foaming stability, emulsibility and emulsion stability. The factors including temperature, pH, concentration of protein, NaCl, CaCl₂, and sucrose.