Protein Hydrolysate and Biocalcium from Salmon Frame : Preparation and their Fortification in Cracker

Abstract

Protein hydrolysates (PH) from two forms of salmon frame named 'chunk' and 'mince' were produced and characterized. Both samples were subjected to hydrolysis using alcalase and papain at 1-3% (w/w protein) for 0-240 min. PH prepared with either protease at 3% for 180 min had the solid yield of 24.05-26.39%. PH contained 79.20- 82.01% proteins, 6.03-6.34% fat, 9.81-11.09% ash and 4.02-5.80% moisture. Amino acid profile showed that all PH had glutamic acid/glutamine (113.45-117.56 mg/g sample), glycine (77.86-86.18 mg/g sample), aspartic acid/asparagine (76.04-78.67 mg/ g sample), lysine (61.97-65.99 mg/g sample) and leucine (54.30-57.31 mg/g sample) as the predominant amino acids. All PH possessed high solubility. The size distributions determined by gel filtration chromatography varied, depending on proteases and the form of frame used for the hydrolysis. Different PH showed varying antioxidant capacities. Biocalcium powders, Bio-cal-A and Bio-cal-H, obtained from alkaline treated and non-alkaline treated salmon frame, a leftover from protein hydrolysis process, were characterized, in comparison with those calcined at 900°C for 6 and 9 h named Cal-A (6 h), Cal-H (6 h), Cal-A (9 h) and Cal-H (9 h). Calcium content in calcined bones (31.54-38.84%) was higher than those in biocalcium powders (27.32-30.88%). Also, phosphorus content was higher in calcined bones (15.16-18.11%), compared to those of biocalcium (13.22-14.40%). The variation of Ca/P ratios were observed among all samples, depending on chemical and heat treatment conditions. Mean particle size of all powders were 22.21-26.53 μm. Bio-cal-A had higher L*(lightness), b* (yellowness), AE* (total difference in color), AC* (chroma) values than others (P<0.05). X-ray diffraction showed a characteristic hydroxyapatite as the dominant phase in all samples and degree of crystallinity was obtained after calcination. Protein, fat, hydroxyproline and TBARS were detected in both biocalcium powders, but not detectable in calcined bone powders. Pretreatment affected the amino acid compositions, abundance of volatile compounds and bioavailability of the biocalciums. Whole wheat cracker fortified with BC and PH powders obtained from salmon frame are the sources of amino acids and calcium, respectively was developed as health promoting food. Fortification of BC and PH powders or their mixtures at different ratios (3:1, 1:1, 1:3) with total substitution of 16.67% based on whole wheat flour was carried out. Characteristics and nutritional value of resulting crackers were determined. Color, thickness, weight and textural properties of crackers varied with different ratios of BC and PH powders added. Incorporation of BC/PH (3:1) mixture showed no negative effect on sensory properties. Developed crackers possessed higher protein, fat, calcium, phosphorus, sodium and cholesterol but lower carbohydrate, sugar, fiber and energy value than the control. Crackers contained saturated fatty acid (0.31-0.38 mg/100g), monounsaturated fatty acid (0.083-0.16 mg/100g) and polyunsaturated fatty acid (0.026-0.045 mg/100g). Scanning electron microscopic images showed that the developed crackers were less porous and had a denser structure, compared to the control. Based on scanning electron microscopy energy dispersive x-ray spectroscopic (SEM-EDX) images, the crackers fortified with BC/PH (3:1) mixture had higher calcium and phosphorus distribution with higher intensity, compared to the control. Overall, salmon frames, wastes from salmon processing industries could serve as an additional source of nutrients when processed into value-added product such as protein hydrolysate and biocalcium, which could be fortified into foods for enrichment of nutrients.