J. Synowiecki

PRODUCTION AND CHARACTERISTICS OF PROTEIN HYDROLYSATES FROM CAPELIN (MALLOTUS VILLOSUS)

Protein hydrolysates were prepared from male and spent capelin (Mallotus villosus) using commercially available Alcalase, Neutrase and papain. Short-time autolysis of proteins by endogenous enzymes in fish viscera was also investigated and compared to procedures of accelerated enzymatic hydrolysis. While protein recovery varied from 51.6 to 70.6% for commercial enzymes, a yield of 22.9% was obtained for autolyzed products. All methods of preparation afforded products containing about 71–78% proteins after dehydration. Alcalase served best for preparation of capelin protein hydrolysates (CPH). Thus, products of Alcalase-assisted hydrolysis of capelin proteins were further assessed for their nutritional and functional characteristics. The amino acid composition of CPH was similar to that of the starting capelin, except for methionine and tryptophan which were present in smaller amounts. The products had excellent solubility (≥84%) over a pH range of 2–11. Incorporation of CPH (up to 3%) in meat model systems resulted in an increase of 4% in cooking yield and inhibition of oxidation (determined by the 2-thiobarbituric acid test) by 17.7–60.4%.

Production, Properties, and Some New Applications of Chitin and Its Derivatives

Chitin is a polysaccharide composed from N-acetyl-D-glucosamine units. It is the second most abundant biopolymer on Earth and found mainly in invertebrates, insects, marine diatoms, algae, fungi, and yeasts. Recent investigations confirm the suitability of chitin and its derivatives in chemistry, biotechnology, medicine, veterinary, dentistry, agriculture, food processing, environmental protection, and textile production. The development of technologies based on the utilization of chitin derivatives is caused by their polyelectrolite properties, the presence of reactive functional groups, gel-forming ability, high adsorption capacity, biodegradability and bacteriostatic, and fungistatic and antitumour influence. Resources of chitin for industrial processing are crustacean shells and fungal mycelia. Fungi contain also chitosan, the product of N-deacetylation of chitin. Traditionally, chitin is isolated from crustacean shells by demineralization with diluted acid and deproteinization in a hot base solution. Furthermore, chitin is converted to chitosan by deacetylation in concentrated NaOH solution. It causes changes in molecular weight and a degree of deacetylation of the product and degradation of nutritionally valuable proteins. Thus, enzymatic procedures for deproteinization of the shells or mold mycelia and for chitin deacetylation were investigated. These studies show that chitin is resistant to enzymatic deacetylation. However, chitin deacetylated partially by chemical treatment can be processed further by deacetylase. Efficiency of enzymatic deproteinization depends on the source of crustacean offal and the process conditions. Mild enzymatic treatment removes about 90% of the protein and carotenoids from shrimp-processing waste, and the carotenoprotein produced is useful for feed supplementation. In contrast, deproteinization of shrimp shells by Alcalase led to the isolation of chitin containing about 4.5% of protein impurities and recovery of protein hydrolysate. Referee: Dr. Norman F. Haard, Professor, Institute of Marine Resources, Department of Food Science & Technology, University of California, Davis, CA 95616

Mycelia of Mucor rouxii as a source of chitin and chitosan

Mycelia of M. rouxii may be used as a source of chitosan for medical, cosmetic and other purposes. The contents of chitin and chitosan in the mycelia from 2-day old cultures were 8.9 and 7.3% on a dry basis, respectively. Prolonged growth did not significantly influence the available amount of these polysaccharides. Chitin and chitosan isolation involved deproteinization of the mycelia with 2% NaOH solution at 90 °C for 2 h, extraction of chitosan with 10% acetic acid at 60 °C for 6 h and subsequent precipitation of chitosan at pH = 9.0. The recovery yield of aminosugars during the isolation process was about 94% of their total content in the mycelia. The chitosan contained 81.3% of glucosamine and its degree of acetylation was about 27.3%.

Protein hydrolyzates from seal meat as phosphate alternatives in food processing applications

Abstract Protein hydrolyzates were prepared from mechanically separated seal meat (MSSM) and used as phosphate alternatives in meat products in order to improve their water-binding capacity. The drip volume from thermally processed MSSM containing 3% ( w w ) seal protein hydrolyzate (SPH) was 5.8% ( v w ) as compared with 12.8% ( v w ) for meats cooked without any added SPH. The cooking loss of MSSM was minimum at a SPH concentration of 3%, similar to that of polyphosphates at the same level, but much higher than that of polyphosphates at their 0.5% maximum allowable limit of use. When compared to different phosphates, the drip volume resulting from use of SPH (54.7% of the drip from MSSM without additives) was lower than that for samples treated with sodium pyrophosphate (72.6%), sodium tripolyphosphate (66.4%) or sodium hexametaphosphate (60.0%).

Chemical composition and nutritional value of processing discards of cod (Gadus morhua)

Cod offal from Atlantic species (Gadus morhua) during the intense summer inshore fisheries, June–August, was analyzed for its chemical composition and energy value. The crude protein content of the samples was 14·3% and this included 2·55% collagen. The total lipid content of the offal was 4·3% and its ash content averaged 3·95%. Thus, the energy value of the offal was calculated as 413 kJ/100 g. The offal had an increased content of glycine, alanine, serine, proline and hydroxyproline as compared to the cod muscle proteins. Based on the content of selected amino acids, the calculated PER value for the offal was 1·88–2·36 as compared to 2·86–3·24 for the cod muscle. The fatty acid composition of the offal was similar to that of the cod-liver oil.

Preparation of hydrolysates from bovine red blood cells and their debittering following plastein reaction

Abstract Protein hydrolysates from bovine red blood cells were prepared using commercially available Alcalase. The best nitrogen recovery (69.2%) was achieved at a degree of hydrolysis (DH) of 25%. However, the product so obtained had a strong bitter taste (4.3 on a 5-point scale). At DH 16%, the nitrogen recovery was 65.9% and the bitter taste of product decreased (to 3.5). The hydrolysate contained 81.8% crude protein (N × 6.25), 2.4% moisture and 15.8% sodium chloride and had excellent solubility characteristics in water in the pH range 2.6–9.5. The Hunter colour parameters of the hydrolysate showed that good release of haem compounds during the process had occurred. Incorporation of hydrolysates (up to 3%) in meat model systems enhanced their cooking yield by about 5%. The protein efficiency ratio value of the hydrolysate was 3.7 as compared with that of beef (2.8), pork (2.5) and cod (2.5) proteins. However, low contents of isoleucine and sulphur-containing amino acids gave an essential amino acid index of 67.3 for the product. The bitterness of hydrolysate was reduced considerably by plastein reaction with diethyl ester of glutamic acid. The resultant product had a crude protein (N × 6.25) content of 96.3% and contained 30.6% of glutamic acid. The total free amino acid content in the product decreased from 18.6 mg g −1 hydrolysate to 1.85 mg g −1 plastein.

Sephadex LH-20 separation of pigments from shells of red sea urchin (Strongylocentrotus franciscanus)

Abstract Extracts of shells of red sea urchin ( Strongylocentrotus franciscanus ) in diethyl ether were separated by Sephadex LH-20 column chromatography. Methanol was used as eluting solvent. Seven fractions were separated, the first four of which did not absorb in the visible range. The last three fractions, which were coloured, are attributed to spinochrome B, echinochrome A and spinochrome E.

The gross chemical composition of Antarctic krill shell waste

Abstract Krill, a small shrimp-like crustacean, is actually being exploited commercially in the Antarctic waters. In order to evaluate the offals generated during the processing of krill to food and feed products, as commercial sources of chitin, three kinds of shell waste were analysed. Depending upon the method of krill processing applied the shell waste contained 49–60% of proteinaceous material. The content of crude chitin in the dried deproteinised shells ranged from 34 to 49%. About 60% of the salt mixture impregnating the shells was phosphates and carbonates of calcium and magnesium.

Nutrient composition of mechanically separated and surimi-like seal meat

Abstract The nutritional value of mechanically separated seal meat (MSSM) and MSSM washed with water or a sodium bicarbonate solution was compared with that of beef, pork, mechanically separated chicken meat (MSCM) and cod. The unwashed MSSM had a higher crude protein content (23·2%) and calculated PER (protein efficiency ratio) value (2·99) than other muscle foods. However, its essential amino acid index (EAA) value was similar to other meats. The caloric values of MSSM, MSCM, beef, pork and cod were 528, 612, 481, 479 and 344 kJ/100 g meat, respectively. Unwashed MSSM had a much larger content of B vitamins than meat from other animals. Calcium (591 mg%) and phosphorus (504 mg%) were the main minerals in MSSM, perhaps due to the presence of small bone particles in the samples. MSSM was a rich source of nutritionally available iron (18·5 mg%). Washings with water or a sodium bicarbonate solution increased the moisture and reduced the crude protein content of the resultant wet tissues. However, the protein content calculated on a dry weight basis was increased from 79·6% in unwashed MSSM to 82·2 and 80·1% after aqueous and bicarbonate washings, respectively. Meanwhile, the collagen content of MSSM was increased due to the above washings from 0·92% to 1·65 and 1·09% and the EAA values of products decreased from 116 to 104 and 113, respectively. The removal of lipids during washings with water or a sodium bicarbonate solution reduced the caloric value of the meat to 282 and 247 kJ/100 g sample.

Insensitivity of the amino acids of canola and rapeseed to methanol-ammonia extraction and commercial processing

Abstract Amino acid composition of rapeseed meals treated with ammonia in absolute or 95% methanol was compared to those of their hexane-extracted counterparts as well as a commercially processed meal. Meals of Altex canola, Midas rapeseed, and Hu You 9 Chinese rapeseed were used. Few differences were found in the essential amino acid contents due to these treatments. Partial extraction of non-protein nitrogen compounds may be responsible for the observed differences. Protein efficiency ratio (PER) values of meals, calculated on the basis of the content of selected amino acids, varied from 1.7 to 2.4, depending on the seed variety. The processing conditions did not affect the calculated PER values to any great extent.