Studies On Nutritional Properties Of Protein And Physicochemical Characteristics Of Collagen From Abalone Muscle

Proximate composition and mineral elements of abalone muscle were investigated,and amino acids composition of water-soluble fraction?AWF?,myofibrillar protein?AMP?,and stroma protein?ASP?extracted from abalone muscle were analyzed in this study.Then,the digestion properties of abalone muscle protein in vivo and in vitro were explored.Finally,the properties of acid-and pepsin-soluble collagen from the abalone muscle were studied and compared.Firstly,proximate composition and mineral elements of abalone muscle were investigated,and amino acids composition of AWF,AMP and ASP extracted from abalone muscle were estimated.The results show that abalone muscle was a high protein and low fat meat,which belongs to be a low sodium/high potassium food.Abalone muscle,AWF and AMP were rich in glutamic acid,aspartic acid and arginine,while ASP was abundant with glycine and imino acids?proline and hydroxyproline?.Among abalone protein,just AWF meet the requirements of high-quality protein recommended by FAO/WHO?1991?.On the results of essential amino acid score,the first limited amino acid of abalone muscle,AMP and ASP was Lysine,while AWF was Tryptophan.The EAAI of AWF was highest and reached 88.13.Then,the digestion properties of AWF,AMP and ASP in vivo and in vitro were explored.In the vitro digestion process,the digestibility of AWF and ASP was approximately and much higher than that of AMP.Their digestion product was mostly existed in digestive juice in the form of polypeptide.And AWF was degraded rapidly by pepsin and trypsin,while AMP was chemically steady exposure to enzyme.AS for ASP,only partly could be degraded by pepsin and then furtherly degraded by trypsin.During digestion in vivo,the AWF,AMP and ASP showed similar digestibility as in vitro.Finally,the physicochemical properties of acid-soluble collagen?ASC?extracted from abalone muscle were investigated,and compared to those of pepsin-soluble collagen?PSC?extracted at different pepsin concentration.As a result,the extraction yield of ASC from abalone muscle was 0.63%,lower than that of each PSC.Irrespective of ASC or any PSC,the amount of Glycine was less than one-third of total amino acids,but each of them had 12?16 Cysteine residues/1000 residues and 10?15 Tyrosine residues/1000 residues.The?subunits of ASC were contained of?₁,?₂ and?₃ with the molecular weight of 160 kDa,140 kDa and 130 kDa,but only?₁ subunit was found in the SDS-PAGE of PSC.The maximum ultraviolet absorption spectrum of ASC was observed at 224 nm,which of PSC was shifted to 228 nm.Significant differences in the viscosity between ASC and PSC were observed,resulting in the obtained higher denature temperature of ASC.Based on the results of zeta potential measurement,it could be found that isoelectic point was near pH 4.9 irrespective of ASC or PSC.The effects of pH and NaCl concentration on the solubility of ASC were similar to those of PSC.However,the solubility of PSC was increased with increasing pepsin concentration,each of which was higher than that of ASC at the same pH or NaCl concentration.In conclusion,the nutritional value of AWF was higher than that of AMP and ASP,and AWF was also more easily digested in vivo and in vitro.During the collagen extraction,the yield and solubility of collagen was increased with increasing pepsin concentration,while the thermal stability was decreased.