| In recent years,with the rapid increase in the consumption of donkey-derived gelatin(commonly known as e-jiao),shortage of donkey skin resource has become a major obstacle to industrial development.Therefore,the development and research of extracting gelatin from other animal skins is extremely important.Oxhide gelatin(it is made from cowhide by boiling)is the same type of traditional Chinese medicine as donkey-hide gelatin,but compared with donkey-hide gelatin,there is less research on oxhide gelatin.At present,the research on the preparation of oxhide gelatin is mainly based on traditional boiling,but this way is time-consuming,and finding a fast and efficient preparation method is a problem urgently solved at present.In this study,yak skin was used as the raw material.The response surface test design was used to screen out the process parameters for rapid preparation of oxhide gelatin.The oxhide gelatin prepared under the optimal conditions was compared with commercially e-jiao and determined their physical and chemical properties.In addition,in order to explore furtherly the changes in the physicochemical properties of gelatinized and concentrated colloids two main stages in the gelatinization process.The effects of different gelatinization times(two gelatinization methods),concentration time,and concentration temperature on the colloid structure,rheology,and functional characteristics were studied with a view to providing a theoretical basis for the industrialized production and application of oxhide gelatin.The main research contents of the full text are as follows:1.Using single factor and response surface test design,the optimal preparation parameters of oxhide gelatin were obtained: high temperature and pressure rapidly prepare gelatin method(0.1 MP,121 ?)gelatinization time 46 min,concentration temperature 80 ?,concentration time 7.4 h.Under this experimental conditions,the yield of oxhide gelatin can reach 36.1%,and the gel strength is 243.5 g.the moisture,ash,and proline content of the obtained products are 5.46%,0.38%,and 12.28%,respectively,which meet the requirements of the 2015 Pharmacopoeia.Gelation temperature,melting temperature,emulsion activity,emulsion stability,foaming properties,foaming stability,and volatile flavor substances are not significantly different from commercially e-jiao.Scanning electron microscopy andmorphological photos showed that the surface of oxhide gelatin was almost free of air bubbles,had high transparency,was bright yellow,and had protein content higher than commercially e-jiao and essential amino acid content that was lower than commercially e-jiao.2.The changes in the colloidal structure of the two gelatinization methods at different treatment times were analyzed.The ultraviolet absorption peaks of the collagen obtained by high-temperature and high-pressure treatment and cooking appeared near 212 and 214 nm,respectively,and there was a weak step-like rising ultraviolet absorption peak near 273 nm.The heat denaturation temperature of the gelatinized collagen reached the maximum value under high temperature and high pressure treatment for 40 min,which could reach 108.35 ?,which was higher than the denaturation temperature of collagen obtained by traditional gelatinization.The gelatinization time continues to increase,the enthalpy value decreases,and the fluorescence value at 308 nm generally decreases,the ?-turn content decreases,and it gradually transforms to random curl.3.The gel viscosity and storage modulus of the two gelatinization methods were measured to analyze the influence of gelatinization on the rheological properties of the collogen.The apparent viscosity and storage modulus of collogen reached the maximum values at high temperature and pressure treatment for 40 min and cooking for 6 h,respectively.During the melting process,the G ? value decreases as the temperature increases.During the heating process,the G ? value of the high-temperature and high-pressure rapid gelatinization is generally lower than that of the collagen obtained by the cooking method,which indicates that the high-temperature and high-pressure treated collagen reduced elastic modulus and enhanced fluidity.4.The foamability,foam stability,and emulsification of the collagen obtained by the two gelatinization methods all showed an increasing trend with the extension of gelatinization time.The high temperature and pressure treatment for 80 min,the collagen emulsification stability reached a maximum.When the cooking time reached 24 h,the collagen emulsification and emulsification stability reached a maximum.5.With the extension of the concentration time,the water content of the glue solution gradually decreased,and the transparency of the oxhide gelatin first increased and then decreased,and reached the maximum value at 8 hours.When concentration time is 7 h,theviscosity,storage modulus,and loss modulus all reached maximum values.The relative content of ?-helix is gradually decreasing as a whole,and the relative content of random curl is gradually increasing,and it can reach 17.48% after 8 h of concentration.With the increase of the concentration temperature,the moisture of the glue solution continues to decrease.At75 ~ 85 ?,the oxhide gelatin has a high transparency.When the concentration temperature is65 ~ 80 ?,with the increase of temperature,the content of irregular curl gradually increased the storage modulus and the loss modulus both reach the maximum at 75 ?.To sum up,the samples prepared under rapidly prepare gelatin method meet the requirements of the Pharmacopoeia,and the difference is not significant compared with the commercially e-jiao overall,but the protein content is higher and the essential amino acid content is lower.Gelatinization under high temperature and high pressure treatment has less collagen damage than traditional cooking methods,and the resulting glue has strong fluidity and excellent functional characteristics.The concentration time is too long,the temperature is too high,and the degree of collagen denaturation is large,which affects the network structure of the colloid and then its quality.This study can provide some theoretical basis for the industrial production and application of oxhide gelatin. |
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