| Silkworm pupa, as a by-product of manufacturing silk, is produced in China in largerquantities; the annual output reaches more than500,000tons, which shares70%of the world.Proximate analysis of silkworm pupa shows that its protein that possesses best amino acidcomposition exceeds45-50%(w/w), indicating that it can be good protein source. Inaddition, silkworm pupa has many pharmacological effects, such as protect liver, improveimmunity, promote growth, decrease the blood sugar and blood pressure, resist cancer etc.However, the application of silkworm pupa in food industry is limited due to its peculiarsmell and poor physicochemical properties, including solubility, emulsification and foamingability.Since the past two century, people have done a lot of research work about modifyingfood proteins to change the functional properties by physical, chemical and enzymatichydrolysis. Researches show that, appropriate enzymatic hydrolysis of protein not only hasmild reaction conditions, safe and reliable process, but also the hydrolysates is superior to thatof acid, alkali hydrolysates in the aspect of nutrition, flavor and technology. Therefore, theenzymatic modification is an effective way to increase the utilization of silkworm puparesources, and attracted the attention of many scholars. The optimum conditions of enzymatichydrolysis of silkworm pupa peptide were obtained in this research. Meanwhiledecolorization, antioxidant activity and functional property of silkworm pupa peptide werestudied.Selection of enzymes was operated firstly during the process of hydrolysis with degreeof hydrolysis (DH) and protein recovery (PR) as index. The single enzyme, double-enzyme,three-enzyme, four-enzyme and five-enzyme experiment was carried out, and themultienzyme compound of Alcalase, Flavourzyme, Trypsin and Neutrase with equal ratiosexhibited the highest ability in the hydrolysis of defatted silkworm pupa (DSP). Theexperiment was investigateed the influence of the solid-liquid ratio, enzyme amount,temperature, pH value and time on hydrolysis of silkworm pupa peptide. Based on singlefactor, the optimal hydrolyzing conditions of silkworm pupa peptide were determined usingresponse surface methodology (RSM) and the optimal hydrolysis conditions were temperature50.80℃, pH8.44, and substrate concentration of10.64%. Under these optimized conditions, aDH of56.7%(w/w) and a PR of78.65%(w/w) were obtained.Because the color of silkworm pupa peptide was dark, silkworm pupa peptide needed tobe decolorized. The decolorization was investigated by adding activated carbon and the effects of activated carbon amount, temperature, and time and pH value were observed. Onthe basis of single factor, the optimum decolorization technology determined by theorthogonal L16(43) design was a ctivated carbon amount7%, temperature70oC, time60min,pH1.5. Under these optimized conditions, the decolorization rate and the loss rate of aminoacids was66.23%and8.68%, respectively.Research of antioxidant activity and physicochemical properties of silkworm pupapeptide were carried out and it showed that the hydrolysates of DSP exhibited excellentantioxidant activities, and with the increase of the degree of hydrolysis, DPPH radicalscavenging ability decreased. The trend of reducing power, superoxide and hydroxyl radicalscavenging activity was different with the degree of hydrolysis. Hydrolysis significantlyenhanced the solubility of defatted silkworm pupa hydrolysates at all pH values. Solubilityreached100%with the increase of the degree of hydrolysis, but with the increase of thedegree of hydrolysis, enzymatic hydrolysate emulsification and foaming capacity decreased.These results revealed that functional properties and antioxidant activity of defatted silkwormpupa hydrolysates have some relevance with the degree of Hydrolysis (P＜0.05).Themolecular weight distribution of the defatted silkworm pupa peptide was concentrated mainlybetween2000-3000Da, indicating that it has far-reaching significance in functional food. |
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