可食性抗菌肽-明胶复合膜的制备及性能表征

为了研究新型的可食性抗菌包装材料,以明胶、甘油、不同浓度的抗菌肽为抗菌剂制备了抗菌肽-明胶复合膜。以光学性能等指标以及傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)和差示扫描量热仪(DSC)对复合膜的性能进行表征。结果表明:添加了抗菌肽的明胶复合膜在250～300 nm波长范围内吸收显著提高,抗菌肽的添加使膜的颜色偏黄,机械性能得到一定的改善,如50 mg/mL的抗菌肽添加量使水蒸气透过率具有一定程度降低(与纯明胶相比降低了17.30%),膜的抗拉强度(TS)和断裂伸长率(EAB)与纯明胶膜相比,分别增加了11.40%和42.90%)。当抗菌肽的添加量为50 mg/mL时,薄膜抗菌能力最为显著(对大肠杆菌和金黄色葡萄球菌的抑菌圈直径分别为14.60 mm和12.30 mm)。FT-IR和SEM显示复合膜有良好的相容性。DSC数据显示抗菌肽对复合膜的热稳定性有一定程度的降低作用。     

明胶/淀粉可食性复合膜研究进展

介绍了明胶、淀粉的结构特点以及作为可食性膜的优缺点,并将明胶、淀粉共混作为复合型可食膜,探讨了增塑剂、增强剂以及相分离等因素对其性质的影响.     

鲢鱼皮明胶-海藻酸钠复合膜的制备与性能

鲢鱼皮明胶膜因具有安全性高和来源丰富等优点受到广泛关注。然而鲢鱼皮明胶膜的力学性能和阻隔性能 较差,若作为食品包装膜将会受到限制。为了改善鲢鱼皮明胶膜的性能,将海藻酸钠与鲢鱼皮明胶共混制成复合 膜。结果发现,制成的复合膜外观透亮,有阻隔紫外线和油脂的性质;当添加体积分数为20%的海藻酸钠时,复合 膜的水溶性和水蒸气透过率达到最小,抗拉强度达到最大。说明复合膜的阻隔性能和力学性能都优于鲢鱼皮明胶 膜。对膜的傅里叶变换红外光谱图和X射线衍射图进行分析,表明鲢鱼皮明胶和海藻酸钠存在较强的相互作用,这 可能是复合膜性能发生变化的主要原因。     

狭鳕鱼皮明胶提取工艺的研究

为了充分利用水产品加工废弃物狭鳕鱼皮,优化狭鳕鱼皮明胶提取工艺,通过单因素试验和响应曲面法对鱼皮明胶提取工艺进行优化。结果表明：狭鳕鱼皮明胶提取的最佳工艺条件为：氢氧化钠浓度0.10%、硫酸浓度0.21%、浸提时间12.1h,此条件下明胶的提取率为17.52%。     

鱼皮明胶/羧甲基壳聚糖复合膜的制备工艺优化

目的 优化鱼皮明胶/羧甲基壳聚糖复合膜的制备工艺。方法 选择成膜液浓度、鱼皮明胶:羧甲基壳聚糖质量比、甘油:山梨醇质量比、pH、增塑剂比例、增塑剂浓度、加热温度、加热时间等因素,以拉伸强度、断裂伸长率为优化指标,结合单因素和正交实验,得到最佳制备工艺参数。结果 成膜液浓度为5%、鱼皮明胶与羧甲基壳聚糖质量比8:2、pH 7.9、增塑剂浓度40%、甘油和山梨醇质量比1:1、加热温度60℃、加热时间80 min为最佳制备工艺,复合膜拉伸强度为(22.83±0.80) MPa,断裂伸长率为138.36%±1.53%。结论 本研究确定了复合膜的最佳制备工艺条件,得到满足GB/T 21302—2007《包装用复合膜、袋通则》食品内包装强度要求的复合膜,拉断力达到国家4级要求,断裂伸长率达到国家3级要求,为保护生态环境和水产资源副产物的开发利用提供新的参考。     

罗非鱼皮明胶的制备及性质研究

以干燥的罗非鱼鱼皮为原料,经脱色溶胀后热水熬胶来制备明胶,通过正交实验法对罗非鱼鱼皮明胶的提取工艺进行优化,并分别对明胶黏度、吸水性、保水性、等电点和氨基酸组成进行了测定。结果表明,鱼皮明胶最佳提取工艺为氢氧化钠浓度2．0％,浸泡24h,盐酸的浓度为0．5％,浸泡4h时,熬胶温度在80℃,时间为8h,提取率为47．54％。     

透明质酸-明胶复合膜的制备及理化性质研究

为研发保鲜效果良好的生物基可食用膜,采用流延法将不同分子量的透明质酸(Hyaluronic acid,HA)与明胶制成透明质酸-明胶复合膜,测定其厚度、密度、抗拉强度、不透明度、色度、溶解性、水蒸气透过率和水分含量等理化指标,分析HA分子量对复合膜理化性质的影响,并使用红外光谱表征复合膜的结构。结果表明,随着HA分子量的增加,复合膜厚度、水分含量和不透明度呈现先增加后降低,溶解性和水蒸气透过率降低。红外光谱中酰胺A区特征峰向短波迁移,表明HA分子与明胶分子之间存在氢键作用。透明质酸分子量为(80~100)×10⁴ Da时,复合膜的综合性能最佳。HA-明胶复合膜的开发在食品包装和保鲜方面有潜在的应用价值。     

基于明胶硬胶囊性能评价的明胶—普鲁兰复合膜研究

制备了明胶—普鲁兰复合膜,通过测定复合膜的性质来指导评价硬胶囊的性能、优化硬胶囊囊材配比及降低其脆碎性和水蒸气透过系数(WVP),并通过透光率、傅立叶红外光谱、扫描电镜来表征明胶与普鲁兰的相容性。结果表明:甘油添加量为10%(干基百分比),明胶/普鲁兰质量比为91时,可用于明胶硬胶囊的共混改性。相比明胶膜,上述条件下制备的复合膜的WVP降低了26%,低湿环境下的断裂延伸率提高了1.19倍,复合膜中明胶与普鲁兰分子间具有良好的相容性,因此机械性能稳定性增强,WVP降低。     

甲壳素-明胶复合膜性能研究

以明胶为基体,甘油为增塑剂,甲壳素为增强相,制备可食用、易降解的功能性复合膜,通过添加不同质量甲壳素来制备甲壳素-明胶复合膜,探讨复合膜的抗拉强度、断裂伸长率、热缩、热差式扫描(differentialscanning calorimeter,DSC)以及膜的宏观、微观图像、吸水性、甲壳素-明胶溶液的黏度等反应膜的性能及规律。结果表明:甲壳素含量为0.5%的复合膜抗拉强度、断裂伸长率、黏度值等方面性能较好,对比空白样抗拉强度增强67.4%,断裂伸长率增强80.6%。     

明胶α亚基和美拉德反应对明胶-海藻酸钠复合膜性质的影响

以罗非鱼皮明胶α1、α2亚基和海藻酸钠为原料制备复合膜,对膜的机械性能、颜色、荧光强度和傅里叶红外光谱（FTIR）进行分析,考察了α亚基和美拉德反应对明胶-海藻酸钠复合膜性质的影响。结果发现,α亚基-海藻酸钠膜的机械性能在60℃、相对湿度（RH）为75%下保存72 h后均出现明显的下降,而荧光强度均出现增强。α1-海藻酸钠（α1-SA）复合膜在放置72 h后,b*值的增大幅度达到64.0%,明显高于明胶-海藻酸钠（G-SA）和α2-海藻酸钠（α2-SA）复合膜。FTIR分析表明,保存过程中α亚基与海藻酸钠发生了美拉德反应,并且α1亚基更容易参与反应。因此明胶α亚基-海藻酸钠复合膜在60℃、75%RH下保存中颜色逐渐变黄。      

Characterization of protein fractions from immature Alaska walleye pollock (Theragra chalcogramma) roe

ABSTRACT:  There are good markets for mature pollock roe; however, immature pollock roe is underutilized. The physical and nutritional properties of immature pollock roe (IPR) have not been reported, which limits its potential use as a food ingredient. The objective of this study was to evaluate the physical and nutritional properties of immature pollock roe and soluble and insoluble protein powders made from the immature roe. IPR samples were obtained during the spring pollock harvest from a seafood processing plant in Kodiak, Alaska. Soluble (SP) and insoluble protein (IP) fractions were produced by heating IPR, separating by centrifugation and freeze drying. The protein contents of freeze-dried IPR, SP, and IP were 81.7%, 63.2%, and 83.0%, respectively. The amino acid contents of IPR and IP were similar except for isoleucine and valine. However, the amino acid contents of IPR and IP were different from values for SP. Lipid contents of IPR, SP, and IP were 9.2%, 9.3%, and 11.1%, respectively. Palmitic acid (C16:0; 21.2%), DHA (C22:6ω3; 21.2%), and EPA (C20:5ω3; 19.0%) were the 3 most abundant fatty acids in fresh IPR. Fat adsorption capacity value for SP was significantly higher than IPR and IP ( P < 0.05). SDS electrophoresis indicated a major protein band with molecular weight of 103 KDa in all samples. Results indicate that IPR can be utilized to make a number of unique food ingredients with good nutritional characteristics and functional properties.     

Properties of soluble protein powders from Alaska pollock (Theragra chalcogramma)

Soluble protein powders were produced from pollock by‐products and evaluated for their functional, nutritional and rheological properties. Soluble protein powders were made from pollock viscera (PVSP), viscera without liver (PVWLSP), heads (PHSP), frames (PFSP), trimmings (PTSP), and liver (PLSP) and had protein contents ranging from 65.0% to 78.9%. Yield of PVWLSP was higher than that of other pollock proteins powder and PTSP had the highest nitrogen solubility value (85.7%). Emulsion capacity and emulsion stability of the pollock protein powders ranged from 29% to 34.5% (mL of oil per 200 mg of protein) and 65.3% to 77.6%, respectively. Highest and lowest fat adsorption values were observed for PFSP (10.6 mL of oil per gram of protein) and PVSP (4.1 mL of oil per gram of protein), respectively. Fish protein powder samples were good sources in K, P, and Mg and amino acids. Emulsions made with pollock soluble protein powders exhibited viscoelastic characteristics.     

Physicochemical properties of gelatin gels from walleye pollock (Theragra chalcogramma) skin cross-linked by gallic acid and rutin

Gelatin gels were cross-linked by gallic acid and rutin. The gel strength, viscoelastic properties, thermal stability, swelling property, ultrastructure, X-ray diffraction patterns and FTIR spectra were determined to evaluate the physicochemical properties of the modified gels. The gel strength increased with increasing gallic acid concentration up to 20 mg/g dry gelatin, and then decreased at further elevated gallic acid concentration, while it continuously increased with increasing levels of rutin. Either cross-linking agent could enhance the elastic modulus (G′) and the viscous modulus (G″) of hydrogels, but the gelling and melting points didn’t show a notable improvement. Rutin boosted the thermal stability of xerogels, but decreased the equilibrium swelling ratio significantly, while as for gallic acid, there were no obvious effects on the thermal stability and equilibrium swelling ratio of xerogels. Scanning electron microscopy (SEM) was applied to observe the ultrastructure changes of the modified xerogels suggesting that gelatin xerogel at rutin concentration of 8 mg/g dry gelatin showed the highest cross-linking density. X-ray diffraction revealed that both gallic acid and rutin could enter the spacing of polypeptide chains of gelatin to reinforce the intermolecular interaction. And FTIR spectra verified that gallic acid and rutin molecules mainly interacted with skeletal C–N–C group and carboxyl group of gelatin molecules in the formation of gels. The results suggested that rutin was a better cross-linking agent for gelatin, and gels treated with rutin could be found with different physicochemical properties.     

Physiochemical and antimicrobial properties of edible aloe/gelatin composite films

Edible antimicrobial aloe/gelatin composite films with different ratio of freeze–dried aloe leaf gel powder and gelatin (aloe/gelatin = 5/0, 4/1, 3/2, 2/3, 1/4 and 0/5) were fabricated. The thickness of the resulting films was between 0.055 (aloe/gelatin = 0/5) and 0.157 mm (aloe/gelatin = 4/1). The mechanical properties including maximum elongation, tensile strength, elongation at break and break strength were determined. The mechanical properties were increased with the increasing amount of gelatin used in the composite formulation. The tensile strength for composite films with the ratio of 4/1, 3/2, 2/3, 1/4 and 0/5 was 4.12, 5.29, 6.96, 11.47 and 37.76 MPa, respectively. Citrobacter freundii, Escherichia coli, Enterobacter aerogens, Serratia marcescens, Staphylococcus aureus and Bacillus cereus were used in antimicrobial activity test. The results showed that antimicrobial activities of the composite films increased as the amount of aloe gel powder used in the composite films increased. The average area of inhibitory zones for films with composition of aloe/gelatin = 1/4 and aloe/gelatin = 4/1 was 1.63–2.38 and 3.82–4.80 cm², respectively.     

Application of recombinant chum salmon cystatin to Alaska pollock (Theragra chalcogramma) surimi to prevent gel weakening

ABSTRACT:  Recombinant chum salmon cystatin (RC) expressed in Saccharomyces cerevisiae was purified by His-select nickel affinity chromatography. The specific inhibitory activities of RC against papain and cathepsin L were 7.45 and 10.24 U/mg, respectively. RC was stable over pH 5.0 to 7.0 and at temperature below 65 °C. RC was used to prevent the gel weakening of Alaska pollock surimi. RC at 100 μg/g showed the highest inhibitory activity against the autolysis of surimi based on the analysis of TCA-soluble peptides. As the concentration of RC increased, both the breaking force and deformation of modori gel greatly increased ( P < 0.05). The addition of RC resulted in less expressible drip, which coincided with the increase of whiteness. More myosin heavy chain (MHC) was retained as the addition of RC increased. Therefore, RC could prevent the degradation of proteins in Alaska pollock surimi and was better than egg white (EW). Thus, RC could be applied to Alaska pollock surimi to prevent gel weakening and RC at 100 μg/g was the optimal concentration.     

Characterization of acid-soluble collagen from the skin of walleye pollock (Theragra chalcogramma)

Acid-soluble collagen (ASC) was extracted from the skin of walleye pollock (Theragra chalcogramma) and partially characterized. It exhibited a maximum absorbance at 220 nm, but little absorbance near to 280 nm. Amino acid composition and SDS-PAGE suggested that the collagen might be classified as type I collagen. Moreover, FTIR investigations showed the existence of helical arrangements of collagen. The denaturation temperature (T_d) and shrinkage temperature (T_s) were 24.6 °C and 47 °C, respectively, both lower than those of mammalian collagens. However, T_d of walleye pollock skin collagen was higher than that of cod skin collagen reported previously. These results indicate that walleye pollock skin is a potential source of collagen and provide the theoretical basis for further research.     

Effect of rainbow trout (Oncorhynchus mykiss) plasma protein on the gelation of Alaska pollock (Theragra chalcogramma) Surimi

ABSTRACT:  The effect of rainbow trout plasma protein (RPP) on the gelation of Alaska pollock surimi was determined to evaluate the possibility of its commercialization as a new protein additive. For modori gel, the breaking force, deformation, whiteness, and water holding capacity increased as the addition amount of RPP (0 to 0.75 mg/g) increased, and decreased at higher concentration of RPP (0.75 to 1.50 mg/g) ( P < 0.05). Protein solubility of modori gel in the mixture of SDS, urea, and β-mercaptoethanol decreased as the addition amount of RPP increased up to 0.75 mg/g, and increased at higher concentration of RPP (0.75 to 1.50 mg/g) ( P < 0.05). The contents of trichloroacetic acid-soluble peptide decreased as the addition amount of RPP (0 to 1.50 mg/g) increased ( P < 0.05). Based on the result of sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE), most myosin heavy chain of surimi was not degraded when RPP was added. Thus, RPP was supposed to act as a protease inhibitor in the gelation of Alaska pollock surimi. An RPP of 0.75 mg/g was the optimal concentration to prevent the gel weakening of Alaska pollock surimi. Compounds with molecular weights less than 10 kDa in RPP had no significant effect on the gelation of Alaska pollock surimi based on the result of the dialyzed RPP.     

Effect of cold atmospheric plasma on the physicochemical and functional properties of myofibrillar protein from Alaska pollock (Theragra chalcogramma)

This study aimed to investigate the effect of cold atmospheric plasma (CAP) on the physicochemical and functional properties of myofibrillar protein isolated from Alaska pollock (Theragra chalcogramma) muscle. Free sulfhydryl content, surface hydrophobicity, turbidity, differential scanning calorimetry, SDS-PAGE, heat-induced myofibrillar protein gel properties and water holding capacity were determined to evaluate the effect of CAP treatment on protein properties. CAP treatment from 10 to 60 kV for 10 min significantly (P < 0.05) increased the water holding capacity, textural properties and colour properties of heat-induced myofibrillar protein gel. As treatment voltage increased, free sulfhydryl content decreased significantly, while the turbidity and surface hydrophobicity of myofibrillar protein were increased. DSC data showed enhancement of thermal stability of the treated samples; however, the electrophoretic profile displayed a significant reduction in the band's intensity of protein at a higher voltage. These results suggest that cold atmospheric plasma (CAP) treatment could be used as an alternative approach to enhance the gelling properties of myofibrillar protein from Alaska pollock.     

Enzymatic hydrolysis of Alaska pollack (Theragra chalcogramma) skin and antioxidant activity of the resulting hydrolysate

BACKGROUND: Fish skin, a by‐product of the food industry, contains a large amount of collagen. However, only a small proportion of fish skin is used in the production of leather materials and animal feedstuffs, most of it being discarded. The aims of this study were to prepare peptides from Alaska pollack (Theragra chalcogramma) skin by enzymatic hydrolysis and to evaluate the antioxidant activity of the resulting hydrolysate. RESULTS: Protamex was the most efficient enzyme for preparing antioxidant peptides from Alaska pollack skin. The optimal hydrolysis conditions were as follows: hydrolysis time 8 h; enzyme/substrate ratio 2:1000; skin/water ratio 1:6; temperature 55 °C; pH 6.0. Under these conditions the highest yield of peptides was 83.44%, with 85.95% of the hydrolysate being mainly composed of oligopeptides with molecular weights ranging from 180 to 1000 Da. The hydrolysate showed 2,2‐diphenyl‐1‐picrylhydrazyl radical‐scavenging activity, with an IC₅₀ value of 2.5 mg mL^?1, and its reducing power was 0.14 at 1 mg mL^?1, 53.8% of that of reduced glutathione at the same concentration. CONCLUSION: This study demonstrated that the hydrolysate of Alaska pollack skin was mainly composed of oligopeptides with two to eight amino acid residues and possessed antioxidant activity. Copyright © 2010 Society of Chemical Industry     

明胶浸润预处理对挤出吹塑淀粉/明胶可食性复合膜性能的影响

对明胶(gelatin,GEL)进行加水润胀(20%、25%、30%,质量分数)预处理,然后分别与氧化羟丙基淀粉(oxidized hydroxypropyl starch,OS)和羟丙基交联淀粉(hydroxypropyl distarch phosphate,HP)混合,添加起酥油作为疏水剂,硬脂酸锌、硬脂酸钙作为润滑剂,采用挤出吹塑工艺制备了可食性淀粉/明胶复合膜。通过扫描电镜(scanning electron microscope,SEM)、X射线衍射(X-ray diffraction,XRD)、差示量热扫描(differential scanning calorimetry,DSC)、低场核磁共振(low differential scanning calorimetry,L-NMR)、红外光谱(infrared spectroscopy,IR),研究了明胶润胀加水量对复合膜性能与结构的影响。结果表明:25%水润胀的明胶与氧化羟丙基淀粉的复合膜存在最好的相容性,具有最好的力学性能和阻水性。适宜的水分添加量有助于淀粉的糊化和明胶的熔融,有助于增强分子间的作用力和膜的均匀性。