Optimization of Extraction Conditions for Pollock Skin Gelatin

ABSTRACT: Seven potential variables, pretreatment temperature, pretreatment time, concentration of OH⁻, concentration of H⁺, extraction temperature, extraction time, and skin/water ratio, were investigated by a 2^7-3 fractional factorial design to identify critical control factors for pollock skin gelatin extraction, and 3 responses, yield, gel strength, and viscosity, were evaluated. The results suggest that 4 variables, pretreatment temperature, concentration of OH⁻, concentration of H⁺, and extraction temperature, have significant effects on gelatin extraction, and these key factors were then selected for the subsequent optimization using response surface methodology with a 4-factor, 5-level central composite rotatable design. It suggests that a concentration of OH⁻ at 0.25 mol/L, a concentration of H⁺ at 0.09 mol/L, a pretreatment temperature at 2°C, and an extraction temperature at 50°C, will give the highest values for the 3 responses. The predicted responses for these extraction conditions are that the yield will be 18%, gel strength will be 460 g, and viscosity will be 6.2 c P.     

Properties of Alaska Pollock Skin Gelatin: A Comparison with Tilapia and Pork Skin Gelatins

ABSTRACT:  The objective of this work was to compare the physiochemical and rheological properties of Alaska pollock skin gelatin (AG) to those obtained for tilapia and pork skin gelatins. Results were also obtained for some mixed gels containing AG and pork skin gelatin, or AG and tilapia gelatin. AG contained about 7% hydroxyproline (Hyp), which was lower than that of tilapia (∼11%) or pork skin gelatin (∼13%). Most of the protein fractions in AG were α chain, β chain, and other oligomers. The gel strength of AG was 98 gram-force at 10 °C, and increased at a greater rate than other gelatins with decreasing temperature. The gel melting point of AG was the lowest with the oil-drop method, while the viscosity of AG was the highest of the samples studied. The rheological properties of gelatins were determined using small amplitude oscillatory shear testing. G' was nearly independent of frequency for most of the gelatin gels, but AG gels showed a slight dependence on G' and a minimum in G". G' was found to be a power law function of concentration for all gelatins used: G'= k × Cⁿ. In rheological measurements, AG also showed the lowest gel melting temperature and sharpest melting region. Increasing gelatin concentration resulted in a higher melting temperature and a broader melting region for all gelatin gels. For both the AG-pork and AG-tilapia mixed gels, the gel melting temperatures decreased and melting regions narrowed as the AG fraction was increased.     

Dehydration of Pollock Skin Prior to Gelatin Production

ABSTRACT: Alaska pollock (Theragra chalcogramma) is the U.S.A.'s largest commercial fishery, with an annual catch of over 1 million tons. During pollock processing, the skins are discarded or made into fish meal, despite their value for gelatin production. The absence of gelatin-processing facilities in Alaska necessitates drying of the skins before transport to decrease the moisture content, but conventional hot-air drying is expensive. This study evaluated a less energy-intensive technology, the use of desiccants for reducing water weight in pollock skins prior to shipment. To ensure that the functional properties of gelatin obtained from dried pollock skins were not affected during desiccation, gelatins were prepared from each skin-drying treatment and compared with gelatin extracted from air-dried pollock skins. None of the desiccation treatments decreased the gel strength of pollock skin gelatin, nor were there major differences in gelling temperature or viscosity among the gelatin solutions. This suggests that pollock skins can be economically stabilized for transport to a gelatin-processing facility through the use of regenerable desiccants that are already common in the food industry. Practical Application: Pollock skins destined for gelatin production can be stabilized using chemical desiccants prior to shipment. The dehydration process does not harm the functional properties of gelatin, such as gel strength, gelling temperature, and viscosity. This research suggests that fish skins can be economically stabilized for transport to a gelatin-processing facility through the use of regenerable desiccants that are already common in the food industry.     

鳕鱼皮明胶的止血活性和机理研究

为了提高水产加工废料的高值化利用,为明胶作为止血产品开发的原料提供依据,研究了明胶的分子量与止血活性之间的关系以及明胶的止血机理。本研究在65℃下采用热水法提取鳕鱼皮明胶,通过SDS-PAGE电泳测定明胶的分子量分布情况。使用100 ku和50 ku的超滤膜对明胶进行超滤处理得到高、中、低三个分子量范围的样品。大鼠断尾止血实验、股动脉止血实验和肝创面止血实验结果表明高分子量组(Mr100 ku)的出血时间最短,分别为4.54 min、2.30 min和1.91 min。说明提取的鳕鱼皮明胶样品与自然止血组相比具有止血效果,并且随着明胶分子量的上升,出血时间和出血量均下降,且高分子量明胶样品止血效果较好。APTT测定结果表明明胶可以明显缩短APTT时间,主要对内源性凝血途径起作用,并且可以促进血小板的聚集,还可以增加血小板活性因子PF4、P-选择素和TXB2的释放量从而缩短出血时间,起到快速止血的作用。     

鳕鱼骨汤的熬制及风味物质释放规律

本文以鳕鱼骨为研究对象,对高压熬制鳕鱼骨汤的最佳熬制工艺参数进行了研究,分析了高压鱼汤在熬制15、30、45、60、75、90、105和120 min过程中的风味变化规律,对比分析了常压和高压鳕鱼骨汤的风味物质差异。研究结果表明,高压熬制最佳工艺条件为料水比1:2、温度110℃、时间2 h,蛋白溶出率为(7.49±0.26) g/100 g鱼骨;高压鱼骨汤在熬制过程中,多肽类物质在30 min后开始稳步地溶出,最终稳定在2.00 mg/L;3种核苷酸在90~105 min的区间内浓度达到最高,有机酸类物质中乳酸含量在90min时达到最高,为67.91mg/L;GC-MS分析结果表明醛类、酮类是构成鱼骨汤风味的主要物质;高压鱼骨汤中的蛋白质溶出率、多肽和5’-AMP的含量分别是常压鱼骨汤的1.54、1.20和4.87倍。在常压鱼骨汤和高压鱼骨汤中分别检测到33和37种挥发性风味物质,同时在高压条件下产生了更多的醛类、酮类物质,具有更好的风味。     

罗非鱼皮明胶的过氧化氢法提取工艺

考察了过氧化氢的添加及其浓度、提取温度、提取时间等因素对罗非鱼皮明胶的提取率和明胶黏度的影响。采用响应面实验设计优化显著影响明胶提取率和明胶黏度的工艺参数,确定最佳提取工艺条件。实验优化结果为过氧化氢浓度0.07 mmol/g、提取温度53℃、提取时间4.6 h,此条件下明胶提取率达87.71%,黏度达8.90(mpa·s)。     

Optimization of Gelatin Extraction from Silver Carp Skin

ABSTRACT:  Fish skins are a by-product of the fish processing industry that can be successfully processed into gelatin. This study was designed to optimize the extraction process to obtain the highest yield, gel strength, and viscosity for gelatin production from silver carp skin. A fractional factorial design (2 levels, resolution III, 2^9-5) was chosen to screen 9 parameters to determine the most significant ones. Those found to be significant were optimized to determine the maximum value for 3 dependent variables mentioned above. The hydroxyproline content and hydroxyproline/protein ratio of the skin were 1.7% and 6.5%, respectively. The protein content of the skin was 26%. The hydroxyproline content of the gelatin for the sample giving the highest hydroxyproline/protein ratio was 10.9%. This sample was arbitrarily called pure gelatin and the purity of the remaining samples was between 71.8% and 97%. The highest protein and gelatin recovery was 78.1% and 98.8% of the total available, respectively. The latter, gelatin recovery, is proposed to be used instead of protein yield. Four variables were determined as significant in screening and these variables were studied by a central composite rotatable design (4-factor and 5-level with 6 central points) to model the system and response surface methodology was used for optimization. The optimum extraction conditions were 50 °C for the extraction temperature, 0.1 N HCl for the acid concentration, 45 min for the acid pretreatment time, and finally 4 : 1 (v/w) for the water/skin ratio. The predicted responses for these extraction conditions were 630 g gel strength, 6.3 cP viscosity, and 80.8% gelatin recovery. The data suggest that silver carp skin gelatin is similar to those of fish gelatins currently being exploited commercially.     

Effects of adding fish gelatin on Alaska pollock surimi gels

Fish gelatin is a food additive obtained after hydrolysis of collagen from fish skin. The importance of fish gelatin as a food additive is increasing due to its increased commercial availability. Surimi is washed minced fish meat used as the raw material for seafood analogs like crabmeat substitutes. The most important attributes of surimi are gelling and whiteness. The objective of this work was to determine the effect of using fish gelatin as an additive in surimi to improve the mechanical and functional properties of gels. Surimi gels were prepared by mixing grade A or FA surimi (Alaska pollock) with salt (20 g/kg w/w) and commercial fish gelatin at 0 (control), 5, 7.5, 10, or 15 g/kg (w/w) previously dissolved in water (200 mL/kg surimi). The solubilized paste was incubated at 40 °C for 30 min followed by cooking at 90 °C for 15 min. Changes in mechanical properties (torsion test), a functional property (expressible water content) and color attributes of surimi gels were measured. Grade FA surimi gels containing 7.5–15 g/kg of fish gelatin showed an improved expressible moisture. However, gelatin added at 15 g/kg showed a disruptive effect detrimental to the mechanical properties. Color parameters were modified slightly. Whiteness attribute as affected by increasing the fish gelatin was instrumentally detected but not observed by sensory panelists. Gelatin did not change the overall color attributes and all gels remained in the grayish region. These results indicated that fish gelatin did not have an advantage for using as a functional additive in Alaska pollock surimi grades A or FA. However, it can be used at up to 10 g/kg without a negative effect on the mechanical properties.     

马哈鱼鱼皮明胶提取温度和甘油质量浓度对其成膜特性的影响

明胶提取温度和甘油质量浓度是影响明胶膜性质的基本因素。本研究以马哈鱼（Oncorhynchus keta） 鱼皮为原料,采用不同温度（40、50、60、70、80、90 ℃）提取明胶,考察不同甘油质量浓度（1.1、1.2、 1.5 g/100 mL）下明胶膜的厚度、机械性能、光学性质、微观结构和红外特性。研究发现,40、50、60 ℃明胶 膜的厚度高于70、80、90 ℃明胶膜的厚度（P＜0.05）。50、60 ℃膜的拉伸强度（tensile strength,TS）高于 70、80、90 ℃膜的（P＜0.05）;添加1.5 g/100 mL甘油,膜的断裂伸长率随提取温度升高而上升（P＜0.05）; 50、70、80 ℃膜的TS随甘油质量浓度升高而下降（P＜0.05）。色差分析表明,膜的a*值随提取温度升高而上升 （P＜0.05）。水蒸气透过率随提取温度和甘油质量浓度的升高而升高（P＜0.05）。明胶膜于200、280 nm波长处 的透光率为0.00%,350～800 nm范围内的透光率为46.53%～74.57%,60 ℃膜的透光率低于40、50 ℃膜的透光率 （P＜0.05）。衰减全反射傅里叶变换红外光谱分析表明膜的图谱呈现典型酰胺A、B、Ⅰ、Ⅱ、Ⅲ带,酰胺A带随 提取温度的升高向低波数移动,且振幅随甘油质量浓度升高而增加。扫描电子显微镜结果显示,膜的截面和表面未 呈现明显断裂或空隙。以上结果表明,温度对马哈鱼鱼皮明胶膜的机械性能、透水性、颜色、透光率影响显著,甘 油质量浓度仅对前二者影响显著,可通过优化提取温度与甘油质量浓度改善马哈鱼鱼皮明胶膜性质。     

兔皮明胶提取工艺优化

以兔皮为原料,研究稀盐酸短时诱导兔皮制备明胶的工艺。以明胶提取率和凝胶强度为评价指标,对兔皮明胶制备工艺中的盐酸质量分数、盐酸处理时间、提胶pH值、提胶温度4 个因素进行了优化,在此基础上通过正交试验确定最佳工艺为盐酸质量分数1%、盐酸处理时间10 min、提胶温度65 ℃、提胶pH 4。在此工艺条件下明胶提取率高达（86.85±1.71）%,凝胶强度为（481.43±16.89）g。明胶基本性质符合GB 6783-2013《食品添加剂：明胶》要求。     

提取温度对罗非鱼皮明胶理化性质的影响

本研究以罗非鱼皮为原料,研究在不同温度(30、40、50、60、70、80、90℃)下提取的明胶所表现的得率、凝冻强度、聚丙烯酰胺凝胶电泳分析、傅里叶红外光谱分析、热变性温度、流变性性能等理化特征。结果表明,提取温度对鱼皮明胶的紫外吸收无明显影响;随着提取温度的升高,鱼皮明胶的得率逐渐增大,在提取温度为60~80℃时差异不显著(p>0.05),在90℃达到最大值(62.60%±0.84%);聚丙烯酰胺凝胶电泳图谱显示,较低温度(30、40、50℃)下提取的鱼皮明胶由α₁、α₂、β 3条肽链组成,提取温度升高后电泳条带强度降低;提取温度为50℃时,罗非鱼皮明胶的凝冻强度最大,高达(884.33±26.76)g;FTIR光谱显示,不同温度下提取的鱼皮明胶在酰胺区都具有特征吸收峰,在光谱中显示出微小的差异;不同温度下提取的鱼皮明胶的热变性温度分别为(101.05±2.97)、(104.35±3.54)、(107.59±0.37)、(97.80±4.21)、(95.35±2.60)、(92.52±3.15)、(89.66±1.23)℃;提取温度通过改变明胶的分子量大小影响明胶溶液内部贮藏能量的多少,进而对明胶溶液的流变性能产生影响。     

Fracture of Alaska Pollock Gels in Water: Effects of Minced Muscle Processing and Test Temperature

The effects of temperature on instrumental textural measurements of cooked Alaska pollock gels were evaluated. Independent variables were: raw materials (minced muscle, washed minced muscle alone or with cryoprotectants), cooking schedule (90°C for 20 min with/without preconditioning at 25°C) and test temperatures. Gels tested at 5°C were more brittle than those tested at 45–55°C. Gels preset at 25°C for 1 hr prior to cooking at 90°C had higher fracture shear stress values and were influenced differently by test temperatures than those not preset suggesting cooking history influenced structure of the gels at the molecular level. Results indicated gels set at 25°C were probably stabilized by more covalent bonds.     

鱼皮明胶的超高压辅助提取工艺

为建立鱼皮明胶清洁生产工艺,对超高压辅助提取鱼皮明胶进行系统研究,考察超高压处理压力、超高压作用时间、提取温度、提取时间对凝胶强度和提取率的影响。结果表明,较优提取工艺为处理压力300MPa、超高压时间10min、提取温度50～60℃、提取时间4h,在此条件下明胶凝胶强度可达274g,得率可达75.03%,溶解温度和凝胶温度分别为23.6℃和16.4℃。     

鱼皮明胶抗紫外线损伤引起的皮肤光老化研究

本文研究了大马哈鱼皮明胶(SG)对光老化小鼠皮肤的保护机制。采用热提法制备了SG并对其分子量和氨基酸组成进行分析。ICR小鼠随机分成5组(每组10只):正常组(NC)、模型组(MC)、维生素C组(PC)、SG低剂量组(SG-L)和SG高剂量组(SG-H)。本文分析了皮肤组织中总超氧化物歧化酶(T-SOD)、谷胱甘肽过氧化物酶(GSH-Px)和过氧化氢酶(CAT)的活力,丙二醛(MDA)和羟脯氨酸(HYP)的含量,并利用HE、Masson染色来评价SG对光老化皮肤的保护作用。结果表明,SG平均分子量在81.31 ku,甘氨酸约占其氨基酸总量的1/3,疏水性氨基酸占49.67%,不含有半胱氨酸和色氨酸。SG可以改善紫外线对皮肤中胶原纤维的损伤,与模型组相比,SG高剂量组可以显著提高T-SOD的活力(p0.05)、HYP含量(p0.01)、降低MDA含量(p0.05),使CAT和GSH-Px平均活力分别提高23.70%和28.30%。SG对紫外线引起的皮肤光老化有保护作用。     

Characterization of Thermorheological Behavior of Alaska Pollock and Pacific Whiting Surimi

ABSTRACT: Thermorheological behavior of Alaska pollock (AP) and Pacific whiting (PW) surimi was evaluated during gelation at different moisture contents (80% to 95%). The temperature sweep data (storage modulus, G', compared with temperature) for both surimi clearly indicated G' minima. Unlike for the PW surimi, the minimum values of the AP surimi was moisture-content dependent and there was a linear relationship between logarithm of concentration and reciprocal absolute temperature at gelation. The activation energy ( Ea ) for aggregation after gelation temperature at each moisture content was calculated by a nonisothermal kinetic model for both AP and PW Surimi. The Ea values increased with moisture content of the system and ranged from 172.8 to 232.9 kJ/mol. Based on the assumption that melting temperature for a thermo-reversible gel may be considered equivalent to gelation temperature for thermo-irreversible gels, an Arrhenius-type model was used to estimate the enthalpy of cross-links formation for AP surimi to be 300.3 kJ/mol.     

Microbial Decontamination of Dried Alaska Pollock Shreds Using Corona Discharge Plasma Jet: Effects on Physicochemical and Sensory Characteristics

Nonthermal techniques for microbial decontamination are becoming more common for ensuring food safety. In this study, a corona discharge plasma jet (CDPJ) was used for inactivation of microbial contaminants of dried Alaska pollock shreds. Corona plasma jet was generated at a current strength of 1.5 A, and a span length of 25 mm was maintained between the electrode tip and the sample. Upon the CDPJ treatment (0 to 3 min) of dried shreds, microbial contaminants namely aerobic and marine bacteria, and Staphylococcus aureus were inactivated by 2.5, 1.5, and >1.0 log units, respectively. Also, a one‐log reduction of molds and yeasts contaminants was observed. The inactivation patterns are fitted well to the pseudo‐first‐order kinetics or Singh‐Heldman model. The CDPJ treatment did not exert statistically significant (P > 0.05) changes in physicochemical properties, namely color characteristics, volatile basic nitrogen, and peroxide value of dried fish shreds, with some exceptions, as compared to untreated controls. Furthermore, CDPJ treatment had no significant impact on the sensory characteristics of dried fish shreds.     

驴皮胶及鹿皮胶的化学品质分析与评价

利用电感耦合等离子体质谱、氨基酸自动分析仪、超高效液相色谱及毛细管气相色谱对驴皮胶及鹿皮胶中的重金属、氨基酸、核苷及脂肪酸含量与组成进行测定与分析。结果显示,驴皮胶及鹿皮胶中的重金属元素中以Pb及Cu含量较高,分别达到1.00?mg/kg及0.80?mg/kg左右,其余元素含量较低,均未到0.1?mg/kg;驴皮胶及鹿皮胶中氨基酸质量分数分别为85.66%及90.02%,必需氨基酸质量分数分别为16.14%及15.89%,其中Glu、Gly、Ala、Pro含量占比较高;驴皮胶中共含有12?种核苷,其中黄嘌呤含量最高为35.46?μg/g;鹿皮胶中共含有9?种核苷,其中次黄嘌呤含量最高为70.44?μg/g;驴皮胶及鹿皮胶中的主要脂肪酸为棕榈酸、棕榈油酸、油酸及亚油酸等;鹿皮胶中饱和脂肪酸及单不饱和脂肪酸含量占比较高;而驴皮胶中多不饱和脂肪酸、必需脂肪酸及n-6型不饱和脂肪酸含量更多;驴皮胶及鹿皮胶中的饱和脂肪酸/单不饱和脂肪酸/多不饱和脂肪酸的比例均接近于健康比例。     

Solid-Phase Microextraction Method for the Determination of Volatile Compounds in Hydrolysates of Alaska Pollock Frame

The volatile compounds in Alaska pollock frame and Alaska pollock frame hydrolysates were analyzed by solid-phase microextraction and gas chromatography-mass spectrometry for identifying and comparing their flavor characteristics. The optimized SPME extraction conditions were 75 μm carboxen/polydimethyl siloxane fiber, adsorption time of 40 min, and extraction temperature of 65°C. Compared to Alaska pollock frame, Alaska pollock frame hydrolysates have more aromas detected and identified. Numerous volatile compounds were responsible for the overall aroma of Alaska pollock frame hydrolysates, such as 1-penten-3-ol, 2-penten-1-ol, ethyl acetate, methacrolein, 3-methylbutanal, hexanal, octanal, nonanal, 6-methyl-5-hepten-2-one, and so on. However, only a relatively small proportion showed similar composition. Although Alaska pollock frame hydrolysates was prepared by the same raw material, each Alaska pollock frame hydrolysate exhibited its individual flavor characteristics. Thus, the type of enzyme was probably one of the important factors affecting the differences of volatile compound composition and Alaska pollock frame hydrolysate flavor. Compared to other Alaska pollock frame hydrolysates, FPH5 (hydrolysates prepared by mixed enzymes for animal proteolysis) exhibited less fishy odor. It can be used as an effective approach to improve product quality.     

鱼皮明胶和多酚组装行为与相互作用

研究不同结构多酚与鱼皮明胶(fish skin gelatin,GLA)间的相互作用及组装行为,期望对水产品加工、副产品的利用和新型食品配料的开发提供科学依据,同时为多酚-蛋白质复合物在食品领域的应用提供理论指导.选取单宁酸(tannic acid,TA)、表没食子儿茶素没食子酸酯(epigallocatechin g...     

姜黄素对鸡皮明胶膜的性能及结构的影响

以新鲜鸡皮提取的明胶为成膜基材,添加具有抗氧化和抗菌作用的姜黄素,采用流延法制备不同浓度的姜黄素-鸡皮明胶膜,旨在研发出一种新型鸡皮明胶复合膜。本文研究了浓度为0.5%、1%、2%和3%的姜黄素对鸡皮明胶膜理化性质的影响,并用红外光谱和热稳定性表征了复合膜的相容性。最终表明:随着姜黄素浓度的增加,鸡皮明胶膜外观颜色逐渐变为黄色,阻隔性能呈现先下降后上升的趋势,抗拉强度与之相反,断裂伸长率和水溶性逐渐降低,抗氧化和抑菌性显著增强(p0.05);红外光谱中酰胺I带右移,发现姜黄素与鸡皮明胶之间有氢键作用,使鸡皮明胶膜从α-螺旋转变为稳定的三螺旋结构,热稳定分析表明了姜黄素的添加提高了鸡皮明胶膜的热稳定性;当姜黄素浓度为2%时复合膜的综合性能最佳。因此,姜黄素-鸡皮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。