Physico-chemical and film-forming properties of bovine-hide and tuna-skin gelatin: A comparative study

A bovine-hide gelatin and a tuna-skin gelatin, both characterized on the basis of their amino acid composition and molecular weight distribution, were used to prepare edible films by casting with glycerol and sorbitol added as plasticizers. The molecular weight distribution of the tuna-skin gelatin exhibited appreciably higher quantities of β-components (covalently linked α-chain dimers), whereas bovine-hide gelatin showed a certain degradation of α₁-chains being indicative of a greater proteolysis. Intrinsic differences in the gelatin attributes affected in diverse manner some of the physical properties of the films. Thus, water vapour permeability was higher in the bovine-hide gelatin film, whereas deformability was considerably higher (10 times higher) in the tuna-skin gelatin film. In contrast, breaking force and water solubility were basically unaffected by gelatin origin. Analysis of the thermal properties revealed both films to be wholly amorphous with similar glass transition temperature values thanks to the plasticizing effects of the glycerol and sorbitol and the low moisture contents.     

Physical and chemical properties of tuna-skin and bovine-hide gelatin films with added aqueous oregano and rosemary extracts

The properties of edible, gelatin-based films with added oregano or rosemary extract (two different concentrations) were studied. Gelatins from different sources (bovine-hides and tuna-skins) were employed with a view to elucidating how inherent gelatin characteristics may affect interaction of the gelatin with the polyphenols in the added extract and hence the properties of the resulting films. The bovine-hide gelatin reacted only slightly with the polyphenols in the extracts as shown by the electrophoretic profile and analysis of the dynamic viscoelastic properties, and consequently the attributes (mechanical properties, water solubility, water vapour permeability) of the films were practically unchanged compared with the film made without any added plant extract. The tuna-skin gelatin did evidence some interactions with the polyphenols in both the oregano and the rosemary extracts, especially for the more concentrated of the two extracts tested, thereby altering the attributes of the corresponding films, namely, a higher glass transition temperature, decreased deformability, and, in particular, increased water solubility. Opacity increased irrespective of gelatin origin and plant extract type and concentration.     

鸡骨明胶的胶凝特性

通过测定动态流变性质和凝胶强度研究鸡骨明胶的胶凝特性.研究表明,鸡骨明胶的胶凝分为凝胶网络的快速形成阶段和网络的缓慢成长两个阶段.相对分子质量越大,胶凝温度越低;明胶浓度越高、pH值越接近等电点、胶凝温度和熔化温度越高,胶凝时间越短,同时形成的凝胶网络的弹性和凝胶强度大;随着陈化时间的延长或温度降低,凝胶网络弹性和凝胶强度增大,且逐渐稳定;适当浓度的尿素和SDS可以阻止凝胶网络的形成;明胶胶凝网络结构的形成主要借助分子间氢键相互作用,同时静电斥力和疏水相互作用也影响凝胶网络的形成.     

鸡骨明胶的流变性研究

研究从鸡骨中提取的明胶的流变性质。结果表明：质量分数为0．5％的鸡骨明胶溶液为塑性流体，其流动需要克服一定的屈服应力，屈服应力的大小受温度影响，温度越高，屈服应力越小；当剪切应力大于屈服应力时，粘度基本不随剪切速率变化，表现出牛顿流体的流动特征；温度越高，鸡骨明胶溶液粘度越小，温度对其的影响符合Arrhenius模型，流动活化能为19．58kJ／mol；鸡骨明胶的粘度随质量分数的增加呈指数递增；鸡骨明胶的粘度受pH值影响，在等电点9附近，鸡骨明胶溶液的粘度最小，偏离pI则粘度增大；鸡骨明胶的粘弹性强烈受温度的影响，质量分数为3％的鸡骨明胶从粘性为主的溶胶体系变成以弹性为主的凝胶体系的转变温度(胶凝点)为23．6℃，而凝胶转变成溶液的转变温度(溶点)为33．6℃。适当质量分数及在室温条件下，鸡骨明胶主要表现为弹性体。     

Utilization of Fish Processing By-Products in the Gelatin Industry

Since the bovine spongiform encephalopathy crisis, there has been a growing interest for finding an alternative source of raw materials for gelatin production. Gelatin produced from fish processing by-products is a potential alternative to mammalian gelatin. Fish processing generates solid wastes that can be as high as 50-80% of the original raw material. These wastes are an excellent raw material for preparation of high protein foods. About 30% of the wastes consists of skin and bone with a high collagen content. Fish gelatin can be obtained by hydrolysis of collagen the principal protein found in skin and bone. Fish skin and bone gelatin can be prepared with bloom strength similar to that obtained from mammalian sources. Fish gelatin has numerous applications, particularly, in the food, pharmaceutical, and photographic industries due to its unique chemical and physical properties. This review presents how fish processing by-products can be utilized in the manufacture of gelatin.     

Microwave processing technology influences the functional and structural properties of fish gelatin

The objective of this study was to evaluate the effects of microwave processing technology (MPT, 240–800 W, 1 and 4 min) on the functional and structural properties of fish gelatin (FG). It showed that MPT could increase gel strength and texture properties of FG, especially for 240 W. MPT greatly increased emulsifying activity index (EAI) of FG, but decreased its emulsion stability index (ESI). Rheology results showed that MPT increased viscosity of FG, but decreased gelation times. Intrinsic fluorescence and Fourier transform infrared (FTIR) spectroscopy results indicated that MPT could unfold gelatin, contributing to the formation of H-bonds. Scanning electron microscopy (SEM) analysis revealed that low power and short time of MPT-treated gelatin gels had much more dense and less voids. This work provided guidance for the applications of MPT to improve the functional properties of FG, and the results show that MPT-treated FG can replace mammalian gelatin and meet the religious requirement.     

Utilization of Fish Processing By-Products in the Gelatin Industry

Since the bovine spongiform encephalopathy crisis, there has been a growing interest for finding an alternative source of raw materials for gelatin production. Gelatin produced from fish processing by-products is a potential alternative to mammalian gelatin. Fish processing generates solid wastes that can be as high as 50–80% of the original raw material. These wastes are an excellent raw material for preparation of high protein foods. About 30% of the wastes consists of skin and bone with a high collagen content. Fish gelatin can be obtained by hydrolysis of collagen the principal protein found in skin and bone. Fish skin and bone gelatin can be prepared with bloom strength similar to that obtained from mammalian sources. Fish gelatin has numerous applications, particularly, in the food, pharmaceutical, and photographic industries due to its unique chemical and physical properties. This review presents how fish processing by-products can be utilized in the manufacture of gelatin.     

Mechanical and structural properties of rabbit skin gelatin films

In this article, the characteristics and structure of rabbit skin gelatin (RG) films were measured and compared with porcine skin gelatin (PG) films. The RG film was 8–10 μm thinner than that of PG film. RG films had better resistance to water and lower water solubility than did the PG film with the same gelatin and glycerol ratio due to the difference in their amino acid composition. The two types of gelatin films were almost transparent, which could give food a good appearance quality if these are used as packaging films. Both showed excellent barrier properties against UV light and could prevent the lipid oxidation reaction induced by ultraviolet light in the food system. The RG and PG films showed similar trends in mechanical properties as the change of their components. In general, the rigidity of the RG films was slightly lower than that of the PG films, but the flexibility was more prominent. This was due to intense interaction between gelatin molecules and glycerol molecules in RG films, but the dominant interaction was between the gelatin molecules in the PG films. The surfaces and cross-section microstructures of the RG and PG films were smooth and homogeneous, however for the RG films were more compact compared with the PG films.     

明胶对纸浆性能影响的研究

详细研究了明胶对草浆性能的影响,考察了它对纸页物理强度及其对浆料助留和助滤的影响.试验结果表明,明胶加入浆中,使得浆料Zeta电位升高,在合适条件下对草浆的留着和强度性能有很好的改善,然而明胶对浆料滤水性有很大影响.为以后进一步研究明胶在造纸中的应用打下基础.     

Physico-chemical and film forming properties of giant squid (Dosidicus gigas) gelatin

Giant squid (Dosidicus gigas) inner and outer tunics were subjected to hydrolysis with pepsin prior to gelatin extraction (G1 gelatin) by a mild-acid procedure. Furthermore, a second gelatin extraction (G2 gelatin) was done using the collagenous residues that remained from the first extraction. Pepsin allows the collagen solubilisation and the extraction yield to increase by yielding extracts high in α-chains. G1 exhibited good gel forming ability but G2 showed poor viscoelastic behaviour and low gel strength, in agreement with the results for the molecular weight distribution, which showed a considerably higher content of low molecular weight components. In spite of these differences, both G1 and G2 showed good filmogenic ability and similar properties were found including the absence of colour, opacity, low water vapour permeability and high puncture deformation. Nevertheless, films made from G1 had a higher puncture force than films made from G2 as a result of the different molecular weight distribution.     

微波-快速冻融耦合鱼皮明胶理化性质分析

本实验采用微波-快速冻融耦合处理鱼皮获得鱼皮明胶，并通过等电点、透射比、凝冻强度测定以及十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、流变学特性、氨基酸组成和傅里叶变换红外光谱分析对鱼皮明胶的理化性质进行表征。结果表明：与市场上的A型和B型明胶不同，微波-快速冻融耦合鱼皮明胶等电点为7，在450 nm波长处透射比为57.13%，在620 nm波长处透射比为78.07%，凝冻强度为524.40 Bloom g，满足GB 6783—2013《食品安全国家标准 食品添加剂 明胶》要求（在450 nm波长处透射比不低于30%，620 nm波长处透射比不低于50%，凝冻强度不低于50 Bloom g）。与传统酸法鱼皮明胶相比，微波-快速冻融耦合明胶氢键含量更高，三螺旋结构较为完整，亚氨基酸比例相近；但由于高分子亚基比例低，导致凝胶特性总体不及传统明胶。总体而言，微波-快速冻融耦合鱼皮明胶符合国标要求，该方法是明胶绿色清洁制备的良好探索。     

明胶与卡拉胶共凝胶体的热力学特性及微观结构的研究

本文通过对明胶与卡拉胶共凝胶体的热力学特性及微观结构的研究,得出明胶与卡拉胶形成的凝胶体的热力学特性随两种大分子的配比、体系的pH值、及盐浓度的不同而不同.微观结构的研究表明胶体的结构决定了其宏观功能特性的表现,两种大子在不同的条件下,其发生作hi的方式不同.     

Rheological and thermal properties of an enteral nutrition formula for nutritional support patients using a combined mixture of gelatin and maltodextrin

Enteral nutrition is a type of nutritional support that provides the necessary sources of energy and protein for patients who suffer from dysphagia, chronic disease, and loss of appetite. In this study, a gelatin-maltodextrin binary biopolymer system has been incorporated into a semi-solid formula. The I-optimal combination design approach was used to create 19 formulations, and the dynamic rheological properties, dynamic laser scattering, and zeta potential responses were evaluated over 30 days of storage at 5°C. Solid viscoelastic behavior has been approved since G′ > G″ in the frequency sweep test with no cross-over point. Maltodextrin may interfere within the gelatin network, and increasing the maltodextrin to gelatin (from 0.14 to 1) may lead to a wider linear viscoelastic (LVE) strain range (2.16%), a lower storage modulus at LVE (52%), a lower yield stress (46%), and a lower glass transition temperature (34%). The presence of maltodextrin may reduce the temperature of the sol-to-solid transformation by 48% and enhance its flexibility. In contrast, increasing the gelatin-to-maltodextrin ratio following melting at 37°C led to an increase in the cumulant mean and polydispersity index, indicating a relatively unstable system. The range of zeta potential values between −4.4 and 1.7 mV confirmed a tendency toward coagulation. Microscopic images revealed instability because of irregular or compact chains formed in the gelatin matrix by using higher amounts of maltodextrin. Finally, the best formula had the best rheological stability and was suitable for tube-feeding patients, with a gelatin-to-maltodextrin ratio of 4.35:3.64% w/w on day 17.4.     

铬革屑酶法提取胶原蛋白制备高分子量产物--Ⅱ.凝胶的改性

铬饼中的凝胶在酶化后交联得到的产物有较好的物性.改性后的凝胶强度、熔点、粘性和凝胶温度都更高.在测定了该产物的其它特性（如发泡性和胶粘性）和分子量分布可以进一步确定它的物性.已经有文献报道过酶化改性后的具有交联特性的各种蛋白用于食品工业中.同时也发现,酶化法改性后的凝胶分子量会增加,尤其对提高质量较差的凝胶特性效果显著.回收后的一系列改性蛋白可以广泛用于各种产品中,包括粘合剂,化妆品,胶片,胶囊和肥料中以及在革产品中作为重要的涂层或填充材料.     

Preparation and Characterization of an Olive Flounder (Paralichthys olivaceus) Skin Gelatin and Polylactic Acid Bilayer Film

Olive flounder skin gelatin (OSG) was used as a film base material. A bilayer film of OSG and polylactic acid (PLA) was prepared using solvent casting method to enhance the film properties. Physical properties of the OSG–PLA film were increased compared with the nonaugmented OSG film. In particular, the PLA lamination decreased water vapor permeability from 2.17 to 0.92 × 10^?9 g·m/m²·s·Pa, as well as of the water solubility from 16.62% to 9.27%, in the bilayer film relative to the OSG film. The oxygen permeability of the OSG–PLA bilayer film was held low by the OSG film, compensating for the high oxygen permeability of the PLA layer. Therefore, the OSG–PLA bilayer film with its enhanced physical properties and high water and oxygen barrier properties can be applied as a food packaging material.     

转谷氨酰胺酶(mTG)改性明胶的物理性质研究

用来源于微生物的转谷氨酰胺酶（mTG）对不同品级和不同类型的明胶进行改性，并考察了改性产物的物理性质与酶用量的关系。结果表明：随着酶用量的增加，低强度明胶改性产物的凝胶强度有所提高，而高强度明胶改性产物的凝胶强度保持不变甚至有所降低；所有改性明胶的熔点都随酶用量的增加而提高，有些甚至达到90℃；所有改性产物在60℃时的粘度都随酶用量的增加而提高；改性产物的凝胶温度不仅受酶用量的影响，而且与明胶的品级和种类有关。这一实验结果显示出源自微生物的转谷氨酰胺酶在提高低品级明胶的使用性能及更充分利用制革废弃物等方面都有广阔的应用前景。     

酪蛋白与明胶的酶促交联与产物的流变学性质

利用转谷氨酰胺酶对酪蛋白和明胶进行酶促混合交联。在酪蛋白与明胶比例为4︰1(质量比)时,以交联产物中羟脯氨酸质量分数为指标,采用单因素试验研究酶添加量、反应时间和温度对交联反应的影响。优化后的适宜交联条件为:底物质量浓度固定为50 g/L,酶添加量为每克蛋白质20 U,反应时间为4 h,温度为45℃。SDS-聚丙烯酰胺凝胶电泳分析表明产物中含有蛋白质聚合物。与原料酪蛋白、转谷氨酰胺酶促交联的酪蛋白相比,所得到的产物的分散液表观黏度和黏弹性均有显著的改变,表明转谷氨酰胺酶催化的酪蛋白和明胶混合可以用于改善其流变学性质。     

不同阳离子下鱼明胶特性的比较分析

配制含有不同浓度（0.01、0.05、0.1、0.5、1.0 mol/L）的5种常见阳离子（Ca2+、K+、Mg2+、Na+、Fe3+）的鱼明胶溶液,采用DHR流变仪、质构仪对鱼明胶溶液进行温度扫描实验和TPA质构分析,并测其起泡性和乳化性,探究食品中常见阳离子对鱼明胶流变特性和质构特性以及起泡性和乳化性的影响。结果表明,低浓度（0.01~0.05 mol/L）的K+、Mg2+、Na+可以增加鱼明胶的弹性模量（G,）和粘性模量（G,,）,从而增加鱼明胶的热稳定性;低浓度（0.01~0.05 mol/L）的K+、Na+可显著提高鱼明胶的融化点和凝固点;低浓度（0.01~0.05 mol/L）的K+、Na+可显著提高鱼明胶的硬度和咀嚼性;高浓度（0.1~1.0 mol/L）的K+、Na+、Fe3+可提高起泡性和起泡性稳定性;低浓度（0.01~0.05 mol/L）的5种阳离子均可提高乳化性和乳化稳定性。说明添加一定浓度的不同阳离子可有效改善鱼明胶特性,其中低浓度的K+、Na+改性效果最显著,该研究结果为拓宽鱼明胶在食品领域的应用提供了科学依据和理论基础。     

Preparation and functional properties of fish gelatin–chitosan blend edible films

With the goal of improving the physico-chemical performance of fish gelatin-based films, composite films were prepared with increasing concentrations of chitosan (Ch) (100G:0Ch, 80G:20Ch, 70G:30Ch, 60G:40Ch and 0G:100Ch, gelatin:Ch), and some of their main physical and functional properties were characterised. The results indicated that the addition of Ch caused significant increase (p < 0.05) in the tensile strength (TS) and elastic modulus, leading to stronger films as compared with gelatin film, but significantly (p < 0.05) decreased the elongation at break. Ch drastically reduced the water vapour permeability (WVP) and solubility of gelatin films, as this decline for the blend film with a 60:40 ratio has been of about 50% (p < 0.05). The light barrier measurements present low values of transparency at 600 nm of the gelatin–chitosan films, indicating that films are very transparent while they have excellent barrier properties against UV light. The structural properties investigated by FTIR and DSC showed a clear interaction between fish gelatin and Ch, forming a new material with enhanced mechanical properties.