酸/碱预处理对美洲鳗鲡（Anguilla rostrata）鱼骨明胶理化性质与凝胶特性的影响

以美洲鳗鲡（Anguilla rostrata）鱼骨为原料,采用酸或碱预处理结合热水浸提制备鱼骨明胶,并通过得率、凝胶强度测定、SDS-PAGE、紫外全波长扫描、红外光谱扫描、动态流变学测定以及扫描电镜等研究鱼骨明胶的理化性质和凝胶特性。结果表明:酸法预处理明胶（AG60）与碱法预处理明胶（BG60）得率分别为13.6%和6.88%,凝胶强度分别为101.95 g和78.74 g。AG60和BG60的羟脯氨酸含量为3.2 g/100 g和2.7 g/100 g。两种明胶均含有β和α₁、α₂链,其中AG60的α₁+α₂含量显著高于BG60。AG60与BG60均具有明胶的特征吸收峰,且无杂蛋白吸收峰。与BG60相比,AG60具有更高的凝胶温度与熔融温度,以及更短的胶凝时间。扫描电镜分析显示,AG60具有更致密、均一的凝胶网络结构。本研究表明,与碱法预处理相比,酸法预处理制备得到的鳗鱼骨明胶具有更高的得率与更好的凝胶特性。     

多功能型明胶黏合剂的制备及应用研究进展

明胶是由胶原蛋白水解得到的一类聚合物,作为一种具有良好生物相容性和生物降解性等生物学性能的天然高分子材料,因其具有良好的发泡性、乳化性和成膜性等特点,在产品包装、增稠、充当递送载体等方面被广泛应用。本文就明胶凝胶强度、黏度、颜色、产量、等电点等理化性质及其影响因素,以及明胶不同类型的改性、交联方式和制备各种功能性明胶基水凝胶进行综述。通过设计使用不同材料,引入不同官能团来合成不同功能特性的明胶复合水凝胶黏合剂,以丰富其在日常生活中的应用,为明胶的提取及综合利用提供一些新的思路。     

金鲳鱼骨明胶的提取工艺及性质研究

以金鲳鱼骨为原料,以明胶提取率为指标,通过单因素及正交试验探究木瓜蛋白酶酶解提取金鲳鱼骨明胶的最佳工艺,并测定金鲳鱼骨明胶的相关性质。结果表明:提取金鲳鱼骨明胶的最佳工艺条件为酶添加量4.0%、酶解温度45℃、酶解时间1.5 h、酶解pH6.5,明胶提取率达到21.87%。金鲳鱼骨凝胶强度为(154.8±3.8)g,明胶黏度为(2.0±0.43)mPa·s,在450、620 nm波长下的透过率分别为(32±0.12)%、(73±0.49)%,起泡性、起泡稳定性以及乳化性均随着明胶浓度的增加而增强,而乳化稳定性却随着明胶浓度的增加先增强后减弱。紫外光谱、红外光谱分析均显示产品具有明显的明胶特征吸收峰。     

Pea protein isolates: Structure,extraction, and functionality

In keeping with emerging consumer trends, the food industry is continually searching for cheaper and healthier protein ingredients to replace those derived from animal sources (e.g., whey, casein, gelatin, and ovalbumin), gluten-based proteins (e.g., wheat), and soy. Pea protein shows promise in filling this niche because it is non-genetically modified organism (GMO), gluten-free, nutritious, and of low allergenicity. This review discusses structure–function relationships of pea protein isolates, the impact of extraction techniques used to produce the isolate, and the impact of cultivar and environment on ingredient performance in terms of solubility, water- and oil-holding capacities, emulsifying, foaming, and gelation properties.     

酸枣仁蛋白的不同蛋白酶酶解产物功能特性及抗氧化活性分析

以酸枣仁为原料,采用碱提酸沉法对酸枣仁蛋白进行提取,用三种不同蛋白酶（碱性蛋白酶、中性蛋白酶和木瓜蛋白酶）对酸枣仁蛋白进行酶解,得到三种酶解物,研究不同酸枣仁蛋白酶解物的功能特性和抗氧化活性。结果表明,与酸枣仁蛋白相比,不同酸枣仁蛋白酶解物的溶解性、持油性、起泡性及其稳定性、乳化性及其稳定性均具有不同程度地提高,其中,木瓜蛋白酶解物的溶解性、持油性、起泡性和乳化性最强,碱性蛋白酶解物的起泡稳定性和乳化稳定性最强;体外抗氧化研究表明,相比于酸枣仁蛋白,不同蛋白酶所得酶解产物的抗氧化活性均明显提高,其中,碱性蛋白酶酶解物的DPPH清除能力、羟基自由基清除能力、超氧阴离子清除率和ABTS自由基清除能力均高于其他酶解产物,当质量浓度为2.5 mg/mL时,DPPH自由基清除率最高为95.87％、超氧阴离子自由基率为44.77％、ABTS自由基清除率为90.84％、羟基自由基清除率为47.77％。本研究表明,酸枣仁蛋白酶解物具有较好的食品加工性能,其抗氧化活性明显增高,可以作为一种潜在的蛋白质资源应用到食品中,为酸枣仁蛋白酶解物在食品行业中的应用提供理论依据。     

Effect of extraction and isolation on physicochemical and functional properties of an underutilized seed protein: Gingerbread plum (Neocarya macrophylla)

The effect of extraction and isolation on the physicochemical and functional properties of gingerbread plum seed protein isolate was studied. Gingerbread plum seed protein isolate was extracted from defatted gingerbread plum seed flour (DGPSF) by alkali solution along with isoelectric precipitation. The protein isolate was subjected to freeze or vacuum drying process. Freeze dried gingerbread plum seed protein isolate (FGPSPI) and vacuum dried gingerbread plum seed protein isolate (VGPSPI) were evaluated for their physicochemical and functional properties (protein solubility, water/oil binding capacity, emulsifying capacity, foaming capacity). Among physicochemical parameters, the proximate composition, amino acid composition, minerals, differential scanning calorimetry (DSC), SDS-PAGE and color attributes were studied. Both FGPSPI and VGPSPI contained over 90% protein versus DGPSF (56.72%) used as raw material. The method of drying had significant effect (p < 0.05) on the physicochemical characteristics of FGPSPI and VGPSPI except for amino acids composition. The functional properties were variable among samples. DGPSF had higher emulsifying, water holding and oil binding capacities compared with FGPSPI and VGPSPI. FGPSPI exhibited better emulsifying capacity and water holding capacity than VGPSPI. FGPSPI also showed comparable oil binding capacity and bulk density to commercial soy protein isolate (SPI). The results indicated that FGPSPI and VGPSPI could be a good source of protein fortification for a variety of food products for protein deficient consumers as well as a potential food ingredient.     

Functional properties of protein preparations from amaranth seeds in model system

The gross chemical composition and functional properties (solubility, emulsifying and foaming properties) of different amaranth protein preparations were studied in model systems and were compared to those of casein and soy protein isolates. Preparations of alkaline-soluble total protein, albumin, globulin, and glutelin-like alkaline-soluble residual protein were produced from two different types of defatted amaranth meals by extraction and fractionation. Although similarity can be shown between protein patterns of legumes (including soy) and amaranth, the emulsifying and foaming properties of amaranth protein preparations are relatively poor in comparison to the reference proteins, except foaming properties of albumin preparations. Nevertheless, taking in mind that these properties depend on interactions with other food components and textural requirements of individual food products, the amaranth protein preparations may be treated as potential protein sources and food ingredients.     

鱼明胶特性及改性对其品质影响的研究进展

明胶是由胶原蛋白部分热水解得到的一种天然多肽聚合物,其由于独特的功能特性而在医药、食品等领域广泛应用。与哺乳动物明胶相比,鱼明胶来源广泛且满足一些特殊人群需要,是一种最具有开发潜力的新型明胶原料。然而,鱼明胶的凝胶性、乳化、起泡和成膜等功能特性较差,在一定程度上限制了其应用。本文对鱼明胶的物理、化学和功能特性展开综述,并总结了近年来有关改善鱼明胶品质的方法,以期为后期相关科研工作者进一步提高鱼明胶的性能和扩大其应用提供一定的理论依据。     

Canola proteins for human consumption: extraction, profile, and functional properties

Canola protein isolate has been suggested as an alternative to other proteins for human food use due to a balanced amino acid profile and potential functional properties such as emulsifying, foaming, and gelling abilities. This is, therefore, a review of the studies on the utilization of canola protein in human food, comprising the extraction processes for protein isolates and fractions, the molecular character of the extracted proteins, as well as their food functional properties. A majority of studies were based on proteins extracted from the meal using alkaline solution, presumably due to its high nitrogen yield, followed by those utilizing salt extraction combined with ultrafiltration. Characteristics of canola and its predecessor rapeseed protein fractions such as nitrogen yield, molecular weight profile, isoelectric point, solubility, and thermal properties have been reported and were found to be largely related to the extraction methods. However, very little research has been carried out on the hydrophobicity and structure profiles of the protein extracts that are highly relevant to a proper understanding of food functional properties. Alkaline extracts were generally not very suitable as functional ingredients and contradictory results about many of the measured properties of canola proteins, especially their emulsification tendencies, have also been documented. Further research into improved extraction methods is recommended, as is a more systematic approach to the measurement of desired food functional properties for valid comparison between studies.     

碱提和超声波辅助提取菜籽蛋白比较研究

以热榨春油菜菜籽粕为原料,研究了碱提和超声波辅助提取两种方法对菜籽蛋白的提取效果,比较了两种方法提取的菜籽蛋白的性质差异。结果表明:超声波辅助提取效果好,提取时间短,提取率高;超声波辅助提取的菜籽蛋白吸水性、氮溶解指数、起泡性及泡沫稳定性、乳化性及乳化稳定性相对碱提法都有很大提高,而且在酸性条件下,超声波辅助提取的菜籽蛋白仍然具有较好的起泡性和泡沫稳定性。研究表明采用超声波辅助提取菜籽蛋白,不仅提取效果好,而且对菜籽蛋白起到了改性作用,提高了其部分功能性质。     

Preparation and characterisation of surface‐active pectin from soya hulls by phosphate‐assisted subcritical water combined with ultrasonic treatment

Surface‐active pectin was efficiently extracted from soya hull using phosphate‐assisted subcritical water combined with ultrasonic treatment (PASW‐UT). The physicochemical and functional properties of soya hull pectin (PSHP) were evaluated. Compared to pectin prepared by traditional acid extraction (ASHP), the yield and purity of PSHP were significantly increased, as well as PSHP also contained more protein moiety and displayed better emulsifying and foaming properties. However, the emulsifying and foaming properties of protein‐depleted soya bean hull pectin (PDSHP) were markedly decreased as compared to PSHP, which was supported by data of dynamic interfacial tension of pectins, suggesting that the emulsifying and foaming capacity of PSHP should be mainly ascribed to the existence of more extensin, as evidenced by the results of hydroxyproline content. In further comparison with commercial sugar beet pectin (SBP), the PSHP exhibited similar emulsifying properties with SBP over the pH range of 2–6. Moreover, the foam ability and stability were even higher than those of SBP, especially at pH 4.0. These findings suggest that PASW‐UT could be used as an effective strategy to prepare novel surface‐active pectin from soya hull.     

Physicochemical,rheological, and molecular characterization of colloidal gelatin produced from Common carp by‐products using microwave and ultrasound‐assisted extraction

The effects of ultrasound‐assisted extraction (UAE) and microwave‐assisted extraction (MAE) methods on molecular and physicochemical characteristics of the resultant gelatin were examined. Before extraction procedure, we investigated the optimum pH for swelling of Common carp by‐products, which is an important pretreatment for gelatin production. The highest swelling yield was achieved at pH 13 among pH 1–14 with unit intervals. Results indicated that the UAE gelatin has a higher gel strength, viscosity, melting point, and gelling point. The power and time of sonication showed a reverse relation with these characteristics. In addition, as the time of microwave heating was raised, the gel strength, viscosity, melting point, and gelling point were decreased. The FT‐IR spectra showed similar peaks but the Amide B in UAE gelatin slightly vanished. The electrophoretic pattern also revealed the higher gel strength and viscosity of UAE gelatin due to the higher intensity of α and β chains compared to MAE gelatin. It can be concluded from all of the results of this study that the produced gelatin using these procedures can be a good source of gelatin in food and drug industries.     

Production and functional properties of beef lung protein concentrates

This work investigated the production and the properties of meat protein concentrates from beef lungs (BLPC) at pilot scale. Protein recovery and functional properties were compared to those of BLPC obtained using membrane technology in a previous work (Selmane, D., Vial, C., & Djelveh, G. (2008). Extraction of proteins from slaughterhouse by-products: Influence of operating conditions on functional properties. Meat Science, 79, 640–647). An alkaline solubilisation method was applied for protein extraction, followed by pI precipitation for concentration. The physicochemical properties of BLPC such as molecular mass, solubility, surface hydrophobicity, surface tension and interfacial tension, as well as technofunctional emulsifying and foaming properties were determined. These were compared to those of commercial protein ingredients, such as sodium caseinates, whey protein isolates, egg white proteins and soy protein isolates. Results showed that proteins from BLPC included a low-molecular-weight fraction and exhibited good solubility and high hydrophobicity with small surface and interfacial tensions. This explained their excellent emulsifying activity, better than sodium caseinates, and their good foaming properties.     

新型改性明胶

提出酶修饰，酯化，醛修饰３种可行的改性方法，在明胶分子中引入疏水基。对己醛修饰作初步试验，效果较好。经改性后的明胶有很好的乳化性能和起泡性能，同时保持原有的优良性能。     

荞麦蛋白的功能特性研究

采用碱萃取酸沉析法提取制备了荞麦蛋白，并较为系统地研究了蛋白质浓度、温度、pH值、氯化钠和蔗糖对荞麦蛋白的三种功能特性（溶解性质、乳化特性和泡沫特性）的影响。结果表明，本实验条件下制备的荞麦蛋白具有优良的溶解性质，其乳化性质与对照样品大豆分离蛋白相当，但泡沫特性较差。     

Compositional and functional properties of buttermilk: a comparison between sweet, sour, and whey buttermilk

Buttermilk is a dairy ingredient widely used in the food industry because of its emulsifying capacity and its positive impact on flavor. Commercial buttermilk is sweet buttermilk, a by-product from churning sweet cream into butter. However, other sources of buttermilk exist, including cultured and whey buttermilk obtained from churning of cultured cream and whey cream, respectively. The compositional and functional properties (protein solubility, viscosity, emulsifying and foaming properties) of sweet, sour, and whey buttermilk were determined at different pH levels and compared with those of skim milk and whey. Composition of sweet and cultured buttermilk was similar to skim milk, and composition of whey buttermilk was similar to whey, with the exception of fat content, which was higher in buttermilk than in skim milk or whey (6 to 20% vs. 0.3 to 0.4%). Functional properties of whey buttermilk were independent of pH, whereas sweet and cultured buttermilk exhibited lower protein solubility and emulsifying properties as well as a higher viscosity at low pH (pH ≤ 5). Sweet, sour, and whey buttermilks showed higher emulsifying properties and lower foaming capacity than milk and whey because of the presence of milk fat globule membrane components. Furthermore, among the various buttermilks, whey buttermilk was the one showing the highest emulsifying properties and the lowest foaming capacity. This could be due to a higher ratio of phospholipids to protein in whey buttermilk compared with cultured or sweet buttermilk. Whey buttermilk appears to be a promising and unique ingredient in the formulation of low pH foods.     

Milk powders ageing: effect on physical and functional properties

Milk powders are now considered as food ingredients, mainly because of the functional properties of milk proteins. During the storage of milk powders, many physicochemical damages, mainly dependent on lactose glass transition occur. They have important consequences on physical (flowability) and functional properties (solubility, emulsifying, and foaming properties) of milk powders. First, lactose crystallization modifies the microstructure and chemical composition of the surface of powder particles. Thus, milk powders flowability is decreased. Since the structure of milk proteins is destabilized, its solubility is damaged. Moreover, particle collapse and caking occur and mainly decrease the physical properties of milk powders (density and flowability). The mechanical stresses involved may also enhance proteins unfolding, which is detrimental to solubility. Finally, molecular mobility is favored upon ageing, and both chemical (Maillard reaction) and enzymatic reactions occur. Maillard reaction and oxidation enhance protein interactions and aggregations, which mainly lessen milk powders solubility. Maillard reaction also decreases emulsifying and foaming properties. Storage temperature and relative humidity have been considered as the predominant factors involved, but time, milk components, and their physical state also have been implied.     

Characterization of the Composition, Physicochemical and Functional Properties of Acid Whey Protein Concentrates

Membrane-processed acid whey protein concentrates were studied for their foaming and emulsifying properties in dilute whey protein solutions and in a 30% fat emulsion. Among the compositional factors and physicochemical characters which significantly correlated with foaming and emulsifying properties were protein hydrophobicity, solubility, free-sulfhydryl content, phosphorus and β-lactoglobulin concentration. Heptane binding was negatively correlated with foam overrun and foam stability of whey protein solutions, whereas, exposed hydrophobicity was positively correlated with overrun in the whipped topping.     

Acid modification of proteins from soymilk residue (okara)

Protein was extracted from soy residue (okara) at alkaline pH, and was modified by mild acid treatments. The degree of deamidation and peptide bond hydrolysis ranged from 10 to 70% and 6 to 15%, respectively. Size exclusion gel filtration chromatography revealed that there was a progressive degradation of the okara protein. Solubility was increased markedly by the modification, while other functional properties such as emulsifying and foaming properties were also improved. The okara protein products have good essential amino acid profiles, and acid modification also increased the in vitro digestability and available lysine content of okara protein. The results indicate that changes in functional properties of okara protein by acid modification were attributed to changes in physicochemical properties such as decreases in molecular size, higher net titratable charge and surface hydrophobicity. The low solubility of okara protein makes it difficult to be incorporated into many food systems. Improved solubility and other functional properties by acid modification will enhance the utilization okara protein as food ingredient.     

高效酶提取鸡肺明胶及其结构与性质的研究

以鸡肺为原料,通过超声辅助酶法提取明胶,采用紫外光谱法、差示扫描量热法、圆二色谱、聚丙烯酰胺凝胶电泳法、激光粒度分布法、扫描电镜等分析超声辅助酶提鸡肺明胶的结构,并研究其乳化性质,探究该法在鸡肺明胶中的应用效果。研究结果表明,与常规热水提取法相比:超声辅助酶提法的明胶得率为30.08%(鸡肺除杂后干重状态原料),是前者提取的3.43倍,提取效率也提高了2.15倍,热变性温度为90.22℃,略低于前者;两种明胶均存在胶原的特征负吸收峰,出现在229 nm处,其中超声辅助酶提明胶的无规则卷曲程度低于常规热水提取明胶。平均粒径为396 nm,颗粒减小了13.7%,多数分布在相对分子质量45000~95000之间,已基本降解为小分子亚基,表面微观结构有明显的破碎;进一步分析发现,两种明胶样品的乳化性无明显差异。因此,超声辅助酶提法可显著提高明胶提取率,有效缩短了生产周期,鸡肺明胶还可作为乳化剂用于食品工业中,该方法制备的鸡肺明胶在食品领域具有潜在的应用前景,可进一步提高肉鸡副产物的附加值。