模糊数学结合响应曲面法优化麻鸭肌原纤维蛋白凝胶工艺

以麻鸭胸脯肉为原料,提取肌原纤维蛋白并对其进行加热诱导形成凝胶,研究不同的因素(蛋白浓度、p H值、凝胶温度、Na Cl浓度)对蛋白凝胶特性的影响并对诱导条件进行优化。在单因素实验基础之上,利用模糊数学对凝胶质构性质和保水性进行综合评价选择p H、加热温度、Na Cl浓度为自变量,蛋白凝胶综合评价得分为响应值,进行响应曲面优化分析。结果表明:蛋白浓度、p H、凝胶温度、Na Cl浓度都会对肌原纤维蛋白凝胶的保水性和质构特性产生影响。得到最佳诱导条件为:p H 7.0、Na Cl浓度0.6 mol/L、凝胶温度72℃;在此条件下得到的蛋白凝胶的综合评价得分为0.541。     

冷却和冷冻对猪背最长肌动态黏弹性和凝胶特性的影响

研究猪背最长肌在热鲜、冷却、冷冻这3种不同处理条件下的pH值、蛋白溶解度、动态黏弹性和凝胶特性(凝胶保水性(WHC)、凝胶强度、凝胶弹性),并比较其差异。结果显示:热鲜肉的pH值和蛋白溶解度均最高,并且具有较好的动态黏弹性和凝胶特性;冷却肉的pH值和蛋白溶解度相对较低,其凝胶特性和动态黏弹性均不如热鲜肉好;冷冻肉的pH值和蛋白溶解度最低,凝胶保水性和动态黏弹性最差,其凝胶强度和凝胶弹性低于热鲜肉却高于冷却肉。说明冷藏处理过程损坏了肉品的功能特性,因此热鲜肉的功能特性相对最佳。     

马铃薯分离蛋白凝胶的制备及其性质研究

以新鲜马铃薯为原料,采用等电点沉淀法制备马铃薯分离蛋白。确定了马铃薯分离蛋白最低凝胶点的蛋白质浓度为6%。考察蛋白质浓度、pH 值、加热温度和加热时间4 个因素对凝胶形成的影响,采用物性仪对不同条件下制备凝胶的质构特性进行研究,通过脆度、硬度、稠度、黏聚性和黏着性这5 个指标对马铃薯分离蛋白的质构特性进行说明。优化结果表明不同评价指标得出的结论不尽相同。对马铃薯分离蛋白凝胶特性进行综合评价,可选用蛋白质浓度12%、pH7.0、加热温度95℃、加热时间15min 制备凝胶。     

肌球蛋白高压凝胶机理的研究进展

超高压加工技术是一项能够影响肉类凝胶功能特性的非热加工技术,肌球蛋白是肉类凝胶形成过程中起主要作用的蛋白质。虽然人们对于高压处理对肉类凝胶影响的机理研究不断深入,但是在肌肉与肌原纤维蛋白层面的研究常受限于其复杂的体系,因此针对单体蛋白的基础研究有助于对这一体系的进一步探索,从而更好地指导实践生产。该文着重于介绍高压处理对肌球蛋白凝胶形成过程机理的研究进展和存在的技术限制以及对未来的展望。     

肌肉蛋白热诱导凝胶特性的影响因素及其机制

肌肉蛋白的凝胶功能特性是决定肉糜类和重组肉制品品质的关键因素,文中综述了影响凝胶形成的肌肉蛋白种类与浓度、pH及离子强度、加热方式等因素,探讨了蛋白凝胶形成机制以及对肉品质的影响。同时讨论了非肉蛋白、TGase、磷酸盐及亲水胶体在凝胶性中的调控作用。     

高压和热结合处理对鸡肉pH、嫩度和脂肪氧化的影响

对不同温度(20～70℃)下高压(0.1～800MPa)处理20min对鸡胸肉pH、嫩度和脂肪氧化的影响进行了研究。结果显示,压力和热或两者结合处理都能使肌肉的pH升高,但两者结合处理对pH的影响无叠加作用。单纯的热处理过程中,随着温度的升高,肌肉的嫩度持续下降,同样,室温下的压力处理时,肌肉的嫩度随压力的升高而降低。40℃时压力处理,肌肉嫩度的变化与室温下相似。然而,当在60℃和70℃温度下压力处理时,200MPa的压力导致肌肉的嫩度显著提高。其原因可能为在此条件下肌肉骨架蛋白质发生了降解。压力和热以及两者结合处理都能加速脂肪的氧化,尤其是在400MPa及其以上压力。压力和热处理导致脂肪氧化的原因,可能与肌肉结构的破坏及过渡金属离子(如铁离子)的释放有关。      

高压和热结合处理对鸡肉pH、嫩度和脂肪氧化的影响

对不同温度(20～70℃)下高压(0.1～800MPa)处理20min对鸡胸肉pH、嫩度和脂肪氧化的影响进行了研究。结果显示,压力和热或两者结合处理都能使肌肉的pH升高,但两者结合处理对pH的影响无叠加作用。单纯的热处理过程中,随着温度的升高,肌肉的嫩度持续下降,同样,室温下的压力处理时,肌肉的嫩度随压力的升高而降低。40℃时压力处理,肌肉嫩度的变化与室温下相似。然而,当在60℃和70℃温度下压力处理时,200MPa的压力导致肌肉的嫩度显著提高。其原因可能为在此条件下肌肉骨架蛋白质发生了降解。压力和热以及两者结合处理都能加速脂肪的氧化,尤其是在400MPa及其以上压力。压力和热处理导致脂肪氧化的原因,可能与肌肉结构的破坏及过渡金属离子(如铁离子)的释放有关。     

高压与热结合处理对鱼糜凝胶质构特性的影响

将高压处理(400MPa和600MPa,40℃,15min)作为鱼糜“凝胶化”的另一种方法,与热处理凝胶化(40℃,75min)比较,然后都作后热处理(90℃,25min)。研究了不同处理方法所得凝胶的质构特性(包括凝胶强度分析TPA和持水性),结果表明,600MPa压力凝胶化再后热处理样品质构特性均不及热处理,而400MPa压力凝胶化再后热处理样品比典型热处理样品表现出更好的质构特性:(1)凝胶强度提高了36·1%;(2)硬度提高13·7%;(3)压出水分含量减少6·0%。而且,400MPa压力凝胶化时间仅为典型热力凝胶化的1/5。所以,400MPa压力凝胶化再后热处理可以作为传统热处理方法的替代方法。     

超高压结合热处理对猪肉肌内脂肪酸组成的影响

为研究高压结合一定的温度处理对肉中肌内脂肪酸组成的影响,以猪背最长肌为原料,经不同压力(300~700 MPa)、温度(20~50℃)和时间(10~20 min)结合处理后,测定各样品总脂、甘油三酯、磷脂和游离脂肪的脂肪酸组成变化。结果表明:压力对猪肉脂肪酸组成的影响最显著,其次是温度,两者的交互作用也显著,而时间的作用不显著;脂肪酸组成变化主要由磷脂和游离脂肪酸引起,而总脂和甘油三酯在整个处理中变化很小;300 MPa及以上的压力结合热处理使磷脂发生明显的降解作用,且其中较多的PUFA发生降解导致其在磷脂中的比例显著降低,而SFA和MUFA的比例显著增加,游离脂肪酸组成的变化与磷脂恰好相反。因此,高压结合热处理对肌内总脂肪、甘油三酯的脂肪酸组成影响不大,而主要影响磷脂和游离脂肪酸。     

超高压结合低温处理对牛肉组织结构及理化特性的影响

以牛肉为研究对象,通过均匀试验设计研究高压(100～600MPa,5～30min)结合低温(20～60℃)处理对牛肉的组织结构和理化性质的影响。结果表明,牛肉的弹性在一定压力(100～600 MPa)和温度(20～54.3℃)范围内增大。当温度低于41.6℃时,pH值因压力(100～600 MPa)的上升而增加,但压力与温度结合处理对pH值的影响无叠加作用。随着压力、保压时间以及温度的上升,肌肉的L值和煮制率均有不同程度的增加。同时,压力可导致肌肉的硬度增大,保压时间(5～30min)和温度(20～60℃)的上升则可引起硬度下降。     

Muscle protein gelation by combined use of high pressure/temperature

One of the various applications of high pressure processing (HPP) in food treatment is to affect myofibrillar proteins and their gel-forming properties, which suggests interesting possibilities for the development of processed muscle-based food. In light of the thermolabile nature of protein meat systems and the variation in the rates at which pressure (P) and temperature (T) changes take place in the product, this article provides an overview of the conditions in which pressure-assisted gelation is achieved in myosystems depending on the sequence in which pressure/temperature combinations are applied. It also analyses other relevant circumstances affecting the conditions in which muscle foods are pressurized, which could place limitations on the interpretation of the results.     

Effect of High Pressure on Physicochemical Properties of Meat

The application of high pressure offers some interesting opportunities in the processing of muscle-based food products. It is well known that high-pressure processing can prolong the shelf life of meat products in addition to chilling but the pressure-labile nature of protein systems limits the commercial range of applications. High pressure can affect the texture and gel-forming properties of myofibrillar proteins and, hence, has been suggested as a physical and additive-free alternative to tenderize and soften or restructure meat and fish products. However, the rate and magnitude at which pressure and temperature effects take place in muscles are variable and depend on a number of circumstances and conditions that are still not precisely known. This review provides an overview of the current knowledge of the effects of high pressure on muscle tissue over a range of temperatures as it relates to meat texture, microstructure, color, enzymes, lipid oxidation, and pressure-induced gelation of myofibrillar proteins.     

Structuring dairy systems through high pressure processing

This review highlights the current knowledge on gelation of hydrocolloids induced by high pressure processing (HPP) of dairy products. Pressure-induced gelation of single systems (casein rich, whey protein rich, gelatin, and polysaccharide solutions) as well as rheological and thermo-mechanical effects of HPP on mixture systems are discussed. The mechanism of dairy protein gelation under pressure, their properties and microstructure, and potential application of HPP to improve physical properties of dairy products (cheese, yoghurt, and ice cream) are included. HPP is a promising tool for future manufacturing of structured dairy products with unique sensorial properties.     

蛋白质类添加物在鱼糜制品中的应用现状及发展趋势

鱼糜制品是一类以鱼糜为原料,经擂溃、成型、凝胶化等过程制成的凝胶状食品。凝胶特性是评价鱼糜品质的重要指标,它直接关系到鱼糜制品的持水性、弹性、黏结性等组织特性。蛋白质是生产过程中常用的一种外源物,其添加可以增强鱼糜制品的品质,降低生产成本。在阐述肌原纤维蛋白的分子组成和凝胶机制的基础上,介绍肌肉蛋白和非肌肉蛋白(酶类蛋白、植物性蛋白和动物蛋白)在鱼糜制品中的应用现状及发展趋势,旨在为各种蛋白质类物质作为鱼糜凝胶增强剂提供参考。     

Effects of high pressure on meat: A review

Extensive investigations in the last decade have revealed the potential benefits of high pressure processing (100-800 MPa) for the preservation and modification of foods. Simultaneously, a few pressurised foods have become commercially available in Japan, Europe and the USA. In the present review, the basic principles underlying the effects of high pressure on food constituents and quality attributes are first presented. Recent data concerning the following specific effects of high pressure on muscle and meat products are then reported and discussed: changes in muscle enzymes and meat proteolysis; modifications in muscle ultrastructure; effects on myofibrillar proteins; meat texture and pressureassisted tenderisation processes; pressure-induced gelation and restructuring of minced meat; changes in myoglobin and meat colour; influence of pressure on lipid oxidation in muscle; high pressure-inactivation of pathogenic and spoilage micro-organisms in meat; combined high pressure-moderate temperature 'pasteurisation' of meat products.     

Influence of Cosolvent Systems on the Gelation Mechanism of Globular Protein: Thermodynamic,Kinetic, and Structural Aspects of Globular Protein Gelation

How thermostability and gelation of globular protein are affected by cosolvent systems present in food systems is critical to understanding their functionality. The expression of these functional attributes depends on the molecular structure and thermal‐mechanical history of the protein, as well as its chemical environment. To improve the design of processing protein‐containing food systems, one must fully understand the thermodynamic, kinetic, and structural impact of cosolvent on globular protein gelation. This review focuses on the impact of weakly interacting neutral cosolvent systems (for example, sugars and polyols) on the gelation of globular proteins. The physicochemical mechanisms by which these cosolvent systems can modulate protein gelation are highlighted from a thermodynamic, kinetic, and structural point of view.     

Combination of high pressure and heat on the gelation of chicken myofibrillar proteins

The effects of combinations of high pressure and heat on chicken myofibrillar gels were investigated. High pressure was either applied simultaneously with heating (heating under pressure, HUP), before heating (PBH) or no high pressure with heat-only (HT). PBH treatment induced many similar properties in gels as did by HT treatment, except that PBH treatment promoted secondary structure transformation and formed more covalent bonds. HUP treatment resulted in less heat denaturation of the protein, induced fewer hydrophobic interactions and covalent bonds, hindered secondary and tertiary structural transformation, and formed a gel with a more porous microstructure. The gels induced by HUP treatment had softer texture and higher water holding capacity than gels induced by PBH or HT treatments. These findings suggest that high pressure with HUP treatment changes gel properties by resisting the heat-induced denaturation and gelation of myofibrillar proteins, while high pressure with PBH treatment alters gel properties by promoting denaturation of myofibrillar proteins.Industrial relevanceThe main constituents in meat are myofibrillar proteins, which are responsible for the functional properties of processed meat products. The gelation of myofibrillar proteins differs according to the sequence in which pressure/temperature combinations are applied. The pressure-modified protein interactions should be considered when adopting high pressure in meat product processing since the microstructure of the meat gel is affected by pressure, which would further affect water holding capacity and textural properties. HUP treatment showed its advantages in forming a fine microstructure and improving water-holding capacity.     

UHT Milk Processing and Effect of Plasmin Activity on Shelf Life: A Review

Abstract: The demand for ultra‐high‐temperature (UHT) processed and aseptically packaged milk is increasing worldwide. A rise of 47% from 187 billion in 2008 to 265 billon in 2013 in pack numbers is expected. Selection of UHT and aseptic packaging systems reflect customer preferences and the processes are designed to ensure commercial sterility and acceptable sensory attributes throughout shelf life. Advantages of UHT processing include extended shelf life, lower energy costs, and the elimination of required refrigeration during storage and distribution. Desirable changes taking place during UHT processing of milk such as destruction of microorganisms and inactivation of enzymes occur, while undesirable effects such as browning, loss of nutrients, sedimentation, fat separation, cooked flavor also take place. Gelation of UHT milk during storage (age gelation) is a major factor limiting its shelf life. Significant factors that influence the onset of gelation include the nature of the heat treatment, proteolysis during storage, milk composition and quality, seasonal milk production factors, and storage temperature. This review is focused on the types of age gelation and the effect of plasmin activity on enzymatic gelation in UHT milk during a prolonged storage period. Measuring enzyme activity is a major concern to commercial producers, and many techniques, such as enzyme‐linked immunosorbent assay, spectrophotometery, high‐performance liquid chromatography, and so on, are available. Extension of shelf life of UHT milk can be achieved by deactivation of enzymes, by deploying low‐temperature inactivation at 55 °C for 60 min, innovative steam injection heating, membrane processing, and high‐pressure treatments.     

Gelation of protein isolates extracted from tilapia light muscle by pH shift processing

The gelation properties of protein isolates extracted from tilapia muscle with acid and alkali-aided processing were compared to washed tilapia muscle. Gels were prepared with and without the addition of 2% NaCl (w/w) slightly above neutral pH and gelation properties and gel quality were determined using various procedures. Hardness and elasticity of gels as assessed by torsion testing was improved using 2% NaCl (w/w) compared to treatments without salt. Small strain oscillatory testing showed that storage modulus (G′) of gel pastes prior to thermal gelation was significantly higher in the absence of salt, while smaller differences were seen after thermal gelation. Small strain oscillatory tests demonstrated a different gel forming mechanism for acid and alkali treated proteins compared to washed muscle. Fold tests demonstrated that acid treated proteins and washed muscle had significantly lower gel quality compared to alkali treated proteins. Addition of salt in gels improved gel water-holding capacity for acid and alkali treated proteins. Overall, the acid treated proteins exhibited poorer gelling ability compared to alkali treated proteins. Total content of SH-groups was measured before and after gelation and S–S bonding did not explain the difference in gel forming ability of different treatments. The results indicate that the alkali-aided process can be used to produce high quality protein gels from tilapia muscle suitable for manufacturing of imitation seafood products.     

Gelation of chicken batters during heating under high pressure

The gelling process of chicken meat batters, which were heated (75 °C) under atmospheric pressure or high pressure (200/400 MPa), was investigated by determining the hardness of batter, residual denaturation enthalpy, microstructure, and protein secondary structure. The results showed that meat batters heated at 200 MPa showed a similar increase in hardness to heat-only samples, but meat batters heated at 400 MPa showed a texture decreasing tendency after a limited increase. High pressure disrupted the myofibrils, promoted protein denaturation and aggregation in the first stage of heating under pressure treatment. In the second stage of treatment, heating was the main driving force for protein gelation, which was disturbed by hindering the structural transformation of proteins in the presence of high pressure during heating. The effect of 200 MPa on muscle proteins was relatively gentle and had a less negative effect. Excessive high pressure should be avoided when applying heating under pressure for gel-type meat products processing.Industry relevanceHigh-pressure processing is increasingly applied in the meat industry. By combining high pressure with heating, their effects on texture improvement and microbial inactivation can be maximized. In this study, the influence of high pressure on the texture of meat products was analyzed, which showed that excessive pressure would significantly interfere with the thermal denaturation of the protein, thus adversely affecting the formation of the gel structure. High pressure at 400 MPa and above should be avoided when applying heating under pressure for gel-type meat products processing.