Effects of elastase from a Bacillus strain on the tenderization of beef meat

The tenderization effect of a new elastase from Bacillus sp. EL31410 was investigated on beef meat. Meat tenderization was done by dipping the meat cut in a solution containing proteolytic enzymes after freeze-dehydration. It was found that a marination time of 4 h was enough for enzyme adsorption. The samples were treated for 4 h in different enzyme solutions and then was stored at 4 °C for 24, 48, 72 h, and subjected to texture measurement, sensory evaluations, biochemical analysis and histological observations. A marked decrease in hardness, by texture measurements, was observed in the meats with papain and elastase and higher sensory scores for tenderness were observed in the meats treated with enzymes than in the control. The papain-treated beef meat received the highest score for tenderness, but the scores given for juiciness and taste were lower than that of the control. Rapid increases of fragmentation of myofibrils from the enzyme-treated meat were observed in the first 24 h of storage, especially for papain-treated meat. Meantime, elastin of myofibrilar structure was selectively degraded by elastase compared with the control when stored at 4 °C for 48 h as shown by electron microscopy. These findings suggest that Bacillus elastase (EL31410) is a promising substitute for papain as a favourable meat tenderizer.     

Meat tenderization by calcium chloride after osmotic dehydration

In this study, meat was tenderized by dipping the meat in a calcium-containing solution after osmotic dehydration. Dehydrated meats were dipped in a 150 mM calcium chloride solution for 3 h, and after that stored for 24, 48, and 168 h at 3 ～ 4°C. Then, meat was subjected to texture measurement, sensory evaluations, biochemical analysis and histological observations. A gradual decrease in the firmness and higher tenderness sensory scores were observed in the meat treated with calcium chloride as compared with the untreated meat. Few differences were observed in water holding capacity by treatment at any stage of storage. A gradual increase in the myofibril fragmentation from the calcium chloride-treated meats was observed throughout the storage compared with the controls. Broadening of the I band and a disordered Z-line were observed in the treated meat. The deformation of the honeycomb-like structure of the endomysium was also observed in the treated samples. Therefore, the dipping in 150 mM calcium chloride solution after dehydration can be applied to improve meat tenderness without detrimental effects on other palatability and quality traits.     

Tenderization of buffalo meat using plant proteases from Cucumis trigonus Roxb (Kachri) and Zingiber officinale roscoe (Ginger rhizome)

This study was conducted to develop a method for improving tenderness and overall qualities of tough buffalo meat using plant proteolytic enzymes from Cucumis trigonus Roxb (Kachri) and Zingiber officinale roscoe (Ginger rhizome). Their tenderizing efficacy was compared with the most popular enzyme papain. 3×3×3 cm chunks from Biceps femoris muscles of spent Murrah buffaloes (4-5 years age) were marinated with distilled water (control), 2% (w/w) powdered cucumis extract, 5% (w/v) ginger extract or 0.2% (w/w) papain for 48 h at 4 °C and subjected to various physico-chemical, histological and sensory evaluations. An increase (p<0.01) in collagen solubility, sarcoplasmic and myofibrillar protein solubility, and reduction (p<0.01) in shear force values were observed in all enzyme-treated samples compared to control. Electrophoretic pattern of muscle proteins also revealed extensive proteolysis and reduction in number of protein bands in all treated samples. Improvement (p<0.01) in flavor, juiciness, tenderness and overall acceptability scores were observed in all enzyme-treated samples compared to controls. Ginger extract-treated meat samples received better scores for appearance, flavor, tenderness and overall acceptability. From these results, it is shown that ginger and cucumis can be used as an effective alternative to papain.     

畜禽宰后肌肉嫩化相关酶研究进展

目前普遍认为参与宰后肌肉嫩化的相关蛋白酶主要有溶酶体组织蛋白酶、蛋白酶体、钙激活蛋白酶、钙激活酶抑制蛋白和半胱天冬酶5 种,然而对于成熟过程中肉的嫩化程度及机理颇具有争议。大量的研究表明,上述5 种嫩化酶在参与肉嫩化过程中其自身生理生化特性在宰后也发生变化。本文综述5 种参与宰后肉嫩化酶的分子质量、存在部位、作用底物、作用位点、激活条件、最适pH值以及对其活性具有一定影响的抑制剂,并就其影响宰后肉嫩度的作用机理及其自身状态的变化进行分析与阐述,旨在为后续研究嫩化酶在宰后改善肉嫩度方面的应用条件提供参考。     

Effects of Ultrasound on Microstructure and Enzyme Penetration in Beef <Emphasis Type="Italic">Longissimus lumborum</Emphasis> Muscle

The present study aims to introduce a novel process for improving enzyme diffusion in meat during artificial tenderization. For this purpose, Longissimus lumborum muscles from five young Holstein bulls were cut into 3?×?3?×?3 cm pieces. The samples thus prepared were then treated with 0.1% papain solution and the ultrasonic probe (20 kHz; at 100 and 300 W for 10, 20, and 30 min) under different experimental conditions. For each treatment, total proteolytic activity and muscle microstructure were studied using light and field emission scanning electron microscopy techniques while sensory properties were also investigated. Results indicated that sonication power and duration had significant effects on enzyme activity. The highest activity was observed when an ultrasound radiation of 100 W was applied for 20 min. Compared to the untreated meat, ultrasonically treated meat, and meat immersed in sonicated papain, the deepest part of the sample exposed simultaneously to both enzyme and ultrasound treatments recorded proteolytic activities higher by 62, 25, and 42%, respectively. Although all the treatments caused microstructural damages in beef, the most severe changes and the highest scores for tenderness and flavor were achieved through simultaneous application of papain and ultrasound, which indicates papain penetration into the internal parts of meat. Based on the results obtained, ultrasound technology may be recommended as a useful means to achieve enhanced enzyme diffusion in meat.     

EFFECTS OF DIETARY SOYBEAN LECITHIN ON SOME SENSORY AND RHEOLOGICAL PROPER TIES OF FROZEN AND NON-FROZEN CHICKEN MEAT

Soy bean lecithin was added to practical rations fed to 144 broiler chicks. The dark and white meats from frozen and non-frozen carcasses were submitted to both mechanical (Warner Bratzler and Instron Universal Testing Machine) and sensory assessments of tenderness. A good correlation was observed between the two types of measurements. Regression equations indicated that higher lecithin contents in the rations decreased sensory toughness of the white meat. Freezing of the meats at – 40°C had little effect on texture.     

MEAT TENDERIZATION: POSSIBLE CAUSES AND MECHANISMS. A REVIEW.

The postmortem meat tenderizing process is complex and not fully understood. The nature of changes associated with the improvement in tenderness and the exact mechanisms involved are still unknown. Based on relevant evidence, old and new, this review attempts to clarify the statement of our knowledge of these aspects. Of the different biochemical and ultrastructural changes occurring in meat, a key role of myofibril disruption taking place at the N₂-line level in meat tenderization has been emphasized. This may be ascribed to the action of lyosomal enzymes, especially cathespin B and L. However, all the changes thus far identified can be only explained by a synergistic action of lysosomal and calcium-dependent proteinases. Besides or together with proteolytic enzymes, weakening of myofibrils may also be mediated by the high ionic strength achieved in postmortem muscles. Both mechanisms possibly involved in the meat tenderizing process have been tentatively tested in relation with the large muscle variability in aging rate. It appears that some concepts are in conflict with the results presented. For instance, no direct relationship was found between aging rate and proteinase content of muscles.     

Chuck Longissimus and lnfraspinatus Muscle Characteristics as Affected by Rigor State, Blade Tenderization and Calcium Chloride Injection

Blade tenderization resulted in increased (P<0.05) tenderness scores of postrigor longissimus muscle after 7 days storage. However, no improvements (P>0.05) in tenderness of prerigor CaCl₂ injected infraspinatus and longissimus muscles were observed due to blade tenderization nor was percentage of collagen affected. Prerigor, blade tenderized CaCl₂ injected muscles were generally less tender (P<0.05), as measured by sensory panel and shear force, than postrigor muscles independent of blade tenderization. Furthermore, prerigor CaCl₂ injected samples had lower texture scores for both muscles and lower flavor scores for infraspinatus than samples from postrigor muscles. Blade tenderization did not affect microbial load or color nor did CaCl₂ influence color.     

酱油种类及添加量对牛肱二头肌的嫩化作用

研究酱油种类及添加量对牛肱二头肌的嫩化作用。将3 种质量浓度15 g/100 mL的酱油溶液与3 g /100 mL的食盐溶液按不同的比例混合,配制9 组腌制液,并以3 g/100 mL的食盐溶液作为对照组（记为C0）,按肉液比为1∶4（m/V）将牛肱二头肌肉块（2.5 cm×2.5 cm×2.5 cm）腌制72 h（4 ℃）,分析酱油种类及添加量对肉样pH值、剪切力、胶原蛋白含量、肌节长度及肌原纤维碎裂指数（myofibrillar fragmentation index,MFI）等指标的影响。结果表明：酱油腌制会降低肉样的pH值（P＜0.05）,但对肉样的持水力和总胶原蛋白含量无显著影响（P＞0.05）;酱油含量高的腌制液具有更低的pH值,使肉样的可溶性胶原蛋白含量及MFI变大、肌节长度变短,进而提高肉的嫩度;当腌制液中的酱油比例较高时,肉样的嫩度与多汁性感官评分更高,总体可接受度更好。在3 种酱油中,低pH值酱油对牛肱二头肌的嫩化效果更好。     

MEAT TEXTURE CHARACTERISATION: COMPARISON OF CHEWING PATTERNS, SENSORY AND MECHANICAL MEASURES

The texture of beef, varied by muscle (semimembranosus and semitendinosus), myofibrillar status (ageing time and cold-shortening) and cooking temperature (60C and 80C), was determined by a sensory profile, chewing patterns (determined from surface electromyograms) and mechanical properties of the cooked meats measured at low and high deformation in compression, shear (cutting) and by dynamic (viscoelasticity) tests. The meat factors were discriminated differently by the different measurements showing that they detected differently the various origins of meat texture. Only the maximum modulus before 70% compression and sensory assessments and EMG gave discrimination among all the meat factors. Two main sensory dimensions were found from the profile: juiciness and tenderness with a third related to the determination of elasticity. Juiciness, which varied most between cooking temperatures, was better related to mechanical parameters at low strain rather than high strain and to initial muscular activity rather than later muscular activity. Conversely, tenderness was better related to high strain mechanical properties and to measurements in the middle or later part of the mastication process suggesting that tenderness assessment requires structural disintegration of meat.     

APPLICATION OF ACTINIDIN FROM KIWIFRUIT TO MEAT TENDERIZATION AND CHARACTERIZATION OF BEEF MUSCLE PROTEIN HYDROLYSIS

The effect of actinidin on the tenderness of broiled bovine semitendinosus (ST) steaks was studied. An actinidin activity of 400 U/mL resulted in Kramer shear values and sensory tenderness scores equivalent to that produced by Adolph's papain-based meat tenderizer (18 U/mL). Both were significantly (P<0.05) more tender than steaks having no tenderizing treatment. Actinidin did not over-tenderize the steak surface as did Adolph's meat tenderizer. Hydrolysis of myofibrillar proteins in enzyme-treated steaks prior to broiling was considerably less for actinidin than for papain when using activities to attain equal Kramer shear values of broiled steaks.     

Effect of pre-slaughter physiological conditions on the oxidative stability of colour and lipid during chill storage of pork

The potential to tenderize beef muscles by the injection of lactic acid (0.5 M, 10% w/w) was studied using the pectoralis profundus muscle from cull cows. The injection was performed either 1 h (pre rigor) or 24 h (post rigor) post mortem, and the meat was stored for 2 or 14 days post mortem. Both treatments caused a rapid pH drop to around 5.0 within 4 h of injection. Other effects were: (1) an accelerated release of lysosomal enzymes into the cytosol; (2) a greater degradation of myosin heavy chains; (3) ultrastructural alterations of the myofibrils which included a general weakening or rupture in the M-lines and, to a lesser extent, in the I-bands; (4) a decreased heat stability of perimysial collagen indicated by a lower insoluble collagen content, lower differential scanning calorimetry transition temperature, and lower transition temperatures in isometric tension tests on muscle strips. The lactic acid injections improved significantly the textural traits of the meat (shear value, tensile strength, sensory scores) at 2 days post mortem with little further improvement when storage was extended to 14 days post mortem. Changes in texture were of similar amplitude at both post mortem injection times. The tenderization mechanisms of lactic acid injection are discussed.     

Tenderization of Meat with Ginger Rhizome Protease

Beef steaks and sliced beef marinated with different levels of crude ginger extract were evaluated for the tenderness and structural changes. A significant (P<0.05) enhancement of tenderness with increasing amounts of ginger extract was observed at low levels of extract (0, 0.05, 0.1, and 0.2 mL/6.5 cm² for the steaks; 0, 0.25, 0.5, and 1 mL/lOOg for the sliced beef), whereas further improvement of tenderness at more than 0.2 mL/6.5 cm² or 1 mL/lOOg was minimal. Electron microscopy of the treated beef revealed the preferential degradation of thin filaments in the I-bands, resulting in extensive fragmentation of myofibrils. Thus, ginger rhizome protease is an effective meat tenderizer and the tenderization is achieved through preferential degradation of thin filaments.     

Applied and Emerging Methods for Meat Tenderization: A Comparative Perspective

The tenderization process, which can be influenced by both pre‐ and post‐slaughter interventions, begins immediately after an animal's death and is followed with the disruption of the muscle structure by endogenous proteolytic systems. The post‐slaughter technological interventions like electrical stimulation, suspension methods, blade tenderization, tumbling, use of exogenous enzymes, and traditional aging are some of the methods currently employed by the meat industry for improving tenderness. Over the time, technological advancement resulted in development of several novel methods, for maximizing the tenderness, which are being projected as quick, economical, nonthermal, green, and energy‐efficient technologies. Comparison of these advanced technological methods with the current applied industrial methods is necessary to understand the feasibility and benefits of the novel technology. This review discusses the benefits and advantages of different emerging tenderization techniques such as hydrodynamic‐pressure processing, high‐pressure processing, pulsed electric field, ultrasound, SmartStretch^?, Pi‐Vac Elasto‐Pack® system, and some of the current applied methods used in the meat industry.     

Effect of Blanch Time on the Development of Mushiness in Ice-Stored Crawfish Meat Packed with Adhering Hepatopancreas

Loss of a desirable firm texture in fresh crawfish meat packed with adhering hepatopancreas was influenced by blanch time. Analysis of texture by Instron Kramer shear force and sensory panel showed that after 20 hr of iced storage, crawfish meat cooked <7 min was significantly (p <0.01) softer than crawfish meat cooked 7 to 13 min. Hepatopancreas tissue obtained from crawfish cooked less than 7 min prevented firm gelation of a 12% aqueous gelatin solution. Results indicated that heat labile proteolytic enzymes were involved in the development of mushiness in fresh crawfish meat.     

Lipolytic and proteolytic properties of dry-cured boneless hams ripened in modified atmospheres

We studied proteolytic and lipolytic properties of dry-cured boneless ham (porcine quadriceps femoris) made with chilled (10°C, 48 h) or frozen/thawed meat (frozen at -20°C frozen for 90 days and followed by thawing at 10°C for 48 h) were determined. Dry-cured meats were stored in modified atmosphere packages (100% N(2) and a mixture of 75% N(2)+25% CO(2)) at 15°C with the intention of reducing ripening space. Results showed that dry-cured hams made with frozen/thawed raw meat had more salt, volatile fatty acids and free fatty acid content after salting and smoking. Whereas, samples prepared with chilled meats contained more nitrogenous compounds (water-soluble nitrogen, non-protein nitrogen, and free amino acids). Volatile and free fatty acid contents in all samples significantly increased with storage. Acetic acid was the predominant volatile fatty acid. To confirm lipolytic activity in dry-cured ham stored in modified atmospheres, we calculated the lipolytic coefficient. The lipolytic coefficients of all samples were positive values and significantly (P<0.05) increased with storage indicating lipolysis in samples were still active. Furthermore, nitrogenous compounds in dry-cured ham significantly (P<0.05) increased with storage indicating proteolysis in samples were not affected by modified atmosphere storage. Aerobic, anaerobic and lactic acid bacteria counts in dry-cured meats were stable to modified atmospheres storage for 20 weeks at 15°C. Flavor, texture and color score in sensory evaluation for dry-cured ham made with chilled meat were significantly higher than that made with frozen/thawed meat. All samples had high overall acceptance scores in sensory evaluation. Results in this study suggested that dry-cured boneless ham stored in modified atmospheres for 20 weeks at 15°C was another feasibility to ripen the meat without affecting lipolysis, proteolysis, microbiology and sensory quality.     

氧化引起肉及肉制品品质劣变的机理及影响因素

肉及肉制品在加工和贮藏过程中品质会下降,如嫩度降低、褪色、形成腐败味道等,而肉品质的降低与肉中含有的主要成分肌红蛋白、肌原纤维蛋白和脂肪的氧化有关,本文主要讨论三者氧化变化以及关联性,并探讨在加工贮藏过程中可能引起氧化的因素,为生产高质量的肉制品提供一定参考。