Minh Ha

Physical Interventions to Manipulate Texture and Tenderness of Fresh Meat: A Review

Meat tenderness is a major eating quality attribute that ensures consumer satisfaction and repeat purchase of red meat. The variability in meat tenderness is related to several factors that are spread across the production chain (biological, on farm, processing, and consumer factors), which can lead to inconsistent tenderness in fresh red meat products. The tenderization process is dictated by physical and biochemical factors, which appear to affect the proteases involved in protein degradation and, consequently, they regulate the rate and extend of tenderization in meat. Several physical, chemical, and biochemical interventions have been investigated to improve the tenderness of meat. The present review discusses the physical interventions used to manipulate the texture of meat and their mechanism of action, optimal tenderizing conditions, and their effects on other meat quality attributes (colour stability, lipid oxidation, and water holding capacity). Attention should be paid to other quality attributes for full evaluation of the differing interventions.

Comparison of the Proteolytic Activities of New Commercially Available Bacterial and Fungal Proteases toward Meat Proteins

UNLABELLED The hydrolytic activity of 3 commercially available protease preparations (bacterial protease G, fungal 31000, and fungal 60000) were examined using fluorescent-labeled casein, azo dye-impregnated collagen, and meat protein extracts from bovine M. semimembranosus and Achilles tendon, and compared to that of papain. Assays showed that all proteases exhibited little activity at low temperature (5 °C), and maximal activity at 45 °C. The pH, at which optimal activity was observed for each of the protease preparations, differed and ranged from pH 5.0 to 8.0. Kinetic parameters (K(M) and V(max) ) were also different between protease preparations, with the bacterial protease G and papain exhibiting significantly higher V(max) values (P < 0.001) and lower K(M) values (P < 0.01) for the casein substrate than the 2 fungal protease preparations. Meat protein hydrolysis was displayed on SDS-PAGE and proteins analyzed with mass spectrometry. The protease preparations were shown to have varying affinity toward different meat proteins. The bacterial protease G preparation was efficient at hydrolyzing most myofibril and collagen proteins, and appeared to be more efficient than papain at hydrolyzing collagen proteins. On the other hand the 2 fungal protease preparations showed a selective specificity toward meat myofibrillar proteins, and the fungal 60000 protease preparation exhibited high affinity toward collagen γ and collagen type I chain B proteins. The results generated in this study demonstrated that these commercial proteases have good potential for use in meat tenderization applications due to their mild and complementary effects on different meat proteins. PRACTICAL APPLICATION Bacterial and fungal protease preparations exhibited varying affinities for hydrolyzing meat proteins. This selective moderate capability of microbial proteases compared to papain is potentially an advantage in avoiding over-tenderization in meat. On the other hand, the bacterial protease G preparation, which appeared to be more efficient at hydrolyzing connective tissue proteins than papain, could be beneficial in tenderizing meat with high connective tissue content. The synergistic effect of these protease preparations could be incorporated into a meat tenderizing formula to give the tenderizer a broad activity spectrum, thus able to target different cuts of meat.

Characterisation of kiwifruit and asparagus enzyme extracts, and their activities toward meat proteins

Two plant enzyme extracts from kiwifruit and asparagus were evaluated for their ability to hydrolyse commercially available substrates and proteins present in both beef connective tissue and topside myofibrillar extracts. The results show significant differences in protease activity depending on the assay used. Protease assays with connective tissue and meat myofibrillar extracts provide a more realistic evaluation of the potential of the enzymes for application in meat tenderization. Overall, the kiwifruit protease extract was found to be more effective at hydrolysing myofibrillar and collagen proteins than the asparagus protease extract. The two protease extracts appeared to target meat myofibrillar and collagen proteins differently, suggesting the potential of a synergistic effect of these proteases in improving the tenderness of specific cuts of meat, based on their intrinsic protein composition.

Characterisation of novel fungal and bacterial protease preparations and evaluation of their ability to hydrolyse meat myofibrillar and connective tissue proteins.

The catalytic capability of four commercially available food-grade fungal and bacterial protease preparations (AFP, FPII, F60K and HT) was evaluated over a range of pH, temperature and substrate conditions using esterase and caseinolytic activity assays and time course hydrolysis over 120 and 60 min of myofibrillar and connective tissue proteins, respectively. The protease preparations displayed similar casein hydrolysis kinetics and were active in hydrolysing BODIPY-FL casein to varying extents at postmortem aging meat pH (5.0-6.0). All of the four proteases exhibited selective hydrolytic activity towards meat myofibrillar proteins including myosin and actin. Significant hydrolysis of two meat tenderisation protein markers troponin T and desmin by the four proteases was detected by western blot. The results obtained indicate that the new fungal protease preparations AFP and FPII, bacterial protease preparation HT and the new source of fungal protease preparation F60K have potential for use in meat tenderising applications.

Systematic review of emerging and innovative technologies for meat tenderisation

Consumers are the final step in the meat supply chain and meeting consumer expectations of quality and tenderness are important for satisfaction and repeat purchase. High pressure processing, shockwaves, ultrasound, pulsed electric field and muscle stretching can be applied to pre- and post-rigor meat for tenderisation. These non-thermal and thermal innovative technologies can be used with varying levels of success to cause physical disruption to muscle structure, enhanced proteolysis and ageing and muscle protein denaturation and solubilisation resulting in changes to texture and juiciness. Results of a meta-analysis are used to compare the effects of these technologies on meat tenderisation. In the future, a combination of new and innovative technologies will be ideally suited to deliver a range of desired textures for meat products.

In-Depth Characterization of Sheep (Ovis aries) Milk Whey Proteome and Comparison with Cow (Bos taurus)

An in-depth proteomic study of sheep milk whey is reported and compared to the data available in the literature for the cow whey proteome. A combinatorial peptide ligand library kit (ProteoMiner) was used to normalize protein abundance in the sheep whey proteome followed by an in-gel digest of a 1D-PAGE display and an in-solution digestion followed by OFFGEL isoelectric focusing fractionation. The peptide fractions obtained were then analyzed by LC-MS/MS. This enabled identification of 669 proteins in sheep whey that, to our knowledge, is the largest inventory of sheep whey proteins identified to date. A comprehensive list of cow whey proteins currently available in the literature (783 proteins from unique genes) was assembled and compared to the sheep whey proteome data obtained in this study (606 proteins from unique genes). This comparison revealed that while the 233 proteins shared by the two species were significantly enriched for immune and inflammatory responses in gene ontology analysis, proteins only found in sheep whey in this study were identified that take part in both cellular development and immune responses, whereas proteins only found in cow whey in this study were identified to be associated with metabolism and cellular growth.

Effects of L- and iso-ascorbic acid on meat protein hydrolyzing activity of four commercial plant and three microbial protease preparations.

The present study investigated the effects of both l- and iso-ascorbic acid (AA) on the activity of four plant proteases (papain, bromelain, actinidin and zingibain) and three microbial proteases (Bacterial Protease G, Fungal 31,000 and Fungal 60,000) preparations using fluorescent-labelled casein, meat myofibrillar and connective tissue extracts to explore their effects on meat structure components upon treatment with individual proteases. While l-AA in the range 0.8-3.2mM inhibited the activity of papain, bromelain and zingibain, iso-AA acted as an inhibitor of papain but as an activator of zingibain and had no significant effect on bromelain. Both AA isoforms acted as an activator of the actinidin protease and the concentration of AA isoforms appeared to affect the level of activation of the protease. The effect of the two AA isoforms on collagen and myofibrillar protein hydrolyzing activity varied depending on the concentration of the two AA isoforms. The results indicate the ability to up and down regulate the activity of the investigated proteases by using an appropriate concentration of the AA isoform.

A meta-analysis of the effects of shockwave and high pressure processing on color and cook loss of fresh meat

Meta-analysis is a statistical approach for investigating experimental differences across studies. Meta-analyses were performed to examine the effects of hydrodynamic processing (shockwave; n=12 papers) and high pressure processing (HPP; n=8 papers) on the color and cook loss of fresh meat. Shockwave did not affect color (L*, a*), whereas cook loss was increased by 0.6% relative to untreated meat. HPP resulted in an increase in lightness (L*) and a decrease in redness (a*), with the effect being greater at higher pressures (>300MPa vs <300MPa). In addition, HPP applied at moderate pressure (<300MPa) reduced cook loss but at high pressure (>300MPa) the cook loss was increased (-1.5% vs 3.0% respectively). The increased cook loss with shockwave and high pressure (>300MPa) processing needs to be balanced against benefits in texture if this technology is applied to meat. The reduced cook loss of meat treated at moderate pressures (<300MPa) is an advantage which would likely improve sensory traits.

Novel techniques to understand consumer responses towards food products: A review with a focus on meat

Consumer evaluation has been used extensively over the past decades to evaluate acceptability and quality of food products. New methods have been developed to overcome some biases of traditional techniques. Testing with meat is challenging due to the high variability of the meat samples. This review outlines (a) the traditional consumer-based techniques for assessing food, and available methods to link consumer responses to sensory properties (b) qualitative measurements, (c) past and current methods for evaluating meat sensory characteristics and the development of the Meat Standard Australia (MSA) protocol, and (d) psychological and physiological factors affecting consumers. Conclusions from this review are: (1) Traditional consumer testing provides important information regarding acceptability but may miss important unconscious responses of consumers (2) Qualitative methods can obtain more holistic responses from consumers, (3) The Meat Standard Australia (MSA) protocol delivers consistent scores of meats juiciness/tenderness/flavour and overall acceptability from consumers, and (4) Physiological responses may help to understand the unbiased emotions of consumers.

Effect of gallic acid/chitosan coating on fresh pork quality in modified atmosphere packaging

Fresh meat safety and quality is a major concern of consumers in the current food market. The objective of this research was to investigate a newly developed gallic acid/chitosan edible coating on the preservation of fresh pork quality in modified atmosphere package (MAP) stored at 4 °C. The pork loins were coated with 2% chitosan (CHI), 0.2% gallic acid in 2% chitosan (CHI/0.2G), or 0.4% gallic acid in 2% chitosan (CHI/0.4G). Results showed that the antimicrobial activity of the chitosan coating was increased with the incorporation of gallic acid. The CHI/0.2G and CHI/0.4G pork loins also had lower lipid oxidation and myoglobin oxidation. However, the CHI/0.4G sample exhibited a pro-protein oxidation effect, suggesting an optimal concentration of gallic acid should be incorporated. This research provides a practical method in application of gallic acid/chitosan coatings on preservation of fresh pork to improve the safety and quality in MAP environment.