Deep freezing to maintain the freshness of pork loin during long-term storage

Effect of Non-Meat Proteins on Storage Characteristics and Amino Acid Composition of Pork Emulsified Sausages

This study was conducted to confirm the following effects of non-meat binders (NMB) on proximate composition, pH, cooking yield, amino acids, volatile basic nitrogen (VBN), thiobarbituric acid reactive substance (TBARS), and correlation of pork emulsified sausages during refrigerated storage. The following groups of sausage samples were manufactured: Control (non-addition), BBP (1% bovine blood plasma); PBP (1% porcine blood plasma), EWP (1% white egg powder), CPPP (1% commercial porcine plasma powder), ISP (1% isolated soy protein), SP (1% seaweed powder), and SC (1% sodium caseinate). When NMB was added, ISP, SP, and SC showed higher heating yields while PBP showed lower heating yields than the control. As a result of amino acid analysis, PBP, CPPP, and SC showed significantly higher serine content than the control. EWP and SC showed significantly lower TBARS values than the control group, and VBN did not exceed 20 mg% in any treatments until the 5th week. These results demonstrate that SC is a NMB that can lower TBARS value while improving heating yield and serine content.

Conditions of the Stepwise Cooling Algorithm for Stable Supercooling Preservation and Freshness of Pork Loin

Supercooling has the advantage of maintaining the freshness of foods without a phase transition. However, it is hard to sustain the supercooled state. Static temperature control, one of the various supercooling technologies, is used for stable supercooling storage. In this experiment, the effect of following external factors in maintaining the supercooled state of foods was investigated. Three main parameters had an effect on the supercooled state of food: (1) properly setting the lower-temperature limit of the supercooling algorithm, (2) slow cooling to the target temperature, and (3) minimizing temperature fluctuation. Accordingly, the following stepwise cooling algorithm for pork loin was designed: a lower-temperature limit of −3.0 °C and a storage period = 36 h followed by a lower-temperature limit of −3.5 °C for 24 h. The samples conserved at −3.0 °C displayed a 100% supercooled state. Physicochemical properties including drip loss, cooking loss, texture, color, total volatile basic nitrogen (TVBN), and total aerobic count (TAC) of pork loin were analyzed. The drip loss values of the supercooled meat samples were lower than those of the superchilled ones. Furthermore, TVBN and TAC of the treated samples were not significantly different from those of the fresh samples (p > 0.05). In conclusion, supercooling storage extended the freshness and quality of pork loin better than refrigerated storage.

Integrated Lipidomic and Metabolomics Analysis Revealing the Effects of Frozen Storage Duration on Pork Lipids

Frozen storage is an important strategy to maintain meat quality for long-term storage and transportation. Lipid oxidation is one of the predominant causes of the deterioration of meat quality during frozen storage. Untargeted lipidomic and targeted metabolomics were employed to comprehensively evaluate the effect of frozen duration on pork lipid profiles and lipid oxidative products including free fatty acids and fatty aldehydes. A total of 688 lipids, 40 fatty acids and 14 aldehydes were successfully screened in a pork sample. We found that ether-linked glycerophospholipids, the predominant type of lipids, gradually decreased during frozen storage. Of these ether-linked glycerophospholipids, ether-linked phosphatidylethanolamine and phosphatidylcholine containing more than one unsaturated bond were greatly influenced by frozen storage, resulting in an increase in free polyunsaturated fatty acids and fatty aldehydes. Among these lipid oxidative products, decanal, cis-11,14-eicosenoic acid and cis-5,8,11,14,17-dicosapentaenoic acid can be considered as potential indicators to calculate the freezing time of unknown frozen pork samples. Moreover, over the three-month frozen storage, the first month was a rapid oxidation stage while the other two months were a slow oxidation stage.

Effect of Different Degrees of Deep Freezing on the Quality of Snowflake Beef during Storage

In order to elucidate whether deep freezing could maintain the quality of snowflake beef, three different deep freezing temperatures (−18 °C, −40 °C, and −60 °C) were used in order to evaluate the changes in tissue structures, quality characteristics and spoilage indexes, and their comparative effects on the quality of snowflake beef. Compared to samples frozen at −18 °C, those stored at −40 °C and −60 °C took a shorter time to exceed the maximum ice crystallization zone (significantly reduced by 2–6 h). In terms of short-term storage, samples frozen at −40 °C and −60 °C had better tissue structure and lower drip loss rate than those frozen at −18 °C; significant differences between groups in drip loss were observed between −18 °C and −60 °C. Moreover, a better bright red color and lower shear force were maintained at −40 °C and −60 °C, with significant differences in shear force between the −18 °C group and the other two groups on day 60. Although there were significant effects on the inhibition of lipid and protein oxidation at −40 °C and −60 °C; no significant variation was observed between these two groups throughout storage. A similar phenomenon was found in flavor, with 1-pentanol identified as an important potential indicator of flavor change in snowflake beef during storage. This study demonstrated that −40 °C and −60 °C had favorable impacts on the quality maintenance of snowflake beef compared to −18 °C. These findings provide a theoretical basis for effective stability of snowflake beef quality during frozen storage.

Proteomics and Metabolomics Profiling of Pork Exudate Reveals Meat Spoilage during Storage

Previous studies have evaluated pork quality by omics methods. However, proteomics coupled with metabolomics to investigate pork freshness by using pork exudates has not been reported. This study determined the changes in the profiles of peptides and metabolites in exudates from pork stored at different temperatures (25, 10, 4, and −2 °C). Multivariate statistical analysis revealed similar changes in profiles in exudates collected from pork stored at −2 and 4 °C, and additional changes following storage at higher temperatures. We identified peptides from 7 proteins and 30 metabolites differing in abundance between fresh and spoiled pork. Significant correlations between pork quality and most of the peptides from these 7 proteins and 30 metabolites were found. The present study provides insight into changes in the peptide and metabolite profiles of exudates from pork during storage at different temperatures, and our analysis suggests that such changes can be used as markers of pork spoilage.

The Investigation of Protein Profile and Meat Quality in Bovine Longissimus thoracic Frozen under Different Temperatures by Data-Independent Acquisition (DIA) Strategy

The influence of freezing on the protein profile and quality traits in bovine Longissimus thoracic (LT) muscle was investigated by the data-independent acquisition (DIA) technique. Compared to fresh meat, a total of 262 proteins were identified as differential abundance proteins (DAPs) in four frozen groups (−12 °C, −18 °C, −38 °C, and −80 °C). According to the bioinformatics analysis, most of the DAPs in the significant Go terms and the KEGG pathway were structure proteins and enzymes. Proteome changes in the frozen bovine muscle at −12 °C and −18 °C were more significant than those at −38 °C and −80 °C. The result was consistent with the deterioration trend of the meat quality. The correlation analysis revealed that 17 proteins were correlated closely with the color, shear force, thawing loss, and cooking loss of the frozen meat, which could be used as putative biomarkers for frozen meat quality. MYO18A and ME3 are newly discovered proteins that are associated with frozen beef quality. In addition, CTTN and SERPINB6 were identified in frozen groups, which exhibited a significant inverse correlation with thawing loss (p < 0.01). These findings reveal the quality changes induced by freezing at the protein molecular level and provide new insights into the control of quality deterioration.

Changes in Physico-Chemical and Storage Properties of Dry-Aged Beef Loin Using Electric Field Refrigeration System

The aim of this study is to establish the dry aging period of beef loin in an electric field refrigeration system. Beef loins (Korea quality grade 2) were dry aged at 0, −1, and −2 °C temperature in an electric field refrigeration system (air velocity, 5 ± 2 m/s) and aging stopped as the value of TPC reached 7 log CFU/g. Samples were examined by aging yield, trimming yield, pH, color, water holding capacity (WHC), cooking yield, shear force, total plate count (TPC), 2-thiobarbituric acid reactive substances (TBARS), and volatile basic nitrogen (VBN). The results for aging yield, trimming yield, redness, yellowness, and chroma decreased with increasing the dry aging period. Contrariwise, those for pH, lightness, hue angle, WHC, and cooking yield increased with the dry aging period. In shear force, the lowest value occurred at four weeks at all temperatures. The results for TPC, TBARS, and VBN increased with aging period, and VBN at 6 weeks at 0 °C and 9 weeks at −1 °C exceed the standard value (20 mg/100 g), while dry aging temperature had an effect on physico-chemical and storage properties by lower temperatures showed slower progress. Therefore, dry aging on an electric field refrigerate system can be used until 4 weeks at 0 °C, 8 weeks at −1 °C, and 10 weeks at −2 °C. However, considering physico-chemical properties, 4 weeks at every temperature is suitable for manufacturing soft dry-aged beef loin.

Antimicrobial property of Pichia pastoris-derived natto peptide against foodborne bacteria and its preservative potential to maintain pork quality during refrigerated storage

Pork spoilage caused by foodborne bacteria contamination always leads to substantial economic loss in the meat industry. The toxicity and drug resistance of chemical preservatives have raised public concerns about their safety and stability. In this study, natto peptide from Pichia pastoris was prepared using DNA recombinant technology. It showed an excellent antibacterial effect against Gram-positive and -negative bacteria, with minimum inhibitory concentrations (MICs) ranging from 6 to 30 μg/ml. Of note, natto peptide exhibited low cytotoxicity and hemolytic activity. The application of natto peptide on pork during refrigerated storage dramatically decreased the growth of Staphylococcus spp., Escherichia spp., and Pseudomonas spp. The bactericidal properties remained in force when natto peptide was used in pork models contaminated with artificial bacteria. Moreover, the application of natto peptide (90 μg/ml) inhibited the increase in pH variation and drip loss, decreased the generation of total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARS), and maintained a high sensory quality score during pork storage. These results implied that P. pastoris-derived natto peptide could extend the storage time of pork, and it has the potential to be a promising antiseptic biopreservative to replace chemical preservatives.