Contribution to energy conservation and quality improvement of frozen pork via contact/contactless immersion freezing in NaCl solution.

High energy consumption and quality deterioration are major challenges in the meat freezing process. In this study, the energy consumption and qualities of frozen pork were investigated using three freezing methods: nonpackaged pork air freezing (NAF), contactless immersion freezing (PIF) and contact immersion freezing (NIF) with NaCl solution as a refrigerant. The results indicated that NIF could improve the energy conservation and freezing efficiency in >4 freezing treatment-times by increasing the unfrozen water content, decreasing the frozen heat load, shortening the freezing time and reducing evaporation loss. NIF could also increase the a* value of the pork and improve the water-holding capacity by facilitating the conversion of free water to immobilized-water. The two immersion freezing methods could reduce freezing-thawing loss and protein loss by alleviating muscle tissue freezing damage. These results provide a suitable application of immersion freezing with energy conservation, high efficiency and good quality of frozen-pork.

Anionic polysaccharides benefit the bioavailability of pork myofibrillar protein gels: Evidence from a perspective of protein absorption and metabolism.

This study aimed to probe the bioavailability of myofibrillar protein (MP) gels in mice as affected by incorporating anionic xanthan (XMP) and sodium alginate (SMP)/cationic chitosan (CSMP)/neutral curdlan (CMP) and konjac (KMP), respectively. The results showed that the numbers of peptides absorbed were obviously higher in anionic XMP and SMP groups (88 and 126, respectively) than in the cationic CSMP (51) group. The contents of free amino acids absorbed in SMP and XMP were significantly greater than that in CSMP and CMP groups (P < 0.05). Furthermore, the antioxidant capacity of bioactive compounds absorbed in the SMP group was higher than those in the other groups (P < 0.05), and the expression of tight junction protein (Occludin and ZO-1) was up-regulated in SMP group. The low contents of free ammonia, indole and p-cresol were observed in the anionic XMP, SMP and neutral KMP groups, compared to CSMP group. This work highlights the benefits of anionic polysaccharides (sodium alginate and xanthan) in developing low-fat meat products with high MP bioavailability.

Insights into the in vitro digestibility of pork myofibrillar protein with different ionic polysaccharides from the perspective of gel characteristics.

In this work, the simulated gastrointestinal digestion of myofibrillar protein gels (MPGs) with anionic xanthan (XMP) and sodium alginate (SMP)/cationic chitosan (CSMP)/neutral curdlan (CMP) and konjac (KMP) was investigated to develop muscle-gelled foods with good qualities before and after eating. The results indicated that the neutral CMP and KMP groups had higher gel strength and protein digestibility than the CSMP group. Xanthan and sodium alginate facilitated myosin degradation in gastrointestinal digestion because of the weak wraps between protein and anionic polysaccharides, gaining plentiful peptides (1790 and 1692 respectively) with molecular weights below 2000 Da. Chitosan and neutral curdlan could improve the strength of MP gel but inhibited proteolysis and resulted in low contents of released amino acids via the strong cross-linked network blocking trypsin contact. This work provides a theoretical basis for developing low-fat meat products with good qualities and digestion behaviors by simply controlling the ionic types of polysaccharides.

In vitro digestion of a mixed gel of pork muscle and resistant starch: Salt-soluble protein perspective.

The in vitro digestion of a mixed gel (MS) of pork muscle and resistant starch (RS) was investigated and the role of the salt-soluble protein (SSP) in the function promotion of the mixed gel was clarified. The results showed that the mixed muscle gel (MS) and the addition of RS to muscle gel (M + S) presented an improved protein digestion, as indicated by a reduced particle size of the hydrolysates, more degradation of proteins with large molecular weight and more generation of free amino acids compared with the RS-free muscle gel (M). Meanwhile, the hydrolysates of the M + S and MS showed intensified DPPH radical scavenging activities. Specifically, the MS exerted preferable properties in protein digestion and antioxidant activity. Similar digestion characteristics were noticed in mixed SSP gels.The current study revealed that the reinforced functionality of the mixed muscle gel was associated with the binding relationships between SSP and RS during cooking.

Effects of Different Ionic Polysaccharides in Cooked Lean Pork Batters on Intestinal Health in Mice.

The effects of cooked lean pork batters with three ionic types of polysaccharides (anionic xanthan-gum/sodium-alginate, neutral curdlan-gum/konjac-gum and cationic chitosan) on the intestinal health of mice were investigated in this study. The results showed that the zeta potential in the sodium-alginate group (−31.35 mV) was higher (p < 0.05) than that in the chitosan group (−26.00 mV), thus promoting the protein hydrolysis in the anionic group because of electrostatic repulsion. The content of total free amino acids in the small intestine in the xanthan-gum and sodium-alginate groups (2754.68 µg and 2733.72 µg, respectively) were higher (p < 0.05) than that in the chitosan group (1949.78 µg), which could decrease the amount of undigested protein entering the colon. The two anionic groups could also increase the abundance of Lactobacillus and the balance of Faecalibaculum and Alistipes in the colon. The content of proinflammatory factor IL−6 of colon tissues in the sodium-alginate group (1.02 ng/mL) was lower (p < 0.05) than that in chitosan, curdlan-gum and konjac-gum groups (1.29, 1.31 and 1.31 ng/mL, respectively). The result of haematoxylin-eosin staining of the colon also revealed that sodium alginate was beneficial for colonic health. The two neutral groups increased the content of faecal short-chain fatty acids in mice. These results demonstrated that anionic polysaccharides have potential for developing functional low-fat meat products.

Gastrointestinal digestion and cecal fermentation of a mixed gel of lean pork meat and resistant starch in mice.

The sensitivity of meat gel to digestive enzymes and the overall digestion pattern of the meat product is vital, and exerts an important influence on the growth and metabolism of mice. In order to provide a comprehensive understanding for better usage of resistant starch (RS) in functional meat products, the effects of a mixed gel (MS, a cooked mixture) of lean pork meat and RS on the gastrointestinal digestion and cecal fermentation of mice were investigated via comparing with those of RS-free meat gel (M) and the addition of RS to meat gel (M + S). The results showed that both M + S and MS promoted gastrointestinal digestion and cecal fermentation in mice. Specifically, the MS diet contributed to the hydrolysis of proteins, the formation of beneficial amino acids, and cecal health in spite of the larger particle size for digestion than that of the M + S group. Collectively, mixed gels of meat and RS are prospective for developing healthier meat products.

Effect of salt mixture on flavor of reduced-sodium restructured bacon with ultrasound treatment.

Flavor loss from sodium reduction is a large challenge faced in the meat industry. The effects of salt mixture (KCl: CaCl2 = 1:1, w/w) content (0%-1.0%) on flavor of reduced-sodium (1.5% NaCl) restructured bacon with ultrasound treatment (UT, 600 w for 30 min) were investigated. The results showed that 0.5% salt mixture (0.25% KCl and 0.25% CaCl2) could significantly (p < .05) enhance the lipid oxidation, the protein oxidation, and the formation of free amino acids of reduced-sodium UT-restructured bacon and could also markedly (p < .05) improve its flavor and the overall quality of sensory evaluation via promoting the release of five kinds of volatile phenolic compounds (o-cresol, m-cresol, 2-methoxy-phenol, 2-methoxy-4-methylphenol, and 2-methoxy-5-methylphenol) and the formation of five kinds of volatile aldehyde compounds (hexanal, nonanal, decanal, furfural, and 5-methyl furfural). It is interesting to understand the mechanism for the effect of salt mixture on flavor and to efficiently develop a technique for improving the flavor of reduced-sodium products in the meat industry.

Effects of water-immersion cooling temperatures on the moisture retention of sodium-reduced pork sausages.

To improve the industrial yield of sodium-reduced meat products, we present a feasible method by adjusting water-immersion cooling temperatures to decrease the water loss of pork sausage during processing. The present results showed that the moisture retention capacity of sodium-reduced pork sausages (SRPS) cooled by the temperatures of 15-20 °C was larger than that of 0-10 °C. The higher cooling temperatures, especially at 20 °C, could change the movement and population of proton of inner water, decrease syneresis and facilitate the formation of homogenous cross-linked network, thus increasing the moisture retention of SRPS. Results of this work indicated that the control of cooling temperature of sodium-reduced sausages after cooking could serve as a feasible approach for improving the economic benefits and quality characteristics of the final products.

Compensation of high-pressure processing for the solubility of sodium-reduced chicken breast myosin with three anion types of potassium salts.

The effect of high-pressure processing (200 MPa, 10 min) on the solubility of chicken breast myosin with 25% molar substitution of Na+ by 3 anion types of potassium salts (KCl, K-lactate, and K-citrate) was investigated. The results showed that the lower hydrophobic group and reactive sulfhydryl group of nonpressurized myosin with the replacement of organic K-lactate or K-citrate possibly contributed to the aggregation of myosin molecules compared with the KCl group and thus decreased the solubility of both. In the presence of lactate or citrate, the high-pressure processing caused an increase in the surface hydrophobicity and reactive sulfhydryl group, indicating the unfolding of myosin molecule. Meanwhile, the increased hydration state and the decreased apparent viscosity suggested the disruption of protein-protein interactions and the strengthening of myosin-water interactions in pressurized myosin, ultimately resulting in increased solubility of the pressurized myosin with both organic potassium salts. The compensation of high-pressure processing is interesting for the efficient selection of the anion type in developing sodium-reduced industrial meat products.

Origin of high-pressure induced changes in the properties of reduced-sodium chicken myofibrillar protein gels containing CaCl2: Physicochemical and molecular modification perspectives.

The improvement mechanism of high pressure processing (HPP, 100-300 MPa, 10 min) on the gelation properties of reduced-sodium (0.3 M sodium chloride) myofibrillar protein containing 20 mM CaCl2 (MP-Ca) were explored. The results showed that the water holding capacity (WHC) and strength of MP-Ca gel reached the maximum values under 200 MPa. This was attributed to substantial solubilization of myosin heavy chain and actin, a decreased protein aggregation ability and the exposure of both tyrosine and tryptophan residues resulting from the unfolding of the protein tertiary structure. However, 300 MPa induced the hydrophobic rearrangement of MP and the disulfide cross-linking of the myosin S-1 subfragment, leading to the formation of large protein aggregates and decreased solubility of MP, thus resulting in a weaker gel with a reduced WHC. Therefore, moderate HPP (approximately 200 MPa) and low concentrations of CaCl2 could potentially improve the gelation properties of reduced-sodium meat products.

Amelioration of Growth Performance, Lipid Accumulation, and Intestinal Health in Mice by a Cooked Mixture of Lean Meat and Resistant Starch.

SCOPE: The intake of resistant starch (RS) may attenuate the risks of chronic illness, including colorectal cancer. However, whether the attenuated functionality of RS is maintained in cooked meat products needs to be clarified. METHODS AND RESULTS: The effects of a cooked mixture of lean pork meat and RS (MS) on the growth performance, lipid accumulation, and intestinal health of mice is investigated compared to those of RS-free cooked meat (M) and the addition of RS to cooked meat (M+S). The results show that both M+S and MS diets improve growth performance, alleviate lipid accumulation, and ameliorate colon health via promoting food intake and body weight gain, attenuating adipose tissue weight and triglyceride levels in liver and serum, regulating short-chain fatty acids and ammonia concentrations, ameliorating gut morphology and remodeling the gut microbiome, including Desulfovibrio, Escherichia-Shigella, Lactococcus, Ruminococcus 2, and the Firmicutes-to-Bacteroidetes ratio in mice, compared to the M diet. In particular, the MS diet exerts preferable effects on promoting growth performance and intestinal benefits and alleviating lipid accumulation in mice. CONCLUSION: Cooked mixtures of meat and RS are promising for developing novel functional meat products for nutritional health interventions.

Small Molecular Weight Aldose (d-Glucose) and Basic Amino Acids (l-Lysine, l-Arginine) Increase the Occurrence of PAHs in Grilled Pork Sausages.

(1) Background: Amino acids and carbohydrates are widely used as additives in the food industry. These compounds have been proven to be an influencing factor in the production of chemical carcinogenic compounds polycyclic aromatic hydrocarbons (PAHs). However, the effect of the properties of the amino acids and carbohydrates on the production of PAHs is still little known. (2) Methods: We added different (i) R groups (the R group represents an aldehyde group in a glucose molecule or a ketone group in a fructose molecule); (ii) molecular weight carbohydrates; (iii) polarities, and (iv) acid-base amino acids to pork sausages. The effects of the molecular properties of carbohydrates and amino acids on the formation of PAHs in grilled pork sausages were investigated. (3) Results: The results showed that a grilled sausage with aldehyde-based d-glucose was capable of producing more PAHs than a sausage with keto-based d-fructose. A higher PAH content was determined in the grilled pork sausage when the smaller molecular weight, d-glucose, was added compared with the sausage where the larger molecular weight, 4-(α-d-glucosido)-d-glucose and cellulose were added. The addition of basic amino acids (l-lysine, l-arginine) was capable of producing more PAHs compared with the addition of acidic amino acids (l-glutamic acid, l-aspartate). When amino acid containing a benzene ring was added, a smaller volume of PAHs was produced compared with the addition of other amino acids. (4) Conclusions: Our study suggests that systematic consideration of molecule properties is necessary when using food additives (amino acids and carbohydrates) for food processing.

Combined effect of CaCl2 and high pressure processing on the solubility of chicken breast myofibrillar proteins under sodium-reduced conditions.

The combined effect of calcium chloride (CaCl2) (20-100 mM) and high pressure processing (HPP, 200 MPa) on the solubility of myofibrillar proteins (MP) was investigated under sodium-reduced conditions (0.3 M sodium chloride). The results revealed that HPP combined with low concentrations (<40 mM) of CaCl2 synergistically increased the solubility of MP, but an antagonistic effect occurred when a high concentration (100 mM) of CaCl2 was present. This synergistic effect could be attributed to a mildly destabilized conformation of myosin, an increased surface hydrophobicity and the decreased total sulfhydryl group content of MP. However, CaCl2 at 100 mM destabilized myosin to a larger extent and induced non-disulfide covalent cross-linking of S-1 subfragment in pressurized MP, thus attenuating the solubilizing effect of HPP on the myosin heavy chain, resulting in the antagonistic effect. Therefore, HPP in combination with low-level CaCl2 (<40 mM) may improve the functional properties of sodium-reduced meat products.

Contribution of three ionic types of polysaccharides to the thermal gelling properties of chicken breast myosin.

The effects of anionic (κ-carrageenan, KCG), neutral (locust bean gum, LBG), and cationic polysaccharides (water-soluble chitosan, WSC) on the water-holding capacity (WHC) and hardness of chicken myosin gels were investigated at 0-1.0% addition levels. The changes of gel properties were explained using different instrumental techniques. The results revealed that KCG and LBG at 0.5-1.0% could respectively cause significant increases of both WHC and hardness of corresponding heat-induced myosin-polysaccharide gels (P < 0.05). These increases could be ascribed to a slower relaxation, reinforced cross-linked extent, enhanced hydrogen bonding, and a fine-stranded gel network, according to the analysis of low-field nuclear magnetic resonance, dynamic rheology, Fourier transform infrared spectroscopy, and scanning electron microscopy measurements. However, the weak molecular interaction within myosin-WSC gels induced an insignificant change of the WHC and hardness (P > 0.05). Therefore, it is interesting to search for the anionic polysaccharide and neutral polysaccharide for use as fat substitutes in the development of low-fat meat products.