Variability in the contents of pork meat nutrients and how it may affect food composition databases

Mulberry Leaf Dietary Supplementation Can Improve the Lipo-Nutritional Quality of Pork and Regulate Gut Microbiota in Pigs: A Comprehensive Multi-Omics Analysis

Mulberry leaves, a common traditional Chinese medicine, represent a potential nutritional strategy to improve the fat profile, also known as the lipo-nutrition, of pork. However, the effects of mulberry leaves on pork lipo-nutrition and the microorganisms and metabolites in the porcine gut remain unclear. In this study, multi-omics analysis was employed in a Yuxi black pig animal model to explore the possible regulatory mechanism of mulberry leaves on pork quality. Sixty Yuxi black pigs were divided into two groups: the control group (n = 15) was fed a standard diet, and the experimental group (n = 45) was fed a diet supplemented with 8% mulberry leaves. Experiments were performed in three replicates (n = 15 per replicate); the two diets were ensured to be nutritionally balanced, and the feeding period was 120 days. The results showed that pigs receiving the diet supplemented with mulberry leaves had significantly reduced backfat thickness (p < 0.05) and increased intramuscular fat (IMF) content (p < 0.05) compared with pigs receiving the standard diet. Lipidomics analysis showed that mulberry leaves improved the lipid profile composition and increased the proportion of triglycerides (TGs). Interestingly, the IMF content was positively correlated with acyl C18:2 and negatively correlated with C18:1 of differential TGs. In addition, the cecal microbiological analysis showed that mulberry leaves could increase the abundance of bacteria such as UCG-005, Muribaculaceae_norank, Prevotellaceae_NK3B31_group, and Limosilactobacillus. Simultaneously, the relative levels of L-tyrosine-ethyl ester, oleic acid methyl ester, 21-deoxycortisol, N-acetyldihydrosphingosine, and mulberrin were increased. Furthermore, we found that mulberry leaf supplementation significantly increased the mRNA expression of lipoprotein lipase, fatty acid-binding protein 4, and peroxisome proliferators-activated receptor γ in muscle (p < 0.01). Mulberry leaf supplementation significantly increased the mRNA expression of diacylglycerol acyltransferase 1 (p < 0.05) while significantly decreasing the expression of acetyl CoA carboxylase in backfat (p < 0.05). Furthermore, mulberry leaf supplementation significantly upregulated the mRNA expression of hormone-sensitive triglyceride lipase and peroxisome proliferator-activated receptor α (p < 0.05) in backfat. In addition, mulberry leaf supplementation led to increased serum leptin and adiponectin (p < 0.01). Collectively, this omic profile is consistent with an increased ratio of IMF to backfat in the pig model.

Active packaging: Development and characterization of polyvinyl alcohol (PVA) and nitrite film for pork preservation

In this study, an active films of polyvinyl alcohol (PVA) films, incorporated with sodium nitrite were developed, characterized and applied to pork stored for six days at 25 °C. As for the film characterization by FTIR, no chemical interactions were observed between nitrite and PVA under the studied conditions. The physical properties of the PVA films were not altered by the presence of nitrite. PVA films incorporated with 100 ppm nitrite reduced TBARS values of refrigerated pork from 0.63 µmol MDA/g (control) to 0.49 µmol MDA/g (PVA 01). Color changes were observed in all meat samples packaged with the film. It is concluded that the presence of nitrite does not interfere in the physical properties of the PVA films and that the developed films have an active potential for application in pork in natura.

Comparison of the Fatty Acid Composition and Small Molecular Metabolites between Yanjin Blackbone Chicken and Piao Chicken Meat

The fatty acid composition and small molecular metabolites in breast and leg meat of Yanjin blackbone chickens (YBC) and Piao chickens (PC) were detected by gas chromatography-mass spectrometry and liquid chromatography-quadrupole static field orbital trap mass spectrometry. Thirty-two fatty acids were detected, and the total fatty acid content of PC was significantly higher than that of YBC (p<0.05). Oleic acid, linoleic acid, palmitic acid, stearic acid, and arachidonic acid were the main fatty acids in the two chicken varieties, and the composition of fatty acids in the two varieties were mainly unsaturated fatty acids, being more than 61.10% of the total fatty acids. Meanwhile, 12 and 16 compounds were screened out from chicken legs and chicken breasts of YBC and PC, respectively, which had important contributions to the differences between groups.

Elemental profiles of swine tissues as descriptors for the traceability of value-added Italian heavy pig production chains

The increasing demand for reliable traceability tools in the meat supply chain has prompted the exploration of innovative approaches that meet stringent quality standards. In this work, 57 elements were quantified by inductively coupled plasma mass spectrometry and direct mercury analysis in 80 muscle and 80 liver samples of Italian heavy pigs to investigate the potential of new tools based on multi-elemental profiles in supporting value-added meat supply chains. Samples from three groups of animals belonging to the protected designation of origin (PDO) Parma Ham circuit (conventionally raised; raised with genetically modified organism (GMO)-free feeds; raised with GMO-free feeds plus the supplementation of omega-3 polyunsaturated fatty acids (n-3 PUFA)) and a fourth group of samples from animals not compliant with the PDO Parma Ham production process were analyzed. Hierarchical cluster analysis allowed for the identification of three macro-clusters of liver or muscle samples, highlighting some inhomogeneities among the target groups. Following SIMCA analysis, better classification models were obtained by using liver elemental profiles (95% correct classification rate), with the highest classification accuracy observed for GMO-free livers (100%). The elements contributing the most to the separation of livers by class membership were La, Ce, and Pb for conventional, Li, Cr, Fe, As, and Sr for GMO-free + n-3 PUFA, and Lu for non-PDO samples. Given these findings, the analysis of the elemental profiles of pig tissues can be regarded as a promising method to confirm the declared pig meat label attributes, deter potential complex fraud, and support meat traceability systems.

Effect of muscle fibre types and carnosine levels on the expression of carnosine-related genes in pig skeletal muscle

It is generally accepted that carnosine (β-alanyl-L-histidine) content is higher in glycolytic than in oxidative muscle fibres, but the underlying mechanisms responsible for this difference remain to be elucidated. A first study to better understand potential mechanisms involved was undertaken (1) to determine whether differences in the expression of carnosine-related enzymes (CARNS1, CNDP2) and transporters (SLC6A6, SLC15A3, SLC15A4, SLC36A1) exist between oxidative and glycolytic myofibres and (2) to study the effect of carnosine on myoblast proliferative growth and on carnosine-related gene expression in cultured myoblasts isolated from glycolytic and oxidative muscles. Immunohistochemistry analyses were conducted to determine the cellular localization of carnosine-related proteins. Laser-capture microdissection and qPCR analyses were performed to measure the expression of carnosine-related genes in different myofibres isolated from the longissimus dorsi muscle of ten crossbred pigs. Myogenic cells originating from glycolytic and oxidative muscles were cultured to assess the effect of carnosine (0, 10, 25 and 50 mM) on their proliferative growth and on carnosine-related gene expression. The mRNA abundance of CNDP2 and of the studied carnosine transporters was higher in oxidative than in glycolytic myofibres. Since carnosine synthase (CARNS1) mRNA abundance was not affected by either the fibre type or the addition of carnosine to myoblasts, its transcriptional regulation would not be the main process by which carnosine content differences are determined in oxidative and glycolytic muscles. The addition of carnosine to myoblasts leading to a dose-dependent increase in SLC15A3 transcripts, however, suggests a role for this transporter in carnosine uptake and/or efflux to maintain cellular homeostasis.

Homeopathic Products as a Complementary Dietary Additive for Pigs in their Growing and Finishing Phases

BACKGROUND

Homeopathic products (HP) have been proposed for the prevention of disease and as a complementary dietary additive in pig farming, with resulting improved performance and quality of life of the animals and with benefits for food safety. The aim of this study was to assess the addition of HP to pig feed and its effects on growth performance, dietary protein utilization, nutrient digestibility, meat quality, and economic feasibility.

METHODS

A total of 80 male pigs, body weight 32.8±2.3kg, were allocated in a randomized design, with two treatments of 10 replications and four animals per experimental unit. Treatments were composed of a control diet (CD) or CD+HP (Finalvitaplus+Figotonus, 1.1kg/ton feed of each product). The outcome measures used were growth performance (body weight gain) and feed efficiency (body weight gain per unit of feed consumed), efficiency of dietary protein utilization (blood urea nitrogen), nutrient digestibility (apparent digestibility coefficient and apparent nutrient digestibility), meat quality (including pH, temperature, color, liquid loss by cooking and thawing, intramuscular fat and meat tenderness), and economic feasibility (cost of the diets).

RESULTS

There was no effect (p >0.05) of treatments on growth performance of the pigs, though the group that received HP showed an 8.93% greater feed efficiency than the control group (p=0.077). The animals in the control group had a 14.37% higher blood urea nitrogen concentration in the finishing I phase (70-100kg body weight) compared with those fed HP (p=0.028), indicating lower protein utilization in the controls. There was comparative improvement in digestibility coefficient and in nutrient digestibility in pigs fed HP in the growing-finishing phase (p <0.05). There was no differential effect of treatments on meat quality or economic feasibility (p >0.05).

CONCLUSION

The addition of HP to the diet of growing-finishing pigs produced some improvement in their dietary protein utilization, nutrient digestibility and feed efficiency, though it did not affect their growth performance, meat quality or economic feasibility.

Biotransformation of pork trimmings into protein hydrolysate using microbial proteases aided by response surface methodology

Meat processing generates significant amounts of by-products such as trimmings that require further valorization. In this study, pork trimmings were transformed with proteases to protein hydrolysates that may find applications as nutritional and/or flavouring ingredients. Four microbial proteases-Flavourzyme, Protamex, Alcalase, and Neutrase were explored to hydrolyze pork trimmings. Flavourzyme, which showed the highest degree of hydrolysis (DH), was selected to optimize the key hydrolytic parameters using response surface methodology (RSM) with Box-Behnken design. The optimal conditions were found to be 6: 100 (enzyme/substrate ratio), 50 °C, and pH 6 for a maximum DH at 48% after 6 h of hydrolysis. The protein hydrolysate was high in free amino acids (17 g/100 g dry weight), of which essential and taste-active amino acids accounted for 42% and 20%, respectively. The obtained hydrolysate may be considered suitable as a nutritional and/or flavouring ingredient.

Effect of Dietary Brown Seaweed (Macrocystis pyrifera) Additive on Meat Quality and Nutrient Composition of Fattening Pigs

The objective of this study was to evaluate the effects of dietary brown seaweed (Macrocystis pyrifera) additive (SWA) on meat quality and nutrient composition of commercial fattening pigs. The treatments were: Regular diet with 0% inclusion of SWA (CON); Regular diet with 2% SWA (2%-SWA); Regular diet with 4% SWA (4%-SWA). After slaughtering, five carcasses from each group were selected, and longissimus lumborum (LL) samples were taken for meat quality and chemical composition analysis. Meat quality traits (except redness intensity) were not affected (p > 0.05) by treatments. Samples from the 4%-SWA treatment showed the lowest a value than those from the 2%-SWA and CON treatments (p = 0.05). Meat samples from the 4%-SWA group contained 3.37 and 3.81 mg/100 g more of muscle cholesterol than CON and 2% SWA groups, respectively (p < 0.05). The SWA treatments affected (p ≤ 0.05) the content of ash, Mn, Fe, and Cu. The LL samples from 4%-SWA had the highest content of ash; however, they showed 0.13, 0.45, and 0.23 less mg/100 g of Mn, Fe, and Zn, respectively, compared to samples from CON (p ≤ 0.05). Fatty acids composition and macro minerals content (Na, Mg, and K) did not show variation due to the SWA treatments. Further studies are needed to understand the biological effects of these components on adipogenesis, cholesterol metabolism, and mineral deposition in muscle.

A systematic review to identify biomarkers of intake for fermented food products

Background

Fermented foods are ubiquitous in human diets and often lauded for their sensory, nutritious, and health-promoting qualities. However, precise associations between the intake of fermented foods and health have not been well-established. This is in part due to the limitations of current dietary assessment tools that rely on subjective reporting, making them prone to memory-related errors and reporting bias. The identification of food intake biomarkers (FIBs) bypasses this challenge by providing an objective measure of intake. Despite numerous studies reporting on FIBs for various types of fermented foods and drinks, unique biomarkers associated with the fermentation process (“fermentation-dependent” biomarkers) have not been well documented. We therefore conducted a comprehensive, systematic review of the literature to identify biomarkers of fermented foods commonly consumed in diets across the world.

Results

After title, abstract, and full-text screening, extraction of data from 301 articles resulted in an extensive list of compounds that were detected in human biofluids following the consumption of various fermented foods, with the majority of articles focusing on coffee (69), wine (69 articles), cocoa (62), beer (34), and bread (29). The identified compounds from all included papers were consolidated and sorted into FIBs proposed for a specific food, for a food group, or for the fermentation process. Alongside food-specific markers (e.g., trigonelline for coffee), and food-group markers (e.g., pentadecanoic acid for dairy intake), several fermentation-dependent markers were revealed. These comprised compounds related to the fermentation process of a particular food, such as mannitol (wine), 2-ethylmalate (beer), methionine (sourdough bread, cheese), theabrownins (tea), and gallic acid (tea, wine), while others were indicative of more general fermentation processes (e.g., ethanol from alcoholic fermentation, 3-phenyllactic acid from lactic fermentation).

Conclusions

Fermented foods comprise a heterogeneous group of foods. While many of the candidate FIBs identified were found to be non-specific, greater specificity may be observed when considering a combination of compounds identified for individual fermented foods, food groups, and from fermentation processes. Future studies that focus on how fermentation impacts the composition and nutritional quality of food substrates could help to identify novel biomarkers of fermented food intake.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12263-021-00686-4.

Evaluation of small molecular metabolites and sensory properties of Xuanwei ham salted with partial replacement of NaCl by KCl

The study was to understand the effect of the partial substitution of NaCl by KCl on small molecular metabolites and sensory quality of Xuanwei ham. Thirty green hams were randomly divided into five treatments, and salted with 100% NaCl (I), 70% NaCl+30% KCl (II), 60% NaCl+40% KCl (III), 50% NaCl+50% KCl (IV) and 40% NaCl+60% KCl (V), respectively. With the increase of KCl substitution, the moisture content of Xuanwei ham increased. Non-targeted ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-Q-Exactive-MS) was used to study the effect of partial substitution of NaCl by KCl, and twenty-eight metabolites were identified as markers of small molecular metabolites in the different treatments. KCl substitution promoted the release of tryptophan, histidine, citrulline, lysine, creatine and oleic acid, which contributed to improve the flavor and taste of ham. Therefore, the treatment II and III could reduce the NaCl content of Xuanwei ham by 30% and 40%, and maintained a better sensory acceptability.

Elemental composition of pork meat from conventional and animal welfare farms by inductively coupled plasma-optical emission spectrometry (ICP-OES) and ICP-mass spectrometry (ICP-MS) and their authentication via multivariate chemometric analysis

The demand of consumers from around the world for natural, nutritional and palatable pork meat is increasing with time. This study analyzed macro (Ca, K, Mg, Na, P), micro (Fe, Zn, Cr, Mn, Ni, Cu, Se, Sr, Cs), trace (Li, Be, V, Co, Ga, Ba, U), and toxic trace (As, Cd, TI, and Pb) elements of pork meat from conventional and animal welfare farms in South Korea. Among the elements analyzed by inductively coupled plasma-optical emission, and mass spectrometric (ICP-OES, ICP-MS) techniques, K, Fe, Mn, and Ni content were higher in animal welfare pork meat. The trace and toxic trace elements content were lower than the standard values. The principal component and linear discriminant analyses (PCA, LDA) explained the highest variance (99.82%, 99.00%) of the group based on toxic elements. These findings can thus be used to evaluate animal welfare and conventional farms pork meat quality in South Korea as well as worldwide.

Authentication of organic pork and identification of geographical origins of pork in four regions of China by combined analysis of stable isotopes and multi-elements

The purpose of this study was to verify that the organic status of pork purchased in the markets from four different regions of China can be authenticated by the combined analysis of stable isotopes and multiple elements. Four stable isotope ratios (δ¹³C, δ¹⁵N, δ²H and δ¹⁸O) and the concentrations of seven elements (K, Na, Mg, Ca, Fe, Cu and Se) were determined in organic and conventional pork samples from four locations of China. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to analyze stable isotope ratios and multi-element concentrations in pork. Based on the limited database of analytical values, the methodology would be potentially able to confirm whether a sample of pork came from the region and organic status it claimed. These results provide a possibility for authenticity of organic agricultural products from a large scope such as a province even a country.

Comparative study of nutritional composition and color traits of meats obtained from the horses and Korean native black pigs raised in Jeju Island

OBJECTIVE

The present study aimed at comparing the nutritional composition and color traits between two meat types: Horse meat and pork from Korean native black pigs raised in Jeju Island.

METHODS

After slaughter 24 h, the longissimus dorsi samples were taken from left side carcasses of the 32-mo-old Jeju female breed horses and the 6-mo-old Korean native black pigs (n = 10 each). The samples were then placed into cool boxes containing ice packs and transported to the Laboratory of Meat Science where all visual fats and connective tissues were trimmed off and then the samples were ground. All the samples were analyzed for nutritional composition (proximate composition, minerals, vitamins, fatty acids, and amino acids) and color traits.

RESULTS

The horse meat contained significantly higher collagen, moisture and protein than the pork (p<0.05). The Jeju horse meat showed more desirable fatty acid profiles such as containing significantly lower saturated fatty acids (SFA), higher polyunsaturated fatty acids (PUFA) contents and PUFA/SFA ratios than the pork (p<0.05). Differences in concentrations of ten amino acids existed between the two meat types in which the horse meat had higher values for all these amino acids, total amino acids (20.33 g/100 g) and essential amino acids (10.06 g/100 g) than the pork (p<0.05). Also, the horse meat showed significantly higher concentrations of Fe (34.21 mg/100 g) and Cu (2.47 mg/100 g) than the pork (Fe, 17.42 mg/100 g and Cu, 1.51 mg/100 g) (p<0.05). All the vitamins detected showed statistical differences between the two meat types in which the horse meat had higher concentrations of vitamin B1 (25.19 mg/100 g), B2 (92.32 mg/100 g), B3 (2,115.51 mg/100 g), and B5 (67.13 mg/100 g) than the pork (p<0.05).

CONCLUSION

Based on the results obtained in the study, it is concluded that the two meat types studied are rich in nutrients and the animal species strongly affected the nutritional values and color traits of the muscle tissues.

1 H-NMR-based water-soluble low molecular weight compound characterization and fatty acid composition of boiled Wuding chicken during processing

BACKGROUND

Boiled Wuding chicken was produced using whole chicken by washing, boiling 1 h with salt, deep frying, and boiling 2 h. The effect of the process on the water-soluble low molecular weight (WLOM) compound profiles of products was characterized using proton nuclear magnetic resonance spectroscopy, and the fatty acid composition of products was analyzed using gas chromatography-mass spectrometry.

RESULTS

The metabolome was dominated by 49 WLOM compounds, and 22 fatty acid compounds were detected. Principal component (PC)1 and PC2 explained a total of 93.4% and 3% of variance respectively. Compared with the control group, the total WLOM compound and fatty acid contents of the chicken breast were significantly decreased in the other three processing stages (P < 0.05). Comprehensive multivariate data analysis showed significant differences about precursor substance between the different processing including creatine, lactate, creatinine, glucose, taurine, anserine, and acetate (P < 0.05).

CONCLUSION

These results contribute to a more accurate understanding of precursor substance changes of flavor in chicken meat during processing. Boiled, treated chicken had significant effects on fatty acid and WLOM compounds. © 2018 Society of Chemical Industry.

Metabolic stability of cells for extended metabolomical measurements using NMR. A comparison between lysed and additionally heat inactivated cells

NMR measurements for metabolic characterization of biological samples like cells, biopsies or plasma, may take several hours for advanced methods. Preanalytical issues, such as sample preparation and stability over the measurement time, may have a high impact on metabolite content, and potentially lead to misinterpretation. The aim of this study was therefore to investigate by ¹H HR-MAS NMR the impact of different cell handling preparation protocols on the stability of the cell metabolite content over the measurement time. For this purpose, the metabolite content of fibroblasts and adrenal cells were measured at different time points after lysis and after additional heating. Interestingly the results showed similar metabolite concentrations between lysed and lysed-heated cells at the beginning of the measurement, but increasing differences after some hours of measurement. In lysed cells, metabolism was ongoing, producing metabolite changes over time, contrary to a stable metabolite content of the lysed-heated cells. These results were confirmed in both fibroblasts and adrenal cells. Therefore, in order to minimize metabolite content modifications over the measurement time, it is suggested to use cell lysis in combination with heat inactivation for extended HR-MAS NMR measurements.

1H NMR-based metabolic characterization of Chinese Wuding chicken meat

The aim of this study was to evaluate the chemical composition of precursor flavor substance of Wuding chicken with the age of 110, 140, 170, 200 and 230 days. The metabolic composition of chicken meat was studied using ¹H nuclear magnetic resonance (NMR) spectroscopy. Compared with 110 days, the total metabolite content was significantly higher in other four periods for the chicken breast and leg meat (P < 0.01). Organic acid and small peptides were the two most metabolites for the chicken breast and leg meat. Comprehensive multivariate data analysis showed significant differences about precursor substance between the chicken samples of 230 days and other four ages including lactate, creatine, IMP, glucose, carnosine, anserine, taurine and glutamine (P < 0.05). These results contribute to a further understanding of changes in chicken meat metabolism as chicken ages, which could be used to help assess the quality of chicken meat.

Non-Destructive Spectroscopic Techniques and Multivariate Analysis for Assessment of Fat Quality in Pork and Pork Products: A Review

Fat is one of the most important traits determining the quality of pork. The composition of the fat greatly influences the quality of pork and its processed products, and contribute to defining the overall carcass value. However, establishing an efficient method for assessing fat quality parameters such as fatty acid composition, solid fat content, oxidative stability, iodine value, and fat color, remains a challenge that must be addressed. Conventional methods such as visual inspection, mechanical methods, and chemical methods are used off the production line, which often results in an inaccurate representation of the process because the dynamics are lost due to the time required to perform the analysis. Consequently, rapid, and non-destructive alternative methods are needed. In this paper, the traditional fat quality assessment techniques are discussed with emphasis on spectroscopic techniques as an alternative. Potential spectroscopic techniques include infrared spectroscopy, nuclear magnetic resonance and Raman spectroscopy. Hyperspectral imaging as an emerging advanced spectroscopy-based technology is introduced and discussed for the recent development of assessment for fat quality attributes. All techniques are described in terms of their operating principles and the research advances involving their application for pork fat quality parameters. Future trends for the non-destructive spectroscopic techniques are also discussed.

Differences on meat colour and composition between ‘Landrace × Large White’ and ‘Iberian’ pigs under identical nutritional and management conditions

In pig production, factors such as nutritional system and genotype affect quality characteristics of meat. This study was aimed to evaluate differences in nutritional composition and colour of meat between Iberian (IB) and Landrace × Large White (LLW) pigs reared under identical nutrition and management conditions. Nutrient composition, mineral content, fatty acid profile and instrumental colour of two muscles (longissimus thoracis and biceps femoris) were examined at two growing stages (50- and 115-kg weight). Significant differences were found in relation to genotype. IB muscles contained higher amounts of intramuscular fat, dry matter, monounsaturated fatty acids, iron and zinc, and were redder (higher a* value) and with less colour saturation (lower hue angle), than those from LLW pigs. Significant relationships between colour coordinates with the mineral content and the lipid profile of muscles were found: redness was mainly linked to iron, zinc and monounsaturated fatty acids levels, whereas yellowness was positively related with copper, polyunsaturated fatty acids and linoleic acid level. The results of the present study support that muscles from the IB pig genotype have special characteristics, which may enhance the overall quality of meat compared with conventional or high-lean porcine breeds, even under identical management system, due to its particular fat composition and colour attributes.

Comparison of the meat metabolite composition of Linwu and Pekin ducks using 600 MHz 1H nuclear magnetic resonance spectroscopy

In an effort to further understand of the differences of meat flavor and texture between Linwu ducks and Pekin ducks at market age, we investigated the meat metabolite composition of the two breeds of ducks using 600 MHz ¹H nuclear magnetic resonance (NMR) spectroscopy. Comprehensive multivariate data analysis including principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal projection to latent structure-discriminant analysis (OPLS-DA) were applied to analyze the ¹H-NMR profiling data to identify the distinguishing metabolites of breast meat between two breeds of ducks. Compared with 42-d-old Pekin duck meat, breast from 72-d-old Linwu duck has higher concentration of anserine, carnosine, homocarnosine, and nicotinamide, but significantly lower concentration of succinate, creatine, and myo-inositol. These results contribute to a better understanding of the differences in meat metabolite composition between 72-d-old Linwu and 42-d-old Pekin ducks, which could be used to help assess the quality of duck meat as a food.

The Impact of Proteolytic Pork Hydrolysate on Microbial, Flavor and Free Amino Acids Compounds of Yogurt

The aim of this study was to investigate the influence of proteolytic pork hydrolysate (PPH) on yoghurt production by Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. Fresh lean pork was cut into pieces and mixed with deionized water and dealt with protease, then the resulting PPH was added to milk to investigate the effects of PPH on yoghurt production. The fermentation time, the viable cell counts, the flavor, free amino acids compounds, and sensory evaluation of yoghurt were evaluated. These results showed that PPH significantly stimulated the growth and acidification of the both bacterial strains. When the content of PPH reached 5% (w/w), the increased acidifying rate occurred, which the fermentation time was one hour less than that of the control, a time saving of up to 20% compared with the control. The viable cell counts, the total free amino acids, and the scores of taste, flavor and overall acceptability in PPH-supplemented yoghurt were higher than the control. Furthermore, the contents of some characteristic flavor compounds including acids, alcohols, aldehydes, ketones and esters were richer than the control. We concluded that the constituents of PPH such as small peptide, vitamins, and minerals together to play the stimulatory roles and result in beneficial effect for the yoghurt starter cultures growth.