Antioxidant activity of venison subjected to in vitro cooking and gastrointestinal digestion and isolation of its 2,2-diphenyl-1-picrylhydrazyl radical scavenging peptides.

Venison, a type of game meat, has several health benefits because it contains not only high protein and low fat but also bioactive peptides with several physiological properties, including antioxidative and angiotensin-converting enzyme inhibitory properties. The aim of the present study was to investigate the antioxidant activity of venison treated by in vitro cooking and gastrointestinal digestion. We subjected venison along with pork and beef to in vitro cooking and digestion and assessed their antioxidant activity via 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH-RS) and hydrophilic oxygen radical absorbance capacity (H-ORAC) assays. The peptide contents of all types of cooked and digested meat samples were higher than those of the untreated and cooked samples. The DPPH-RS activities and H-ORAC of digested venison, pork, and beef were increased compared with those of untreated samples. DPPH-RS activity was significantly higher in the digested venison samples than in the digested pork and beef samples. In this study, several fractions of digested venison from the chromatography exhibited DPPH-RS activity. Peptide analysis, using liquid-chromatography with tandem mass spectrometry, unveiled two peptides DIDDLELTLAK and TQTVCNFTDGALVQHQEWDGK with high DPPH-RS activities. Thus, venison is a rich source of antioxidant peptides and potentially demonstrate an antioxidation ability by digestive enzymes in vivo.

Reducing Effects of Whey Protein Hydrolysate on Coloration of Cured Sausages.

Curing produces a characteristic pink color during meat processing through the production of nitrosyl myoglobin (NOMb), which requires nitric oxide (NO). Nitrites and nitrates in coloring agents are crucial NO sources; however, a reducing agent is necessary to facilitate their chemical conversion to NO. This study aimed to investigate the effect of the reducing properties of whey protein hydrolysate (WPH) on the reddening of cured meat products. Cured and cooked sausage models were treated with WPH, which enhanced the reddening of the meat color and increased the a* value in the models compared with that of the controls. Additionally, ethanol-extracted WPH induced Fe3⁺ reduction, lowered oxidation-reduction potential, and decreased nitrite (NO2-) levels. Moreover, ethanol-extracted WPH promoted the formation of NOMb in myoglobin solution. This effect was also observed when ethanol-extracted WPH treated with maleimide was used, implying that certain peptides rather than the thiol group of WPH are involved in promoting NOMb formation. Furthermore, the peptides that decreased NO2- levels were isolated from ethanol-extracted WPH, identified, and synthesized. These synthesized peptides, particularly the FFVAPFPEVFGK peptide, showed NO2--reducing activity. Hence, WPH may promote the coloration of cured meat products through the reducing potential of the peptides contained within.

Effects of Inherent Lactic Acid Bacteria on Inhibition of Angiotensin I-Converting Enzyme and Antioxidant Activities in Dry-Cured Meat Products.

The aim of this study was to investigate the inherent bacteria that contribute to expressing the angiotensin I-converting enzyme (ACE) inhibitory activity and the antioxidant activity of dry-cured meat products without a bacterial starter. Among the ten dry-cured meat product samples, Coppa and Milano salami exhibited high ACE inhibitory activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability, and oxygen radical absorbance capacity (ORAC). No consistent trend was observed in the pH values or the total peptide and imidazole dipeptide concentration of the products that exhibited high ACE inhibitory and antioxidant activities in the tested samples. To investigate the bacteria contributing to the ACE inhibitory and antioxidant activities of the product, 16S rRNA sequencing analysis, isolation, and identification of bacteria were performed using not only Coppa and Milano salami but also the Jamon Serrano and Parma prosciutto products that had low functional activities. Results suggest the Lactobacillales order, particularly the species Latilactobacillus sakei and Pediococcus pentosaceus, were the main inherent bacteria in Coppa and Milano salami, respectively, compared with the Jamon Serrano and Parma prosciutto products. Therefore, the inherent lactic acid bacteria in dry-cured meat products without bacterial starter is important for ACE inhibitory and antioxidant activities of the products.

The effects of different protease treatments on the techno-functional, structural, and bioactive properties of bovine casein.

In this study, bovine sodium caseinate (NaCas) was hydrolyzed with four proteases, alcalase, savinase, subtilisin A, and flavourzyme. In addition to the structural changes occurred through the enzymatic hydrolysis, the solubility, oil binding capacity, zeta potential, emulsification properties, and in vitro antioxidant capacity, anti-carcinogenic and antidiabetic properties of hydrolysates were determined. FTIR combined with hierarchical cluster analysis (HCA) made in Amide I region enable to classification of the samples based on the changes of the secondary structure depending on the enzyme type and degree of fragmentation. Technological properties of NaCas were enhanced through the enzymatic hydrolysis, and those were more prominent in serine-type enzymes, regardless of the enzyme type, all hydrolysates showed high antioxidant capacities. All hydrolysates, specifically those produced by savinase and alcalase, reduced the viability of the carcinogenic Caco-2 cells in a dose-dependent manner and showed a very low level of cytotoxicity against healthy HEK-293 cells. The hydrolysis treatment made a significant contribution to the antidiabetic activity of NaCas. Particularly alcalase and savinase hydrolysates suppressed the activity of α- amylase and α- glucosidase. Therefore, the generated milk protein hydrolysates could be used in functional food developments for specific dietary purposes.

Isolation, Evaluation, and Identification of Angiotensin I-Converting Enzyme Inhibitory Peptides from Game Meat.

Game meat has been underutilized, while it offers the potential to diversify not only the human diet but also increase food production and the nutritional value of meat products. This study aimed to determine the angiotensin I-converting enzyme (ACE) inhibitory activities of the digested game meats (venison and boar meat) compared with those of livestock meats (beef and pork). Through the sodium dodecyl sulfate polyacrylamide gel electrophoresis and size chromatography results, we found that the digested products from each meat had different molecular weights. The ACE inhibitory ratio in all tested samples had gradually increased following by the enzyme treatments. ACE inhibitory ratios and the half maximal inhibitory concentration values indicated that digested venison was the most potent inhibitor of ACE activity, followed by the digested boar meat. The level of anserine in digested venison was higher than that in the other meats, but the carnosine level was lower. Through fractionations and liquid chromatography-tandem mass spectrometry analysis, five ACE inhibitory peptides were identified from the digested venison. Of these peptides, Isoleucine-Lysine- Glutamic Acid-Valine-Threonine-Glutamic Acid-Arginine (IKEVTER) demonstrated the highest ACE inhibitory activity. Therefore, the game meat is food that is believed potentially to offer high bioactivities, particularly antihypertensive forces.

The investigation of probiotic potential of lactic acid bacteria isolated from traditional Mongolian dairy products.

The aims of this study were to investigate the diversity of lactic acid bacteria (LAB) isolated from traditional Mongolian dairy products, and to estimate the probiotic potential of the isolated strains. We collected 66 samples of the traditional Mongolian dairy products tarag (n = 45), airag (n = 7), aaruul (n = 8), byasulag (n = 1) and eezgii (n = 5), from which 543 LAB strains were isolated and identified based on 16S ribosomal DNA sequence. The predominant species of those products were Lactobacillus (L.) delbrueckii ssp. bulgaricus, L. helveticus, L. fermentum, L. delbrueckii ssp. lactis and Lactococcus lactis ssp. lactis. However, we could not detect any LAB strains from eezgii. All LAB isolates were screened for tolerance to low pH and to bile acid, gas production from glucose, and adherence to Caco-2 cells. In vitro, we found 10 strains possess probiotic properties, and almost identified them as L. plantarum or L. paracasei subspecies, based on 16S ribosomal DNA and carbohydrate fermentation pattern. These strains were differentiated from each other individually by randomly amplified polymorphic DNA analysis. Additionally, it was notable that 6/10 strains were isolated from camel milk tarag from the Dornogovi province.

Changes in water-holding capacity and textural properties of chicken gizzard stored at 4 degrees C.

The water-holding capacity (WHC), and toughness (shear force) of chicken gizzard were evaluated during postmortem storage for 4.5, 7, 12, 24, 48, 72 and 96 h at 4 degrees C. Degradation of the cytoskeletal proteins desmin, talin and vinculin were monitored by sodium dodecyl sulfate--polyacrylamide gel electrophoresis and Western blotting during the same designated storage period. The WHC of the gizzards decreased significantly from 12 h to 72 h of storage, but by 96 h the WHC was restored to the level measured after storage for 12 h. The shear force value of the gizzards increased rapidly until 12 h and then decreased until 24 h, with a further slight decrease by 48 h. Degradation products of desmin, talin and vinculin appeared at 96 h, 12 h and 48 h postmortem, respectively. The intensity of immunolabeling for desmin, talin and vinculin after storage for 96 h decreased to 51%, 25% and 52% of the initial value. The appearance of desmin degradation products was accompanied by an increase in WHC. This suggests that the postmortem degradation of desmin is involved in the increase of WHC in chicken gizzard during storage at 4 degrees C, and talin and vinculin may be involved.

A cattle heart protein hydrolysate ameliorates hypercholesterolemia accompanied by suppression of the cholesterol absorption in rats and Caco-2 cells.

The mechanism for the hypocholesterolemic action of a cattle heart protein hydrolysate (HPH) is clarified. The micellar solubility of cholesterol in vitro was significantly lower in the presence of HPH than in the presence of casein. The suppression of cholesterol uptake by Caco-2 cells was significantly higher in the cholesterol micelles containing HPH than in the cholesterol micelles containing casein. The serum cholesterol concentrations and atherogenic index were significantly lower in the rats fed with HPH than in those fed with casein. The cholesterol absorption measured by [(3)H]-cholesterol was significantly lower by HPH feeding than by casein feeding in rats in vivo accompanying the changes in fecal steroid excretion. Thus, the hypocholesterolemic action of HPH involved the inhibition of jejunal cholesterol absorption. The cattle heart protein hydrolysate ultra-filtrate (HPHU, MW < ca. 1,000 Da peptide fraction) derived from HPH imparted stronger hypocholesterolemic activity than HPH in rats.

Impact of transglutaminase on the textural, physicochemical, and structural properties of chicken skeletal, smooth, and cardiac muscles.

This study examined the effects of microbial transglutaminase (MTG; 3.1mg/ml) on chicken skeletal, smooth, and cardiac muscles; the meat containing the different muscle types was shaped into sausages and treated at 40°C and/or 78°C for 30min. Although the three muscle types were obtained from the same bird, the effects of MTG addition were not uniform. All the muscle types showed a significant increase in the breaking strength (P<0.01), but skeletal muscle exhibited the maximum increase. All samples showed a decrease in the fluorescence intensity and a significant reduction in the concentration of proteins that were extracted in a high ionic strength solution (P<0.05). Scanning electron microscopy images and histological studies revealed that different muscle types had different physical structures and frameworks after MTG treatment, which is a reflection of the differences in the reaction specificity of MTG with different muscle proteins. Histological studies revealed that the reactions of MTG with meat proteins are both exogenous and endogenous. Cooking loss data suggested that MTG did not have any negative effect on water retention during cooking. MTG appears to be a functional and contributive substance since the results suggest that MTG can function on all muscle types that are mechanically processed for different industrial applications. MTG aggregates muscle proteins in different ways that improve their organoleptic properties such as texture, appearance, and water retention.

Evaluation of the performance of osmotic dehydration sheets on freshness parameters in cold-stored beef biceps femoris muscle.

This study aimed to evaluate the effects of osmotic dehydration sheet (ODS) packaging on the quality parameters of beef biceps femoris muscle samples stored at 4°C for 0, 1, 3 and 7 days. Quality indices such as Hunter color values (L(∗), a(∗) and b(∗), the percentage of metmyoglobin (Met-Mb%), K value (freshness index), and the contents of adenosine triphosphate (ATP)-related compounds (ARCs), thiobarbituric acid reactive substances (TBA-RS) and volatile basic nitrogen (VBN) were measured. ODS gave lower a(∗) and b(∗) values and lower Met-Mb% compared with control samples wrapped in polyvinylidene chloride film (PVDCF) (P<0.01), but had no effect on L(∗) (P<0.01). As a result, with higher levels of osmotic dehydration produced by the ODS, the percentage of weight loss and the total contents of ARCs and inosine monophosphate of the samples also increased (P<0.05). The K values of ODS samples were also significantly lower than PVDCF-wrapped samples (P<0.05). Low performance ODS wrapping reduced the TBA-RS values below those found with PVDCF and high performance ODS processing (P<0.01). Moreover, the use of ODS had no effect on VBN values. Thus, although the bright red of beef samples changed to a dark purple color and the weights of samples decreased, the ODS approach has potential as a tool for decreasing the deterioration of other quality indices such as Met-Mb%, TBA-RS, ARCs, K values and the VBN content of cold-stored beef.

Porcine skeletal muscle troponin is a good source of peptides with Angiotensin-I converting enzyme inhibitory activity and antihypertensive effects in spontaneously hypertensive rats.

In the search for novel peptides that inhibit the angiotensin I-converting enzyme (ACE), porcine skeletal troponin was hydrolyzed with pepsin, and the products were subjected to various types of chromatography to isolate active peptides. Glu-Lys-Glu-Arg-Glu-Arg-Gln (EKERERQ) and Lys-Arg-Gln-Lys-Tyr-Asp-Ile (KRQKYDI) were identified as active peptides, and their 50% inhibitory concentrations were found to be 552.5 and 26.2 microM, respectively. These are novel ACE inhibitory peptides, and the activity of KRQKYDI was the strongest among previously reported troponin-originated peptides. KRQKYDI was slowly hydrolyzed by treatment with ACE, and kinetic studies indicated that this peptide was a competitive inhibitor of the enzyme. When KRQKYDI was administered orally to spontaneously hypertensive rats (SHR) at a dose of 10 mg/kg, a temporary antihypertensive activity was observed at 3 and 6 h after administration.

Differentiation in improvements of gel strength in chicken and beef sausages induced by transglutaminase.

This research investigated the improvement in the texture of chicken and beef sausages induced by using microbial transglutaminase (MTG). The ε-(γ-glutamyl)lysine (G-L) content and the extractability of myofibrillar proteins from these sausages were also investigated. Treatment with MTG significantly affected the breaking strength score in both meat types, especially for beef cooked at 80°C (p<0.001). The protein concentration of both meat types treated with MTG and extracted in water-soluble protein solution (WSP) was slightly decreased; compared with a significant decrease (p<0.003) in samples extracted in Guba-Straub-ATP solution (GS-ATP). The variation in protein extractability of both meat types could lead to some considerations of the mechanisms and the high affinity reaction between MTG and myosin heavy chain (MHC). SDS-PAGE analysis revealed significant changes in the density of the bands after adding MTG, especially for the beef samples. The G-L content in the presence of MTG was double that in control samples of both meat types. The amount of crosslinking in chicken and beef meat was different and found to be reasonable. Collectively, this suggests that the binding ability of myofibrillar proteins with MTG is strong and dominated by MHC. There was a unique reaction among MHC proteins with MTG molecules considered as a very advantageous reaction. This leads us to suggest that the functional properties of MTG make it a beneficial protein-binding agent, positively helping the functionality of proteins to improve the texture and gelation of meat products that are treated mechanically, such as sausages. Some variation in gel improvement level between chicken and beef sausages was observed; this resulted from the variation in meat proteins in response to MTG, as well as to the original glutamyl and lysine contents.