Joanna Stadnik

Meat and fermented meat products as a source of bioactive peptides.

Bioactive peptides are short amino acid sequences, that upon release from the parent protein may play different physiological roles, including antioxidant, antihypertensive, antimicrobial, and other bioactivities. They have been identified from a range of foods, including those of animal origin, e.g., milk and muscle sources (with pork, beef, or chicken and various species of fish and marine organism). Bioactive peptides are encrypted within the sequence of the parent protein molecule and latent until released and activated by enzymatic proteolysis, e.g. during gastrointestinal digestion or food processing. Bioactive peptides derived from food sources have the potential for incorporation into functional foods and nutraceuticals. The aim of this paper is to present an overview of the muscle-derived bioactive peptides, especially those of fermented meats and the potential benefits of these bioactive compounds to human health.

Biogenic amines content during extended ageing of dry-cured pork loins inoculated with probiotics

The study determined the content of biogenic amines in dry-cured pork loins inoculated with Lactobacillus casei ŁOCK 0900 probiotic strain, in 4, 8 and 16 month-old samples. Cadaverine, putrescine and tryptamine levels showed a time-dependent increase during ageing. Histamine and spermidine were not detected. Spermine which was present at very low concentrations, tended to decrease. Cadaverine and tryptamine were the main biogenic amines at the end of the ageing period with average values of 39.6 mg/kg and 49.2 mg/kg respectively. The results were within the values reported for other dry-cured meat products and below the suggested toxic levels. The pH of samples increased significantly (p<0.05) with ageing time. The a(w) values decreased significantly (p<0.05) during ageing, with a mean value of 0.953±0.007 for samples aged for 4 months, and 0.852±0.007 for samples aged for 16-months.

Effect of protein-xanthophylls (PX) concentrate of alfalfa supplementation on physico-chemical properties of turkey breast and thigh muscles during ageing

The objective was to evaluate the effects of a dietary protein-xanthophylls (PX) concentrate of alfalfa to turkey diets (at 15 and 30 g kg(-1) feed) on the physico-chemical properties of breast and thigh muscles during ageing. The experiment involved 120 turkeys (Big-6 type) allotted to 3 groups (group I-control group; group II--with 1.5% supplementation of the protein-xanthophylls (PX) concentrate; group III--with 3% supplementation of the protein-xanthophylls (PX) concentrate). Measurements of pH, water holding capacity, color, oxymyoglobin content, TBARS and oxidation-reduction potential showed that the addition of protein-xanthophylls (PX) concentrate of alfalfa to a turkey diet did not cause deterioration of breast and thigh meat quality. In addition, changes in color, oxymyoglobin content, TBARS and oxidation-reduction potential values suggested that the inclusion of the concentrate to turkey diets acts as an antioxidant in the raw meat.

Effect of Inoculation with Probiotics and Ageing Time on Selected Functional Properties and Oxidation of Proteins in Dry-Cured Pork Loins

The effect of inoculation with a probiotic strain Lactobacillus casei ŁOCK 0900 on changes in selected functional properties and protein oxidation of dry-cured pork loins during ageing was studied. The protein carbonyls content tended to increase significantly (p < 0.05) throughout ageing to reach a maximum level which was approximately two-fold the initial level in both samples. No statistically significant differences (p < 0.05) in carbonyl content were found between the control sample and sample inoculated with L. casei. The passage of ageing time was coupled with a statistically significant (p < 0.05) increase in the trichloroacetic acid soluble peptides concentration in examined loins. Inoculation with a probiotic strain did not have an influence on trichloroacetic acid soluble peptides concentration during the shortest ageing period. Results of measurements carried out for the control sample after 21 and 28 days of ageing were significantly lower (p < 0.05) than those obtained for the sample inoculated with L. casei ŁOCK 0900. Free α-amino acids content in both samples increased continuously with increasing ageing time (p < 0.05). Inoculation of loins with a probiotic strain Lactobacillus casei ŁOCK 0900 resulted in significantly higher peptides and free amino acids content. These differences might affect their organoleptic characteristics that need further investigations.

Changes in selected parameters related to proteolysis during ageing of dry-cured pork loins inoculated with probiotics

The effect of inoculation with a probiotic strain, Lactobacillus casei ŁOCK 0900, on selected parameters related to proteolysis of dry-cured pork loins during ageing was studied. Moisture content decreased significantly (p<0.05) throughout ageing, accompanied by a progressive reduction in water activity. The total nitrogen (TN) content increased during ageing with no effect (p<0.05) of inoculation with L. casei on its level. The greatest increase in non-protein nitrogen (NPN) content during ageing occurred in an inoculated sample, corresponding with the more pronounced decrease in pH. The intensity of proteolysis, as assessed by proteolysis index (PI), remained statistically significantly (p<0.05) unchanged during examined ageing periods. Inoculation with a probiotic strain does not significantly affect the degree of proteolysis in examined meat products after 21 and 28 days of ageing.

Effect of genetically modified feeds on physico-chemical properties of pork

Effect of Genetically Modified Feeds on Physico-Chemical Properties of Pork The objective of this study was to evaluate the effects of genetically modified (GM), insect-resistant Bt maize (MON810) and the meal made of glyphosate-tolerant soybean (Roundup Ready MON40-3-2) used as the dietary components for pigs on the physico-chemical properties of meat. Forty-eight fatteners derived from Polish Landrace x Polish Large White sows mated to a Duroc x Pietrain boar were used. All animals received isonitrogenous and isoenergetic diets containing or not containing the genetically modified components. The design of the experiment was as follows: group I (control) - non-modified soybean meal and maize; group II - GM soybean meal and non-modified maize; group III - non-modified soybean meal and GM maize; group IV - GM soybean meal and GM maize. The examination of the pH values of loin and neck muscles indicated no statistically significant differences between pigs fed diets containing non-transgenic or transgenic feeds. No statistical differences were observed for water holding capacity (WHC) within dietary treatments. The introduction of transgenic maize and soybean meal into pig diets did not significantly affect the a* colour parameter of loin as well as neck muscles. The use of transgenic maize or soybean meal did not cause significant changes in the L* colour value of loin. Results obtained for neck muscles were more differentiated, possibly due to the natural heterogeneity of this primal cut. Pigs which had consumed the transgenic diet exhibited slightly decreased lipid stability of loin, as indicated by thiobarbituric acid reactive substances (TBARS). The decrease was statistically significant only in the case of muscles from group II. The addition of feeds derived from genetically modified crops into pig diets did not significantly affect the stability of neck muscle lipids; however, TBARS values of these muscles were twice those of loin muscles. Wpływ pasz modyfikowanych genetycznie na właściwości fizykochemiczne wieprzowiny Celem pracy była ocena wpływu ziarna genetycznie modyfikowanej, odpornej na insekty kukurydzy Bt (MON810) oraz poekstrakcyjnej śruty otrzymanej z soi odpornej na glifosat (Roundup Ready MON40-3-2), jako składników diety świń, na fizykochemiczne właściwości mięsa. W doświadczeniu wykorzystano 48 tuczników pochodzących od loch (pbz x wbp) pokrytych knurem (Du x Pi). Wszystkie zwierzęta otrzymywały mieszanki paszowe o zbliżonej zawartości składników pokarmowych i energii metabolicznej, różniące się obecnością lub brakiem komponentów genetycznie modyfikowanych, według następującego schematu: grupa I (kontrolna) - śruta sojowa niemodyfikowana i kukurydza niemodyfikowana, grupa II - śruta sojowa GM i kukurydza niemodyfikowana, grupa III - niemodyfikowana śruta sojowa i kukurydza GM, grupa IV - śruta sojowa GM i kukurydza GM. Ocena wartości pH schabu i mięśni karkówki nie wykazała istotnych różnic pomiędzy próbami pochodzącymi od zwierząt żywionych paszą zawierającą lub nie surowce genetycznie modyfikowane. Odnotowano brak statystycznie istotnych różnic wodochłonności (WHC) prób w obrębie badanych grup żywieniowych. Włączenie modyfikowanej genetycznie kukurydzy i soi do diety świń nie wpłynęło istotnie na wartość parametru a* barwy, zarówno schabu, jak i mięśni karkówki. Użycie modyfikowanej genetycznie kukurydzy i soi nie spowodowało istotnych zmian wartości parametru L* schabu. W przypadku mięśni karkówki wartości tego parametru były bardziej zróżnicowane, czego przyczyną mogła być naturalna niejednorodność tego elementu. Świnie żywione paszą z udziałem komponentów modyfikowanych genetycznie charakteryzowały się nieco niższą stabilnością lipidów zawartych w schabie, lecz różnice te zostały statystycznie potwierdzone jedynie w przypadku grupy II. Udział w paszy surowców modyfikowanych genetycznie nie wpłynął na stabilność tłuszczu mięśni karkówki, aczkolwiek wartości TBARS dla tych mięśni były dwukrotnie wyższe w stosunku do mięśni schabu.

Antimicrobial Peptides of Meat Origin - An In Silico and In Vitro Analysis.

The aim of this study was to evaluate the antimicrobial activity of meat protein-derived peptides against selected Gram-positive and Gram-negative bacteria. The in silico and in vitro approach was combined to determine the potency of antimicrobial peptides derived from pig (Sus scrofa) and cow (Bos taurus) proteins. The in silico studies consisted of an analysis of the amino acid composition of peptides obtained from the CAMPR database, their molecular weight and other physicochemical properties (isoelectric point, molar extinction coefficient, instability index, aliphatic index, hydropathy index and net charge). The degree of similarity was estimated between the antimicrobial peptide sequences derived from the slaughtered animals and the main meat proteins. Antimicrobial activity of peptides isolated from dry-cured meat products was analysed (in vitro) against two strains of pathogenic bacteria using the disc diffusion method. There was no evidence of growthinhibitory properties of peptides isolated from dry-cured meat products against Escherichia coli K12 ATCC 10798 and Staphylococcus aureus ATCC 25923.

Characteristic of antioxidant activity of dry-cured pork loins inoculated with probiotic strains of LAB

ABSTRACT This study investigated the antioxidant activity of peptides isolated from dry-cured pork loins inoculated with probiotic strains of lactic acid bacteria (LAB). The antioxidant activity of the isolated peptide fraction (an average of 13 kDa) was determined by radical-scavenging activities: ABTS and DPPH, reducing power and metal chelating assay (Fe2+ and Cu2+). The highest antioxidant activity was noted against ABTS and DPPH. The results suggest no influence of probiotic LAB on the relative quantity of peptides and the lack of relationship between this parameter and antioxidant activity measures. The differences in antioxidant activity among the tested batches may be associated with the influence of the LAB strains on the peptides’ composition and the amino acid position in them.

Potential of bacteriocins from lab to improve microbial quality of dry-cured and fermented meat products

Meat and meat products are an important component of the daily diet. Nevertheless, they are perishable goods and are prone to microbial contamination, which leads to an increased risk to the health of consumers as well as economic losses in the meat industry. Fermentation has been used for thousands of years to preserve meat. As a result of extensive biochemical reactions occurring in meat during fermentation and ripening, the condi- tions inhibiting the growth of pathogenic and spoilage bacteria are formed. These changes are catalyzed by endogenous meat enzymes and exogenous enzymes derived from natural contaminating bacteria or starter cultures applied. In dry-cured and fermented meat products they are represented mainly by lactic acid bacte- ria (LAB) that produce a wide range of compounds, such as bacteriocins, directed against other microorgan- isms. The use of bactericidal peptides does not affect the sensory quality of foodstuffs, so that they attract attention as alternative means of preserving the stability and safety of dry-cured products.

Stability of Antiradical Activity of Protein Extracts and Hydrolysates from Dry-Cured Pork Loins with Probiotic Strains of LAB

The application of starter cultures to improve quality and safety has become a very common practice in the meat industry. Probiotic strains of lactic acid bacteria (LAB) can also bring health benefits by releasing bioactive peptides. The aim of this work was to evaluate the stability of antiradical activity of protein extracts from LAB-inoculated dry-cured pork loins during long-term aging and evaluate their hydrolysates after simulated gastrointestinal digestion. Analyses of hydrolysates by using liquid chromatography-tandem mass spectrometry (LC-MS/MS) were strengthened with in silico analysis. The highest antiradical activity of the protein extracts was observed after 180 days of aging. The influence of the strain used (LOCK, BAUER, or BB12) on the inactivation ability of ABTS radicals varied during long-term aging. The IC50 values indicated the higher antiradical properties of salt-soluble (SSF) compared to water-soluble fraction (WSF) of proteins. The peptides generated by in vitro digestion have MW between 700 and 4232 Da and their length ranged from 5 to 47 amino acids in a sequence where Leu, Pro, Lys, Glu, and His had the largest share. This study demonstrates that the degradation of pork muscle proteins during gastrointestinal digestion may give rise to a wide variety of peptides with antiradical properties.