Effect of starter culture on proteolytic changes during processing of fermented beef sausages

Impact and correlation of fermentation temperature on the bacterial community, flavor characteristics, and proteolysis of Harbin dry sausages

Proteins undergo degradation to produce peptides and free amino acids, which in turn promote the production of volatile compounds with important contributions to the taste and aroma. This study investigated the effect of fermentation temperatures (8, 15, and 25 °C) on the bacterial community, flavor profile, and protein degradation of Harbin dry sausages. The physical and chemical properties were improved at 25 °C compared with 8 and 15 °C. Staphylococcus xylosus increased with the increase in fermentation temperature, whereas Latilactobacillus sakei decreased. The degree of protein degradation increased, and the content and proportion of taste peptides and free amino acids increased. Similarly, a higher fermentation temperature led to an increase in volatile compounds, such as aldehydes, alcohols, and esters. In conclusion, there is an inseparable relationship between proteolysis and microbial proteases. The fermentation temperature of 25 °C best contributed to the sensory quality and flavor characteristics of Harbin dry sausages.

The effects of Lactiplantibacillus plantarum 3-19 and Pediococcus pentosaceus 18-1 on preventing the accumulation of biogenic amines and promoting the production of volatile organic compounds during sour meat fermentation

Lactic acid bacteria (LAB) are frequently used in meat fermentation, and mixed stater cultures are reported to perform better than single ones. Lactiplantibacillus plantarum 3-19 and Pediococcus pentosaceus 18-1 were chosen from 28 sour-meat-origin strains to examine the effects of single and combined inoculation on sour meat quality. Natural fermentation was used as a control to investigate changes in pH, water activity (aw), amino acid nitrogen (AN), texture, microbial diversity, and volatile organic compounds (VOCs) during fermentation. The pH and aw of each inoculation group were significantly decreased, and AN content was significantly increased. The inoculation of P. pentosaceus 18-1 significantly reduced putrescine, cadaverine, and tryptamine content (p < 0.05), while the inoculation of Lpb. plantarum 3-19 significantly reduced cadaverine amounts (p < 0.05). At the fermentation endpoint, the total biogenic amines content in the C group was 992.96 ± 14.07, which was 1.65, 2.57, and 3.07 times higher than that in the Lp, Pe, and M groups, respectively. The mixed inoculation group combined the advantages of both strains and decreased total biogenic amines most significantly. At the end of fermentation, the VOCs in C, Lp, Pe, and M groups were 10.11, 11.56, 12.45, and 13.39 times higher than those at the beginning of fermentation. Inoculation promoted the production of key VOCs (OAV > 2000) such as heptanal, octanal, and (E)-2-nonanal. The mixed inoculation group had the highest variety and content of VOCs and the highest content of the above key VOCs, significantly enhancing its fruity, floral, ester, and other aromas. Sensory evaluation indicated that the M group had the best overall acceptability. Finally, it was suggested that a combination of Lpb. plantarum 3-19 and P. pentosaceus 18-1 is a novel and efficient starter culture for processing sour meat since they lower the amounts of biogenic amines in the meat and promote the production of VOCs.

Lipid Hydrolysis, Oxidation, and Fatty Acid Formation Pathway Mapping of Synergistically Fermented Sausage and Characterization of Lipid Mediating Genes

Starter cultures play a significant role in lipid hydrolysis, prevention of lipid oxidation, and synthesis of fatty acid in fermented sausage, enhancing product quality. In this study, five synergistic bacterial strains were used, including Pediococcus pentosaceus (B-3), Latilactobacillus sakei DLS-24 (D-24), Latilactobacillus acidophilus DLS-29 (D-29), Lactiplantibacillus pentosus (B-1), and Lactiplantibacillus plantarum (B-2). Sausage B1B3D24 gave the highest free fatty acid with 39.45 g/100 g at 45-Day. Based on 2-thiobarbituric acid reactive substance, B2B3 contains 112.68 MDA/kg. Lipoxygenase activity displays the lowest in B1B3D24 with 0.095 μmol/min·mg followed by B2B3 with 0.145 μmol/min·mg. B1B3D24 contains 11.35 g/kg of monounsaturated fatty acid with the highest content in eicosenoic acid (C20:1) and palmitoleic acid (C16:1). The fatty acid synthesis pathway in B1B3D24 contains an active positive interaction with PUFA to increase the isotopomers of ω-3 and ω-6 fatty acids. In addition, lipid mediating genes in B1B3D24 show the highest counts in fatty-acid synthase, carbonyl reductase 4, 3-oxoacyl-[acyl-carrier-protein] synthase III, hydroxysteroid 17-beta dehydrogenase 8, and acetyl-CoA carboxylase.

Effect of the Addition of Dandelion (Taraxacum officinale) on the Protein Profile, Antiradical Activity, and Microbiological Status of Raw-Ripening Pork Sausage

The study evaluated the effect of adding dandelion extract on the characteristics of raw-ripening pork sausages while reducing the nitrite addition from 150 to 80 mg/kg. The sausages were made primarily from pork ham (80%) and pork jowl (20%). The process involved curing, preparing the meat stuffing, forming the links, and then subjecting the sausages to a 21-day ripening period. Physicochemical parameters such as pH, water activity, and oxidation-reduction potential were compared at the beginning of production and after the ripening process. The study also examined the impact of ripening on protein metabolism in pork sausages and compared the protein profiles of different sausage variants. The obtained research results indicate that dandelion-leaf extract (Taraxacum officinale) were rich in phenolic acids, flavonoids, coumarins, and their derivatives (LC-QTOF-MS method). Antiradical activity test against the ABTS+* and DPPH radical, and the TBARS index, demonstrated that addition of dandelion (0.5-1%) significantly improved the oxidative stability of raw-ripening sausages with nitrite content reduction to 80 mg/kg. A microbiological evaluation of the sausages was also carried out to assess the correctness of the ripening process. The total number of viable bacteria, lactic acid bacteria, and coliforms were evaluated and subsequently identified by mass spectrometry.

Comparative study of a liposome and emulsion system with cinnamon essential oil on the quality and proteolysis of refrigerated minced pork

Essential oils have been recognized for their strong antibacterial property, making them an innovative approach for preserving meat. However, their chemical instability and direct impact on meat proteins limit their application. To overcome these limitations, various loading systems have been explored. This study aimed to compare the effect of cinnamon essential oil (CEO) loaded in a liposome and emulsion system on the proteolysis of minced pork and to evaluate the advantages of each delivery system in preventing microorganism-induced quality deterioration of meat. Minced pork treated with CEO-liposomes exhibited lower pH, total volatile basic nitrogen (TVB-N), and total viable count (TVC) values than CEO-emulsions and provided better protection against microorganisms. SDS-polyacrylamide gel electrophoresis (PAGE) analysis confirmed that CEO-liposome was more effective in protecting proteins from degradation. Moreover, CEO-liposome produced lower amount of bitter amino acids and harmful biogenic amines. Antibacterial mechanisms indicated that CEO-liposome exhibited a stronger inhibitory effect against major spoilage bacteria in meat products by increasing cell membrane permeability. The membrane damage was further supported by an increase in conductivity and the leakage of nucleic acids. Compared to the CEO-emulsion system, CEO-liposome emerged as an effective preservative for minced pork. These results provided important theoretical support for using a bioactive compound delivery system to prevent microorganism-induced quality deterioration in meat.

A proteomic study of "Coppa Piacentina": A typical Italian dry-cured Salami

Coppa Piacentina is considered a peculiar dry cured salami, since it is manufactured by the entire neck muscles stuffed and matured in natural casings, the same as dry cured ham and fermented dry cured sausages. In this work the proteolysis of external and internal portions was investigated by a proteomic approach and by amino acids analysis. Samples of "Coppa Piacentina" were analyzed at 0 days and after 5 and 8 months of ripening through mono- and two-dimensional gel electrophoresis. Image analysis of 2D electrophoretic maps indicated a more intense enzyme activity on the external part, mainly due to endogenous enzymes. They favored, respectively, myofibrillar or sarcoplasmic proteins at 5 or 8 months of ripening. Free amino acids determination proved that lysine and glutamic acid were the most represented ones, followed by a free amino acids sequence like that of dry cured ham. The peculiarities of "Coppa Piacentina" were characterized by a slow proteolysis, due to sacking and binding of the whole cut of the pork neck.

Effects of anaerobic and respiratory adaptation of Lacticaseibacillus casei N87 on fermented sausages production

Lacticaseibacillus casei N87 was used as starter culture for the production of fermented sausages. The strain was cultivated in anaerobic (A) and respiratory (growth in presence of oxygen and supplementation with haeme and menaquinone in the growth medium; R) conditions. Control without the starter culture inoculation and with the addition of 150 mg/kg of nitrate was also included. The effect on physico-chemical parameters (pH, Aw, weight loss, and color), microbial population, volatilome, proteolysis as well as the survival of the strain was evaluated during 90 days of ripening. Q-PCR and DGGE-PCR analyses demonstrated the ability of the strain used in this study to adapt to this environment and carry out the sausage's fermentation process. The inoculation of the strain did not have any effect on the Aw values, which decreased similarly in the different samples whereas the pH was lower in A samples (5.2) and the weight loss in R samples (2.5% less than the others). The color parameters of the samples inoculated with the starter cultures were comparable to those of the control added with nitrate. The concentration of aldehydes that usually are identified as marker of oxidation processes was similar in the samples inoculated with the starter cultures adapted under respiratory conditions and in the control. On the contrary, a higher level was detected in the samples inoculated with the starter cultivated under anaerobic conditions. The proteolysis that occurred during the ripening indicates the differentiation of the A samples from the others. Nonetheless, the volatile profiles of the inoculated fermented sausages were similar. The study demonstrated that aerobic adaptation of Lcb. casei N87 starter culture gave similar color parameters and amounts of aldehydes in sausages fermentations without nitrate compared to conventional fermentations with nitrate.

Purification of Extracellular Protease from Staphylococcus simulans QB7and Its Ability in Generating Antioxidant and Anti-inflammatory Peptides from Meat Proteins

Proteases, especially microbial proteases, are widely used in food processing. The purpose of this study was aimed to purify an extracellular protease produced by the strain Staphylococcus simulans QB7 and to evaluate its ability in hydrolyzing meat proteins and generating antioxidant and anti-inflammatory peptides. The optimal conditions for producing the enzyme were as follows: inoculum ratio, 10%; initial pH, 6.5; temperature, 32 °C; incubation time, 36 h; and rotation speed, 160 rpm. The protease had a molecular weight of approximately 47 kDa, possessing the optimal activity at 50 °C, pH 7.0, The protease was stable at pH 4.0-8.0 and 30-60 °C, and the activity was improved by Na⁺, Mg²⁺, Ca²⁺, and Zn²⁺ ions, whereas it was inhibited by Cu²⁺, Co²⁺, Fe³⁺, Ba²⁺, Fe²⁺, β-M, and ethylene diamine tetraacetic acid disodium salt (EDTA). The protease could effectively hydrolyze meat proteins, and the generated hydrolysate could significantly inhibit tumor necrosis factor-alpha (TNFα)-induced oxidative stress, including superoxide and malondialdehyde levels and inflammation (vascular adhesion molecule-1 [VCAM-1] and cyclooxygenase 2 [COX2)) in human vascular EA.hy926 cells. The present findings support the ability of S. simulans QB7 protease in generating antioxidant and anti-inflammatory peptides during the fermentation of meat products.

Starter inoculums assisted fermentation of Puntius sp. - role of Lactiplantibacillus plantarum and Staphylococcus piscifermentans to reduce fermentation time while increasing safety

AIMS

To evaluate the role of starter inoculums to reduce total fermentation time as well as improve safety and quality of Sheedal, a fermented fish-product of India.

METHODS AND RESULTS

Lactiplantibacillus plantarum and Staphylococcus piscifermentans were isolated from the Sheedal and used as starter inoculums. To justify fermenting and probiotic properties of the starter inoculums, characteristics like proteolytic and lipolytic activity, cell-surface hydrophobicity, cell auto-aggregation and co-aggregation, antibiotic susceptibility and antimicrobial assay were performed. Changes of the count of lactic acid bacteria, staphylococci and Enterobacteriaceae were studied periodically.

CONCLUSIONS

Higher increase of α-amino nitrogen and TCA-soluble peptides during fermentation was observed in treatment which was inoculated with both L. plantarum and S. piscifermentans. Poor competitiveness of staphylococci in presence of LAB was found. Inoculation of both L. plantarum and S. piscifermentans as starter showed positive effect to reduce significantly the fermentation period from usual 4-5 months to 75 days, whereas, same was achieved after 105^th and 120^th by the use of either L. plantarum or S. piscifermentans, respectively.

SIGNIFICANCE AND IMPACT OF STUDY

Reduction of the total fermentation period is considered as an additional advantage in Sheedal technology in addition to the safety of the product as evidenced by low pH and high titratable acidity.

Effect of Mixed Starters on Proteolysis and Formation of Biogenic Amines in Dry Fermented Mutton Sausages

In this study, by comparing the four groups of sausages, namely, CO (without starter culture), LB (with Lactobacillus sakei), LS (with L. sakei 3X-2B + Staphylococcus xylosus SZ-8), and LSS (with L. sakei 3X-2B + S. xylosus SZ-8 + S. carnosus SZ-2), the effects of mixed starter cultures on physical-chemical quality, proteolysis, and biogenic amines (BAs) during fermentation and ripening were investigated. Inoculation of the mixed starter cultures increased the number of lactic acid bacteria and staphylococci in sausages during fermentation and ripening for 0 to 5 days. The L. sakei 3X-2B + S. xylosus SZ-8 + S. carnosus SZ-2 mixed starter accelerated the rate of acid production and water activity reduction of sausages and improved the redness value. Compared with CO, the mixed starter effectively inhibited Enterobacteriaceae. At the end of ripening, the LSS group was approximately 1.25 CFU/g, which was less than the CO group, thereby reducing the total volatile basic nitrogen (TVB-N) in the LSS group. The free amino acids in the LS and LSS groups (224.97 and 235.53 mg/kg dry sausage, respectively) were significantly (p < 0.001) higher than that in the CO group (170.93 mg/kg dry sausage). The level of histamine, cadaverine, putrescine, and common BAs showed an opposite trend to the increase of the corresponding precursor amino acid content, which were significantly lower (p < 0.001) in the LS and LSS sausages than in CO. This study showed that L. sakei 3X-2B + S. xylosus SZ-8 + S. carnosus SZ-2 is a potential mixed starter for fermented meat products.

New Insights into the Chemical Reactivity of Dry-Cured Fermented Sausages: Focus on Nitrosation, Nitrosylation and Oxidation

Nitrite and nitrate are added to cured meat for their bacteriological, technological and sensorial properties. However, they are suspected to be involved in the formation of nitroso compounds (NOCs), such as potentially mutagenic nitrosamines, nitrosylheme and nitrosothiols. Controlling the sanitary and sensorial qualities of cured meat products by reducing these additives requires elucidating the mechanisms involved in the formation of NOCs. To this end, we studied the dose-response relationship of added sodium nitrite and/or sodium nitrate (0/0, 80/80, 0/200, and 120/120 ppm) on the formation of NOCs in dry cured fermented sausages. The results showed a basal heme iron nitrosylation in the absence of NaNO2/NaNO3 due to starter cultures. This reaction was promoted by the addition of NaNO2/NaNO3 in the other conditions. Reducing the dose to 80/80 ppm still limits lipid oxidation without the formation of non-volatile nitrosamines. Conversely, the addition of NO2/NO3 slightly increases protein oxidation through higher carbonyl content. The use of 80/80 ppm could be a means of reducing these additives in dry-cured fermented meat products.

Fat Inclusion Level, NaCl Content and LAB Starter Cultures in the Manufacturing of Italian-Type Ostrich Salami: Weight Loss and Nutritional Traits

The experiment studied the effect of two different fat inclusion levels (30% and 40%), NaCl contents (2.4 and 2.6%) and starter cultures (lactic acid bacteria (LAB) 6: L. curvatus/S. xylosus; LAB 8: L. sakei/S. xylosus) on the weight loss and nutritional composition of Italian-type ostrich salami. With this purpose, 8 batches of 9 salami each (n = 72) were prepared. Salami were ripened for 20 weeks: weight loss was monitored throughout the experiment, while salami nutritional composition was evaluated at 10 and 20 weeks of ripening. The lowest fat and highest salt inclusion levels provided the highest cumulative weight loss throughout the trial. At 10 weeks of ripening, salami with 40% fat were the richest in moisture and fat, whereas the leanest ones had the highest protein, ash and cholesterol contents. LAB 6 provided salami with the highest moisture and protein, while LAB 8 increased fat and cholesterol contents. At 20 weeks of ripening the proximate composition of ostrich salami was solely affected by fat inclusion level, with similar findings to those observed at 10 weeks. Overall, fat inclusion level had a great impact on the weight loss and nutritional composition of Italian-style ostrich salami. Reducing the NaCl inclusion from 2.6% to 2.4%, the weight loss of ostrich salami was retarded by approximately 1 week, without affecting the nutritional composition of the final product. Results of the study suggested that it is feasible to produce salami with lower fat and salt contents, while ensuring satisfactory product quality.

Effect of Marination Time on the Antioxidant Properties of Peptides Extracted from Organic Dry-Fermented Beef

In this study, we evaluated the effect of marination time on changes in the antioxidant properties of peptides extracted from bovine semimembranosus muscle. We measured antiradical scavenging capacity and reducing power of the peptides using a spectrophotometric decolorization method; inhibition of lipid oxidation was also assessed by estimating the level of malondialdehyde formed. According to our results, there was no benefit from the doubling of marinating time (from 24 to 48 h) as part of the preprocessing of beef. Samples from S1 batch (24 h marination) showed better antioxidant properties than those from S2 batch. We also tested various color parameters as a reflection of the inhibition of oxidative processes, in which case, the most favorable parameters from the consumer point of view were found to be lightness and redness. The effect of marination time on the degree of proteolytic changes was estimated using peptidomic approach. The degradation of myoglobin, hemoglobin, creatine kinase-type M, and beta-enolase-as the most sensitive proteins to proteolytic degradation-was observed during the 62 days of processing. It seems that the prolongation of marination time as a preprocessing step intensifies the hydrolytic degradation of proteins and peptides during the processing step. This results in the loss (or it has no effect) of antioxidative properties in organic dry-fermented beef.

Impact of fructooligosaccharides and probiotic strains on the quality parameters of low-fat Spanish Salchichón

The substitution of dietary fiber and probiotic strains to reduce fat content of fermented sausages has been used for the development of innovative and healthier meat products. For this study, pork back fat was partially replaced by fructooligosaccharides (FOS) and the probiotic strains Lactobacillus paracasei and Lactobacillus rhamanosus. The fat replacement resulted in a significant decrease (P ≤ .05) in fat content (29%) compared with the control formulation (no fat substitution). The addition of FOS did not have a significant effect on microbial counts; however, reductions in Enterobacteriaceae and yeast were observed when Lactobacillus strains were also incorporated. The inclusion of FOS and probiotic strains did not show any significant effect on lipid oxidation and proteolysis. The partial fat replacement and the addition of Lactobacillus rhamanosus GG as probiotic strain in Spanish Salchichón can be considered a successful reformulation strategy for the meat product market.

Effects of different starter culture combinations on microbial counts and physico-chemical properties in dry fermented mutton sausages

This study was conducted to evaluate the effects of inoculation with different mixed starter culture combinations on microbial counts, physico-chemical properties, and proteolytic and lipolytic properties of dry fermented mutton sausages during fermentation and ripening. Four different batches of mutton sausages were manufactured: CO batch, no starter cultures, used as control; LB batch with Lactobacillus sakei; LS batch with L. sakei + Staphylococcus xylosus; and LSS batch with L. sakei + S. xylosus + Staphylococcus carnosus. The results showed that adding starter culture caused Lactobacillus and Staphylococcus to become dominant bacteria and reduced the Enterobacteriaceae count in the inoculated sausages. The mixed starter cultures (LS & LSS) accelerated acidification and reduced water activity and lipid oxidation. Statistical analysis revealed that the use of mixed starter cultures, especially the combination L. sakei + S. xylosus + S. carnosus, contributed to proteolysis and lipolysis, increasing total free amino acids and polyunsaturated fatty acids. The above results demonstrate that the use of mixed starter cultures contributes to improving the composition of free amino acids and free fatty acids as well as the hygienic quality of dry fermented mutton sausages.

Effect of starter culture on microbiological, physiochemical and nutrition quality of Xiangxi sausage

Fermented sausages have a long tradition originating from China. In this study, three starter microorganisms including Pediococcus pentosaceus (P), Staphylococcus xylosus (S), and a combination of P. pentosaceus and S. xylosus (P + S) were conducted for the manufacture of traditional Xiangxi (a city in China) fermented sausages. The physicochemical changes of the above three kinds of sausages during fermentation were studied and discussed, and also compared with these properties on the natural fermented sausage (N, i.e., control). The results revealed that five kinds of bacterial phases were existed at different fermentation stages in N, P, S and P + S fermented sausages, respectively. The microbiological data showed that an initial enterobacteria count of approximately 5.3 log CFU/g for all four batches of sausages. The enterobacteria count in the inoculated sausages of P and P + S groups decreased significantly to about 1 log CFU/g whereas group N and S had a count of about 3.3 log CFU/g after fermentation. In the early stages of fermentation, the pH rapidly decreased below 5.3. FAA and FFA were significantly increased in all groups and TBARS value in group P was higher than that of the other three groups. In conclusion, starter cultures can be used to improve the hygiene level of Xiangxi sausages without significant effects on pH, A_W, and nitrite residue.

Microbiota of Iberian dry-cured ham as influenced by chemical composition, high pressure processing and prolonged refrigerated storage

The effect of high pressure processing (HPP) on the microbiota of ripened Iberian ham of different water activity, salt concentration and intramuscular fat content was investigated before and after a 5-month refrigeration period. At the beginning of the refrigeration period, the only significant effects of chemical composition were those of water activity on psychrotrophs and Micrococcaceae in untreated hams, and of the salt-in-lean ratio on lactic acid bacteria in HPP-treated hams. At the end of the refrigeration period, the only significant effect was that of intramuscular fat content on moulds and yeasts in HPP-treated samples. All microbial groups were significantly affected by HPP, with reductions ranging from 1.7 to 2.0 log cycles after treatment. A significant recovery of all microbial groups took place in HPP-treated hams during the refrigeration period, with increases ranging from 0.5 to 1.1 log cycles. In spite of this recovery, microbial levels in HPP-treated hams remained significantly lower than in untreated hams. Staphylococcus accounted for 93.4% of Iberian ham bacterial isolates, with S. equorum as the most abundant species. Representatives of the Tetragenococcus, Carnobacterium and Streptomyces genera, not previously reported in dry-cured ham, were also isolated. Most of the yeast isolates (75.0%) were identified as Debaryomyces hansenii.

Effect of Fermentation with Different Lactic Acid Bacteria Starter Cultures on Biogenic Amine Content and Ripening Patterns in Dry Fermented Sausages

In the present study, two different diameter (small and large) Milano-type dry fermented sausages were industrially produced to evaluate the effect of two different LAB starter cultures (Lactobacillus sakei and Pediococcus pentosaceus) on biogenic amines (BAs) content, proteolysis, and lipolysis taking place during both fermentation and ripening. With regard to BAs, putrescine and tyramine were mostly found in fermented sausages having large diameter and those inoculated with P. pentosaceus/S. xylosus exhibited significantly higher accumulation of these compounds. Overall, the small size sausages showed a more pronounced proteolysis taking place during processing. In addition, aside from the distinctive electrophoretic bands detected with both starter cultures, a more pronounced proteolysis and a faster protein hydrolysis was observed in salami inoculated with P. pentosaceus/S. xylosus. As for lipolysis, a significantly higher amount of diacylglycerols was observed at the end of ripening in the sausages inoculated with L. sakei/S. xylosus, which concurrently exhibited an increased D32, D34, and D36 series. The results of the present study confirms profound differences in BAs concentration, proteolysis, and lipolysis. These findings are strictly dependent on the starter cultures, which demonstrates that the choice of an appropriate starter optimized for peculiar products and processes should be the key factor to improve safety and quality features of traditional fermented sausages.

Proteolytic effect of starter culture during ripening of smoked horse sausage

In this study, we assessed the effect of bacterial and endogenous enzymes on the proteolysis of smoked horse sausage. Commercial starter culture (Staphylococcus xylosus + Lactobacillus sakei) was used in smoked horse sausage. Cathepsin B + L and cathepsin B activities, microbiological growth, pH, and water activity (aw) were measured. Based on PCR-DGGE fingerprint analyses, the starter culture inhibited endogenous bacterial growth. During ripening, the residual activity of cathepsin B + L and cathepsin B was higher in batch C (control) than in batch S (containing starter cultures). The starter and endogenous enzymes promote the degradation of sarcoplasmic and myofibrillar proteins; however, the degradation of these proteins was higher in batch S than in batch C. Therefore, bacterial enzymes played a major role in the degradation of proteins during the ripening of smoked horse sausage.

Different Flour Microbial Communities Drive to Sourdoughs Characterized by Diverse Bacterial Strains and Free Amino Acid Profiles

This work aimed to investigate whether different microbial assemblies in flour may influence the microbiological and biochemical characteristics of traditional sourdough. To reach this purpose, members of lactic acid bacteria, enterobacteria, and yeasts were isolated from durum wheat flour. Secondly, the isolated microorganisms (Pediococcus pentosaceus, Saccharomyces cerevisiae, Pantoea agglomerans, and Escherichia hermannii) were inoculated in doughs prepared with irradiated flour (gamma rays at 10 kGy), so that eight different microbial assemblies were obtained. Two non-inoculated controls were prepared, one of which (C-IF) using irradiated flour and the other (C) using non-irradiated flour. As shown by plate counts, irradiation of flour caused total inactivation of yeasts and a decrease of all the other microbial populations. However, acidification occurred also in the dough C-IF, due to metabolic activity of P. pentosaceus that had survived irradiation. After six fermentations, P. pentosaceus was the dominant lactic acid bacterium species in all the sourdoughs produced with irradiated flour (IF). Yet, IF-based sourdoughs broadly differed from each other in terms of strains of P. pentosaceus, probably due to the different microorganisms initially inoculated. Quantitative and qualitative differences of free amino acids concentration were found among the sourdoughs, possibly because of different microbial communities. In addition, as shown by culture-independent analysis (16S metagenetics), irradiation of flour lowered and modified microbial diversity of sourdough ecosystem.

Effect of high intensity ultrasound on the fermentation profile of Lactobacillus sakei in a meat model system

The objective of this study was to investigate the efficacy of high intensity ultrasound on the fermentation profile of Lactobacillus sakei in a meat model system. Ultrasound power level (0-68.5 W) and sonication time (0-9 min) at 20 °C were assessed against the growth of L. sakei using a Microplate reader over a period of 24h. The L. sakei growth data showed a good fit with the Gompertz model (R(2)>0.90; SE<0.042). Second order polynomial models demonstrated the effect of ultrasonic power and sonication time on the specific growth rate (SGR, μ, h(-1)) and lag phase (λ, h). A higher SGR and a shorter lag phase were observed at low power (2.99 W for 5 min) compared to control. Conversely, a decrease (p<0.05) in SGR with an increase in lag phase was observed with an increase in ultrasonic power level. Cell-free extracts obtained after 24h fermentation of ultrasound treated samples showed antimicrobial activity against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Salmonella typhimurium at lower concentrations compared to control. No significant difference (p<0.05) among treatments was observed for lactic acid content after a 24h fermentation period. This study showed that both stimulation and retardation of L. sakei is possible, depending on the ultrasonic power and sonication time employed. Hence, fermentation process involving probiotics to develop functional food products can be tailored by selection of ultrasound processing parameters.

A comparison of endogenous and microbial proteolytic activities during fast fermentation of silver carp inoculated with Lactobacillus plantarum

The study was aimed to investigate different roles of endogenous and Lactobacillus plantarum proteases during fast fermentation of silver carp. The results show that endogenous proteases could degrade both sarcoplasmic and myofibrillar proteins. In contrast, L. plantarum had low proteinase activities and could only hydrolyze sarcoplasmic peptides. This indicates that gel properties could be mainly affected by endogenous proteolysis while microbial proteolysis contributed to the production of smaller peptides and free amino acids which may be related to flavor and taste. Texture and free amino acid analyses verified these hypotheses. It shows that endogenous lysosomal proteases were the major contributors for the decrease of gel strength while L. plantarum proteolytic activities could lead to the increase of aspartic acid, glutamic acid, and alanine, which may result in umami and sweet taste; and also lead to a rise in some amino acids which were volatile compounds precursors.

Identification of small peptides arising from hydrolysis of meat proteins in dry fermented sausages

In this study, proteolysis and low molecular weight (LMW) peptides (<3kDa) from commercial Argentinean fermented sausages were characterized by applying a peptidomic approach. Protein profiles and peptides obtained by Tricine-SDS-PAGE and RP-HPLC-MS, respectively, allowed distinguishing two different types of fermented sausages, although no specific biomarkers relating to commercial brands or quality were recognized. From electrophoresis, α-actin, myoglobin, creatine kinase M-type and L-lactate dehydrogenase were degraded at different intensities. In addition, a partial characterization of fermented sausage peptidome through the identification of 36 peptides, in the range of 1000-2100 Da, arising from sarcoplasmic (28) and myofibrillar (8) proteins was achieved. These peptides had been originated from α-actin, myoglobin, and creatine kinase M-type, but also from the hydrolysis of other proteins not previously reported. Although muscle enzymes exerted a major role on peptidogenesis, microbial contribution cannot be excluded as it was postulated herein. This work represents a first peptidomic approach for fermented sausages, thereby providing a baseline to define key peptides acting as potential biomarkers.