Competition between Starter Cultures and Wild Microbial Population in Sausage Fermentation: A Case Study Regarding a Typical Italian Salami (Ventricina)

Effect of staphylococci fermentation and their synergistic Lactobacillus on the physicochemical characteristics and nonvolatile metabolites of Chinese bacon

The impacts of Staphylococcus cohnii, S. saprophyticus and their synergistic Lactobacillus plantarum on the quality and flavor of Chinese bacon were investigated by monitoring the physicochemical characteristics and characterizing metabolites with non-targeted metabolomics. Results showed that S. cohnii could increase the tenderness and decrease the oxidation of muscle, while S. saprophyticus stabilized the springiness and increased the proteolysis. The metabolites produced by the co-fermentation of S. cohnii and S. saprophyticus showed a higher hierarchy, then exhibited the highest hierarchy in synergy with L. plantarum. The promising flavor may be related to the arginine biosynthesis, nicotinic acid and nicotinamide metabolism, and pyrimidine metabolism pathways. Staphylococcus contributed to flavor by promoting the accumulation of di- and tripeptides and activating the amino acid metabolic pathway through arginine metabolism. These findings provide thoughts for understanding the fermentation mechanism of Staphylococcus and the targeted modulation of the flavor of Chinese bacon.

The Contribution of Microorganisms to the Quality and Flavor Formation of Chinese Traditional Fermented Meat and Fish Products

Guizhou sour meat and sour fish, Chaoshan fish sauce, Sichuan sausage and bacon, Cantonese sausage, Jinhua ham, and Xinjiang air-dried beef are eight representatives of Chinese traditional fermented meat and fish products (FMFPs), which are favored by Chinese consumers due to their high nutritional value and quality. The quality of the spontaneously fermented Chinese traditional FMFP is closely correlated with microorganisms. Moreover, the dominant microorganisms are significantly different due to regional differences. The effects of microorganisms on the texture, color, flavor, nutrition, functional properties, and safety of Chinese traditional FMFPs have not been not fully described. Additionally, metabolic pathways for flavor formation of Chinese traditional FMFPs have not well been summarized. This article describes the seven characteristic Chinese traditional FMFPs and correlated dominant microorganisms in different regions of China. The effects of microorganisms on the texture, color, and flavor of Chinese traditional FMFPs are discussed. Furthermore, the metabolic pathways of microbial regulation of flavor formation in Chinese traditional FMFPs are proposed. This work provides a theoretical basis for improvement of Chinese traditional FMFPs by inoculating functional microorganisms isolated from Chinese traditional fermented foods.

Use of two autochthonous bacteriocinogenic strains as starter cultures in the production of salchichónes, a type of Spanish fermented sausages

In this work, two autochthonous LAB strains (Lactiplantibacillus paraplantarum BPF2 and Pediococcus acidilactici ST6), isolated from spontaneously fermented sausages produced in Spain, were tested to produce Spanish fermented sausages (salchichón) in pilot plants, due to their promising technological and anti-listerial activity. These products were compared with a sample obtained with a commercial starter (RAP) and a spontaneously fermented control sample. Physico-chemical parameters, microbial counts, metagenomic analysis, biogenic amines content and organoleptic profile of the obtained samples were studied to assess the performances of the native starters. In fact, traditional and artisanal products obtained through spontaneous fermentations can represent an important biodiversity reservoir of strains to be exploited as new potential starter cultures, to improve the safety, quality and local differentiation of traditional products. The data underlined that ST6 strain resulted in a final lower percentage if compared with the other LAB used as starter cultures. The use of starters reduced the BA concentration observed in the sausages obtained with spontaneous fermentation and the BPF2 and ST6 strains were able to decrease the level of products rancidity. Moreover, a challenge test against L. monocytogenes were performed. The data confirmed the effectiveness in the inhibition of L. monocytogenes by the two bacteriocinogenic strains tested, with respect to RAP and control samples, highlighting their ability to produce bacteriocins in real food systems. This work demonstrated the promising application in meat industry of these autochthonous strains as starter cultures to improve sensory differentiation and recognizability of typical fermented sausages.

Microbial Spoilage of Traditional Goose Sausages Produced in a Northern Region of Italy

Recently, during the ripening of goose sausage, a defect consisting of ammonia and vinegar smell was noticed. The producer of the craft facility, located in Lombardia, a Northern region of Italy, asked us to identify the cause of that defect. Therefore, this study aimed to identify the potential responsible agents for the spoilage of this lot of goose sausages. Spoilage was first detected by sensory analysis using the "needle probing" technique; however, the spoiled sausages were not marketable due to the high ammonia and vinegar smell. The added starter culture did not limit or inhibit the spoilage microorganisms, which were represented by Levilactobacillus brevis, the predominant species, and by Enterococcus faecalis and E. faecium. These microorganisms grew during ripening and produced a large amount of biogenic amines, which could represent a risk for consumers. Furthermore, Lev. brevis, being a heterofermentative lactic acid bacteria (LAB), also produced ethanol, acetic acid, and a variation in the sausage colour. The production of biogenic amines was confirmed in vitro. Furthermore, as observed in a previous study, the second cause of spoilage can be attributed to moulds which grew during ripening; both the isolated strains, Penicillium nalgiovense, added as a starter culture, and P. lanosocoeruleum, present as an environmental contaminant, grew between the meat and casing, producing a large amount of total volatile nitrogen, responsible for the ammonia smell perceived in the ripening area and in the sausages. This is the first description of Levilactobacillus brevis predominance in spoiled goose sausage.

Challenge tests reveal limited outgrowth of proteolytic Clostridium botulinum during the production of nitrate- and nitrite-free fermented sausages

Nitrate and nitrite salts perform a versatile role in fermented meats, including the inhibition of food pathogens (in particular proteolytic group I Clostridium botulinum). Despite the increasing interest in clean-label products, little is known about the behaviour of this pathogen in response to the removal of chemical preservatives from fermented meat formulations. Therefore, challenge tests with a cocktail of nontoxigenic group I C. botulinum strains were performed to produce nitrate/nitrite-free fermented sausages under different acidification conditions and starter culture formulations, including the use of an anticlostridial Mammaliicoccus sciuri strain. Results showed limited outgrowth of C. botulinum, even in the absence of acidification. The anticlostridial starter culture did not lead to an additional inhibitory effect. The selective plating procedure adopted within this study proofed robust to follow germination and growth of C. botulinum, inhibiting common fermentative meat microbiota. The challenge tests constitute a suitable tool to assess the behaviour of this food pathogen within fermented meats upon nitrate- and nitrite omission.

Influence of Lactobacillus helveticus ZF22 and TR1-1-3 strains on the aromatic flavor of fermented sausages

In this study, five strains isolated from traditional Inner Mongolian air-dried meat products were used, two Lactobacillus helveticus strains, ZF22 and TR1-1-3, with potent antibacterial activity, acid, salt, and nitrite tolerance, were selected for this study. Lactic acid bacteria (LAB) (Lactobacillus helveticus ZF22 and TR1-1-3) were inoculated into fermented sausages at 10⁷ CFU/g and their volatiles were studied during fermentation and storage. Clustering heat map and principal component analysis (PCA) were used to identify differentiating flavor components in uninoculated and inoculated sausages. The results showed that 72 volatile flavor substances were identified during the fermentation of the fermented sausages and that inoculation with Lactobacillus helveticus ZF22 and TR1-1-3 increased the proportion of acids, ketones and alkanes. Moreover, the clustering heat map demonstrated that esters such as ethyl isobutyrate, ethyl acetate, and ethyl valerate were more abundant in TR1-1-3 and ZF22 than ZR. The PCA analysis showed that the volatile compounds of the three fermented sausages were distributed in separate quadrants, suggesting that the volatile compound compositions of the three fermented sausages differed significantly. Our findings suggest that inoculating fermented sausages with Lactobacillus helveticus TR1-1-3 and ZF22 can improve flavor by enhancing the type and amount of flavor compounds.

Identification of Optimal Fermentation Temperature for Dry-Fermented Sausage Using Strains Isolated from Korean Fermented Foods

This study aims at identifying the optimal fermentation temperature for dry-fermented sausage using strains isolated from Kimchi (GK1, Pediococcus pentosaceus-GK1; NK3, P. pentosaceus-NK3), Doenjang (D1, Debaryomyces hansenii-D1), and commercial fermented sausage (S6, spontaneously generated Penicillium nalgiovense-S6). The microbial population, pH, moisture content, color, thiobarbituric acid reactive substance (TBARS), volatile basic nitrogen (VBN), and electronic nose (E-nose) were analyzed to identify the optimal fermentation temperature. The dry-fermented sausages were inoculated with three types of starter cultures [CS (commercial starter culture), GD (GK1 + D1 + S6), and ND (NK3 + D1 + S6)]. The fermentation was performed for 3 days at 20 °C and 25 °C, and dried for 28 days. The Lactobacillus spp. plate count and TBARS showed significantly higher values in the 25 °C group than in the 20 °C group (p < 0.05). The Staphylococcus spp. plate count of GD and ND were significantly higher than CS group at all temperatures. On day 31, the moisture content and VBN values of all groups were less than 35 % and 20 mg%, respectively. According to E-nose, the highest amount of acetoin was detected at the GD group fermented at 25 °C. Thus, the optimal fermentation temperature is expected at 25 °C after using GD in the manufacturing of dry-fermented sausages.

Effects of Starter Cultures and Type of Casings on the Microbial Features and Volatile Profile of Fermented Sausages

In the literature, the effect of the type of casing on fermented sausages is quite unexplored, while several studies are focused on the impact of starter cultures. Therefore, this paper studied the effect of three commercial starter cultures and two casings (natural or collagen) on Italian fermented sausages. Physico-chemical parameters (aw, pH, weight loss), microbiota, aroma profile and sensory analysis were evaluated. Results showed that collagen casings promoted a higher reduction of pH and weight loss. Concerning the microbiota, samples with natural casing had higher counts of lactic acid bacteria, while yeast proliferation was promoted in those with collagen. Regardless of the starters and casings applied, levels of enterococci and Enterobacteriaceae were low (≤2 log CFU/g). The aroma profile was significantly affected by casing: despite the starter applied, the presence of collagen casing favoured acid accumulation (mainly acetate and butanoate) and reduction of ketones. Sensory analysis highlighted significant differences only for odour, colour intensity and sourness. The differences observed suggest that collagen casings may provide a greater availability of oxygen. Overall, casings rather than starter cultures impact the microbial and sensorial features of fermented sausages.

Freeze-Dried Powder of Fermented Chili Paste-New Approach to Cured Salami Production

Fermented chili powders were obtained through the freeze-drying of fermented chili pastes and used as a condiment, acidifier, antioxidant, colorant, and microbial starter carrier in fermented salami production. Fermented chili powders were examined regarding carbohydrates, organic acids, vitamin C, phenolic compounds, carotenoids, and aroma profile. High concentrations of lactic (10.57-12.20%) and acetic acids (3.39-4.10%) were recorded. Vitamin C content was identified in the range of 398-1107 mg/100 g, with maximum values for C. annuum cv. Cayenne chili powder. Phenolic compounds showed values between 302-771 mg/100 g. Total carotenoid content was identified between 544-2462 µg/g, with high concentrations of capsanthin esters. Aroma profile analysis evidenced specific compounds (1-hexanol, 2-hexanol, hexenal, E-2-hexenal) with sensory importance and a more complex spectrum for Capsicum chinense cultivar. Plant-specific lactic acid bacteria showed dominance both in fermented chili paste, chili powder, and salami. Lactic and acetic acids from the fermented chili powder reduced the pH of the filling immediately, having a stabilizing effect on the meat. Nor molds or pathogens were identified in outer limits. Based on these results, fermented chili powders could be used as starter carriers in the production of fermented meat products for exceptional sensory properties and food safety management.