Employment of autochthonous microflora in Pecorino Sardo cheese manufacturing and evolution of physicochemical parameters during ripening

Autochthonous cultures to improve the quality of PGI Castellano cheese: Impact on proteolysis, microstructure and texture during ripening

The aim of this research was to find out the effect of different combinations of starter and non-starter cultures on the proteolysis of Castellano cheese during ripening. Four cheese batches were prepared, each containing autochthonous lactobacilli and or Leuconostoc, and were compared with each other and with a control batch, that used only a commercial starter. To achieve this, nitrogen fractions (pH 4.4-soluble nitrogen and 12 % trichloroacetic acid soluble nitrogen, polypeptide nitrogen and casein nitrogen), levels of free amino acids and biogenic amines were assessed. Texture and microstructure of cheeses were also evaluated. Significant differences in nitrogen fractions were observed between batches at different stages of ripening. The free amino acid content increased throughout the cheese ripening process, with a more significant increase occurring after the first 30 days. Cheeses containing non-starter lactic acid bacteria exhibited the highest values at the end of the ripening period. Among the main amino acids, GABA was particularly abundant, especially in three of the cheese batches at the end of ripening. The autochthonous lactic acid bacteria were previously selected as non-producers of biogenic amines and this resulted in the absence of these compounds in the cheeses. Analysis of the microstructure of the cheese reflected the impact of proteolysis. Additionally, the texture profile analysis demonstrated that the cheese's hardness intensified as the ripening period progressed. The inclusion of autochthonous non-starter lactic acid bacteria in Castellano cheese production accelerated the proteolysis process, increasing significantly the free amino acids levels and improving the sensory quality of the cheeses.

Effect of Commercial and Autochthonous Bioprotective Cultures for Controlling Listeria monocytogenes Contamination of Pecorino Sardo Dolce PDO Cheese

The composition and physicochemical characteristics of short-aged Pecorino Sardo PDO (Protected Designation of Origin) cheese makes it permissive to Listeria monocytogenes growth. The PDO product specification stipulates that this cheese is produced with whole sheep's milk inoculated with cultures from the area of origin. Therefore, the use of bioprotective cultures for the inhibition of pathogens in PDO cheeses is allowed only if autochthonous microorganisms are used. Furthermore, bioprotective cultures are generally used on the cheese surface to prevent the outgrowth of L. monocytogenes, the application of which can be time-consuming and require specialist technical knowledge. In this study, we examine the direct addition of bioprotective cultures to the cheese vat and compare the activity of a commercial bioprotective culture (Lactiplantibacillus plantarum) and an autochthonous lactic acid bacterium with bioprotective properties (Lactobacillus delbruekii sups. sunkii), for the inhibition of L. monocytogenes in Pecorino Sardo PDO cheese. Three types of Pecorino Sardo PDO cheese were made with bioprotective cultures added directly to the cheese milk along with the starter inoculum: PSA, with the commercial bioprotective culture; PSB, with the autochthonous bioprotective culture; and a CTRL cheese with no bioprotective culture. A challenge test was performed on each of these cheeses by artificially contaminating the cheese surface with L. monocytogenes (2 Log10 CFU/g). Three batches of each cheese type were analyzed to enumerate mesophilic and thermophilic lactic acid bacteria and to investigate the growth potential of L. monocytogenes during manufacturing, at the end of ripening, at the end of shelf-life, and after 180 days from cheese production. Both bioprotective cultures tested in this study showed inhibitory action against the pathogen with 0.3-1.8 Log10 CFU/g (colony-forming unit per gram) reduction levels. The autochthonous organism, L. sunkii, was as effective as the commercially supplied culture, and the addition of the bioprotective cultures to the cheese-making procedure offered protection against L. monocytogenes. The direct addition of bioprotective cultures to the making procedure of Pecorino Sardo PDO cheese is a potentially innovative strategy to improve the safety of this product.

Effect of Bear Garlic Addition on the Chemical Composition, Microbiological Quality, Antioxidant Capacity, and Degree of Proteolysis in Soft Rennet Cheeses Produced from Milk of Polish Red and Polish Holstein-Friesian Cows

This study aimed to assess the effect of milk source and bear garlic addition on the selected properties of soft rennet cheese. Cheeses were produced from cow milk derived from two sources: Polish Red cows (PR) and Polish Holstein-Friesian cows (PHF) with a 0.5% (w/w) addition of bear garlic (Allium ursinum L.) dried leaves. Chemical composition and fatty acid profiles (GC) were determined in fresh cheeses. Fresh and stored for two weeks cheeses were subjected to microbiological studies, i.e., total aerobic bacteria count (TABC); count of Lactococcus sp., yeast and molds; coliforms; analysis of the proteolysis extension by means of o-phthaldialdehyde (OPA) assay and free amino acids content (HPLC); antioxidant capacity as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP); as well as pH and water activity. Cheeses with bear garlic herbs were more prone to proteolysis but this was not accompanied by any effect on the microbial counts, water activity or pH. Cheeses produced from PR milk contained less monounsaturated fatty acids (MUFA) but were richer in n-3 PUFA and had a lower n-6/n-3 FA ratio than cheeses from PHF milk. Bear garlic addition increased DPPH anti-radical power but had less of an effect on the FRAP values.

Relationship between the Dynamics of Gross Composition, Free Fatty Acids and Biogenic Amines, and Microbial Shifts during the Ripening of Raw Ewe Milk-Derived Idiazabal Cheese

This study reports for the first time the relationship between bacterial succession, characterized by high-throughput sequencing (sequencing of V3-V4 16S rRNA regions), and the evolution of gross composition, free fatty acids (FFAs) and biogenic amines (BAs) during cheese ripening. Specifically, Idiazabal PDO cheese, a raw ewe milk-derived semi-hard o hard cheese, was analysed. Altogether, 8 gross parameters were monitored (pH, dry matter, protein, fat, Ca, Mg, P and NaCl) and 21 FFAs and 8 BAs were detected. The ripening time influenced the concentration of most physico-chemical parameters, whereas the producer mainly affected the gross composition and FFAs. Through an O2PLS approach, the non-starter lactic acid bacteria Lactobacillus, Enterococcus and Streptococcus were reported as positively related to the evolution of gross composition and FFAs release, while only Lactobacillus was positively related to BAs production. Several environmental or non-desirable bacteria showed negative correlations, which could indicate the negative impact of gross composition on their growth, the antimicrobial effect of FFAs and/or the metabolic use of FFAs by these genera, and their ability to degrade BAs. Nonetheless, Obesumbacterium and Chromohalobacter were positively associated with the synthesis of FFAs and BAs, respectively. This research work provides novel information that may contribute to the understanding of possible functional relationships between bacterial communities and the evolution of several cheese quality and safety parameters.

Contents of Functionally Bioactive Peptides, Free Amino Acids, and Biogenic Amines in Dutch-Type Cheese Models Produced with Different Lactobacilli

Cheese ripening involves a number of biochemical processes, mainly of a proteolytic nature, which are initially triggered principally by milk-coagulating enzymes and, afterward, by microorganisms or enzymes of microbial origin. The proteolytic reactions affect, primarily, the synthesis of macro- and medium-molecular peptides from casein. In turn, the advanced proteolysis ends in the formation of short peptides and free amino acids. Further reactions may lead to the formation of nutritionally unfavorable biogenic amines. The present study aimed to determine changes in the contents of bioactive peptides (anserine and L-carnosine), free amino acids, and biogenic amines throughout the ripening of cheese models produced with the addition of Lactobacillus genus bacteria. The contents of amino acids varied considerably in the cheese models, depending on the bacterial strain added and ripening time. After five weeks of ripening, the total content of free amino acids in the cheese models ranged from 611.02 (a cheese model with Lactobacillus casei 2639) to 1596.64 mg kg⁻¹ (a cheese model with Lb. acidophilus 2499). After the same time, the contents of the total biogenic amines in the cheese models with the addition of lactobacilli were lower than in the control cheese model (except for the model with Lb. rhamnosus 489). Anserine was detected in all cheese models (79.29–119.02 mg kg⁻¹), whereas no L-carnosine was found over a five-week ripening period in the cheese models with Lb. delbrueckii 490 and Lb. casei 2639. After a five-week ripening, the highest total content of bioactive peptides was determined in the cheese models containing Lb. acidophilus 2499 (136.11 mg kg⁻¹).

Diversity of non-starter lactic acid bacteria in autochthonous dairy products from Western Balkan Countries - Technological and probiotic properties

The aim of this review was to summarize the data regarding diversity of non-starter lactic acid bacteria (NSLAB) isolated from various artisanal dairy products manufactured in Western Balkan Countries. The dairy products examined were manufactured from raw cow's, sheep's or goat's milk or mixed milk, in the traditional way without the addition of commercial starter cultures. Dairy products such as white brined cheese, fresh cheese, hard cheese, yogurt, sour cream and kajmak were sampled in the households of Serbia, Croatia, Slovenia, Bosnia and Herzegovina, Montenegro, and North Macedonia. It has been established that the diversity of lactic acid bacteria (LAB) from raw milk artisanal dairy products is extensive. In the reviewed literature, 28 LAB species and a large number of strains belonging to the Lactobacillus, Lactococcus, Enterococcus, Streptococcus, Pediococcus, Leuconostoc and Weissella genera were isolated from various dairy products. Over 3000 LAB strains were obtained and characterized for their technological and probiotic properties including: acidification and coagulation of milk, production of aromatic compounds, proteolytic activity, bacteriocins production and competitive exclusion of pathogens, production of exopolysaccharides, aggregation ability and immunomodulatory effect. Results show that many of the isolated NSLAB strains had one, two or more of the properties mentioned. The data presented emphasize the importance of artisanal products as a valuable source of NSLAB with unique technological and probiotic features important both as a base for scientific research as well as for designing novel starter cultures for functional dairy food.

Impact of Nisin-Producing Strains of Lactococcus lactis on the Contents of Bioactive Dipeptides, Free Amino Acids, and Biogenic Amines in Dutch-Type Cheese Models

The goal of this study was to determine changes in contents of free amino acids, biogenic amines, and bioactive dipeptides (anserine and L-carnosine) in cheese models produced with the addition of nisin-producing strains of Lactococcus lactis over their ripening period. After 5 weeks of ripening, contents of total biogenic amines in the cheese models with the addition of L. lactis strains were lower than in the control cheese model. The cheese models examined differed significantly in contents of free amino acids through the ripening period. Individual free amino acids, such as ornithine, were found in some of the cheese models, which is indicative of their specific microbial activities. Both anserine and L-carnosine were detected in all variants of the cheese models. After 5-week ripening, the highest total content of bioactive dipeptides was determined in the cheese models produced with the nisin-producing culture of L. lactis 11454 (142.15 mg∙kg⁻¹).

Bioactive characteristics of a semi-hard non-starter culture cheese made from raw or pasteurized sheep's milk

In this study, the effect of pasteurization and use of starter cultures on physicochemical, microbiological and functional properties of a traditional Iranian semi-hard cheese (Lighvan cheese) was evaluated during stages of ripening (1, 60, 120 days). Profiles of polar metabolites were analyzed by gas-chromatography mass-spectrometry (GC-MS). Considerable free amino acids such as gamma-aminobutyric acid (GABA) were found in samples that have higher microbial communities i.e. raw sheep's milk without use of starter cultures and pasteurized sheep's milk cheese with co-culture. However, GABA was not found in pasteurized sheep's milk cheese without starter culture during ripening. Conclusively, the application of the starter culture could reduce the ripening time of sheep's milk cheese and could be an appropriate approach to increase the functionality of the sheep's milk cheese.

Production of sheep milk cheese with high γ-aminobutyric acid and ornithine concentration and with reduced biogenic amines level using autochthonous lactic acid bacteria strains

Consumer demand for health-promoting foods is generating the need to develop biofunctional dairy products. Lactic acid bacteria are employed in cheese-making and some of them are able to produce beneficial compounds on human health such as γ-aminobutyric acid (GABA) and ornithine but also to synthetize biogenic amines. The aim was to investigate the effect of four selected autochthonous co-cultures on the free amino acid profile, with special emphasis on GABA and ornithine, and on the biogenic amine content of pasteurized sheep milk cheese during ripening. High average concentrations of GABA (1296.75 mg/kg cheese) and ornithine (2355.76 mg/kg cheese) were found in all the cheese batches at 240 days of ripening. Batch 2, manufactured with the co-culture containing autochthonous Lactococcus lactis strains as starter and Lactobacillus plantarum TAUL1588 as adjunct, showed 2.37 fold reduced biogenic amines concentration with respect to the batch 1 made with the starter during the ripening time. The microstructure and microbiological counts of cheeses were affected (P ≤ 0.001) by the ripening time, without appreciating differences (P ≥ 0.05) in the physico-chemical composition between batches. This study could be a good approach to the development of functional sheep milk cheese.

Selection of Leuconostoc strains isolated from artisanal Serrano Catarinense cheese for use as adjuncts in cheese manufacture

BACKGROUND

Serrano Catarinense cheese is a raw bovine milk cheese produced in the region of Santa Catarina, Brazil. Twelve representative strains of Leuconostoc isolated from 20 samples of this artisanal cheese were selected and submitted for evaluation of the acidifying, proteolytic, autolytic, aminopeptidase and lipolytic activities, NaCl and acid resistance, production of dextran and biogenic amines and antimicrobial activity. The aim was to genetically and technologically characterize the Leuconostoc strains in order to use them in mixed starter cultures for cheese manufacture.

RESULTS

Leuconostoc mesenteroides subsp. mesenteroides was the species that accounted for the largest proportion of isolates of Leuconostoc genus. Two leuconostoc isolates stood out in the acidifying activity, with reduction in pH of 1.12 and 1.04 units. The isolates showed low proteolytic and autolytic activity. Most of the isolates were dextran producers, presented good resistance to the salt and pH conditions of the cheese and showed antimicrobial activity against cheese pathogen bacteria, and none of them produced biogenic amines.

CONCLUSION

These results allowed the selection of five strains (UEL 04, UEL 12, UEL 18, UEL 21 and UEL 28) as good candidates for use as adjunct cultures for cheese manufacture. © 2018 Society of Chemical Industry.

In vitro assessment of Pediococcus acidilactici Kp10 for its potential use in the food industry

Background

Selection of a microbial strain for the incorporation into food products requires in vitro and in vivo evaluations. A bacteriocin-producing lactic acid bacterium (LAB), Pediococcus acidilactici Kp10, isolated from a traditional dried curd was assessed in vitro for its beneficial properties as a potential probiotic and starter culture. The inhibitory spectra of the bacterial strain against different gram-positive and gram-negative bacteria, its cell surface hydrophobicity and resistance to phenol, its haemolytic, amylolytic and proteolytic activities, ability to produce acid and coagulate milk together with its enzymatic characteristics and adhesion property were all evaluated in vitro.

Results

P. acidilactici Kp10 was moderately tolerant to phenol and adhere to mammalian epithelial cells (Vero cells and ileal mucosal epithelium). The bacterium also exhibited antimicrobial activity against several gram-positive and gram-negative food-spoilage and food-borne pathogens such as Listeria monocytgenes ATCC 15313, Salmonella enterica ATCC 13311, Shigella sonnei ATCC 9290, Klebsiella oxytoca ATCC 13182, Enterobacter cloaca ATCC 35030 and Streptococcus pyogenes ATCC 12378. The absence of haemolytic activity and proteinase (trypsin) and the presence of a strong peptidase (leucine-arylamidase) and esterase-lipase (C4 and C8) were observed in this LAB strain. P. acidilactici Kp10 also produced acid, coagulated milk and has demonstrated proteolytic and amylolactic activities.

Conclusion

The properties exhibited by P. acidilactici Kp10 suggested its potential application as probiotic and starter culture in the food industry.

Isolation, enumeration, molecular identification and probiotic potential evaluation of lactic acid bacteria isolated from sheep milk

Lactic acid bacteria species were molecularly identified in milk from Lacaune, Santa Inês and crossbred sheep breeds and their in vitro probiotic potential was evaluated. The species identified were Enterococcus faecium (56.25%), E. durans (31.25%) and E. casseliflavus (12.5%). No other lactic acid bacteria species, such as lactobacilli, was identified. Most of the isolated enterococci were resistant to gastric pH (2.0) and to 0.3% oxgall. All tested enterococci were resistant to ceftazidime, oxacillin and streptomycin and sensible to clindamycin, erythromycin and penicillin. The resistance to ciprofloxacin, gentamicin, tetracycline and vancomycin varied among tested species. All tested enterococci strongly inhibited (P<0.05) Escherichia coli and Listeria monocytogenes, moderately inhibited E. faecalis and Staphylococcus aureus and did not inhibit Pseudomonas aeruginosa, Salmonella enterica var. Typhimurium and also one E. durans sample isolated from sheep milk. Four samples of E. faecium, one of E. durans and one of E. casseliflavus presented the best probiotic potential.

Influence of controlled inoculation of malolactic fermentation on the sensory properties of industrial cider

Given the lack of research in the traditional cider making field when compared to the efforts devoted to winemaking, this work focused on the effects of controlled inoculation of the malolactic fermentation (MLF) on the sensory properties of cider. MLF develops spontaneously in cider making at industrial level. In this work, industrial cider samples were inoculated with selected indigenous Oenococcus oeni strains and the benefits on the aroma and flavour in cider production compared to non-inoculated ciders were evaluated. Randomly amplified polymorphic DNA PCR was used to monitor strain colonization ability, outnumbering the indigenous microbiota, after completion of the alcoholic fermentation at industrial scale (20,000 l). Aroma-active compounds of experimentally inoculated ciders were analysed by HPLC and GC–MS, and sensory profiles were determined by fractioning aroma extracts using reversed-phase HPLC. Principal component analysis allowed the identification of relationships and differences among ciders with or without inoculation, including several highly appreciated commercial ones obtained under spontaneous conditions. Under controlled inoculation conditions, not only could MLF be shortened by half but, interestingly, enhancement of aroma complexity and flavour resulted in ciders enriched with a higher fruity note. In addition, important aromatic groups analysed here had not been previously described, thus affording deeper knowledge on aroma characterization of apple cider.

Influence of autochthonous lactic acid bacteria and enzymatic yeast extracts on the microbiological, biochemical and sensorial properties of Lben generic products

In this study we identified Lactococcus lactis subsp. lactis, Lc. lactis subsp. lactis biovar diacetylactis, Kluyveromices lactis and Saccharomyces cerevisiae as the dominant microorganisms of traditional Moroccan acid-alcoholic fermented milk named Lben. The low pH (3·8±0·3), lactose (16·8±3·4 mg/l) and lactic acid (8·16±0·6 mg/l) content indicated that a strong fermentation occurred in the traditional product which was also characterised by the substantial presence of ethanol and typical volatile carbonyl compounds (i.e., acetoin, diacetyl and acetaldehyde). Microbiological analyses of experimental Lben manufactured with selected strains (isolated from the traditional product) of Lc. lactis subsp. lactis and Lc. lactis subsp. lactis biovar. diacetylactis alone (batch A) and in combination with enzymatic extract of a K. lactis strain (batch B) indicated a good effectiveness of the starters employed (∼1010 CFU/g of lactococci after 8 h of incubation) and a significant effect of the yeast enzyme extract on lactococci viability. Despite slight changes in the physicochemical characteristics of the two Lben during the 15 d storage period, volatile compounds (i.e. ethanol, acetaldehyde, diacetyl and acetoin) were consistently higher in batch B. Moreover, sensorial analysis performed after 15 d of storage, highlighted higher odour and flavour intensity, vegetable odour and viscosity in batch B while batch A displayed higher astringency.