Preliminary observations on proteolysis in Manchego cheese made with a defined-strain starter culture and adjunct starter (Lactobacillus plantarum) or a commercial starter

Formation of Free Amino Acids and Bioactive Peptides During the Ripening of Bulgarian White Brined Cheeses

Bioactive peptides and free amino acids obtained from Bulgarian goat, sheep and cow white brined cheeses, produced with same starter culture, during ripening were evaluated. The concentration of total free amino acids was increasing in all tested cheeses in the first 30 days of ripening. In the next 30 days in sheep cheeses, the concentration increased as recorded for most of the amino acids. Amino acids with highest levels detected throughout the whole ripening period in goat, sheep and cow cheese types were leucine, phenylalanine, arginine, valine and lysine. MALDI-TOF analysis of evaluated cheeses resulted in detection of production of bioactive peptide derivates from milk proteins: 51 peptides in cow, 31 peptides in sheep and 22 peptides in goat cheeses. Peptide αs1-CN (f35-40) was found only in cow cheese. In cow cheese, higher intensity was detected for αs1-CN (f1-9) and β-CN (f194-203 and f203-219) peptides. In goat cheese was recorded αs1-CN peptides, and there was a tendency to increase the peptides released from β-CN, with the highest intensity of fragments αs1-CN (f1-9 and f24-30) and β-CN (f194-209 and f203-219). In sheep cheese, the recorded primarily peptides were αs1-CN and peptides released from β-CN. Different bioactive peptides, derivate from casein, were detected as follows: 6 peptides were ACE inhibitory peptides, 3 peptides were αS1-casokinins, 1 peptide was caseinophopeptide, 1 peptide was immunopeptide. Twelve bioactive peptides were recorded to be derivates from β-casein: 1 peptide was ACE peptide, 4 peptides were caseino-phosphopeptides, 1 peptide was immunopeptide, 1 peptide β-casokinin, 1 antibacterial peptide and 4 multifunctional peptides. Of peptides released by proteolysis of αS2-CN was found 1 bioactive peptide with antimicrobial activity. On our best knowledge, this paper contributes new data about free amino acids and bioactive peptides in the connection between type of milk and period for cheese ripening in the Bulgarian goat, sheep and cow white brined cheeses.

Salt Distribution in Raw Sheep Milk Cheese during Ripening and the Effect on Proteolysis and Lipolysis

The salt distribution process in artisanal sheep cheese with an innovative shape of eight lobes was investigated. The cheese was subjected to two brining conditions: 24 h with brine at 16°Baumé and 12 h at 22°Baumé. The chemical composition (pH, water activity, dry matter, fat, and protein content), proteolysis (nitrogen fractions and free amino acids), and lipolysis (free fatty acids) were evaluated in two sampling zones (internal and external) at 1, 15, 30, 60, 90, 120, 180, and 240 days of ripening. The whole cheese reached a homogeneous salt distribution at 180 days of ripening. Brining conditions did not have an influence on the rate of salt penetration, but on the final sodium chloride (NaCl) content. Cheese with higher salt content (3.0%) showed increased proteolysis and lipolysis as compared to cheese with lower salt content (2.2%). Proteolysis index and total free fatty acids did not differ significantly (p > 0.05) between internal and external zones of cheese. It is suggested that producers start marketing this artisanal cheese at 6 months of ripening, when it has uniform composition and salt distribution.

Fermented Foods as a Dietary Source of Live Organisms

The popularity of fermented foods and beverages is due to their enhanced shelf-life, safety, functionality, sensory, and nutritional properties. The latter includes the presence of bioactive molecules, vitamins, and other constituents with increased availability due to the process of fermentation. Many fermented foods also contain live microorganisms that may improve gastrointestinal health and provide other health benefits, including lowering the risk of type two diabetes and cardiovascular diseases. The number of organisms in fermented foods can vary significantly, depending on how products were manufactured and processed, as well as conditions and duration of storage. In this review, we surveyed published studies in which lactic acid and other relevant bacteria were enumerated from the most commonly consumed fermented foods, including cultured dairy products, cheese, fermented sausage, fermented vegetables, soy-fermented foods, and fermented cereal products. Most of the reported data were based on retail food samples, rather than experimentally produced products made on a laboratory scale. Results indicated that many of these fermented foods contained 105-7 lactic acid bacteria per mL or gram, although there was considerable variation based on geographical region and sampling time. In general, cultured dairy products consistently contained higher levels, up to 109/mL or g. Although few specific recommendations and claim legislations for what constitutes a relevant dose exist, the findings from this survey revealed that many fermented foods are a good source of live lactic acid bacteria, including species that reportedly provide human health benefits.

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.

Characterization of the Microbial Diversity and Chemical Composition of Gouda Cheese Made by Potential Probiotic Strains as an Adjunct Starter Culture

This study characterized the microbial diversity and chemical properties of Gouda cheese made by probiotics during ripening periods. Lactobacillus plantarum H4 (H4) and Lactobacillus fermentum H9 (H9), which demonstrate probiotic properties and bioactivity, were used as adjunct starter cultures. Gouda cheese made with H4 (GCP1) and H9 (GCP2) demonstrated the highest production of formic acid and propionic acid, respectively. Moreover, the bacterial diversity, including richness and evenness of nonstarter lactic acid bacteria (NSLAB), increased in probiotic cheeses. Specifically, Lactobacillus, Leuconostoc, and Streptococcaceae were present at higher concentrations in probiotic cheeses than in control Gouda cheese (GCC). The proportion of H4 in GCP1 increased and culminated at 1.76%, whereas H9 in GCP2 decreased during ripening. Peptide profiles were altered by the addition of probiotics and included various bioactive peptides. In particular, three peptide fragments are newly detected. Therefore, Gouda cheese could be used as an effective probiotic carrier for H4 and H9.

Traditional cheeses: rich and diverse microbiota with associated benefits

The risks and benefits of traditional cheeses, mainly raw milk cheeses, are rarely set out objectively, whence the recurrent confused debate over their pros and cons. This review starts by emphasizing the particularities of the microbiota in traditional cheeses. It then describes the sensory, hygiene, and possible health benefits associated with traditional cheeses. The microbial diversity underlying the benefits of raw milk cheese depends on both the milk microbiota and on traditional practices, including inoculation practices. Traditional know-how from farming to cheese processing helps to maintain both the richness of the microbiota in individual cheeses and the diversity between cheeses throughout processing. All in all more than 400 species of lactic acid bacteria, Gram and catalase-positive bacteria, Gram-negative bacteria, yeasts and moulds have been detected in raw milk. This biodiversity decreases in cheese cores, where a small number of lactic acid bacteria species are numerically dominant, but persists on the cheese surfaces, which harbour numerous species of bacteria, yeasts and moulds. Diversity between cheeses is due particularly to wide variations in the dynamics of the same species in different cheeses. Flavour is more intense and rich in raw milk cheeses than in processed ones. This is mainly because an abundant native microbiota can express in raw milk cheeses, which is not the case in cheeses made from pasteurized or microfiltered milk. Compared to commercial strains, indigenous lactic acid bacteria isolated from milk/cheese, and surface bacteria and yeasts isolated from traditional brines, were associated with more complex volatile profiles and higher scores for some sensorial attributes. The ability of traditional cheeses to combat pathogens is related more to native antipathogenic strains or microbial consortia than to natural non-microbial inhibitor(s) from milk. Quite different native microbiota can protect against Listeria monocytogenes in cheeses (in both core and surface) and on the wooden surfaces of traditional equipment. The inhibition seems to be associated with their qualitative and quantitative composition rather than with their degree of diversity. The inhibitory mechanisms are not well elucidated. Both cross-sectional and cohort studies have evidenced a strong association of raw-milk consumption with protection against allergic/atopic diseases; further studies are needed to determine whether such association extends to traditional raw-milk cheese consumption. In the future, the use of meta-omics methods should help to decipher how traditional cheese ecosystems form and function, opening the way to new methods of risk-benefit management from farm to ripened cheese.

Effect of starters and ripening time on the physicochemical, nitrogen fraction and texture profile of goat's cheese coagulated with a vegetable coagulant (Cynara cardunculus)

BACKGROUND

The increase in the demand for goat's cheese throughout the world has encouraged research into the development of new related products with different textural characteristics. The aim of this work was to study the effect of three commercial starter cultures through the assessment of physicochemical and textural characteristics of goat's milk cheeses made with vegetable coagulant (Cynara cardunculus) during ripening.

RESULTS

Use of the different starter cultures produced a significant effect (P < 0.05) on moisture, proteins, pH, nitrogen fractions and hardness of the cheeses. Results show that the addition of mesophilic starters ensures the correct acidification rate and produced cheeses with lower pH values and greater hardness. Use of thermophilic starter cultures produces cheeses with less instrumental hardness and the use of mixed cultures produced less proteolysis.

CONCLUSION

These results are found useful for selecting the most suitable starter for the development of new goat's cheeses.

Influence of autochthonous adjunct cultures on ripening parameters of Argentinean goat's milk cheeses

BACKGROUND

Argentinean semi-hard goat's cheeses manufactured with and without the addition of autochthonous adjunct cultures of Lactobacillus plantarum ETC17, Lactobacillus rhamnosus ETC14 and Enterococcus faecium ETC3 were analysed to evaluate the effect of these strains on ripening parameters.

RESULTS

Gross composition was similar among cheeses. Microbiological analysis indicated that lactic acid bacteria added to cheeses reached high levels. None of the strains assayed affected the primary proteolysis. Overall, E. faecium had a clearer effect on the peptide and lipolysis profiles of cheeses. Analysis of the volatile fraction of cheeses indicated that the levels of several compounds involved in the overall flavour of goat's cheeses were affected by the presence of E. faecium. This could explain the differences detected in the global perception of cheeses made with this strain compared with control cheeses.

CONCLUSION

The present work represents a first contribution to knowledge of the ripening process of Argentinean goat's cheeses made with the addition of autochthonous adjunct cultures. The results suggest that E. faecium ETC3 showed a significant effect during ripening, which was reflected both in the profiles of proteolysis, lipolysis and volatile compounds and in the global sensory perception of cheeses.

Two strains of nonstarter lactobacilli increased the production of flavor compounds in soft cheeses

The contribution to flavor generation and secondary proteolysis of 2 strains of mesophilic lactobacilli isolated from cheese was studied. Miniature soft cheeses (200 g) were produced with or without the inclusion of a culture of Lactobacillus plantarum I91 or Lactobacillus casei I90 in the starter composed of Streptococcus thermophilus. During ripening, cheeses containing the added lactobacilli showed an increased content of total free amino acids, but this increase was only significant in cheeses with Lb. plantarum I91. In addition, free amino acid profiles were modified by selective increases of some amino acids, such as Asp, Ser, Arg, Leu, and Phe. Cheeses inoculated with Lb. plantarum I91 or Lb. casei I90 were also characterized by a significantly higher concentration of diacetyl, a key flavor compound, and an increased content of acetoin. Results suggest an increase in the catabolism of either citrate or aspartate, with the production of the derived aroma compounds. Overall, aspartate content increased in both lactobacilli-added cheeses, whereas citrate was more or less constant, suggesting that aspartate could be the source of increased diacetyl and acetoin. A triangle aroma test showed that the addition of the lactobacilli strains significantly changed the sensory attributes of cheeses. At least 11 of 12 panelists commented that the aroma of cheeses with adjuncts was more buttery than that of control cheeses, which is desirable in most soft cheeses. Both Lb. plantarum I91 and Lb. casei I90 performed well as adjunct cultures by influencing cheese aroma development and cheese proteolysis.

Chemical and instrumental approaches to cheese analysis

Overcoming the complexity of cheese matrix to reliably analyze cheese composition, flavor, and ripening changes has been a challenge. Several sample isolation or fractionation methods, chemical and enzymatic assays, and instrumental methods have been developed over the decades. While some of the methods are well established standard methods, some still need to be researched and improved. This chapter reviews the chemical and instrumental methods available to determine cheese composition and monitor biochemical events (e.g., glycolysis, lipolysis, and proteolysis) during cheese ripening that lead to the formation of cheese flavor. Chemical and enzymatic methods available for analysis of cheese composition (fat, protein, lactose, salt, nitrogen content, moisture, etc.) are presented. Electrophoretic, chromatographic, and spectroscopic techniques are also reviewed in the light of their application to monitor cheese ripening and flavor compounds. Novel instrumental methods based on Fourier-transform infrared spectroscopy that are currently being researched and applied to cheese analysis are introduced.

Characterisation of proteolysis profile of Argentinean sheep cheeses made by two different production methods

BACKGROUND

In this work the proteolysis profiles of Argentinean sheep cheeses made by two different production methods were studied in order to develop products with typical and defined features. Cheeses with a starter of Streptococcus thermophilus, curd cut to corn grain size, washed and heated to 43 degrees C (S cheeses) and cheeses with a mixed starter of Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus bulgaricus, curd cut to rice grain size, unwashed and heated to 47 degrees C (L cheeses) were manufactured. The cheeses were ripened at 12 degrees C and 80% relative humidity for 180 days and samples were taken throughout this period.

RESULTS

Gross composition and primary proteolysis were similar for both types of cheeses. Streptococci counts diminished from 10(9) to 10(7) colony-forming units g(-1) during ripening in both S and L cheeses. Lactobacilli counts in L cheeses decreased during ripening and disappeared at 180 days. L cheeses had significantly lower pH values and showed higher peptidolysis than S cheeses. Triangle sensory evaluation indicated important differences between the two types of cheeses.

CONCLUSION

S cheeses had a low proteolysis level and a soft flavour, making them appropriate for consumption after a short ripening time. L cheeses had a higher proteolysis level and more intense sensory characteristics, making them appropriate for consumption after a longer ripening time.

Genotypic and technological characterization of Leuconostoc isolates to be used as adjunct starters in Manchego cheese manufacture

Twenty-seven Leuconostoc (Ln.) isolates from Manchego cheese were characterized by phenotypic and genotypic methods, and their technological abilities studied in order to test their potential use as dairy starter components. While phenotypic diversity was evaluated by studying the biochemical characteristics of technological interest (i.e. acidifying and aminopeptidase activities), genotypic diversity was evidenced by using Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR). Additional technological abilities such as lipolytic, proteolytic and autolytic activities, salt and pH tolerance and production of dextran, flavour compounds and biogenic amines, were investigated. The marked differences among strains reflected the existing biodiversity in naturally fermented products. After statistically evaluating their performance, strains C0W2, belonging to Ln. lactis, and C16W5 and N2W5, belonging to Ln. mesenteroides subsp. dextranicum, revealed the best properties to be used in mixed dairy starter cultures. This study evidences the fact that natural environments can be considered as a proper source of useful strains, for the dairy industry.

Viability and contribution to proteolysis of an adjunct culture of Lactobacillus plantarum in two model cheese systems: cheddar cheese-type and soft-cheese type

AIMS

The influence of the cheese-making process, ripening conditions and primary starter on the viability and proteolytic activity of an adjunct culture of Lactobacillus plantarum I91 was assessed in two miniature cheese models, representative of Cremoso Argentino and Cheddar cheeses.

METHODS AND RESULTS

Cheeses with and without adjunct culture were made under controlled microbiological conditions and sampled during ripening for physicochemical and microbiological analyses. The addition of lactobacilli neither contributed to acid production nor caused changes to the composition of the cheeses. The strain studied exhibited good development and survival and showed a similar growth pattern in both cheese matrices. The adjunct culture caused changes to secondary proteolysis of both cheese types, which were evidenced by modification of peptide profiles and the increase in the levels of some individual amino acids as well as the total content of free amino acids. The changes observed were consistent with the acceleration of proteolysis in the two cheese models assayed.

CONCLUSION

Lactobacillus plantarum I91 has desirable and robust technological properties, which makes it a suitable adjunct culture for cheese-making.

SIGNIFICANCE AND IMPACT OF THE STUDY

Other cultures and environmental conditions prevailing in the food may affect the viability of adjunct cultures and its biochemical activities; this is the first report describing the successful performance of an adjunct culture of Lact. plantarum I91 in two different model cheese systems.

Characterization of Italian cheeses ripened under nonconventional conditions

Four Italian cheeses (Casciotta di Urbino, Barricato San Martino, Vento d'Estate, and Ubriaco di Raboso) nonconventionally ripened under different plant materials (walnut leaves, herbs, hay, and wine by-products, respectively) were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for gross composition were rather similar. Because primary starters were not used for manufacture, the endogenous lactic acid bacteria were mainly present (7.0 to 9.0 log10 cfu/g). Except for Lactobacillus paracasei and Leuconostoc mesenteroides, which were commonly identified in 3 cheeses, Lactococcus lactis, Enterococcus sanguinicola, Lactobacillus brevis, Enterococcus durans/Enterococcus faecium, Lactobacillus plantarum, and Weissella cibaria/Weissella confusa were variously found in the 4 cheeses. Random amplification of polymorphic DNA-PCR analysis showed the biodiversity among the strains, and the species of lactobacilli were in part grouped according to their origin. As shown by the principal component analysis of reverse-phase fast protein liquid chromatography data for the pH 4.6-soluble fractions and by the determination of free AA, the secondary proteolysis of Barricato San Martino and Vento d'Estate mainly differed from the other 2 cheeses. Purge-and-trap and solid-phase microextraction were coupled with gas chromatography-mass spectrometry to determine volatile compounds. Vento d'Estate showed the highest levels of almost all chemical classes, and Casciotta di Urbino was characterized by a very low level of volatile components. Esters, ketones, and terpenes were the chemical classes that mainly differentiated the cheeses. Several volatile compounds seemed to be released directly from the plant materials used for ripening, especially terpenes for Vento d'Estate cheese. The lowest level of volatile free fatty acids was found in Casciotta d'Urbino, in which rennet paste was not used during manufacture. The highest concentration of free fatty acids, especially butyric and caproic acids, was found in Vento d'Estate cheese.

Characterization of Fiore Sardo cheese manufactured with the addition of autochthonous cultures

This work evaluated the effect of adjunct autochthonous cultures on the chemical, microbiological and sensory characteristics of Fiore Sardo cheese during ripening. A total of twelve batches of cheeses were manufactured according to the technical Disciplinary of Fiore Sardo cheese, with and without different combinations of autochthonous strains isolated from the native microflora of artisanal Fiore Sardo. There were no significant differences in the cheese compositional parameters between experimental and control cheeses, but the addition of cultures led to a statistically significant decrease in pH values in experimental cheeses. The evolution of total mesophilic bacteria, total coliforms and lactic acid bacteria were significantly influenced by the addition of autochthonous cultures in most of the experimental cheeses. As for sensory characteristics, all the experimental cheeses reported significantly higher scores especially for shape, texture, interior openings, taste and aftertaste. This study demonstrated the beneficial effect of the addition of selected autochthonous cultures in accelerating the disappearance of undesirable flora and improving the typical sensory characteristics of the cheese, and confirmed the importance of ewes' milk as a source of technologically interesting strains that could be used to ensure a higher quality of artisanal cheese productions.

Comparison of the Compositional, Microbiological, Biochemical, and Volatile Profile Characteristics of Nine Italian Ewes’ Milk Cheeses

Nine Italian ewes' milk cheeses were compared for compositional, microbiological, biochemical, and volatile profile characteristics. Mean values for the gross composition were rather similar among cheeses. The lowest pH values were found for cheeses that used primary starters. At the end of ripening, cheeses made from raw milk contained >6.0 log10 cfu/g of nonstarter lactic acid bacteria. Several species of lactobacilli were identified, but Lactobacillus plantarum and Lactobacillus paracasei were dominant. Random amplified polymorphic DNA-PCR analysis showed the biodiversity among the strains, and in several cases a relationship with the cheese of provenance. Cheeses differed mainly for secondary proteolysis, as shown by the principal component analysis applied to reversed-phase fast protein liquid chromatography data of the pH 4.6-soluble fractions and by determination of the free AA. A total of 113 volatile components were identified in the Italian Pecorino cheeses by solid-phase microextraction coupled with gas chromatography-mass spectrometry analysis. The volatile profiles of the 9 cheeses differed significantly. Quantitatively, alcohols were the most abundant chemical class for some cheeses, whereas ketones were the most abundant for other cheeses. Esters and carboxylic acids were largely found. Specific volatile components seemed to distinguish specific cheeses.