Comparison of microflora, chemical and sensory characteristics of artisanal Manchego cheeses from two dairies

Comparative qualitative and quantitative analysis of lactic acid bacteria by molecular methods in different Greek cheeses

In the present research communication, we report on identification and quantification of four main lactic acid bacteria (LAB) genera (Lactococcus, Lactobacillus, Streptococcus and Leuconostoc), most common in Greek cheeses, by a novel culture-independent method. More specifically, new primers were designed to be used in both multiplex PCR for simultaneous identification and in real-time PCR for quantification of the LAB. The method was validated by applying it in parallel to culture-dependent method in a variety of cheeses from different Greek geographical locations, of different animal milk origins and of different production methods. While the standard plate culture method showed absence of Leuconostoc sp. in all cheeses, the culture-independent methods detected all four LAB genera studied. Furthermore, the relative presence of the four genera detected by the culture-independent method showed a pattern present in almost all cheese samples tested, indicating Lactococcus genus as the dominant one.

Ripening Changes of the Chemical Composition, Proteolysis, and Lipolysis of a Hair Sheep Milk Mexican Manchego-Style Cheese: Effect of Nano-Emulsified Curcumin

The influence of nano-emulsified curcumin (NEC) added to the hair sheep milk, prior to cheese-making, on the chemical composition, lipolysis, and proteolysis of manchego-style cheeses were evaluated throughout 80 days of ripening. The addition of NEC to the milk resulted in cheeses with the same moisture content (42.23%), total protein (23.16%), and water activity (0.969) (p > 0.05). However, it increased the fat and ash levels from 26.82% and 3.64% in B 10 ppm to 30.08% and 3.85% in C 10 ppm, respectively, at the end of the ripening (p < 0.05). The total phenolic content and antioxidant activity of experimental cheeses increased during ripening, and the fatty acid groups showed significant changes occurred to a greater extent in the first days of ripening (p < 0.05). The lipolysis increased consistently in all cheeses until day 40 of ripening, to decrease at the end, while proteolysis increased during all ripening time in all samples (p < 0.05); the addition of NEC did not alter the primary proteolysis of manchego-style cheeses, but it modified secondary proteolysis and lipolysis (p < 0.05). Principal component analysis was useful for discriminating cheeses according to their chemical composition and classified into four groups according to their ripening time. This research highlights the potential of CNE to fortify dairy foods to enhance their functionality.

Antimicrobial Activity of Myrtus communis L. and Rosmarinus officinalis L. Essential Oils against Listeria monocytogenes in Cheese

Listeria monocytogenes has been referred to as a concern microorganism in cheese making due to its ability to survive and grow in a wide range of environmental conditions, such as refrigeration temperatures, low pH and high salt concentration at the end of the production process. Since cheese may be a potential hazard for consumers, especially high-risk consumers (e.g., pregnant, young children, the elderly, people with medical conditions), efforts of the dairy industry have been aimed at investigating new conservation techniques based on natural additives to meet consumers’ demands on less processed foods without compromising the food safety. Thus, the aim of this study was to evaluate the efficacy of Myrtus communis L. (myrtle) and Rosmarinus officinalis L. (rosemary) essential oils (EO) against Listeria monocytogenes ATCC 679 spiked in sheep cheese before ripening. After the cheesemaking process, the samples were stored at 8 °C for 2 h, 1 d, 3 d, 14 d and 28 d. The composition of EO was identified by gas chromatography-mass spectrometry (GC-MS) analysis. Constituents such as 1,8-cineole, limonene, methyl-eugenol, α-pinene, α-terpineol, α-terpinolene and β-pinene were present in both EO, accounting for 44.61% and 39.76% from the total of chemical compounds identified for myrtle and rosemary EO, respectively. According to the chemical classification, both EO were mainly composed of monoterpenes. Minimum inhibitory concentration (MIC) against L. monocytogenes was obtained at 31.25 μL/mL to myrtle EO and at 0.40 μL/mL to rosemary EO. Then, cheeses were inoculated with L. monocytogenes (Ca. 6 log CFU/mL) and EO was added at MIC value. The addition of rosemary and myrtle EO displayed lower counts of L. monocytogenes (p < 0.01) (about 1–2 log CFU/g) during the ripening period compared to control samples. Ripening only influences (p < 0.001) the growth of L. monocytogenes in control samples. Since rosemary and myrtle EO do not exert any negative impact on the growth of native microflora (p > 0.05), their use as natural antimicrobial additives in cheese demonstrated a potential for dairy processors to assure safety against L. monocytogenes.

Physicochemical Composition, Antioxidant Status, Fatty Acid Profile, and Volatile Compounds of Milk and Fresh and Ripened Ewes' Cheese from a Sustainable Part-Time Grazing System

We conducted the first nutritional analysis of dairy products from the traditional Roja Mallorquina sheep breed. Samples of bulk raw milk were taken twice a month from December 2015 to March 2016 from sheep fed using a part-time grazing system, and fresh soft (FC, n = 8) and ripened (RC, n = 8) cheeses were made. The variability in vitamins, total phenolic compounds (TPC), total antioxidant capacity (TAC), and fatty acid (FA) content was influenced by the cheese-making process (differences between the cheese and the original milk) and by the type of cheese-making technology (mainly related to heating, the use of starter culture, and ripening). The most notable physicochemical characteristic of the cheeses was low fat content (24.1 and 29.6 g/100 g for FC and RC). Milk and RC were characterised by major concentrations of retinol (211.4 and 233.6 μg/100 g dry matter (DM), respectively) and TPC (18.7 and 54.6 μg/100 g DM, respectively), while FC was characterised by major concentrations of retinol (376.4 μg) and α-tocopherol (361.7 μg). The fat-soluble components of the FC generally exhibited better nutritional value for human health than those of the milk and RC, with a higher level of retinol and α-tocopherol; lower values for saturated FA, atherogenic, and thrombogenic indices; and higher levels of monounsaturated FA, polyunsaturated FA, n-3, and n-6. Acids, alcohols, and ketones comprised almost 95% of the volatile compounds detected. Acetoin and products of lactose and citrate metabolism played an important role in the development of the aromatic attributes of both kinds of cheese. This preliminary study can contribute to add value to these traditional products according to healthy nutritional criteria and supports the implementation of strategies to promote their commercialisation and obtain product labelling as “pasture-fed” or specific marks.

Behaviour of Non-O157 STEC and Atypical EPEC during the Manufacturing and Ripening of Raw Milk Cheese

This study was carried out to assess the survival of Shiga toxin-producing E. coli (STEC) and atypical enteropathogenic Escherichia coli (aEPEC) during the traditional manufacturing and ripening of Spanish hard cheese from raw cow’s milk. Milk samples were spiked with up to 3.1–3.5 log cfu/mL of one strain of STEC (O140:H32 serotype) and one of aEPEC (serotype O25:H2). The first steps of cheesemaking allow for a STEC and aEPEC increase of more than 1 log cfu/mL (up to 4.74 log cfu/g and 4.55 log cfu/g, respectively). After cheese pressing, a steady reduction of both populations was observed, with the STEC strain being more sensitive. The studied pathogenic E. coli populations decreased by 1.32 log cfu/g in STEC and 0.59 log cfu/g in aEPEC in cheese ripened during a minimum period of 60 d. Therefore, a moderate contamination by these diarrhoeagenic E. coli pathotypes, in particular, with aEPEC, on cheese manufactured from raw milk may not be totally controlled through the cheesemaking process and during a maturation of 90 d. These findings remark the importance of improvement in bacteriological quality of raw milk and cross-contamination prevention with diarrhoeagenic E. coli in the dairy industry.

High Hydrostatic Pressure as a Tool to Reduce Formation of Biogenic Amines in Artisanal Spanish Cheeses

Two artisanal varieties of cheese made in Spain, one made of ewes' raw milk and the other of goats' raw milk were selected to evaluate the effect of a high hydrostatic pressure (HHP) treatment at 400 MPa during 10 min at 2 °C on the formation of biogenic amines (BA). These conditions were applied at the beginning of the ripening (before the 5th day; HHP1) and in the case of ewes' milk cheeses also after 15th days (HHP15). BA formation was greatly influenced by HHP treatments in both types of cheese. HHP1 treatments significantly reduced the amounts of BA after ripening, being tyramine and putrescine the most affected BA in goats' milk cheeses and tyramine and cadaverine in ewes' milk cheeses. The BA reduction in the HHP1 samples could be explained by the significant decrease in microbiological counts, especially in the LAB, enteroccocci and enterobacteria groups at the beginning of ripening. The proteolysis in these samples was also affected reducing the amount of free amino acids. Although proteolysis in ewes' milk cheeses HHP15 was similar than in control samples a reduction of BA was observed probably because the decrease caused on microbial counts.

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.

Chemical, microbiological, textural, color, and sensory characteristics of pressed ewe milk cheeses with saffron (Crocus sativus L.) during ripening

Adding saffron to dairy products represents an innovative practice to introduce them to niche markets. This paper represents a contribution to this field, as few studies have evaluated the influence of this spice on general aspects and ripening parameters of cheese. In this work, pasteurized ewe milk pressed cheeses with saffron were made to study compositional, microbiological, color, textural, and sensory characteristics in relation to saffron concentration and ripening time. The main changes were observed on sensory characteristics and color. In addition, compositional, textural, and microbiological changes could be observed; among them, saffron cheeses were firmer and more elastic but less prone to fracture. A remarkable result that could lead to further studies is that saffron addition slightly slowed down growth of total and lactic acid bacteria. This resulted in a slightly lower rate of pH decrease during pressing and, as a consequence, lower salt and water content. Compositional differences were not evident by the end of the ripening period.

Microbiological and chemical characterization of a typical Italian cheese: Robiola di Roccaverano

Robiola di Roccaverano is a traditional Italian goat's milk cheese carrying a Protected Designation of Origin (PDO). The present work studied both cheese microflora and cheese physicochemical characteristics to obtain a more accurate description of this PDO product. Multivariate statistical analysis (PCA) was performed to evaluate the influence of cheesemaking (artisanal and industrial), ripening time, and season of production on cheese characteristics. Multiplex PCR and fatty acid methyl esters (FAMEs) were used to identify the kind of milk employed by Robiola di Roccaverano producers. The results obtained highlight some product differences between the artisanal and industrial products. These differences were most evident in the microbiological data. The use of PCA allowed cheese samples to cluster on the basis of their age (fresh or ripened), the origin of production (artisanal and industrial), and even the season of production. Gross composition, microbiological parameters, and gas chromatographic analyses of FAMEs provided the most important parameters for Robiola di Roccaverano cheese characterization.