Lactic Acid Bacteria (LAB) exert a fundamental activity in cheese production, as starter LAB in curd acidification, or non-starter LAB (NSLAB) during ripening, in particular in flavor formation. ...NSLAB originate from the farm and dairy environment, becoming natural contaminants of raw milk where they are present in very low concentrations. Afterward, throughout the different cheesemaking processes, they withstand chemical and physical stresses becoming dominant in ripened cheeses. However, despite a great body of knowledge is available in the literature about NSLAB effect on cheese ripening, the investigations regarding their presence and abundance in raw milk are still poor. With the aim to answer the initial question: "which and how many LAB are present in cow raw milk used for cheese production?," this review has been divided in two main parts. The first one gives an overview of LAB presence in the complex microbiota of raw milk through the meta-analysis of recent taxonomic studies. In the second part, we present a collection of data about LAB quantification in raw milk by culture-dependent analysis, retrieved through a systematic review. Essentially, the revision of data obtained by plate counts on selective agar media showed an average higher concentration of coccoid LAB than lactobacilli, which was found to be consistent with meta-taxonomic analysis. The advantages of the impedometric technique applied to the quantification of LAB in raw milk were also briefly discussed with a focus on the statistical significance of the obtainable data. Furthermore, this approach was also found to be more accurate in highlighting that microorganisms other than LAB are the major component of raw milk. Nevertheless, the variability of the results observed in the studies based on the same counting methodology, highlights that different sampling methods, as well as the "history" of milk before analysis, are variables of great importance that need to be considered in raw milk analysis.
Members of the
group, including species classified currently as
,
, and
, are among the most frequently found species in raw milk, hard cooked, long-ripened cheeses. Starting from very low numbers in ...raw milk, they become dominant in the cheese during ripening, selected by physical and chemical changes produced by cheese making and ripening. Their presence at different stages of cheese making and ripening is crucial in defining product features. For these reasons, the scientific community has been more and more interested in studying these "tiny but mighty microbes" and their implications during cheese making and ripening. The present paper reviews the current literature on the effect of
in cheeses, with particular reference to the case of Parmigiano Reggiano and Grana Padano, two of the most famous PDO (Protected Designation of Origin) Italian cheeses. Recent advances regarding the selection of new wild strains able to persist until the end of ripening and carrying out slow but crucial activities resulting in specific aromatic features, are also presented.
BackgroundBiologically appropriate raw food (BARF) diet is becoming more and more popular among pet owners in Europe. However, there are documented microbiological risks associated with raw feeding, ...and this study aimed to determine the presence of human pathogens in commercially frozen BARF products sold in Italy.Methods Salmonella species, Escherichia coli O157:H7, Listeria monocytogenes and Campylobacter species were identified. The general microbiological quality of BARF products and hygiene were also evaluated. Sample size was limited and therefore the study may not be representative of a larger sample.ResultsNone of the tested samples showed total bacterial count (TBC) higher than the limit set to consider a sample unacceptable. However, 14 out of 21 samples showed TBC higher than the limit set to consider a sample marginally acceptable. A high percentage of samples were contaminated by the aforementioned pathogens, highlighting the need for pet owners to be aware of the risks of this feeding strategy both to themselves and to their pets.ConclusionsConsidering that BARF diet meals can be prepared at home using the hands, as well as tools and spaces that could be shared, guidelines on safer handling of these pet food products should be recommended by veterinarians and nutritionists.
Lactic acid bacteria (LAB) are involved in producing a considerable number of fermented products consumed worldwide. Many of those LAB fermented foods are recognized as beneficial for human health ...due to probiotic LAB or their metabolites produced during food fermentation or after food digestion. In this review, we aim to gather and discuss available information on the health-related effects of LAB-fermented foods. In particular, we focused on the most widely consumed LAB-fermented foods such as yoghurt, kefir, cheese, and plant-based products such as sauerkrauts and kimchi.
Impedance microbiology is a method that enables tracing microbial growth by measuring the change in the electrical conductivity. Different systems, able to perform this measurement, are available in ...commerce and are commonly used for food control analysis by mean of measuring a point of the impedance curve, defined "time of detection." With this work we wanted to find an objective way to interpret the metabolic significance of impedance curves and propose it as a valid approach to evaluate the potential acidifying performances of starter lactic acid bacteria to be employed in milk transformation. To do this it was firstly investigated the possibility to use the Gompertz equation to describe the data coming from the impedance curve obtained by mean of BacTrac 4300®. Lag time (λ), maximum specific M% rate (μmax), and maximum value of M% (Yend) have been calculated and, given the similarity of the impedance fitted curve to the bacterial growth curve, their meaning has been interpreted. Potential acidifying performances of eighty strains belonging to
subsp.
, and
species have been evaluated by using the kinetics parameters, obtained from Excel add-in DMFit version 2.1. The novelty and importance of our findings, obtained by means of BacTrac 4300®, is that they can also be applied to data obtained from other devices. Moreover, the meaning of λ, μmax, and Yend that we have extrapolated from Modified Gompertz equation and discussed for lactic acid bacteria in milk, can be exploited also to other food environment or other bacteria, assuming that they can give a curve and that curve is properly fitted with Gompertz equation.
Time of ripening has a strong impact on shaping the valuable and recognizable characteristics of long-ripened types of cheese such as Parmigiano Reggiano (PR) due to the interrelationship between ...microbiota and proteolysis that occurs during ripening. The derived peptide profile is linked to cheese quality and represents the canvas for enzymes upon digestion, which could be responsible for the release of potentially bioactive peptides (BPs). In this study, we aimed at investigating the presence of BP in 72 PR cheese samples of different ripening times, from curd to 24 months of ripening, produced in six different dairies, and following their fate after simulated gastrointestinal digestion. A small number of peptide sequences sharing 100% similarity with known antimicrobial, antioxidant, and ACE-inhibitor sequences were found in PR cheeses, while a higher number of potential BPs were found after their simulated gastrointestinal digestion, in different amounts according to ripening time. Taking advantage of the complex organization of the sampling plan, we were able to follow the fate of peptides considered quality drivers during cheese ripening to their release as functional compounds upon digestion.
Plant derived beverages have recently gained consumers' interest, particularly due to their intrinsic functional properties. They can also act as non-dairy carriers for probiotics and prebiotics, ...meeting the needs of lactose allergic/intolerant people and vegans. Direct fermentation of fruit and vegetables juices by probiotic lactic acid bacteria could be a tool to increase safety, shelf-life, nutrients bioavailability and to improve sensorial features of plant derived juices. This study aims to screen wild
-group strains isolated from dairy matrices for probiotic features, such as acid and bile salts resistance, and test them for the potentiality to ferment celery and orange juices. Strains' ability to produce exopolysaccharides (EPS) in situ is also checked. These evaluations were performed for the first time in fruit and vegetables matrices by means of an impedometric analysis, recently shown to be a suitable and rapid method to measure microorganisms' growth, acidification performances and EPS production. This study allowed the selection of three potentially probiotic
-group wild strains able to ferment fruit and vegetable juices and also producing EPS. These strains with three-in-one abilities could be used to produce new functional fermented plant derived juices.
Despite the fact that strains belonging to
species have not yet been approved for use as starter culture, recent toxicological studies open new perspectives on their potential employment. The aim of ...this study was to evaluate the ability of a wild
(
4451) strain to modify milk viscosity compared to
subsp.
, which is commonly used for this purpose in dairy products. To reach this goal, milk viscosity has been evaluated by means of two very different instruments: one rotational viscometer and the Ford cup. Moreover, water holding capacity was evaluated.
4451, previously isolated from sourdough, was able to acidify milk, to produce polysaccharides
and thus improve milk viscosity. The ability of
4451 to produce at the same time lactic acid and high amounts of polysaccharides makes it a good candidate to improve the composition of starters for dairy products. Ford cup turned out to be a simple method to measure fermented milk viscosity by small- or medium-sized dairies.
Cheese microbiota contribute significantly to the final characteristics of cheeses due to the growth and interaction between cheese microorganisms during processing and ripening. For raw milk ...cheeses, such as Parmigiano Reggiano (PR), the microbiota derive from the raw milk itself, the dairy environment, and the starter. The process of cheese making and time of ripening shape this complex ecosystem through the selection of different species and biotypes that will drive the quality of the final product by performing functions of their metabolism such as proteolysis. The diversity in the final peptide and amino acid composition of the cheese is thus mostly linked to the diversity of this microbiota. The purpose of this study was to get more insight into the factors affecting PR cheese diversity and, more specifically, to evaluate whether the composition of the bacterial community of cheeses along with the specific peptide composition are more affected by the ripening times or by the cheese making process. To this end, the microbiota and the peptide fractions of 69 cheese samples (from curd to cheese ripened 24 months) were analyzed during 6 complete PR production cycles, which were performed in six different dairies located in the PR production area. The relation among microbial dynamics, peptide evolution, and ripening times were investigated in this unique and tightly controlled production and sampling set up. The study of microbial and peptide moieties in products from different dairies – from curd to at least 12 months, the earliest time from which the cheese can be sold, and up to a maximum of 24 months of ripening – highlighted the presence of differences between samples coming from different dairies, probably due to small differences in the cheese making process. Besides these differences, however, ripening time had by far the greatest impact on microbial dynamics and, consequently, on peptide composition.
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