The aim of the present study was to characterize LAB isolates from raw-milk cheeses, to evaluate some of their technological properties and to select a few ‘wild’ LAB strains that could potentially be used as starter cultures. LAB strains were isolated and identified from raw milk, curd, and cheese at 30, 60, and 90 days of ripening. A total of 100 strains were isolated, 20 from each phase of ripening. All isolates were tested for acidification ability, curd formation, and aroma production at 32 °C and 42 °C after 24 and 48 h. Following the acidification test, 42 strains were selected for identification and characterization of their technological properties. A high proportion of lactic acid bacteria and Gram + cocci were found throughout the cheese-making process. Enterococci reached their maximum proportion on the 7th day of ripening while Lactobacilli increased significantly during the first month of ripening. Forty-two strains were identified by phenotypic, biochemical, and molecular techniques. Lactococci were predominant in raw milk and curd while Lactobacilli in the ripening of the cheese. Four LAB strains including one Leuconostoc pseudomenteroides, two Lacticaseibacillus paracasei subsp. paracasei and one Enterococcus hirae, were proposed for their potential use as starters or secondary cultures.

Pectin and polyphenols have been obtained from choice peach flesh using microwave extraction, with the resulting extracts used in functionalizing strained yogurt gels. A Box-Behnken design was utilized in order to co-optimize the extraction process. Soluble solid content, total phenolic content, and particle size distributions were measured in the extracts. Extraction at pH 1 yielded the highest phenolic content, while increases in the liquid-to-solid ratio resulted in a decrease in soluble solids and an increase in particle diameter. Selected extracts were then incorporated into strained yogurt, and the resulting gel products were assessed for color and texture over a two-week period. All samples were darker and had more red tones than the control set yogurt, while exhibiting less yellow tones. The cohesiveness of all samples remained stable over the gels' aging of two weeks (break-up times always remaining within 6 s and 9 s), which is close to the expected shelf-life of such products. The work required for the deformation of most samples increases with time, indicating that the products became firmer due to the macromolecular rearrangements in the gel matrix. The extracts obtained with the highest microwave power (700 W) give less firm samples. This was due to the microwave-induced loss of conformation and self-assembly of the extracted pectins. The hardness of all samples increased over time, gaining from 20 to 50% of the initial hardness due to the rearrangement of the pectin and yogurt proteins over time. The products with pectin extracted at 700 W were again exceptions, losing hardness or remaining stable after some time. Overall, this work combines the sourcing of polyphenols and pectin from choice fruit; it uses MAE for isolating the materials of interest; it mechanically examines the resulting gels; and it performs all the above under a specifically-set experimental design aiming towards optimizing the overall process.

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.

This study was conducted to evaluate the microbiological status of cheese made from unpasteurized cows' milk, to examine the safety of the cheese and to observe the changes that occurred in its microbial community during ripening and storage. Furthermore, the pH, the moisture and salt concentration were also monitored throughout processing, ripening and storage. Seven cheesemaking trials took place along with the microbiological and physicochemical analysis of the milk, curd and cheese produced. The milk used for the cheesemaking, two curd samples before the heating and two after the heating, two cheese samples at days 3, 7, 15, 30, 60 and 90 were subjected to microbiological analysis for total mesophilic bacterial count (for milk only), Enterobacteriaceae, E. coli, Staphylococcus, Salmonella, Listeria, and Clostridium. The microbiological quality of raw milk was found to be good. It was initially slightly above the EU limit but improvements associated with farm biosecurity and milking equipment hygiene led to a significantly improved milk quality. A small increase in the prevalence of indicator microorganisms in curd and cheese samples was observed for the first few days, followed by a relatively stable condition as manufacturing proceeded and throughout the ripening of the final product. In two cheesemaking trials, Clostridium perfringens and Salmonella spp. were detected, the first originating from the milk and the second from the environment. The use of good-quality raw milk under sanitary conditions, the application of good manufacturing practices and a maturation period in a controlled environment were found to be the necessary prerequisites for the production of safe raw cheese products.

The objective of this study was to assess the detection sensitivity of four commercial microbial inhibition assays (MIAs) in comparison with the results by High Pressure Liquid Chromatography with Diode Array Detection (HPLC-DAD) for residues of three tetracyclines, trimethoprim and sulfadiazine in fortified raw milk samples. MIAs showed fairly good results at detecting sulfadiazine residues, whereas concerning tetracyclines and trimethoprim residues, most of the kits showed insufficient results. HPLC analysis revealed high recoveries of examined compounds with detection limits below their respective maximum residue levels (MRLs). The HPLC method was validated determining linearity, accuracy, precision, detection capability and decision limit. Subsequently, both methods were used to monitor several cow and sheep milk samples for the presence of antibacterial agents. Results obtained showed that MIAs could be successfully used for the analysis of different milk types. However, milk spoilage which was observed in some cases could decrease the sensitivity of the kits, a fact that does not seem to influence the effectiveness of HPLC-DAD method.

Souvlaki is a popular Greek meat product consisting of small chunks or cubes of pork threaded on a small wooden or metal skewer. In the present study, 105 samples of raw pork souvlaki obtained from retail shops in Thessaloniki (Northern Greece) were screened for the incidence of Salmonella, Listeria, and Campylobacter and their susceptibility to various antimicrobial agents; serotyping of the isolates was also performed. Of the samples tested, 1.9% were positive for Salmonella and yielded 3 serovars (S. SaintPaul, S. Fyris and S. Typhimurium); 31.4% proved positive for Listeria spp. with 6.7% yielding L. monocytogenes isolates belonged to molecular serogroups 2 (serotypes 1/2c and 3c) and 4 (serotypes 4b, 4d, and 4e). Campylobacter spp. were not detected in any of the samples tested. The antimicrobial susceptibility to various antimicrobial agents of 11 Salmonella strains and 7 L. monocytogenes strains was also determined by disc diffusion method. Salmonella spp. were susceptible to a panel of 12 antibiotics but displayed intermediate resistance to tetracycline. L. monocytogenes isolates were resistant to nalidixic acid and ceftriaxone, partly resistant to clindamycin and cefotaxime, but sensitive to all antibiotics commonly used in veterinary and human listeriosis. Our findings indicate that souvlaki could be a potential vehicle of food borne infections due to strains of L. monocytogenes and Salmonella spp. in the case of inadequate thermal processing. In addition, good hygienic practices must be applied to avoid cross-contamination during preparation or handling of the product.

The present study was carried out to assess the detection sensitivity of four microbial inhibition assays (MIAs) in comparison with the results obtained by the High Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD) method for antibiotics of the β-lactam group and chloramphenicol in fortified raw milk samples. MIAs presented fairly good results when detecting β-lactams, whereas none were able to detect chloramphenicol at or above the permissible limits. HPLC analysis revealed high recoveries of examined compounds, whereas all detection limits observed were lower than their respective maximum residue limits (MRL) values. The extraction and clean-up procedure of antibiotics was performed by a modified matrix solid phase dispersion procedure using a mixture of Plexa by Agilent and QuEChERS as a sorbent. The HPLC method developed was validated, determining the accuracy, precision, linearity, decision limit, and detection capability. Both methods were used to monitor raw milk samples of several cows and sheep, obtained from producers in different regions of Greece, for the presence of examined antibiotic residues. Results obtained showed that MIAs could be used effectively and routinely to detect antibiotic residues in several milk types. However, in some cases, spoilage of milk samples revealed that the kits' sensitivity could be strongly affected, whereas this fact does not affect the effectiveness of HPLC-DAD analysis.

One hundred and two samples of mussels (Mytilus galloprovincialis), harvested from approved shellfish coastal water in northern Greece, were screened for the presence and antimicrobial resistance of Listeria monocytogenes. Listeria spp. were isolated according to International Organization for Standardization method 11290-1: 1996/FDAM 1: 2004(E) and identified using a multiplex polymerase chain reaction (PCR) system. The serovar identity of L. monocytogenes isolates was also determined with a multiplex PCR assay. The antimicrobial profile of the isolates was determined by the disk diffusion method. Listeria spp. were present in 8 of 102 samples tested (8%) and only 1 (1%) yielded L. monocytogenes. The isolate identified as L. monocytogenes was defined as serogroup I and found to be resistant to nalidixic acid and streptomycin. In conclusion, this study demonstrated that L. monocytogenes is not commonly found in mussels harvested in the North Aegean Sea, whereas there is a higher possibility of mussels' contamination with other Listeria species.

The flow behavior, pH and the main microbial populations of kefir, produced from commercial pasteurized and homogenized bovine milk with fat contents of 0, 1.5 or 3.5% (w/w) and the addition of 1, 3 or 7% (w/w) of kefir grains, were examined after storage for 0, 7 and 14 days at 4C. Increasing the kefir grain inoculum or the storage time of the final product resulted in pH reduction. The viscosity of kefir increased as the fat content of the milk increased, whereas it was reduced during storage for 14 days. Samples prepared with 7% kefir grains exhibited greater viscosity values when compared with samples prepared with 1 and 3%. The increase of kefir grain content resulted in a reduction of lactococci and an increase of yeasts, whereas increasing storage time of kefir resulted in population reduction for lactococci and lactobacilli and to an increase of yeasts. PRACTICAL APPLICATIONS Kefir is a dairy product with noticeable nutritional and health-related attributes increasing its market potential in today's health-oriented food market. The quality of the product, its standardization and the parameters affecting it is of scientific and commercial interest. The present study investigates the effect of milk fat content, kefir grain inoculum and storage time on the microbial populations, the pH and especially the rheological properties of the product. A prototype pneumatic tube rheometer was used for the study of the rheological properties of kefir and their development during fermentation and storage.

Yeast isolates from infant faeces and Feta cheese were characterized to species level by phenotypic criteria, Randomly Amplified Polymorphic DNA (RAPD)-PCR and mitochondrial DNA (mt-DNA) restriction analysis. Results suggested that there is a good agreement between phenotypic characterization of yeasts and RAPD-PCR at species level; in addition, RAPD-PCR as well as mt-DNA restriction analysis provided good discrimination at strain level. Some technological and probiotic properties of selected strains were also investigated. The test strains exhibited lipolytic and proteolytic activities. They also tolerated low pH and survived satisfactory in gastric juice in vitro as well as in the presence of bile. In general, the isolates from faeces were more resistant to low pH and bile than those from Feta cheese. Selected strains could be used as starter supplements for industrial fermentations.

In the present work randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) with primers M13 and RF2 was applied to the identification at species level of yeast strains isolated from cheeses. RAPD-PCR analysis of the type strains of different yeast species gave distinctive band profiles that allowed a clear differentiation of all the considered species. Forty-two of the 48 dairy associated yeasts were clearly assigned to the species Saccharomyces cerevisiae, Kluyveromyces marxianus (anamorph Candida kefyr), Kluyveromyces lactis (anamorph Candida sphaerica), Debaryomyces hansenii (anamorph Candida famata), Yarrowia lipolytica and Torulaspora delbrueckii (anamorph Candida colliculosa). The method, which is rapid and easy to perform, could be a useful tool for the identification of yeasts present in dairy products.