Growth and enterotoxin production of Staphylococcus aureus in Iranian ultra‐filtered white cheese

This study aimed to investigate the growth and enterotoxin production of Staphylococcus aureus during the ripening and storage of Iranian ultra‐filtered white cheese (IUFWC). According to the results, the addition of starter culture had significant inhibitory effects on the growth and enterotoxin production of S. aureus. Moreover, prolong survival and enterotoxin production were observed in the samples with the highest inoculum (5 log CFU/g) of S. aureus. It was concluded that proper activity of the starter culture together with the refrigeration storage of IUFWC was the key element in inhibiting the growth and enterotoxin production of S. aureus.     

Effects of Mentha longifolia L. essential oil and Lactobacillus casei on the organoleptic properties and on the growth of Staphylococcus aureus and Listeria monocytogenes during manufacturing,ripening and storage of Iranian white‐brined cheese

This research evaluated the effects of Mentha longifolia L. essential oil (EO) in concentrations 0, 50, 150 and 300 ppm and Lactobacillus casei (10⁸–10⁹ CFU/mL) on the growth of Staphylococcus aureus and Listeria monocytogenes during the manufacturing, ripening and storage of Iranian white‐brined cheese. The growth of the two pathogens was significantly reduced (P < 0.01) by both EO concentrations ≥50 ppm and probiotic and their combination in the standard manufacturing and storage process conditions of the cheese. Furthermore, the treatment containing 150 ppm of this EO combined with probiotic had a favourable inhibitory effect on the growth of two pathogenic micro‐organisms and also was the most appropriate treatment in sensory assessment. The synergistic effects of the above‐mentioned concentration level between the essential oil and probiotic were significant compared to other treatments, including essential oil and probiotic only. Thus, a lower concentration of this EO can be used when it is combined with this probiotic.     

Occurrence and antibiotic resistance of Escherichia coli,Staphylococcus aureus and Bacillus cereus in raw milk and dairy products in Turkey

In this survey, 150 samples of raw milk, white cheese and ice cream from three different dairy‐processing plants in Ankara were analysed to find out if they were contaminated with Escherichia coli, Staphylococcus aureus or Bacillus cereus. The highest contamination percentages were found in raw milk samples as follows: B. cereus (90%), E. coli (74%) and S. aureus (56%) followed by cheese (70% B. cereus, 60% E. coli, and 48% S. aureus) and ice cream (56% E. coli, 36% S. aureus and 20% B. cereus). The survey showed that 2% of cheese samples were contaminated with E. coli O157. It was also found that the numbers of S. aureus and E. coli in raw milk, cheese and ice cream samples exceeded the numbers permitted under the Turkish Food Codex (TFC). The number of B. cereus in raw milk, cheese and ice cream samples was lower than the limit given in the TFC standards. The study also showed that E. coli and S. aureus exhibit resistance to ampicillin, penicillin, tetracycline, erythromycin, gentamicin and trimethoprim/sulfamethoxazole. Escherichia coli isolates also showed resistance to chloramphenicol and ciprofloxacin but none of them exhibited resistance to cefotaxime. All S. aureus isolates were found to be susceptible to cefotaxime, chloramphenicol, and ciprofloxacin. Bacillus cereus isolates were found to be resistant to ampicillin, penicillin and trimethoprim/sulfamethoxazole and sensitive to cefotaxime, chloramphenicol, ciprofloxacin erythromycin, gentamicin and tetracycline.     

Production of angiotensin-converting enzyme inhibitory peptides in Iranian ultrafiltered white cheese prepared with Lactobacillus brevis KX572382

In this study, ultrafiltered (UF) Iranian white cheese made with adjunct cultures including six Lactobacillus isolates (Lactobacillus brevis, L. casei and L. plantarum) from traditional Iranian Motal cheese. The peptide extract (<5 kDa) of cheese samples were assessed for angiotensin-converting enzyme (ACE)-inhibitory activity during ripening (5 °C). Among the strains used, L. brevis KX572382 (M8) was selected because of the greater increase in (ACE)-inhibitory activity in the cheese (P < 0.05). The highest activity of M8 extract was observed on the 28th (71.72%) day of ripening (P < 0.05). Proteolytic activity assessment and RP-HPLC peptide profile of M8 water-soluble extracts (WSEs) indicated the effect of M8 on further protein degradation due to secondary proteolysis. A total of 7 different peptide sequences, previously known in the literature for their ACE-inhibitory activity, were tentatively identified by LC/ESI-MS in 28-day M8 peptide extract. Although the effect of M8 on pH and the proteolysis development in cheese was significant, no adverse effect was observed on the sensory properties. In conclusion, M8 strain can enhance the functional properties of Iranian UF white cheese.     

Analysis and mathematical modelling of the behaviour of Escherichia coli in the mascarpone cheese during cold storage

The aim of this work was to study the behaviour of E. coli in mascarpone cheese during storage at the temperatures ranging from 3 to 15 °C, as well as application of predictive microbiology to describe the experimental data. The Baranyi, Gompertz and logistic models were fitted at the stage of primary modelling. Although all applied primary models described the growth of micro‐organisms accurately, the most accurate goodness of fit was obtained for the Gompertz model and the growth rates generated by this model were used for secondary modelling. The polynomial model predicted accurately the influence of temperature on the growth rate of E. coli, reaching the adjusted coefficient of linear regression 0.99. Generated predictive model that describes the growth of E. coli in mascarpone cheese constitutes a valuable tool in assessing the microbiological stability of the food product with similar physicochemical properties.     

Effect of high‐pressure treatments on microbial loads and physicochemical characteristics during refrigerated storage of raw milk Serra da Estrela cheese samples

This work studied the effect of high pressure processing (HPP) at 400, 500 and 600 MPa during 10, 5 and 3 min, respectively, on samples ewe cheese manufactured from raw milk, during storage (100 days) at 5 °C. Total aerobic mesophilic and lactic acid bacteria were slightly affected, decreasing by about 1.0 and 0.82 log CFU g^?1, respectively, immediately after HPP treatment at 600 MPa for 3 min, while Enterobacteriaceae, yeasts and moulds, and Listeria innocua were reduced to below the quantification limits. Lactic acid bacteria decreased further during storage, showing increasing inactivation as the pressure level increased. Physicochemical parameters (water activity, moisture content, pH and titratable acidity) were generally not affected by HPP, while lipid oxidation increased throughout storage, with HPP samples showing lower values (50–66%) at 100 days of storage. The results indicated that HPP has potential to improve cheese microbial safety and shelf‐life, with a lower lipid oxidation level than nonpressurised cheese.     

Effect of nisin‐producing Lactococcus lactis starter cultures on the inhibition of two pathogens in ripened cheeses

The effect of Lactococcus lactis nisin‐producing strains, isolated from Italian fermented foods, on the survival of two foodborne pathogens namely Listeria monocytogenes and Staphylococcus aureus was investigated in experimental cheese production. One of the three Lactobacillus lactis nisin innoculated as starters, Lactobacillus lactis 41FL1 lowered S. aureus count by 1.73 log colony‐forming units (cfu)/g within the first 3 days, reaching the highest reduction, 3.54 log cfu/g, by the end of ripening period of 60 days. There was no effect on L. monocytogenes. The application of L. lactis 41FL1 as bioprotective culture in controlling S. aureus shows considerable promise.     

Nutritional composition and sensory attributes of Alaskan flatfishes compared to plaice (Pleuronectes platessa)

Proximate composition, fatty acids profiles and other nutritional values were evaluated for fillets of Limanda aspera (yellowfin sole), Lepidopsetta bilineata (southern rock sole) and Lepidopsetta polyxystra (northern rock sole) and compared to North Sea plaice (Pleuronectes platessa). Additional information is given on the composition of fillets from arrowtooth flounder (Atheresthes stomias). Plaice (0.8% lipid) and Alaska soles (1.0–1.2% lipid) can be classified as lean species, resulting in low 0.3–0.5 g ∑EPA+DHA/100 g muscle, although the fatty acid profiles of the extracted lipids were characterised by high amount of n‐3 fatty acids (33.2–47.3%). Arrowtooth flounder belong to the medium‐fat species (4.3%). Taurine was the most prevalent free amino acid; mean values ranging between 221 mg100 g^?1 and 247 mg100 g^?1 wet weight. The selenium content varied between 130 and 310 μg kg^?1 ww. Sensory attributes of Southern and Northern rock sole were comparable to plaice.     

Detection of Salmonella spp., Yersinia enterocolitica,Listeria monocytogenes and Campylobacter spp. by real‐time multiplex PCR using amplicon DNA melting analysis and probe‐based assay

Syto9 and probe‐based multiplex real‐time PCR assays for simultaneous detection of a group of foodborne pathogens (named SYLC group), targeting Salmonella spp. (invA gene), Yersinia enterocolitica (ystA gene), Listeria monocytogenes (hly gene) and Campylobacter spp. (rrna gene), have been developed. The Syto9 assay generates amplicon DNA melting curve with four peaks of 86.5 ± 0.5, 84 ± 0.5, 81.5 ± 0.5 and 90.5 ± 0.5 °C corresponding Salmonella spp., Y. enterocolitica, L. monocytogenes and Campylobacter spp. targets, respectively. The sensitivities of the Syto9 and TaqMan assays in artificially inoculated chicken wing rinses were in a range of 3.2 × 10² to 3.1 × 10⁴ and 9.8 × 10² to 1.9 × 10⁴ colony‐forming units per millilitre, respectively, depending on the pathogen. All tested target strains (n = 100) were correctly detected by the both assays, whereas nontarget strains (n = 100) demonstrated no cross‐reactivity representing 100% specificity. The assays are suitable for application in qualitative and quantitative detection of SYLC group pathogens in food matrices.     

Effect of Penicillium roqueforti and incorporation of whey cheese on volatile profiles and sensory characteristics of mould‐ripened Civil cheese

In this study, four different types of mould‐ripened Civil cheese were manufactured. A defined (nontoxigenic) strain of a Penicillium roqueforti (SC 509) was used as secondary starter for the manufacture of mould‐ripened Civil cheese with and without addition of the whey cheese Lor; in parallel, secondary starter‐free counterparts were manufactured. A total of 83 compounds were identified. Ketones, alcohols and esters were the principal classes of volatile components. Principal component analysis of the headspace volatiles grouped cheeses by age and type. P. roqueforti inoculated cheese was clearly separated from the other cheeses at 180 days of ripening, and these cheeses were characterised with high levels of ketones (e.g., 2‐butanone, 2‐heptanone). Differences in the panel scores between the cheese samples were not significant during the first stage of ripening (up to 60 days); as ripening proceeded, these differences were become evident and P. roqueforti inoculated cheeses received higher scores than others. Addition of Lor in the manufacture of mould‐ripened Civil cheese caused lower points by the sensory panel, and the cheese inoculated with P. roqueforti and Lor‐free was the best type of mould‐ripened Civil cheese. The results showed that the use of P. roqueforti in the manufacture of mould‐ripened Civil cheese has significant impact on the volatile profiles and sensory attributes.     

Effects of Penicillium roqueforti and whey cheese on gross composition,microbiology and proteolysis of mould‐ripened Civil cheese during ripening

Four different types of mould‐ripened Civil cheese were manufactured. A defined (nontoxigenic) strain of a Penicillium roqueforti (SC 509) was used as the secondary starter with and without addition of the whey cheese (Lor); in parallel, secondary starter‐free counterparts were manufactured. Chemical composition, microbiology and proteolysis were studied during the ripening. The incorporation of whey cheese in the manufacture of mould‐ripened Civil cheese altered the gross composition and adversely affected proteolysis in the cheeses. The inoculated P. roqueforti moulds appeared to grow slowly on those cheeses, and little proteolysis was evident in all cheese treatments during the first 90 days of ripening. However, sharp increases in the soluble nitrogen fractions were observed in all cheeses after 90 days. Microbiological analysis showed that the microbial counts in the cheeses were at high levels at the beginning of ripening, while their counts decreased approximately 1–2 log cfu/g towards the end of ripening.     

Comparison of buffalo cottage cheese made from aqueous extract of Withania coagulans with commercial calf rennet

An aqueous extract of Withania coagulans was used to prepare cottage cheese from buffalo milk and its quality attributes were compared with cheese made from commercial rennet. Both cheeses contain satisfactory ranges of 49.6–54.7% moisture, 21.3–24.3% fat and 21.4–23.6% protein. The type of coagulant had no significant effect on acidity, protein and ash contents of both the cheeses. W. coagulans cheese showed a significantly (P < 0.05%) higher pH and moisture contents. Similarly, no marked differences were observed in their organoleptic evaluation, actual and theoretical yield. These results supported the fact that W. coagulans is a promising rennet substitute for cottage cheesemaking.     

Behaviour of Listeria monocytogenes in Lighvan cheese following artificial contamination during making,ripening and storage in different conditions

This study investigated the behaviour and fate of Listeria monocytogenes at different ripening temperatures and NaCl concentrations in traditional Lighvan cheese. L. monocytogenes was added to raw sheep's milk. After producing the cheese, they were stored in 8%, 12% and 15% NaCl at 4, 9 and 14 °C. Sampling was performed for 150 days. Different temperature and NaCl concentrations had a significant effect on the survival of L. monocytogenes (P < 0.001). The lowest growth and survival rates of L. monocytogenes were in 15% NaCl at 14 °C and 12% NaCl at 14 °C, respectively. Also, the highest growth and survival rates of the bacterium were in 8% NaCl at 4 °C.     

Changes in degradation and phosphorylation level of titin in three ovine muscles during postmortem

The objective of this study was to investigate the degradation of titin and its phosphorylation level in three muscles from sheep. The MFI and pH from the longissimus lumborum (LL), semimembranosus (SM) and psoas major (PM) muscles were measured at 30 min, 1, 2, 7, 14, 21 and 28 days postmortem. Myofibrillar proteins were extracted, separated by SDS‐PAGE and quantified by phosphor‐specific staining. Phosphorylation of titin was predicted by Pro‐Q Diamond‐SYPRO Ruby staining. Two days after exsanguination, the pH and MFI of the PM were higher than those of the LL and SM muscles (P < 0.05). The sarcomere length of the PM muscle was also longer than that of the LL and SM muscle (P < 0.05). PM muscles had a highest phosphorylation level (P < 0.05) at 0.5 h postmortem and showed the greatest degree of titin degradation over 28 days. This suggests that phosphorylation of titin might accelerate its degradation.     

Developing a potential prebiotic of yogurt: growth of Bifidobacterium and yogurt cultures with addition of glycomacropeptide hydrolysate

This study is aimed at investigating the feasibility of casein glycomacropeptide (GMP) hydrolysates as potential prebiotics in yogurt. The growth performance of Bifidobacterium animalis subsp. lactis (Bb12) was determined in the presence of GMP hydrolysates produced by the action of proteolytic enzymes (trypsin and papain) with various degrees of hydrolysis. The growth‐promoting effect of GHP on Lactobacillus bulgaricus and Streptococcu thermophilus were also evaluated. Results showed that the optimum hydrolysis time of GMP with trypsin or papain for Bb12 growth promotion was 2 and 0.5 h, respectively. Compared with GMP and its trypsin hydrolysate, the GMP hydrolysate produced with papain (GHP) was the best for Bb12 growth, which obtained the highest viable count (9.3 log cfu mL^?1) and the lowest pH of 4.69. The obtained GHP significantly improved the growth of S. thermophilus (P < 0.05), while it had little effect on the growth of L. bulgaricus (P > 0.05)., The viable count of Bb12 of the yogurt obtained with the addition of 1.5% GHP was about four times higher than that of the control without GHP addition. The growth‐promoting effect of GHP might be related to its high content of Glu, Leu and Ala while had no direct relationship with sialic acid content.     

Effects of Mentha longifolia L. essential oil on viability and cellular ultrastructure of Lactobacillus casei during ripening of probiotic Feta cheese

The effects of Mentha longifolia L. essential oil during ripening and storage probiotic Feta cheese were studied, in relation to viability and cellular ultrastructure of Lactobacillus casei. The addition of the essential oil in the concentrations from 0.0 to 0.03% was trialled: the 0.03% treatment resulted in the highest viability of L. casei and the lowest pH value compared with other treatments (P < 0.05). Electron microscopy showed that essential oil caused no harm to L. casei. This study demonstrated the favourable effects of M. longifolia on optimal maintenance of L. casei at the end of cheese storage period.     

Effect of edible coating and gamma irradiation on inhibition of mould growth and quality retention of strawberry during refrigerated storage

The aim of this study was to investigate the effect of edible coating and gamma irradiation treatment on mould growth and storage quality of strawberry. Strawberry fruit after harvest were treated with 0.5–1.0% (w/v) carboxymethyl cellulose (CMC) coating followed by irradiation at 2.0 kGy and subsequent storage under refrigerated conditions for 21 days. The investigations revealed that CMC coating alone at levels 0.5% and 0.75% w/v was not effective in delaying the decay and inhibiting the appearance of mould growth in strawberry fruit. Treatment of irradiation in combination with 1.0% w/v CMC coating was found significantly (P ≤ 0.05) effective compared with other treatments in maintaining the quality and delaying the decay and appearance of the mould growth in strawberry up to 18 days of refrigerated storage. Combinatory treatment of irradiation and coating can help to a greater extent in facilitating the marketing of the strawberry fruit to distant markets other than the local market, thereby benefiting growers and consumers.     

Lactobacillus parabuchneri produces histamine in refrigerated cheese at a temperature‐dependent rate

High histamine concentrations in food can cause histamine poisoning. In spite of the cold chain, cheeses with high concentrations of histamine are on the market. In this work, we studied whether Lactobacillus parabuchneri, the microorganism mainly responsible for histamine accumulation in cheese, is able to grow and produce histamine at the usual temperature range of refrigerators. Further, we analysed whether refrigeration is really effective to prevent the accumulation of histamine in different types of cheeses supplemented with histidine and contaminated with L. parabuchneri. Our results showed L. parabuchneri to be able to grow and produce histamine at refrigeration temperatures. Moreover, L. parabuchneri produced toxic histamine concentrations in refrigerated cheeses from only 14 days. The results obtained in this work show that in the presence of L. parabuchneri, refrigeration delays but does not prevent the accumulation of toxic histamine levels in cheese.     

The effect of enzymatic hydrolysis on the biological properties of Oenothera biennis,Borago officinalis and Nigella sativa seedcake by‐products from oil pressing

The biological properties of ethanolic (50%, v/v) extracts from Oenothera biennis, Borago officinalis, Nigella sativa seedcake before and after enzymatic hydrolysis by alpha‐amylase (EC 3.2.1.1) from Aspergillus oryzae, beta‐glucosidase (EC 3.2.1.21) and beta‐glucanase (EC 3.2.1.6) from Aspergillus niger combinations in a ratio of 1:1:1 were investigated. Total phenolic, flavonoid and reducing sugar content for O. biennis extract after enzymatic hydrolysis was, respectively, 0.5, 1.5 and 2 times higher in comparison with nonhydrolysed extract. Iron‐chelating and radical‐scavenging activity of O. biennis seedcake extract after hydrolysis (IC₅₀ = 0.076 mg mL^?1 and IC₅₀ = 0.050 mg mL^?1) was at a similar level as that nonhydrolyeed (IC₅₀ = 0.070 mg mL^?1 and IC₅₀ = 0.065 mg mL^?1). The antioxidant activity was two times higher after hydrolysis than before enzymatic hydrolysis of O. biennis seedcake extract. Also strong elastase inhibition activity has been shown to O. biennis seedcake extract before (IC₅₀ = 0.095 mg mL^?1) and after enzymatic hydrolysis (IC₅₀ = 0.07 mg mL^?1), respectively. Oenothera biennis and B. officinalis seedcake extracts before and after hydrolysis have stronger antibacterial activity against Pseudomonas aeruginosa strain in comparison with N. sativa seedcake.     

Anti‐inflammatory and cytotoxic effects of ginseng extract bioconverted by Leuconostoc mesenteroides KCCM 12010P isolated from kimchi

A bioconversion technique using microorganisms has been applied to ginseng to increase content of bioactive ginsenoside and biofunctionality such as anticancer, anti‐obesity and antioxidant activities. The objective of this study was to screen lactic acid bacteria for bioconversion of ginsenosides and to evaluate anti‐inflammatory and cytotoxic effects of bioconverted ginseng extract. Strains isolated from kimchi were screened for their β‐glucosidase activities using esculin agar. Selected strain was identified based on 16S rRNA sequencing and carbohydrate fermentation. During ginseng fermentation, viable cell number and pH were determined. Bioconverted ginsenosides were analysed by HPLC. Anti‐inflammatory effects were evaluated using RAW 264.7 cells, and cytotoxic effects were determined by MTT assay. Among 166 isolates screened, Leuconostoc mesenteroides was selected for ginseng bioconversion, as it showed a higher β‐glucosidase activity and viable cell number than any of the other tested strains. After fermentation for 2 days, viable cell number was 8.8 log CFU mL^?1 and final pH was 4.8. Ginsenoside Rb₂ was bioconverted into ginsenoside Rg₃ (Rb₂ → Rd → Rg₃) by L. mesenteroides. The nitric oxide contents of 2‐day‐fermented extract decreased by as much as 25%, compared to a non‐fermented extract. The cell viabilities of HepG2, HT‐29, HeLa and LoVo treated with fermented ginseng extract also decreased by 49.7%, 20.2%, 21.0% and 8.7%, respectively, compared to those of control cells treated with non‐fermented extract. Ginseng extract bioconverted by L. mesenteroides showed anti‐inflammatory and anticancer effects. Therefore, bioconverted ginseng extract might have applications in the pharmaceutical and/or functional food industry.