A combined morphologic and molecular approach for characterizing fungal microflora from a traditional Italian cheese (Fossa cheese)

Phenotypic and genotypic methods were used to identify filamentous fungi that characterize traditional Italian Fossa cheese and its ripening environment. After ageing for 60 days at a dairy, it was ripened for an additional three months in a pit. In the fully ripened cheese, moulds ranged from 3 to 3.4 log cfu g^?1 and Penicillium was the prevalent species. Pit environmental fungi ranged from 530 to 750 cfu m^?3 (air) and from 130 to 340 cfu cm^?2 (surfaces). The dominant pit strains were Alternaria spp., Aspergillus spp., Cladosporium spp. and Penicillium spp. Phylogenetic analyses of 18S rRNA gene and ITS1-5.8S-ITS2 regions highlighted Penicillium camemberti, Aspergillus nidulans and Aspergillus versicolor as traceable species occurring in both the cheese and pit environment, suggesting their involvement in the development of typical Fossa cheese characteristics. This approach may be used for the identification of microflora on other cheese varieties to better understand the fungal contribution in cheese ripening.     

Effects of treatment with nisin on the microbial flora and sensory properties of a Greek soft acid-curd cheese stored aerobically at 4 °C

The present study evaluated the use of nisin as an antimicrobial treatment for shelf-life extension of Galotyri, a Greek soft acid-curd cheese, stored aerobically under refrigeration for a period of 42 days. Three different treatments were tested: N0, control sample with no nisin added; N1, 50 IU g⁻¹ nisin; and N2, 150 IU g⁻¹ nisin, the latter two treatments added post-production to the Galotyri cheese. Of all microorganisms enumerated, lactobacilli, lactococci and yeasts were the groups that prevailed in cheese samples, irrespective of antimicrobial treatment. Based primarily on sensory evaluation (appearance and taste) and a microbiological acceptability limit for yeasts (5 log cfu g⁻¹), the use of nisin treatments extended the shelf-life of fresh Galotyri cheese stored at 4 °C by ca. 7 days (N1) and 21 days (N2) with cheese maintaining good sensory characteristics.     

Inactivation kinetics of Listeria monocytogenes,Salmonella enterica serovar Typhimurium,and Campylobacter jejuni in ready-to-eat sliced ham using UV-C irradiation

To investigate the applicability of UV-C irradiation on the inactivation of foodborne pathogenic bacteria in ready-to-eat sliced ham, UV-C treatment was evaluated. Irradiation dose required for 90% reduction of the populations of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Campylobacter jejuni were determined to be 2.48, 2.39, and 2.18 J/m². Ready-to-eat sliced hams were inoculated with the pathogens and irradiated with UV-C light of 1000, 2000, 4000, 6000, and 8000 J/m². Microbiological data indicated that foodborne pathogen populations significantly (p < 0.05) decreased with increasing UV-C irradiation. In particular, UV-C irradiation at 8000 J/m² reduced the populations of L. monocytogenes, S. Typhimurium, and C. jejuni in the ham by 2.74, 2.02, and 1.72 log CFU/g. The results indicate that UV-C irradiation can be used as a microbial inactivation method for ready-to-eat sliced ham, and inactivation kinetics of the foodborne pathogens fit the Weibull model better than the first-order kinetics model.     

Evaluation of pulsed electric field and minimal heat treatments for inactivation of pseudomonads and enhancement of milk shelf-life

Pulsed Electric Field (PEF) treatment of milk provides the opportunity to increase the shelf-life of fresh milk for distribution to distant markets. PEF treatments were evaluated in sterile (UHT) milk to determine the inactivation of added spoilage Pseudomonas isolates and the subsequent gains in microbial shelf-life (time taken to reach 10⁷ CFU mL^− 1). Little inactivation of Pseudomonas was achieved at 15 or 40 °C compared with 50 or 55 °C. The greatest inactivation (> 5 logs) was achieved by processing at 55 °C with 31 kV cm^− 1 (139.4 kJ L^− 1). Heat treatment at the application temperature without PEF treatment caused minimal inactivation of Pseudomonas (only 0.2 logs), demonstrating that the inactivation of the Pseudomonas was due to the PEF treatment rather than the heat applied to the milk. At added Pseudomonas levels of 10³ and 10⁵ CFU mL^− 1, the microbial shelf-life of PEF-treated milk was extended by at least 8 days at 4 °C compared with untreated milk. The total microbial shelf-life of the PEF-treated milk was 13 and 11 days for inoculation levels of 10³ and 10⁵ CFU mL^− 1 respectively. The results indicate that PEF treatment is useful for the reduction of pseudomonads, the major spoilage bacteria of milk.Industrial relevancePseudomonads are the major psychrotrophic spoilage microflora of refrigerated, stored HTST pasteurised milk. Long-life (UHT) products are an important component of milk sales in South-East Asia, but in recent years there has been an increasing demand for less processed milk products with extended shelf-life. The recent practice of shipping fresh bulk milk from Australia to South-East Asian countries has necessitated additional heat treatment prior to export and on arrival, to achieve the required shelf-life. Pulsed electric field treatment of HTST milk, applied alone or in combination with mild heat under optimised conditions, offers the opportunity of shelf-life extension, while limiting the reduction in quality attributes of milk associated with more severe additional heat treatments.     

Survival of Listeria monocytogenes in Galotyri,a traditional Greek soft acid-curd cheese,stored aerobically at 4°C and 12°C

Galotyri is a traditional Greek soft acid-curd cheese, which is made from ewes’ or goats’ milk and is consumed fresh. Because cheese processing may allow Listeria monocytogenes post-process contamination, this study evaluated survival of the pathogen in fresh cheese during storage. Portions (0.5 kg) of two commercial types (<2% salt) of Galotyri, one artisan (pH 4.0±0.1) and the other industrial (pH 3.8±0.1), were inoculated with ca. 3 or 7 log cfu g⁻¹ of a five-strain cocktail of L. monocytogenes and stored aerobically at 4°C and 12°C. After 3 days, average declines of pathogen's populations (PALCAM agar) were 1.3–1.6 and 3.7–4.6 log cfu g⁻¹ in cheese samples for the low and high inocula, respectively. These declines were independent (P>0.05) of the cheese type or the storage temperature. From day 3, however, declines shifted to small or minimal to result in 1.4–1.8 log cfu g⁻¹ of survivors at 28 days of storage of all cheeses at 4°C, indicating a strong “tailing” independent of initial level of contamination. Low (1.2–1.7 log cfu g⁻¹) survival of L. monocytogenes also occurred in cheeses at 12°C for 14 days, which were prone to surface yeast spoilage. When ca. 3 log cfu g⁻¹ of L. monocytogenes were inoculated in laboratory scale prepared Galotyri of pH ≅4.4 and ≅3% salt, the pathogen died off at 14 and 21 days at 12°C and 4°C, respectively, in artisan type cheeses fermented with the natural starter. In contrast, the pathogen survived for 28 days in cheeses fermented with the industrial starter. These results indicate that L. monocytogenes cannot grow but may survive during retail storage of Galotyri despite its low pH of or slightly below 4.0. Although contamination of Galotyri with L. monocytogenes may be expected low (<100 cfu g⁻¹) in practice, that long-term survival of the pathogen in commercial cheeses was shown to be unaffected by the artificial contamination level (3 or 7 logs) and the storage temperature (4°C or 12°C), which should be a concern.     

Processing of clear and turbid grape juice by a continuous flow UV system

The inactivation of inoculated (S. cerevisiae) and spoilage microorganisms, i.e. yeasts and lactic acid bacteria (LAB), in clear and turbid grape juice was investigated using a pilot scale UV system. The biodosimetry method was used for UV dose prediction in a continuous flow UV reactor. Weibull model was applied for fitting the inactivation data. The flow rates (774, 820 ml/min) in this system were very close to the ones used in fruit juice processing. S. cerevisiae in clear juice was reduced by 3.39 ± 0.04 at 65.50 mJ/cm² of UV dose. 1.54 ± 0.04 and 1.64 ± 0.03 log CFU/ml reductions were obtained for spoilage yeasts and LAB in turbid juice at UV dose of 78.56 and 67.97 mJ/cm², respectively. The soluble solids (°Brix) and pH of grape juice samples were not affected by UV-C treatment (p > 0.05). Although the color parameters slightly were changed after irradiation, the color of PCGJ and FSTGJ did not show visual difference compared to the untreated samples.Industrial relevanceUV light has a potential to reduce the levels of microbial contamination in liquid foods. Although grape juice has many beneficial health effects, it has a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics have markedly expanded in recent years. In the current study, the microbial inactivation efficiency of a pilot scale UV system for non-thermal treatment of clear and turbid grape juice was evaluated under conservative conditions. Most of the physicochemical properties of grape juice samples were not significantly affected from UV-C treatment (p > 0.05). This would be a major advantage in the processing of nutritious juice products.     

Combined effect of ozonated water and chitosan on the shelf-life of Pacific oyster (Crassostrea gigas)

Effects of ozonated water and chitosan treatment on the shelf-life extension of Pacific oysters (Crassostrea gigas) stored at 5 ± 1 °C were studied. Results indicated that ozonated water treatment reduced the total microbial load of fresh oysters by about 10-fold (from 3.2 × 10³ CFU/g to 1.8 × 10² CFU/g) before storage and the microbial flora was different with that of raw samples. The wide-spectrum antibacterial property of chitosan against bacteria isolated from oysters was confirmed, and chitosan concentration of 5.0 g/l was eventually determined for application in oyster preservation. Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-lives of 8–9 days for control, 10–12 days for ozonated water treated samples, 14–15 days for chitosan treated samples and 20–21 days for samples with combined treatment were observed, indicating that ozonated water and chitosan have a great potential for oyster preservation.Industrial relevanceAs seafood, Pacific oysters have a short shelf-life. Improvements in the shelf-life of oysters can have an important economic impact by reducing losses and by allowing the products to reach distant and new markets.In this work, Shelf-life of oysters with combined treatment of ozonated water and chitosan doubled, which has great practical meaning, and the process could be fully adopted by the food industry.We also did some research about the changes in microbial flora after ozonated water treatment. This work could help in preservation of oysters when ozone or ozonated water concerned.We discovered Wide-spectrum antibacterial property of chitosan against the strains isolated from raw oysters. The potential for using chitosan as a natural preservative in oysters was approved.     

UV-C irradiation as an alternative disinfection technique: Study of its effect on polyphenols and antioxidant activity of apple juice

Ultraviolet (UV-C) irradiation is a non-thermal disinfection method, effective against a range of bacteria and viruses, which is being considered as an alternative to pasteurization of fruit juices. The objective of this study was to investigate the effect of UV-C irradiation on the polyphenolic content and in-vitro total antioxidant activity of apple juice. UV irradiation doses ranging from 0 to 240 mJ·cm^− 2 were delivered to apple juice and polyphenols, sugars, in-vitro total antioxidant activity and total phenols were profiled. The results demonstrated that UV-C irradiation in apple juices at relevant commercial disinfection doses induced significant reduction in the concentrations of chlorogenic acid, phloridzin, and epicatechin (p < 0.05). The induced changes were relatively minor for the above mentioned polyphenols, except phloridzin (50% reduction) at 240 mJ·cm^− 2. Epicatechin concentrations were reduced significantly (p < 0.05), whereas increase in catechin concentration was observed with increase in UV-C exposure to 240 mJ·cm^− 2. There was a minor reduction in sugar (glucose and fructose) concentrations with increasing exposure levels from 0 to 40 mJ·cm^− 2 (p > 0.05). In contrast, a slight increase in sugar concentrations as increase in UV-C exposure after 40 mJ·cm^− 2 was observed. These changes were not significantly different from control. Total phenolic content was well retained regardless of the UV-C exposure for apple juice. In-vitro total antioxidant activity changed when UV-C exposure exceeded 40 mJ·cm^− 2, but remained unchanged at the maximum UV-C dose of 240 mJ·cm^− 2. These results suggested that UV-C irradiation could be an effective alternative to conventional thermal processing for production of high quality apple juice.Industrial RelevanceThis research paper provides scientific evidence of the potential for UV-C irradiation to achieve meaningful levels of disinfection while retaining important bioactive compounds (polyphenols) in apple juice. In-vitro antioxidant activity and individual polyphenols were well retained at commercially relevant doses of 40 mJ·cm^− 2. From a nutritional perspective, UV-C irradiation is an attractive food preservation technology and offers opportunities for horticultural and food processing industries to meet the growing demand from consumers for healthier food products. Therefore, UV-C irradiated foods could be sold at a premium price to their thermally-processed counterparts, as they have retained their fresh-like properties. This study would provide technical information relevant for commercialization of UV-C treatment of juices.     

Competitive interactions inside mixed-culture biofilms of Salmonella Typhimurium and cultivable indigenous microorganisms on lettuce enhance microbial resistance of their sessile cells to ultraviolet C (UV-C) irradiation

Salmonella Typhimurium (ST) is one of the leading causes of foodborne diseases in fresh produce, such as lettuce. Despite this, the role of the possible interactions between lettuce indigenous microorganisms and ST on their ability to form biofilm on lettuce and subsequently on the sensitivity of their sessile cells to ultraviolet C (UV-C) irradiation, remains relatively unexplored. Here, the interaction of a mixed-culture of ST and cultivable indigenous microorganisms (CIMs) was examined, as well as the efficacy of UV-C. Initially, the CIMs were isolated and cultured with ST at 15 °C either planktonically or left to form biofilms on stainless steel (SS) and lettuce leaves. Microbial growth, biofilm formation, and survival following UV-C treatment were monitored using traditional plate count methods while biofilm formation, production of extracellular polymeric substance (EPS), and stomatal colonization were also observed by field emission scanning electron microscopy (FESEM). Internalization strength, color, and texture were analyzed by standard methods. Results revealed that the mixed-culture of ST and CIMs presented significantly (p < 0.05) decreased biofilm formation on lettuce leaves compared to mono-cultures (i.e. ST or CIMs alone), which indicated competitive interaction between them, while no interactions were observed for biofilms on SS and for the planktonic cultures. It was also demonstrated that a mixed-culture biofilm on lettuce presented significantly higher resistance (p < 0.05) to UV-C treatment compared to mono-culture biofilms, but such an effect was not observed for biofilms formed on SS and for the planktonic cultures. The Weibull model fitted well to microbial inactivation curves with R² values that ranged from 0.90 to 0.97. Regarding the mixed-culture conditions, a UV-C fluency of 35 mJ/cm² was required to achieve a 5.0 log CFU/mL or cm² reduction in planktonic and biofilms on the SS for the mixed-culture, while 360 mJ/cm² was required to reduce biofilm cell number by approximately 2.0 log CFU/cm² on lettuce. Furthermore, FESEM analysis indicated higher EPS production, and greater stomatal colonization on lettuce mixed-cultures compared to mono-cultures. Finally, internalization strength was significantly higher (p < 0.05) for the mixed-culture on lettuce, thus supporting the notion that internalization in lettuce is a factor that contributes to microbial UV-C resistance. The absence of adverse effects of UV-C on the color and texture of the lettuce suggests it as an alternative means of eliminating ST.     

Shelf-life of a Greek whey cheese under modified atmosphere packaging

“Anthotryros” cheese was packaged under vacuum (VP) or modified atmosphere (MAP) and stored at 4 or 12 °C. MAP mixtures were 30%/70% CO₂/N₂ (M1) or 70%/30% CO₂/N₂ (M2), while VP was taken as the control sample. Microbiological results showed that M1 and M2 delayed microbial growth compared with VP samples. Of the two modified atmospheres, gas mixture M1 was the most effective for inhibition of growth of mesophilic bacteria. Based primarily on sensory evaluation, the use of both MAP conditions extended the shelf-life of fresh Anthotyros cheese stored at 4 °C by ca. 10 days (M1) or 20 days (M2) compared with VP, and by ca. 2 days (M1) and 4 days (M2) at 12 °C, with cheese maintaining good sensory characteristics.     

Preservation of salted,vacuum-packaged,refrigerated sea bream (Sparus aurata) fillets by irradiation: microbiological,chemical and sensory attributes

The effect of gamma irradiation (1 and 3 kGy) on the shelf-life of salted, vacuum-packaged sea bream (Sparus aurata) fillets stored under refrigeration was studied by monitoring the microbiological, chemical and organoleptic changes occurring in fish samples. Non-irradiated, salted, vacuum-packaged fish served as control samples. Irradiation affected populations of bacteria, namely, Pseudomonas spp., H₂S-producing bacteria, Brochothrix thermosphacta, Enterobacteriaceae and lactic acid bacteria. The effect was more pronounced at the higher dose (3 kGy) applied. Of the chemical indicators of spoilage, trimethylamine (TMA) values of non-irradiated, salted sea bream increased slowly to 8.87 mg N (100 g)⁻¹ flesh (whereas for irradiated, salted samples significantly lower values were obtained, reaching a final TMA value of 6.17 and 4.52 mg N (100 g)⁻¹ flesh at 1 and 3 kGy, respectively (day 42). Total volatile base nitrogen values increased slowly attaining a value of 60.52 mg N (100 g)⁻¹ for non-irradiated, salted sea bream during refrigerated storage whereas for irradiated fish, lower values of 48.13 and 37.21 mg N (100 g)⁻¹ muscle were recorded at 1 and 3 kGy, respectively (day 42). Thiobarbituric acid values for irradiated, salted sea bream samples were higher than respective non-irradiated (salted) fish, and increased slowly until day 28 of storage reaching final values of 1.01 (non-irradiated, salted), 2.15 (1 kGy) and 3.26 mg malonaldehyde kg⁻¹ flesh (3 kGy), respectively (day 42). Sensory evaluation (taste) showed a reasonably good correlation with bacterial populations. On the basis of sensorial evaluation, a shelf-life of 27–28 days was obtained for vacuum-packaged, salted sea bream irradiated at 1 or 3 kGy, compared to a shelf-life of 14–15 days for the non-irradiated, salted sample.     

High pressure carbon dioxide combined with high power ultrasound processing of dry cured ham spiked with Listeria monocytogenes

Traditionally, thermal treatments for the inactivation of Listeria monocytogenes in meat products involve undesirable changes of the product quality. In recent years, efforts have been carried out to develop alternative methods to inactivate L. monocytogenes without affecting the product quality attributes. In this context, the feasibility of combined high pressure carbon dioxide and high power ultrasound (HPCO₂ + HPU) treatment to inactivate L. monocytogenes inoculated on the surface of dry cured ham was investigated. Inactivation data were determined at 6, 8 and 12 MPa, as a function of temperature (22, 35, 45 °C) and treatment time (0.5 to 30 min), and compared to those obtained after thermal and HPCO₂ treatments.Color, pH and acidity changes of the samples after both thermal and HPCO₂ + HPU treatments were measured and compared, sensorial profile of the treated samples was evaluated by a sensory panel and shelf-life was determined by a storage study for 4 weeks at 4 °C.The results clearly revealed that HPU alone was not able to induce any microbial inactivation while HPCO₂ + HPU treatment always assured a certain level of inactivation, variable with the process temperature used: the inactivation efficiency was demonstrated higher at 35 °C rather than 22 °C and no enhancement was observed at 45 °C compared to 35 °C. Process conditions of 12 MPa, 35 °C, at 10 W for 5 min assured inactivation to undetectable level of L. monocytogenes spiked on the surface of the product with an initial concentration of about 10⁹ CFU/g. No differences were detected between acidity, pH, color and sensory attributes of the untreated and HPCO₂ + HPU treated dry cured ham surface, while slight differences were measured between the values obtained for the untreated and thermally treated samples. Additionally, the storage study demonstrated that a full microbial and quality shelf-life was assured for 4 weeks at 4 °C. The results obtained may open the doors to the application of such an innovative process at industrial level, in particular to treat ham-type or meat products.     

Application of FT-NIR and FT-IR spectroscopy to study the shelf-life of Crescenza cheese

Crescenza is a fresh cheese in which “freshness” is associated with low acidity, limited proteolysis, and no bitter taste. In this study, FT-NIR and FT-IR spectroscopy was applied to evaluate the shelf-life period in which “freshness” is maintained. Cheese samples were analysed at different times for 20 days. Spectral data were collected using a FT-NIR spectrometer with an optic fibre (from 12000 to 4000 cm⁻¹), and a FT-IR spectrometer with an ATR cell (from 4000 to 700 cm⁻¹). Principal component analysis was able to detect the decrease of Crescenza “freshness” and to define the critical day during shelf-life. These results are in agreement both with those reported in previous studies and with those of physico-chemical and chemical tests. The principal absorption bands relating to the milk components involved were determined. The advantage of using IR spectroscopy is to rapidly draw a profile of the product related to its total quality.     

Evaluation of a pre-cut heat treatment as an alternative to chlorine in minimally processed shredded carrot

The effect of a pre-cut heat treatment (100 °C/45 s) as an alternative decontamination treatment to chlorinated-water (200 ppm active chlorine/1 min, 5 °C) was evaluated in minimally processed carrot (shredded). The quality of shredded carrots was studied just after minimal processing and during storage at 5 °C (10 days) by evaluating microbial (total mesophilic aerobic, yeast and moulds and lactic acid bacteria counts), physical–chemical (soluble solids content, pH, titratable acidity, whiteness index), physiological (peroxidase activity and headspace analysis) and sensorial attributes (colour, fresh-like appearance, aroma and general acceptance). The relationships between sensory perception of undesired changes, microbial contamination threshold, physico-chemical and physiological indices were investigated and compared between heat-treated and control samples. The use of heat in pre-cut carrot proved to be more efficient than chlorinated-water concerning microbial control (threshold concentration of 7 Log₁₀ cfu g^? 1), providing an acceptable fresh-like quality product during 10 days of storage (5 °C), which corresponds to a 3-day shelf-life extension compared to control samples. Heat-treated shredded carrot showed lower respiratory and POD activities than chlorinated samples suggesting that the use of heat provides a metabolic activity lowering effect besides the microbial effect which could be important to shelf-life extension of the fresh-cut product.Industrial relevanceIn minimally processed vegetables, namely in shredded carrot, chlorine solutions have been widely used by the industry for sanitization purposes. However, reduced microbiological efficiency allied to sensorial changes and eventual formation of carcinogenic chlorinated compounds pointed out the need for alternative decontamination methodologies. Also, the evermore conscious consumers are demanding minimization of the potentially negative impact of food processing on human health and the environment. From the practical experience of a fresh-cut industry directly involved in the R&D research project which supported this study, the marketability of minimally processed shredded carrot is limited due to rapid microbial growth and colour loss (decrease of orange intensity and/or whitening of the shreds). As a result, a pilot-plant scale study was performed, evaluating quality attributes of shredded carrot processed according to a clean pre-cut alternative decontamination process.     

Determination of lipase activity in cheese using trivalerin as substrate

Lipolysis during cheese ripening is usually assessed by the accumulation of free fatty acids (FFA). An assay to determine total lipolytic activity present in a cheese during ripening was established. Finely grated cheese (1 g) was directly incubated with trivalerin (204 mg) as a substrate at 35 °C for 4 h. Free valeric acid was extracted and quantified by gas chromatography. The assay was linear with time up to 24 h and up to 0.11 Lipase Units g⁻¹ cheese. The total amount of lipolytic activity determined with this assay was consistent with the total amount of FFA present in 5 types of cheese. In Idiazabal cheese samples manufactured with or without lipase added, the total lipolytic activity determined during ripening remained constant up to 6 months of ripening. In addition to trivalerin, other possible substrates investigated were triolein, triundecanoin and the endogenous butyric acid-containing triacylglycerols present in the cheese sample. Activities measured with these substrates were considerably lower than values obtained with trivalerin due to the high levels of oleic acid present in cheese, or to difficulties in mixing triundecanoin (solid at 35 °C) with the grated cheese sample. Endogenous triacylglycerols gave increasingly lower activity values as ripening time progressed due to substrate depletion.     

Reduction effect of the selected chemical and physical treatments to reduce L. monocytogenes biofilms formed on lettuce and cabbage

As people shift their attention away from unhealthy foods, healthy fresh produce has become popular. However, fresh produce has contributed to many outbreaks of Listeria monocytogenes, which can form a mature biofilm within 24 h. Recent control strategies have proved ineffective in ensuring safe food production. This study focuses on L. monocytogenes biofilms formed on lettuces and cabbages using a viable plate count method and field emission electron microscopy. We investigated the reduction efficacy of treatment with 200 parts per million (ppm) chlorine, 2% each of citric, lactic, and malic acids, 32 Hz ultrasonication (US), 390 mJ/cm² ultraviolet-C (UV-C), or 750 mJ/cm² cold oxygen plasma (COP) on L. monocytogenes biofilms. Following treatment, the quality of the vegetables was analyzed with standard procedures. UV-C and COP showed the best CFU reduction, regardless of the nature of the vegetable surface, while US failed to produce any significant reduction (P > 0.05). Furthermore, chemical treatments reduced count by < 1 log colony forming unit (CFU)/cm² on lettuces, whereas a > 2 log reduction was observed on cabbages. The effect of chemical treatment largely depended on the particular vegetable, while UV-C and COP achieved high reduction regardless of the vegetable, and had no effect on quality. We, therefore, speculate that UV-C and COP show promise in overcoming L. monocytogenes biofilms on food produce.     

Microbial shelf-life of high-pressure-homogenised milk

The anti-bacterial effect of high pressure homogenisation (HPH) on milk is widely reported but the shelf-life of HPH-treated milk, as reported in this communication has not been studied thus far. Raw whole milk was homogenised at 200 or 250 MPa at 55 or 70 °C and counts of total bacteria (TBC), psychrotrophs, pseudomonads, coliforms, lactobacilli, Bacillus cereus and Staphylococcus aureus were determined throughout subsequent storage for 14 days at 4 °C. Immediately after HPH treatment, counts of all bacteria were below the level of detection but after storage for 14 days at 4 °C, TBC, psychrotroph and pseudomonad counts had reached ∼10⁸ cfu mL⁻¹ in all samples treated with HPH. The limited shelf-life obtained indicates that HPH of milk at these processing parameters it is not a suitable alternative to pasteurisation for extending the shelf-life of milk.     

A comparison of the chemical,microbiological and sensory characteristics of bovine and ovine Halloumi cheese

Commercial samples of fresh and mature Halloumi cheeses made from ovine or bovine milk were studied in order to establish their chemical, microbiological and sensory characteristics. Significant differences were observed between the two types of Halloumi cheese both when fresh and mature. The free volatile fatty acid (FVFA) content of the cheeses increased with maturation from 483 to 1356 mg kg⁻¹ for the ovine product, but lower values (380–1248 mg kg⁻¹) were found in the bovine cheese. During maturation for 40 days, Enterococcus faecium, which dominated the microflora of fresh ovine cheese, was replaced by lactobacilli, including a new species, Lactobacillus cypricasei, which was not found in the bovine samples. Fewer than 100 cfu g⁻¹ lactic acid bacteria (LAB) were present in the fresh bovine cheeses, but a microflora dominated by lactobacilli developed with time. Yeast counts in the mature ovine and bovine cheeses reached 2.3–2.8×10⁵ cfu g⁻¹ and, as some of the yeasts were proteolytic and/or lipolytic, it was assumed that they were having a positive impact of the flavour of the cheeses. The sensory panel distinguished significant differences in texture and flavour between the fresh and mature samples of both ovine and bovine cheeses and, overall, there was a significant preference for the ovine brand.     

Calcium Supplementation of Cottage Cheese

Cottage cheese (100 g) provides only 6% of the calcium Recommended Daily Allowance for adults. Samples of fresh cheese were supplemented with calcium salts (chloride, lactate, or phosphate monobasic) to double the calcium content of the cheese to approximately 145 mg/100 g, and the effects of the supplementation on taste and microbial stability were studied. Supplementations did not affect pH or microbial stability during 21 d of refrigerated storage. Sensory evaluation results of a 12-member taste panel showed higher flavor and preference scores for control than for all supplemented samples (P<.05) but no difference in odor, color, or texture. Overall, chloride appeared to be preferable for calcium content supplementation because only .26% (wt/wt) of the salt was required to obtain the desired calcium content level and the mineral was evenly distributed in the cheese.     

Comparative Studies of Ginger (Zingiber officinale) and West African Black Pepper (Piper guineense) Extracts at Different Concentrations on the Microbial Quality of Soymilk and Kunun-zaki

Extracts of two spices, namely ginger (Zingiber officinale) and black pepper (Piper guineense) were prepared in 0.4%, 1.2%, 2.4% and 3.6% concentrations. Soymilk and kunun-zaki were treated respectively with the different concentrations and stored at ambient temperature for 5 days. The microbial load and identification were determined every day of storage until samples were adjudged spoilt.On the first day, 0.4% ginger extract in soymilk and kunun-zaki had a microbial load of 7.77 × 10^6b and 5.17 × 10^6b respectively. 3.6% ginger extract in soymilk and kunun-zaki recorded 3.73 × 10^6b and 3.30 × 106 each. 0.4% black pepper extract in soymilk had 6.273 × 10^6b and recorded 4.63 × 10^6b in kunun-zaki. 3.6% black pepper extract in soymilk and kunun-zaki had a microbial load of 3.20 × 10^6d and 2.90 × 10^6c respectively. On the third day the microbial load increased for both ginger and black pepper extract. Ginger extract recorded 9.13 × 10^6b in soymilk and 5.60 × 10^6b in kunun-zaki at 0.4% concentration. Black pepper extracts recorded 7.43 × 10^6b in soymilk and 3.27 × 10^6b in kunun-zaki also at 0.4% extract. 3.6% black pepper extract recorded 4.10 × 10^6a in soymilk and 2.20 × 106c in kunun-zaki.There was linear reduction of microbial load as spice concentration increased. Black pepper recorded lower microbial load, thus having more antimicrobial activity and may be preferred to be used as natural antimicrobial preservatives to extend the shelf-life of food.