Effect of plant polyphenols and ascorbic acid on lipid oxidation,residual nitrite and N‐nitrosamines formation in dry‐cured sausage

The effects of green tea,grape seed polyphenols and ascorbic acid on pH, water activity (a_w), microbiological counts, TBARS, residual nitrite and N‐nitrosamines were determined in dry‐cured sausages during the ripening period. Results showed that TBARS increased gradually during ripening (P < 0.05), but were significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Green tea polyphenol (GTP) was most effective (P < 0.05) in reducing TBARS. Plant polyphenols and ascorbic acid significantly decreased residual nitrite, ascorbic acid being most effective (P < 0.05). The amount of N‐nitrosamines increased during ripening, but was significantly reduced with plant polyphenols and ascorbic acid (P < 0.05). Plant polyphenols had no significant effects on moisture content, a_w, pH or microbiological counts in dry‐cured sausage during ripening (P > 0.05). It was concluded that plant polyphenols and ascorbic acid were effective in maintaining the quality and safety of dry‐cured sausages.     

Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Resistance of phages lytic to pathogenic Escherichia coli to sanitisers used by the food industry and in home settings

Phages are potentially useful as antimicrobial agents in food‐processing environments, provided they can remain active upon extended storage and in the presence of sanitisers. Survival of six phages lytic against enteropathogenic (EPEC) and shiga‐toxigenic (STEC) Escherichia coli strains was assessed upon storage at 4 °C, ?20 °C and ?70 °C in phosphate‐buffered‐saline (PBS) and Tris‐magnesium‐gelatine buffer (TMG) for up to 1 year. The phages were also exposed to ethanol, sodium hypochlorite, peracetic acid, quaternary ammonium chloride (biocide A), hydrogen peroxide/peracetic acid/peroctanoic acid (biocide B), p‐toluensulfonchloroamide (biocide D) and alkaline chloride foam (biocide C). Plaque‐forming units remained unchanged when the phages were stored at 4 °C in both buffers tested, but decreased by 3.5 and 5.7 log₁₀ PFU when stored in PBS at ?20 and ?70 °C, respectively. Moreover, TMG seems to be the most protective suspension medium with decreasing temperature because a 1?log₁₀ PFU reduction was observed at ?20 and ?70 °C. Incubation in 100% ethanol for 24 h reduced plaque counts only by 2.5 log₁₀ PFU. In 10 ppm of sodium hypochlorite and in biocide B (0.13%), the counts decreased by ~5 and ~6 log₁₀ PFU after 15 min. Finally, biocide A and D reduced counts by 4 and 2–4 log₁₀ PFU after 30 min and 8 h of incubation, respectively. Phages were completely inactivated only by peracetic acid and biocides C and E. Therefore, the phages evaluated might be potentially applied together with classical sanitisers such as ethanol and industrial biocides A, B and D, in disinfection programs against pathogenic STEC and EPEC strains.     

Quality of fresh‐cut purple‐fleshed sweet potatoes after X‐ray irradiation treatment and refrigerated storage

The effect of X‐ray irradiation on the quality of fresh‐cut, refrigerated purple‐fleshed sweet potato (PFSP) cubes was investigated. Packaged sweet potato cubes were treated with 0, 250, 500, 750 or 1000 Gy X‐ray irradiation and stored at 4 ± 1 °C for 14 days. After 14 days, total aerobic bacteria counts were 4.1 and 3.2 log₁₀ CFU g^?1, and mould–yeast counts were 3.3 and 3.0 log₁₀ CFU g^?1 in 750 and 1000 Gy treated samples, respectively. Doses up to 1000 Gy did not affect the firmness, moisture content and anthocyanin content of PFSP cubes throughout storage. PFSP cubes' flesh colour did not change during the first week of storage, but lightness (L*) increased after 14 days. Also, irradiation doses at 750 and 1000 Gy decreased saturation (C*) significantly, producing duller flesh colour than controls. Results indicate that X‐ray irradiation treatment at doses up to 1000 Gy can reduce microbial populations while maintaining the physical quality and anthocyanin content of PFSP cubes up to 14 days of storage.     

Microbiological Attributes of Turkish Butters Sold Under Market Conditions

In this study, microbiological quality of 45 butter samples sold under market conditions at Manisa (Turkey) was investigated. Total coliform, total fecal coliform, Escherichia coli and yeast and mould counts were found between < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1 and < 1.0 – > 6.62 log₁₀ cfu.g^-1 respectively. Only in one sample Salmonella was detected. Staphylococcus aureus was not detected in any of the samples. To that extent butters sold under market conditions in Manisa have high coliform, yeast and mould contamination.     

Isomaltooligosaccharide increases the Lactobacillus rhamnosus viable count in Cheddar cheese

Five batches of Cheddar cheese were manufactured containing different levels of isomaltooligosaccharide (IMO) and a probiotic strain of Lactobacillus rhamnosus to study the effect of IMO on the survival of starter lactococci and probiotic micro‐organisms, on proteolytic patterns, cheese composition and sensory properties. The cheese was exposed to conditions simulating those found in the gastrointestinal tract to evaluate the survival of Lb. rhamnosus. Results demonstrated that the addition of Lb. rhamnosus and IMO did not affect the main compositional variables of Cheddar cheese. The counts of starter culture and probiotic organisms increased in cheese which contained Isomaltooligosaccharide (Batches 3, 4 and 5) more than in the control (Batches 1 and 2) during the fermentation. The probiotic counts in fresh cheese (B‐4) was 9.23 log₁₀ cfu/g which was more than one log cycle greater than in the control (B‐2). The probiotic counts remained above 8 log₁₀ cfu/g at the end of the manufacturing process. Primary proteolysis was not affected by the addition of probiotic bacteria and IMO, but the level of secondary proteolysis was slightly higher compared with the control group. The addition of IMO improved the texture and sensory quality of the cheese and the probiotic bacterium had the same effect. Under conditions that simulated the gastrointestinal tract, the probiotic bacteria in cheese (B‐4) exhibited good survival and remained above the recommended 6–7 log₁₀ cfu/g.     

Microbiological Attributes of Turkish Butters Sold Under Market Conditions

In this study, microbiological quality of 45 butter samples sold under market conditions at Manisa (Turkey) was investigated. Total coliform, total fecal coliform, Escherichia coli and yeast and mould counts were found between < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1, < 1.0 – > 3.15 log₁₀ cfu.g^-1 and < 1.0 – > 6.62 log₁₀ cfu.g^-1 respectively. Only in one sample Salmonella was detected. Staphylococcus aureus was not detected in any of the samples. To that extent butters sold under market conditions in Manisa have high coliform, yeast and mould contamination. Received: April 29, 2008; received in revised form: May 28, 2008; accepted: June 3, 2008     

Efficacy of Neutral Electrolyzed Water,Quaternary Ammonium and Lactic Acid‐Based Solutions in Controlling Microbial Contamination of Food Cutting Boards Using a Manual Spraying Technique

Bactericidal activity of neutral electrolyzed water (NEW), quaternary ammonium (QUAT), and lactic acid‐based solutions was investigated using a manual spraying technique against Salmonella Typhimurium, Escherichia coli O157:H7, Campylobacter jejuni, Listeria monocytogenes and Staphylococcus aureus that were inoculated onto the surface of scarred polypropylene and wooden food cutting boards. Antimicrobial activity was also examined when using cutting boards in preparation of raw chopped beef, chicken tenders or salmon fillets. Viable counts of survivors were determined as log₁₀ CFU/100 cm² within 0 (untreated control), 1, 3, and 5 min of treatment at ambient temperature. Within the first minute of treatment, NEW and QUAT solutions caused more than 3 log₁₀ bacterial reductions on polypropylene surfaces whereas less than 3 log₁₀ reductions were achieved on wooden surfaces. After 5 min of treatment, more than 5 log₁₀ reductions were achieved for all bacterial strains inoculated onto polypropylene surfaces. Using NEW and QUAT solutions within 5 min reduced Gram‐negative bacteria by 4.58 to 4.85 log₁₀ compared to more than 5 log₁₀ reductions in Gram‐positive bacteria inoculated onto wooden surfaces. Lactic acid treatment was significantly less effective (P < 0.05) compared to NEW and QUAT treatments. A decline in antimicrobial effectiveness was observed (0.5 to <2 log₁₀ reductions were achieved within the first minute) when both cutting board types were used to prepare raw chopped beef, chicken tenders or salmon fillets.     

Effect of different levels of fat and inulin on the microbial growth and metabolites in probiotic yogurt containing nonviable bacteria

Effects of different levels of fat and inulin on bacterial cell counts, degree of proteolysis and concentrations of organic acids in the yogurt containing inactivated cells of probiotic strains Bifidobacterium animalis and Lactobacillus acidophilus were investigated. Results showed that both L. acidophilus and B. animalis grew well in the yogurt samples reaching cell counts higher than 10⁶ CFU mL^?1 at the final pH of 4.5. Inulin at the concentration of 1% had no significant effects on the production of organic acids and cell counts of L. acidophilus, but promoted the growth of B. animalis with a reduction in the degree of proteolysis. Generally, different fat levels showed significant effects on the production of organic acids and nonsignificant effects on the cell counts of probiotic bacteria and degree of proteolysis. In case of lactic acid, the ratio of L‐ (+)to D‐ (?) isomer ranged from 50/50 to 80/20 in yogurt samples.     

A bacteriophage JN02 infecting multidrug-resistant Shiga toxin-producing Escherichia coli: isolation,characterisation and application as a biocontrol agent in foods

Bacteriophages are increasingly considered as novel biocontrol agents against Multidrug-resistant (MDR) Shiga toxin-producing Escherichia coli (STEC). In this study, a virulent phage JN02 capable of infecting MDR STEC was isolated, characterised and evaluating its efficacy in reducing MDR STEC in foods. One-step growth and stability assay showed that JN02 had a relatively short latent period (15 min), large burst sizes (69 PFU/cell), and high physicochemical stability (temperature (30–60°C), pH (2–11), 0.1%, 1% pig bile salt, biocides and food additives (100% chloroform, 0.1% acetic acid, 1% potassium sorbate). In spot tests, 18 E. coli strains were sensitive to JN02. In efficiency of plating (EOP), 4 E. coli strains were sensitive to JN02. Electron microscopy and genome sequencing showed that JN02 belongs to the family Myoviridae. Importantly, no known virulence-associated, lysogenic and antibiotic genes were identified in the genome of JN02. Viable cell counts of MDR STEC were significantly (P < 0.05) reduced in milk (no viable counts) and beef samples (1.0–1.9 log₁₀ CFU cm⁻² reduction) when treated with JN02 at 4 °C. The results indicated that JN02 might be a new potential natural biological control agent for MDR STEC in foods.     

Bacillus and Paenibacillus species associated with extended shelf life milk during processing and storage

Characterisation of spore formers associated with extended shelf life milk was performed by analysing the bacteriological quality of milk samples collected at various processing stages and during storage. Isolates were identified with MALDI‐TOF‐MS. Milk had spore counts <2 log₁₀ cfu/mL and 4 log₁₀ cfu/mL during processing and storage, respectively. Bacillus pumilus dominated the bacterial population. Bacterial species were inoculated into sterile milk for a shelf life study, and the population change was observed over 42 days at 7 °C. Although the extended shelf life milk process was effective in reducing bacterial counts and species diversity, the presence of Bacillus cereus shows a potential safety problem in extended shelf life milk.     

Preparation of alcalase hydrolysed rice bran protein concentrate and its inhibitory effect on soybean lipoxygenase activity

Rice bran protein concentrate (RBPC) was prepared from defatted rice bran and hydrolysed by alcalase at different hydrolysis times. As the hydrolysis times increased, the degree of hydrolysis (DHs) increased. RBPC hydrolysate obtained at 50 min (RBPCH‐50) had the highest inhibitory efficiency on soybean lipoxygenase (LOX) activity (66%). The inhibition kinetics of the reaction analysed by Lineweaver–Burk plots indicates that RBPCH‐50 is a competitive inhibitor. RBPCH‐50 inhibited soybean LOX with an IC₅₀ of 11.73 μg μL^?1 RBPCH‐50, and the obtained K_I was 4.59 μg μL^?1 RBPCH‐50. LOX inhibitory activity of RBPCH‐50 was significantly higher than that of 50 and 100 ppm butylated hydroxyanisole (BHA) and 50, 100, and 200 ppm butylated hydroxytoluene (BHT) (P ≤ 0.05); however, LOX inhibitory activity of RBPCH‐50 was similar to that of 200 ppm BHA (P > 0.05). Therefore, RBPCH might potentially be used as a natural LOX inhibitor.     

Bacterial inactivation and quality changes of fresh‐cut avocados as affected by intense light pulses of specific spectra

Intense light pulses (ILP) treatments have good prospects for becoming an alternative to traditional thermal methods for decontamination of food surfaces. The aim of this work was to evaluate which ranges of the light spectrum are responsible for bacterial inactivation and their effect on the quality of fresh‐cut avocado. Results show that the effectiveness of ILP treatment decreases when the ultraviolet (UV) spectral region is blocked (particularly UV‐C). ILP treatments without UV‐C light (305–1100 nm) and an overall fluence of 10.68 J cm^?2 caused reductions of 2.47 and 1.35 log CFU g^?1 in the initial counts of inoculated Escherichia coli and Listeria innocua, respectively, in comparison with those treated using only VIS–NIR light (0.83 and 0.68 log CFU g^?1, respectively). Treatments applying light of a wavelength between 305 and 1100 nm had a more pronounced impact on colour, texture and headspace gas composition than treatments that did not contain UV light (400–1100 nm).     

Use of ultrasonication to enhance pea seed germination and microbial quality of pea sprouts

This study investigated the effects of ultrasonication, heating and chemical washing on decontamination of seeds of three pea (Pisum sativum) varieties and the microbial safety of their sprouts. Most of the decontamination treatments increased germination, decreased microbial load and enhanced sprout growth. Ultrasonication and NaOCl treatments reduced total aerobic counts on sprouts by 5.86 and 5.51 log units (averages of three varieties), respectively; while other chemical treatments (350 mL L^?1 ethanol, 350 mL L^?1 vinegar and 10 g L^?1 NaCl solutions) failed to reduce total aerobic counts sufficiently enough to secure microbial safety. The ultrasonication not only improved germination (increased from an average of 83 to 97%), but also reduced the total aerobic counts to 2.21 log₁₀ CFU g^?1 on seed sprouts. Ultrasonication also increased the sprouts yield to 301.83 g per 10 g seeds. Therefore, ultrasonication can be used as a microbial control treatment for pea sprout production.     

Encapsulation of probiotic Lactobacillus acidophilus by ionic gelation with electrostatic extrusion for enhancement of survival under simulated gastric conditions and during refrigerated storage

The probiotic Lactobacillus acidophilus was encapsulated in biodegradable and biocompatible capsules prepared by ionic gelation between phytic acid (PA) and chitosan (CS) with an electrostatic extrusion method. Calcium carbonate (CaCO₃) and starch were used as co‐encapsulants for improvement of capsule stability. Capsules were characterised and evaluated for survival of encapsulated L. acidophilus cells in simulated gastric fluid (SGF) and during refrigerated storage. Loading capacity values of PA‐CS capsules, PA‐CS‐starch capsules and PA‐CS‐CaCO₃ capsules were 8.20, 8.12 and 7.81 log CFU g^?1 of wet capsule, respectively. Capsules showed particle sizes of 1.3–1.5 mm and a uniform spherical shape. PA‐CS‐CaCO₃ capsules were the most stable vehicles for the protection of probiotic cells against acidic damage, particularly at pH 1.5 and pH 2. L. acidophilus cells from PA‐CS‐CaCO₃ capsules showed only a 0.64 log CFU reduction in numbers after 2 h in pH 1.5 SGF conditions. The numbers of L. acidophilus encapsulated in PA‐CS‐CaCO₃ capsules were decreased by only 0.69 log CFU g^?1, while PA‐CS capsules and PA‐CS‐starch capsule numbers were reduced by more than 1.45 log CFU g^?1 after 4 weeks at 4 °C. Addition of calcium carbonate to PA‐CS capsules provided protection against acid injury via antacid and buffering effects for encapsulation of L. acidophilus.     

Viability of Lactobacillus acidophilus in rice bran‐enriched stirred yoghurt and the physicochemical and sensory characteristics of product during refrigerated storage

This study was aimed at investigating the fortification of probiotic yoghurt with rice bran to increase nutritional properties of the product. The different levels of rice bran (0.3%, 0.6%, 0.9% and 1.2%) were incorporated into milk. The yoghurt samples were produced after pasteurisation, addition of starter culture and 1% Lactobacillus acidophilus suspension (6 × 10⁸ CFU mL^?1) and incubation. During sample storage in refrigerator, the viability of L. acidophilus, viscosity and physicochemical and sensory properties of product were investigated. Rice bran significantly increased the viability of L. acidophilus (P < 0.05). In addition, all probiotic yoghurts incorporating rice bran indicated higher viscosity and acidity and lower pH and syneresis compared to plain yoghurts. Furthermore, increments in rice bran incorporation levels resulted in a reduction in consumers' sample preferences. In general, the addition of rice bran at a suitable level could increase L. acidophilus viability and improve quality attributes of yoghurt.     

A new approach to modelling the shelf life of Gilthead seabream (Sparus aurata)

A total of 217 Gilthead seabreams were subdivided in four groups, according to four different storage conditions. All fish were evaluated by both Quality Index Method (QIM) and microbiological analysis, sampling skin, gills and flesh, separately. A QIM score predictive system was set by modelling the growth of microflora of skin, gills and flesh and coupling these predictions to each related partial QIM score (QIM_Skin, QIM_Gills, QIM_Flesh). The expression of QIM score as a function of bacterial behaviour was carried out by the employment of two coefficients. The predicted mean bacterial concentrations corresponding to the QIM score at 14 days were always near to Log 8 CFU g^?1 in the case of ‘S’ (skin) and ‘G’ (gills) series. Moreover, predicted QIM scores were in a good agreement with observed data, reproducing the observed mean time of rejection as well as the bacterial spoilage level (Log 8 CFU g^?1), for all kinds of storage condition.     

Effect of dietary humate on the pH,TBARS and microbiological properties of vacuum‐ and aerobic‐packed breast and drumstick meats of broilers

The current trial determined the influence of dietary humate, including humic, fulvic and ulmic acids and some microminerals on the pH, TBARS and microbiological properties of vacuum‐packed and aerobic‐packed breast fillets and drumsticks of broilers. A total of 240 male broiler chicks (Ross‐308) were randomly allocated into four dietary treatments (H₀, H₁, H₂ and H₃ groups). A basal diet (H₀), basal diet plus 0.1 (H₁), 0.2 (H₂) and 0.3% (H₃) humate (Farmagulator DRY^?, Humate, Farmavet International Inc, Kocaeli 41 400, Turkey) were offered during the experimental feeding period. At the end of the trial all chicks were slaughtered. After standard dissection of carcasses, the breasts and drumsticks were divided into two groups for vacuum packaging or aerobic packaging. Packed breasts and drumsticks were stored at 3 °C for 12 days. The breasts and drumsticks were analyzed for pH, TBARS, total mesophilic, total psychrotrophic, lactic acid bacteria and Enterobacteriacea counts at 0, 2, 4, 6, 8, 10 and 12 days of storage. The feeding of humate decreased pH values of breast fillets and drumstick muscles (p < 0.01), especially at the 0.1% level. The TBARS value decreased (p < 0.01) when compared with the without‐humate group (H₀). Total aerobic mesophilic (p < 0.01), total aerobic psychrotrophic (p < 0.01) and lactic acid bacteria (p < 0.05) counts were lower in the H₃ group than the other groups. The effect of meat type on pH, TBARS, total aerobic mesophilic (p < 0.01) and lactic acid bacteria (p < 0.05) and Enterobacteriacea counts was significant. While the pH and TBARS values of breast fillets were lower than those of drumstick meats, the total mesophilic, total psychrotrophic, lactic acid bacteria and Enterobacteriacea counts of drumstick meats were higher than those of breast fillets. The effect of packaging type on pH (p < 0.01), TBARS (p < 0.01), total aerobic psychrotrophic bacteria (p < 0.01) and Enterobacteriacea counts (p < 0.01) was found statistically significant and the maximum values were determined in the aerobic‐packed samples. In addition, investigated parameters were also affected by storage period. While the total aerobic mesophilic count decreased, the other parameters increased when compared with zero day of storage. Copyright © 2005 Society of Chemical Industry     

Effects of aqueous ozone treatments on microbial load reduction and shelf life extension of fresh‐cut apple

Aqueous ozone was first used to take the place of chlorine as fresh‐cut apples sanitiser. Aqueous ozone (1.4 mg L^?1) treatments were evaluated for their effectiveness on microbial growth, quality attributes and shelf life of fresh‐cut apples. The results indicated that aqueous ozone treatments for 5 and 10 min achieved accepted microbial quality and, respectively, reduced total bacteria counts by 1.83 and 2.13 log₁₀CFU g^?1 compared with the control samples on the 12th day. The ethylene production, polyphenol oxidase and peroxidase activities, and total phenol and malondialdehyde contents were reduced by aqueous ozone treatments. In addition, this sanitiser also delayed the quality deterioration of fresh‐cut apples and enhanced their antioxidant capacity. Therefore, it was recommended to sanitise fresh‐cut apples with aqueous ozone (1.4 mg L^?1) for 5 min, which applied to industrial production requirement for both efficiency and costs and could extend the shelf life up to 10 days.     

Characterisation of malolactic conversion by Oenococcus oeni to reduce the acidity of apple juice

The high concentration of malic acid is responsible for the acidity and sourness in apple juice. Bio‐conversion of malic acid to lactic acid through malolactic conversion (MC) in apple juice using Oenococcus oeni was investigated. When apple juice was inoculated with O. oeni (1 × 10⁶ CFU mL^?1), over 90% of malic acid was converted into lactic acid within 96 h at room temperature. When pH of apple juice was adjusted to 4.1 prior to inoculation, MC was completed within 60 h. MC was enhanced at a higher temperature (30°C) when compared with room temperature. The rate of MC was directly proportional to the number of bacteria added and MC was completed within 24 h at 1 × 10⁹ CFU mL^?1 initial cell density. MC occurred equally under aerobic and anaerobic conditions. The sensory analysis of partial MC‐applied juice when compared against control revealed potential for use of MC for manufacture of low‐acid apple juice.