Lactic Acid Bacterial Counts Research Articles

Antimicrobial effect of ammonium hydroxide when used as an alkaline agent in the formulation of injection brine solutions.

Paired U.S. Department of Agriculture Select strip loins were injected with either a conventional brine (4.5% potassium and sodium polyphosphate blend [Brifisol 750], 3.6% NaCl, 1% Herbalox seasoning HT-S, and 90.9% ice water) or an ammonium hydroxide (AH) brine (1% AH, 3.6% NaCl, 1% Herbalox seasoning HT-S, and 94.4% ice water). The steaks were sliced, high-oxygen modified atmosphere packaged, placed at 5°C in dark storage for 5 days, and then transferred to a retail display at 5°C for another 14 days. Steaks injected with AH brine appeared to have lower counts of psychrotrophic, mesophilic, and gram-negative bacteria. Immediately after injection, there was ∼1 log CFU/g difference between treatments in gram-negative bacterial counts. No differences in coliform and lactic acid bacterial counts were found.

포장재와 저장온도에 따른 소포장 김치의 품질특성

Cabbage (Baechu) Kimchi in its truncated form was placed in four different packing materials, Ny/PE/LLDP, OPP/AL/PE, PP and PET, and quality changes were observed during storage. Changes in pH and total acidity showed an x-shaped cross-curve as pH decreased and total acidity increased during storage. PP tray showed the slowest change at <TEX>$5^{\circ}C$</TEX> with time. The pH was initially 6.25, but decreased to 4.12~4.16 at 20 days, and total acidity showed a 4 to 4.8-fold increase after 20 days of storage compared to the initial value. During storage at <TEX>$5^{\circ}C$</TEX>, total bacterial count and lactic acid bacterial count rapidly increased after 4 days. The total bacterial quantity decreased after a period of time and there were differences according to packaging material; OPP/AL/PE packaging showed the most dramatic decrease. Change in microbial count mostly followed a similar pattern to that of total acidity for all packaging materials. Changes in the color of Kimchi liquid, when examined by color index in <TEX>$L{\cdot}b$</TEX>/a form, rapidly decreased over time, similar to pH. Small Ny/PE/PP and OPP/AL/PE packages of Kimchi were examined for changes in free volume inside the packaging. After 13 days of storage at <TEX>$5^{\circ}C$</TEX>, the volume was 243 mL, but storage at <TEX>$20^{\circ}C$</TEX> resulted in a volume of 372 mL, a more than 1.5-fold increase in free volume. There were changes in the quality characteristics of small package Kimchi according to storage temperature and packaging material, and large changes in pH, total acidity, and microbial count were evident upon storage at <TEX>$5^{\circ}C$</TEX> for 8 days, which was the optimum palatability period. Mostly, PP treatment showed the slowest quality changes upon storage at <TEX>$5^{\circ}C$</TEX>. However, due to small package Kimchi's fast consumption system, the appropriate choice of packaging material must consider the product's turnover ratio. Further, the varieties of small package Kimchi should be diversified according to different consumer preferences by offering Kimchi with different maturity levels. Further, since the leading consumer base ranges in age from the teens to thirties, the development of various products targeting such consumers is necessary.

A dietary sodium gluconate supplement improves growth performance and prebiotic activity in the small intestine of nursery pigs grown under tropical conditions

This study was conducted to evaluate the effect of sodium gluconate (SG) supplementation in diets on growth performance, small intestinal morphology and short chain fatty acid concentration in the caecum of nursery pigs. One-hundred and forty-four piglets (bodyweight ~10.5 kg) were raised in conventional open housing and divided into four treatments with six replications. The pigs received diet supplemented without (control), or with SG at a level of 1000, 2500 or 5000 ppm for 6 weeks. The results indicated that increasing SG supplementation from 0 to 5000 ppm linearly improved final bodyweight, average daily gain, feed : gain ratio, caecal propionic acid and total short-chain fatty acid concentration (linear P &lt; 0.05). Adding SG in diet tended to reduce Escherichia coli counts in the caecum (P = 0.09) and adding SG at 2500–5000 ppm significantly increased the villous height in the duodenum (linear, P &lt; 0.01), whereas there were no increase in caecal acetic acid and lactic acid bacterial counts in the caecum and rectum, and E. coli counts in the rectum when compared with the control group. SG supplementation did not affect the pH values in gastrointestinal tract of nursery pigs. This study implied that SG supplementation improved growth rate and may be useful as a prebiotic to accomplish the maximum growth performances in nursery pigs.

발효초유 급여가 Holstein 송아지의 성장과 설사발생에 미치는 효과

Jong Ho Ahn* and Jung Kil ParkDepartment of Dairy Science, Hankyong National UniversityABSTRACTIn this study, feeding fermented colostrum to Holstein calves was investigated to find out the effects on their growth and inhibition of diarrhea. The results of this study showed that the mixture of L. rhamnosus and E. faecium would be proper bacteria for fermentation of colostrum because of favorable odor, inhibition of coliform bacteria and high number of lactic acid bacterial count. Among the groups of calves fed 0, 5, 10 and 20% of fermented colostrums, average body weight gain for 28 days on feeding fermented colostrum were 16.6, 16.6, 17.4 and 18kg, respectively showing that calves fed 20% fermented colostrum achieved the highest body weight gain. Occurrence of diarrhea due to feeding various levels of fermented colostrum was also recorded. Three calves out of 5 suffered diarrhea in 0%, 5%, and 20% group, on the other hand, all 5 calves suffered diarrhea in 10% group. Diarrhea persisted for durations were 2.7, 2.4, 4.0, and 2.4 days in 0, 5, 10, and 20% group, respectively. Fermented colostrum did not prevent the occurrence of diarrhea.In overall, addition of fermented colostrum above 10% level showed favorable effects in gaining body weight under the conditions of adding more portions of the fermented colostrum either for 14 days or longer feeding period of the fermented colostrum. On the other hand, fermented colostrum showed no beneficial effect in prevention of diarrhea in this study.(Key words :Fermented colostrum, Holstein calves, Growth, Diarrhea)

부재료 침지처리가 김치의 냄새 및 발효 특성에 미치는 영향

김치와 각각의 부재료들의 향기 성분을 비교하기 위하여 GC/MS로 정성 분석한 결과, 김치의 향기 성분은 sulfide 계열의 황 화합물과 유기산, 알코올류 등으로 나타났고, 김치의 냄새를 구성하는 물질들은 김치의 냄새를 각각의 부재료에서 검출된 향기 성분들로부터 유래한 것으로 확인되었다. 김치 특유의 이취를 저감시키기 위하여 김치의 부재료인 마늘, 생강, 양파 및 파를 각각 5 ㎜의 길이와 0.3 ㎜의 두께로 세절하고 100℃에서 2분간 데친 후, 정수된 물 4℃에서 12시간 동안 침지처리 하였다. 부재료 침지처리가 김치의 군덕내(moldy odor)와 신내(sour odor)에 미치는 영향을 관능검사로 평가한 결과, 세절침지처리김치에서 일반김치에 비하여 신내와 군덕내가 크게 감소한 것으로 나타났다. 또한 부재료의 침지처리가 숙성 중 김치에서 pH, 산도, 유산균수에 영향을 미치는 것으로 나타났다.

Comparison of different application strategies of divergicin M35 for inactivation of Listeria monocytogenes in cold-smoked wild salmon

Cold-smoked salmon treated with divergicin M35-producing Carnobacterium divergens M35, C. divergens ATCC 35677 (a non-producer of bacteriocin), purified divergicin M35 or supernatants of C. divergens M35 culture in snow crab hepatopancreas (SCH) medium or MRS broth was challenged with Listeria monocytogenes (up to 10 3 CFU/g). Samples were stored at 4 °C for up to four weeks. L. monocytogenes, total bacterial and lactic acid bacterial counts were determined along with changes in total volatile base nitrogen (TVBN) and biogenic amine production as well as texture, color and odor. A 2.6 log CFU/g reduction in L. monocytogenes was obtained for up to 10 days of storage in samples treated with C. divergens M35. Purified divergicin M35 (50 μg/g), SCH supernatant or MRS supernatant brought reductions of 1 log CFU/g at the beginning of storage. However, the anti-listerial activity of the supernatants lasted for 15 days compared to 3 days for purified divergicin M35. Color and texture were affected little in samples containing C. divergens M35 compared to un-inoculated samples. TVBN and biogenic amine production, particularly tyramine, remained below the maximum acceptable level in fish appreciation. These results clearly show the potential of C. divergens M35 culture as well as divergicin M35 bio-ingredient for application to the inactivation of L. monocytogenes in ready-to-eat seafood.

Biochemical composition and storage stability of a yogurt‐like product from African yam bean (Sphenostylis stenocarpa)

SummaryThe biochemical and storage properties of African yam bean (Sphenostylis stenocarpa) yoghurt‐like product were evaluated. Milk extracted from the bean flour using hot water was supplemented with 4% milk protein concentrate (MPC), 0.15% dairy calcium (DC) and 0.5% gelatine (G) (singly or in combination). The milk was fermented with Streptococcus thermophilus and Lactobacillus delbrueckii spp bulgaricus at 43 °C for 3–5 h. Supplemented African yam bean (AYB) yoghurts had a gel‐like consistency unlike the control (unsupplemented) sample. Total solids, protein, fat, ash, lactic acid bacterial count, lightness (L‐value) and viscosity were improved by supplementation. Riboflavin and antioxidants were reduced; macroelements and thiamine were increased by 0.71–15.6% and 16.7%, respectively, because of fermentation. The stability of the product during storage at 4 °C was improved by supplementation and stirring. The pH of the supplemented product ranged from 4.45 to 4.54 and microbial counts from 2.6 × 106 to 1.6 × 108 during storage for not more than 3 weeks.

Quality of Irradiated Plain Yogurt during Storage at Different Temperatures

To develop a safer yogurt for immuno-compromised or allergy patients and to extend shelf-life, a plain yogurt was irradiated with doses of 0, 1, 3, 5, and 10 kGy using a gamma ray and the chemical and microbiological quality and allergenicity change were investigated. There was no difference in the content of protein, total solid, and amino acids of the plain yogurt by irradiation treatment and different storage temperatures (4, 20, and 35°C). The lactic acid bacterial counts of irradiated plain yogurt had approximately 3-decimal reduction at 3 kGy, and no viable cell at 10 kGy regardless of storage time and temperature. The binding ability of rabbit antiserum to milk proteins in irradiated plain yogurt showed that 10 kGy of irradiation produced significantly higher binding ability than other treatments. Sensory evaluation indicated that only appearance of the plain yogurt irradiated at 3 kGy or higher had a lower value than the non-irradiated control when stored at 20°C. Results suggest that irradiation of plain yogurt does not significantly affect the chemical and sensory quality of plain yogurt, but can extend the shelf-life, possibly reduce allergenicity, and provide a safer product.

Effect of antimicrobial agents on some chemical and microbiological characteristics of vacuum: Packaged ground buffalo meat stored under refregerated condition

The chemical characteristics and microbiological examination of vacuum packaged ground buffalo meat during cold storage for 24 days were determined in order to evaluate two different antimicrobial agents sodium lactate, sodium chloride and their mixture. The results indicated that the use of sodium lactate with or without sodium chloride delayed the proliferation of aerobic plate count, psychotropic count, and lactic acid bacterial count, and extended the shelf life up to more than 24 and 21 days respectively, compared to 8 days for the control samples. The TBA values for the samples treated by sodium chloride was not affected, while at the end of storage period the TBA values of samples treated by sodium lactate were significantly reduce the oxidation changes. Therefore, the use of sodium lactate with or without sodium chloride could be used to extend the shelf life of ground buffalo meat during refrigerated storage by reducing both chemical and microbiological changes. .

Potential use of probiotic Lactobacillus plantarum SS2 isolated from a fermented plant beverage: safety assessment and persistence in the murine gastrointestinal tract

A strain of Lactobacillus plantarum SS2 isolated from a fermented star fruit (Averrhoa carambola) beverage product in Thailand has been reported to have some probiotic properties, in vitro. In the present study, its in vivo safety and gastrointestinal survival following oral administration to mice was investigated. The acute toxicity test on ICR mice by force-feeding of a single dose of 109 and 1012 cells per mouse over 14 days after ingestion showed no adverse effects related to the normal behavior of the laboratory mouse. Although the weight gains of the dosed mice were lower than the control they were still within normal values. There were no significant differences in liver weight ratio or spleen weight index among tested mice and control mice and no evidence of bacteremia. Live SS2 cells labeled with a fluorescent dye (cFDA-SE) and administered orally at 109 cells per mouse were shown to persist in the gastrointestinal tract for 7 days. Colonies similar to the SS2 were detected in fecal samples from the test mice even though the fecal lactic acid bacterial count showed no significant difference in any mice. The strain SS2 is therefore considered to be a possible alternative choice for an inoculum to produce fermented plant beverages.

Raw potato starch in weaned pig diets and its influence on postweaning scours and the molecular microbial ecology of the digestive tract1

We evaluated the effect of raw potato starch (RPS) on growth performance, postweaning diarrhea, and gastrointestinal microbial populations in weaned piglets. Eighty-four piglets were weaned at 17 +/- 2 d of age with an average BW of 6.0 +/- 0.9 kg. Pigs were blocked by BW and assigned to 1 of 4 diets in a randomized complete block design with 7 replicate pens per diet and 3 pigs per pen. Treatments were 1) a positive control (PC) containing an antibiotic, 2) a negative control (NC) with no RPS and no antibiotic, 3) NC + 7% RPS (7% RPS), and 4) NC + 14% RPS (14% RPS). Diets were corn-wheat-soybean meal-based and formulated to meet NRC (1998) recommendations. The ADG, ADFI, and G:F ratio were determined weekly. Fecal consistency (FC) scoring was determined daily. After wk 3, 1 pig with a BW closest to the pen mean was killed to evaluate ileal and colonic mucosal-attached Escherichia coli and lactic acid bacteria, as well as digesta pH, VFA, and ammonia N concentrations. The DNA was extracted from ileum and colon digesta and used for molecular microbial evaluations using terminal-RFLP analysis of 16S rDNA genes. The ADG for wk 1 was greater (P < 0.01) for the PC diet, but diet had no effect on ADG during wk 3. The ADFI did not differ among treatments during the first 2 wk, and ADFI was least for 7% RPS diet during wk 3. The NC diet had a greater (P < 0.05) FC score during wk 1 than other treatments, but diet had no effect on FC score during wk 2 and 3. Diets had no effect on the colon lactic acid bacterial counts; however, the PC diet had decreased (P < 0.05) colon E. coli counts than other treatments. Ileum and colon digesta pH and total VFA concentrations did not differ among treatments. Pigs fed with 7 and 14% RPS diets had greater (P < 0.05) ileum ammonia N concentration compared with pigs fed with other diets. There was more diarrhea (P < 0.05) in the 14% than the 7% RPS and control treatments at d 21. This difference correlated with a decline (P < 0.05) in microbial diversity in the colon. We concluded that 7% RPS can be used to prevent postweaning diarrhea in weaned piglets, but there are no effects on growth performance.

땅두릅 잎김치의 저장기간에 따른 품질특성

본 연구에서는 땅두릅잎을 이용하여 전래되어온 제조 방법으로 잎김치를 제조하여 적합가능성을 알아보고 저장기간에 따른 품질특성을 조사하여 다음과 같은 결과를 얻었다. 땅두릅 잎김치의 이화학적 특성에서 pH 및 총산의 변화는 pH가 감소하면 산도는 증가하는 경향으로 양념에 따라 다소 차이를 보였으며, 염도의 경우 저장초기 급격히 증가하였고 그 이후부터는 저장기간이 증가함에 따라 미미하게 증가하는 경향을 나타내었다. 미생물학적 특성에서 총균수와 젖산균수의 변화는 비슷한 양상으로 저장기간이 증가할수록 서서히 증가하기 시작하여 저장 4개월에 최고치에 이른 후 감소하여 일정 수준을 유지하였다. 물리화학 특성에서 색도는 저장초기 서서히 증가하다가 저장 4개월에 명도는 급격히 감소 경향을 보인 반면 적색도와 황색도는 증가하였으며 총색차 ΔE는 저장초기에 서서히 감소하기 시작하다가 발효가 진행된 저장 4개월에 완만하게 증가했다가 다시 감소하였다. 경도변화의 경우 저장기간이 증가할수록 증가하다가 다소 감소하는 경향을 보였다. 관능적 특성은 간장, 고춧가루, 젓갈양념 등 3가지 종류 모두에서 전반적으로 5점 이상을 받아 우수하게 평가되어 땅두릅 잎김치로서의 가능성을 강하게 시사하였다. 위와 같이 땅두릅잎이 잎김치로서 적합함이 확인되었으며 우리 농산물의 농가 소득의 부가가치 향상을 위한 일환으로 땅두릅잎을 다양하게 활용한다면 이용가치가 높을 것으로 기대된다.

β‐Carotene‐rich sweet potato curd: production, nutritional and proximate composition

SummarySweet potato (SP) is an important root crop grown all over the world and consumed as a vegetable, boiled, baked or often fermented into food and beverages. A curd‐like product was prepared by fermenting boiled β‐carotene‐rich SP puree and cow milk with curd (starter) culture (Lactobacillus bulgaricus, Streptococcus lactis, Streptococcus diacetilactis, etc.). There were not much variation in pH (3.6–3.9), titratable acidity (10–11.8 g kg−1 curd) and lactic acid (LA) (7.9–5.3 g kg−1 curd) contents in SP curd consisting different concentration of SP puree. However, curd with 12–16% SP puree was most preferred by a consumer's panellist. The addition of SP puree (12–16%) made the curd quite firm and imparted flavour, body/texture, minerals, nutrients, antidiabetic substances, β‐carotene pigments (antioxidant), dietary fibres and starch (carbohydrate source). The LA bacterial counts in the curd after 18 h of fermentation having 8% and 16% SP were 7 × 107 and 14 × 107 (CFU mL−1), respectively. The consumer evaluation scores ranged from 7 to 8 (in a hedonic scale of 1–9), from moderate liking to very much liking of the SP curd, taking into consideration the sensory attributes such as colour, texture, flavour, sweetness, appearance, etc. Principal component analysis (PCA) reduced the fourteen original analytical (proximate) variables to four independent components (factors), which accounted for 97% of the total variations. Similarly, PCA analysis reduced the seven original sensory attributes to three independent components that accounted for 70% of the total variations.

ANTIOXIDATIVE AND ANTIMICROBIAL PROPERTIES OF LACTOFERRIN IN HOT-BONED GROUND PORK DURING STORAGE

The effect of lactoferrin concentration on the antioxidative and antimicrobial activities of hot-boned (4–5 h after death) ground pork during storage at 4C for 9 days was examined. The total iron content increased with the addition of lactoferrin. Meat samples with added lactoferrin (40 or 80 mg/kg) had lower thiobarbituric acid reactive substances (TBARS) than controls at 3, 6 and 9 days; however, the differences in TBARS between the 40- and 80-mg lactoferrin/kg treatments were not significant. With the addition of lactoferrin (40 or 80 mg/kg), ground pork had lower (P < 0.05) total plate counts than controls at 3, 6 and 9 days of storage. However, the differences in total plate counts between the 40- and 80-mg lactoferrin/kg treatments were only significant (P < 0.05) at days 3 and 6. The addition of lactoferrin (80 mg/kg) decreased lactic acid bacterial counts at days 0, 3 and 9. The pH values of hot-boned ground pork were unaffected by the addition of lactoferrin, but slightly increased with storage time.

Growth Depth Effects of Bacteria in Ground Turkey Meat Patties Subjected to High Carbon Dioxide or High Oxygen Atmospheres

Modified atmosphere packaging (MAP) is used to extend the shelf life of ground meats by altering the gas atmosphere surrounding the meat. This study evaluated how deep MAP bactericidal effects penetrate into a ground meat patty. Patties made from freshly ground turkey breasts were subjected to 2 MAP treatments of high CO(2) (97%) or high O(2) (80% O(2), 20% CO(2)). Total plate and lactic acid bacterial counts were determined for 3 patty depths (top, middle, bottom). Meat surface color and the package gas headspace composition were also measured. All analyses were performed on 0, 3, 6, 9, and 12 d. Changes in gas headspace and meat surface color were also measured at 0, 3, 6, 9, and 12 d. High CO(2) atmosphere maintained a better meat surface color than high O(2) atmosphere over the whole storage period. Overall counts were lower (P < or = 0.05) in a high-CO(2) atmosphere compared with a high-O(2) modified atmosphere. Patties stored under a high-CO(2) atmosphere displayed slower bacterial growth in the top layer compared with the middle and bottom layers. Total plate count did not differ (P > or = 0.05) in layers for patties pack-aged in a high-O(2) atmosphere Lactic acid bacterial counts increased in the high-O(2) modified atmosphere by d 9 and 12 of storage; no increase was observed in CO(2)-packaged patties. Thus, high-CO(2) MAP slowed the growth of total bacteria as well as lactic acid bacteria. Also, there was slower growth in the top meat layer exposed to CO(2) compared with interior layers.

Acidified sodium chlorite as an alternative to chlorine to control microbial growth on shredded carrots while maintaining quality

AbstractShredded carrots are particularly susceptible to microbial growth and quality deterioration as a result of a large cut surface area to mass ratio. Acidified sodium chlorite (ASC) in the concentration range 500–1200 µL L−1 has been shown to have stronger efficacy against pathogens and spoilage bacteria than chlorine and does not form carcinogenic products. However, ASC in this concentration range aggravates tissue damage. The objective of this study was to optimize ASC treatment parameters to balance antimicrobial activity with quality retention of shredded carrots. Shredded carrots were immersed for either 1 min in 100, 250 or 500 µL L−1 ASC solutions or 2 min in 200 µL L−1 chlorine or water (control). Treated samples were spin‐dried and packaged in polypropylene bags and stored at 5 °C for up to 21 days. Carrots were evaluated at 7‐day intervals for visual appearance, package atmosphere composition (O2 and CO2), product firmness, tissue electrolyte leakage and pH. The microbial growth, including total aerobic bacterial counts, total coliforms/Escherichia coli, yeast and mold counts and lactic acid bacterial counts on the products was also determined. Treatments with all concentrations of ASC reduced the aerobic bacterial counts, coliform/E. coli counts, yeast mold and counts and lactic acid bacterial populations by 1.2–2.0 log cfu g−1 when compared with the water‐washed and unwashed samples. During storage, unwashed samples had a sharp increase in lactic acid bacterial populations accompanied by a sharp decline in pH readings and rapid loss in firmness and tissue integrity; samples washed with 100 µL L−1 ASC maintained the best overall visual quality, accompanied by the retention of tissue integrity and firmness. Therefore, 100 µL L−1 was determined as the optimum concentration of ASC for maintaining overall quality and firmness, inhibiting microbial growth and prolonging the shelf‐life of shredded carrots. Copyright © 2006 Society of Chemical Industry

EFFECT OF A DIETARY PROBIOTIC ON SOME QUALITY CHARACTERISTICS OF RAW BROILER DRUMSTICKS AND BREAST MEAT

ABSTRACT The effect of probiotics in broiler feeding was investigated by evaluating poultry carcass meat quality. Feeds supplemented with different levels of a probiotic (0.0, 0.1 and 0.2%) containing Saccharomyces cerevisiae (115‐Biogallinox) were used in feeding Ross 308 male chicks for 49 days. At the end of the trial period all broilers were sacrificed. After standard dissection of the carcasses, breasts and drumsticks were divided into two groups and vacuum or aerobically packaged than stored at 3 ± 0.5C for 12 days. The breasts and drumsticks were analyzed for pH, thiobarbituric acid reactive substances (TBARS), total mesophilic, total psychrotrophic, lactic acid and Enterobacteriaceae counts every two days during storage. The feeding of probiotic in broiler diets increased pH values of breast and drumstick (P &lt; 0.01) but TBARS, total psychrotrophic bacteria and Enterobacteriaceae counts decreased (P &lt; 0.01). It was determined that pH, TBARS and Enterobacteriaceae counts were lower in breast than drumstick (P &lt; 0.05); but lactic acid bacterial count was higher (P &lt; 0.05) in the drumstick samples. The pH, TBARS and bacterial counts increased during storage (P &lt; 0.01) except for total mesophilic bacteria. The pH, TBARS, total aerobic psychrotrophic bacteria and Enterobacteriacea counts were lower in vacuum than in aerobically packaged samples (P &lt; 0.05).

Non-lactic acid, contaminating microbial flora in ready-to-eat foods: A potential food-quality index

The bacteriological profile of 87 samples of commercially available ready-to-eat (RTE) dairy and meat-products, packaged sandwiches and salads was obtained by testing for aerobic colony count, for lactic acid bacterial (LAB) count, for the presence and the extent of non-LAB microflora (contaminating microflora), and by testing for certain food-borne pathogens. The pathogens Listeria monocytogenes, Salmonella spp. and sulfite-reducing clostridia were not detected in any of the analysed samples. Whereas only three samples (3.4%) were deemed unacceptable for consumption for exceeding the established pathogen tolerance levels (for Staphylococcus aureus and Escherichia coli), several samples were found to contain non-lactic acid contaminating microflora of considerable magnitude. The log 10 cfu g −1 counts for contaminating microflora in the food categories examined were as follows: hard cheeses 4.85 (SD 1.17); semi-hard cheeses 5.39 (SD 1.37); soft cheeses 5.13 (SD 1.03); whey cheeses 6.55 (1.24); fermented meat-products 4.18 (SD 1.48); heat-treated meat-products 3.47 (SD 1.99); salads 3.37 (SD 1.56) and sandwiches 5.04 (SD 0.96). Approximately 1 in every 30 to 80 bacterial cells found on different types of cheeses and salads was a non-LAB microorganism; the respective ratios for fermented meat-products, heat-treated meat-products and sandwiches were 1 in 6, 2.5 and 15. The assessment of the contaminating microflora magnitude at various steps during the manufacture and distribution of RTE foods can serve as an index for monitoring the microbiological quality of the starting materials, the sanitation efficacy during processing and possible temperature abuse during processing, transportation or storage.

Effect of gamma irradiation on Listeria ivanovii inoculated to iceberg lettuce stored at cold temperature

A low-dose gamma irradiation considerably reduced the total plate counts, psychrotrophic bacteria, lactic acid bacteria, and inoculated Listeria ivanovii on shredded iceberg lettuce. The total plate count of the lettuce irradiated at 1.0 kGy was reduced by 3.38 log 10 cfu/g on 0 storage day and to below the limit of detection (<2 log 10 cfu/g) as the cold storage was extended. Irradiation at 0.5 kGy effectively reduced the psychrotrophic bacterial counts and lactic acid bacterial counts in the lettuce to below the limit of detection (2 log 10 cfu/g). Irradiation at 1.0 kGy reduced L. ivanovii inoculated onto the shredded iceberg lettuce to below the limit of detection. The results showed that an irradiation at 1 kGy eliminates the bacterial contamination from the lettuce sample without any sensorial quality defect.

Microbiological, physicochemical, and sensory characteristics of kefir during storage

Changes in certain microbiological, physicochemical, and sensory parameters of kefir were studied during refrigerated storage. Kefir batches were prepared using 1% and 5% added kefir grains, and samples for analysis were taken 24 h after inoculation and then after 2, 7, 14, 21, and 28 days of storage at 5 ± 1 °C. After fermentation for 24 h after inoculation, lactobacilli and lactococci were present at levels of 10 8 cfu/ml, and yeasts and acetic acid bacteria were present at levels of 10 5 and 10 6 cfu/ml, respectively. The lactic acid flora decreased by about 1.5 log units between days 7 and 14 and then stabilized at that level. Yeast and acetic acid bacterial counts, lactose, and pH all remained constant over the storage period, while the total fat content and dry matter decreased. The percentage inoculate did exert an influence, and the sample batches made using 1% added kefir grains had higher lactic acid bacterial counts, lactose, and pH, while the sample batches made using 5% added kefir grains had higher yeast and acetic acid bacterial counts and viscosity. The total fat and dry matter contents were similar in both sample batches. Sensory analysis of the kefir samples revealed maximum acceptability levels in the first 2 days of storage.