Populations Of Total Aerobic Bacteria Research Articles

Benefits of isochoric freezing for carrot juice preservation.

Isochoric freezing (IF) at -5°C/77 and -10°C/100MPa was used to preserve carrot juice for 12 weeks. The juice qualities were compared to those using heat treatment (HT) at 95°C for 15s followed by cold storage at 4°C. The native population of total aerobic bacteria, yeasts, and molds in isochoric frozen juice remained below the detection limit for 12 weeks. In comparison, microbes started to grow in heat-treated juices after 3 weeks of refrigeration. The color of isochoric frozen juice appeared more deep orange than the fresh juice due to an increase in carotenoid extractability. IF was not effective in reducing the activities of peroxidase, polyphenol oxidase, and pectin methyl esterase compared with HT. However, the isochoric samples showed higher carotenoid content, polyphenol content, and antioxidant capacity compared to the fresh and heat-treated juices. PRACTICAL APPLICATION: Isochoric freezing was used to produce carrot juice with extended shelf life. Isochoric freezing could be a beneficial alternative to conventional heat treatment for carrot juice processing as the applied pressures reached total inactivation levels of spoilage microorganisms. Moreover, the low processing temperatures better retained desirable compounds and quality attributes of fresh juice throughout its shelf life.

Impact of Stocking Densities on the Microbiota of the Cloaca, Eggshell, and Egg Content of White Egg Layers in Colony Cages

Food safety is a major concern for commercial poultry producers and consumers. Currently, there is also pressure from retailers and legislators to increase the space per hen in cages. Five different density treatments consisting of six (208 in2/bird), nine (139 in2/bird), twelve (104 in2/bird), fifteen (83 in2/bird), and eighteen birds (69 in2/bird) per cage were examined in colony cage environments. Microbiological tests were performed at 39, 55, and 68 weeks of age. The populations of total aerobic bacteria; E. coli/coliform; Enterobacteriaceae; and yeasts and molds from an eggshell rinse, egg content, and cloacal swabs were enumerated. The prevalence of Salmonella spp. in these samples was also monitored. Overall, no bacteria were detected in any of the egg content, and there were no differences (p > 0.05) between treatments for the shell rinse. Stocking density did not influence the eggshell microbiota of the hens. Hens housed at 104 in2 per hen showed higher levels of total aerobic bacterial counts from the cloaca compared to hens at 208 in2 and 69 in2 per hen. Hens housed at 139 in2 per hen had the highest level of cloacal molds. This research demonstrates that stocking density does not influence eggshell microbiota or Salmonella contamination of the eggshell or cloaca, thereby indicating that allowing more space per hen will not positively or negatively affect the prevalence or concentration of foodborne pathogen-associated bacteria in or on the eggs.

Changes in N-nitrosamines, Residual Nitrites, Lipid Oxidation, Biogenic Amines, and Microbiota in Chinese Sausages Following Treatment with Tea Polyphenols and Their Palmitic Acid-modified Derivatives

This study aimed to investigate the effects of tea polyphenol (TP), epigallocatechin gallate (EGCG), and their palmitic acid-modified derivatives palmitoyl-TP (pTP) and palmitoyl-EGCG (pEGCG) on the accumulation of N-nitrosamine and biogenic amines (BAs), residual nitrites, and lipid oxidation in Chinese sausages. The microorganisms, color, and texture properties of sausages were evaluated. TP, EGCG, pTP, or pEGCG significantly inhibited the accumulation of N-nitrosodimethylamine (NDMA) and BAs, residual nitrites, and lipid oxidation, but enhanced the redness, hardness, and chewiness of sausages. The concentration of NDMA in sausages was reduced by 58.11%, 63.51%, 36.49%, and 44.59%, respectively, after treatment with TP, EGCG, pTP, and pEGCG. Both EGCG and pEGCG exhibited excellent inhibitory effects on the predominant BAs, including putrescine, tyramine, cadaverine, histamine, and 2-phenylethylamine. Palmitoyl-EGCG was found to be the strongest inhibitor of lipid oxidation. Besides, the four antioxidants weakly affected the population of total aerobic bacteria and lactic acid bacteria but totally suppressed the growth of undesirable Enterobacteriaceae. The principal component and correlation analyses proved that BAs, nitrites, lipid oxidation, and microbiota were responsible for the formation of NDMA. The results indicated that palmitic acid-modified TPs and similar derivatives might serve as potential preservatives to improve the safety and quality of fermented meat products.

Yucca schidigera extract depressed ammonia emission in manure incubation and green-house gases release in artificial rumen of cows

The influences of ammonia (NH3) and greenhouse gas (GHG) emissions from livestock on environment recently become a major concern of the worldwide. The objective of the study was to evaluate the effects of Yucca schidigera extract (YSE) on ammonia emission in manure and the release of green-house gases including methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) in artificial rumen of cows. Addition of YSE significantly decreased ammonia nitrogen (NH3-N) concentration (P < 0.01) and increased the percentage of total nitrogen (N) (P < 0.005) in manure incubation. The populations of total aerobic bacteria were significantly decreased by the addition of YSE with 1% and 2% (P < 0.05), while the populations of Lactobacilli were significantly increased in dose-dependent manner (P <0.001) in manure. In 1-12 h and 13-24h of ruminal fermentation in vitro, the yields of CH4, CO2 and N2O were dose-dependently reduced by the addition of YSE (P < 0.05). Results showed that YSE inhibit ammonia emission in manure and the release of green-house gases in artificial rumen of cows.

Effects of different X-ray irradiation doses on quality traits and metabolites of marinated ground beef during storage

The effect of X-ray irradiation on quality traits and metabolites identified by the 1H nuclear magnetic resonance (NMR) of marinated ground beef was studied during 14 d of cold storage. The samples were vacuum packaged and irradiated at 2.5, 5, 7, and 10 kGy. The population of total aerobic bacteria in the samples significantly decreased as the X-ray irradiation doses increased during storage. No bacterial growth was observed in the samples irradiated at 10 kGy. The redness of the samples increased significantly as the dose levels increased. Lipid oxidation in the samples was unaffected by the irradiation doses. For volatile organic compounds, the contents of methanethiol, 2-methylfuran, and S (+)-2-butanol increased as the dose and storage period increased. X-ray irradiation at 7 kGy was effective for microbial inactivation of ground beef without compromising quality such as off-odor generation. In addition, the metabolites profile of samples can distinguish irradiation dose levels during storage.

Occurrence of antibiotic-resistant bacteria on hydroponically grown butterhead lettuce (Lactuca sativa var. capitata).

Antibiotics used during production of food crops to control plant diseases may result in selection of antibiotic‐resistant bacteria and occurrence of antibiotic residues. The aim of this research was to evaluate the effect of antibiotics used in butterhead lettuce production on persistence of commensal microbiota. Butterhead lettuce were treated with antibiotics (oxytetracycline, gentamicin, and streptomycin) at different concentrations (100, 200, 300, 400 and 500 ppm) starting at 5 weeks’ growth by spraying once daily for 4 weeks and harvesting 7 days after the final spray application. The population of total aerobic bacteria and antibiotic‐resistant bacteria were determined. The results showed antibiotic usage significantly decreased bacterial populations on lettuce. Moreover, increased concentration of antibiotics resulted in significantly greater decrease in bacterial populations. At a concentration of 500 ppm, all antibiotics achieved an approximate 2 log CFU/g decrease in bacterial populations. A stable population (4 log CFU/g) of potentially antibiotic‐resistant commensal microbiota were maintained throughout production. Screening for level of susceptibility indicated that bacteria exhibited greater resistance to oxytetracycline than gentamicin. In conclusion, application of antibiotics failed to eliminate commensal microbiota, demonstrating large populations of antibiotic‐resistant bacteria reside on lettuce grown under conditions used in the present study. This is the first study focused on antibiotic usage on hydroponic systems. Results of this study suggest regulations directed at antibiotic use on food crops must be developed and implemented to control the selection and spread of antibiotic‐resistant bacteria that present a global health concern.

Pasteurization of carrot juice by combining UV-C and mild heat: Impact on shelf-life and quality compared to conventional thermal treatment

The combination of UV-C radiation and mild heat (UV-H) treatment is a promising strategy for synergistically increasing microbial inactivation in low UV-transmitting juices. In this research, we explored the suitability of UV-H treatment in carrot juice pasteurization and its impact on juice quality during shelf-life compared to that of thermal pasteurization. UV-H treatment at 60 °C (3.92 J/mL, 3.6 min) enabled reductions of over 5 log10 cycles in the reference pathogens and a significant reduction in spoilage yeasts, bacteria, and bacterial spores. The activity of pectin methylesterase and polyphenol oxidase was reduced by UV-H treatment to levels close to those of low-temperature pasteurization (60 °C/18.1 min). The native population of total aerobic bacteria, lactic acid bacteria, and yeasts and molds of UV-H-treated juice remained undetectable during 29 days of cold storage. Furthermore, viscosity, cloud stability, and the color of fresh juice were better preserved by UV-H treatment than by thermal pasteurization throughout storage.Industrial relevanceThis study demonstrates that UV-H treatment is a beneficial alternative to conventional thermal processing in carrot juice pasteurization, since appropriate inactivation levels of pathogenic and spoilage microorganisms can be reached while better preserving the quality attributes of fresh juice throughout its shelf-life.

Effect of plasma-activated water on microbial quality and physicochemical characteristics of mung bean sprouts

Abstract The efficacy of nonthermal plasma-activated water (PAW) in the decontamination of mung bean sprouts was evaluated in this work. After being treated with PAW for 30 min, the populations of total aerobic bacteria and total yeasts and moulds on mung bean sprouts were decreased by 2.32- and 2.84- log10 CFU/g, respectively. The PAW treatment had no significant effect on the antioxidant potential of mung bean sprouts as shown by using 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH•) scavenging activity assay, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) method, and ferric reducing antioxidant power (FRAP) assay (p > 0.05). Additionally, the PAW treatment caused no significant changes in the total phenolic and flavonoid contents, nor the sensory characteristics of mung bean sprouts (p > 0.05). Reactive species such as nitrates, nitrites, and H2O2 were generated in PAW, which presumably contributed to the disinfection efficacy of PAW. These data show that PAW can be used as a promising nonthermal technology for the control of microbial contamination in sprouts. Industrial relevance Edible sprouts are common food ingredients across the world. However, sprouts can be contaminated by pathogenic microorganisms, which may result in health risks to humans. Recently, PAW has been shown to be a safe and effective method for food surface sanitation. However, the application of PAW in the microbial control for sprouts is less investigated. In this study, the influences of PAW on the microbial load, chemical and sensory quality of mung bean sprouts were investigated for the first time. The results showed that PAW could effectively inactivate bacteria and yeasts and moulds on mung bean sprouts without resulting in significant changes in the antioxidant capacities, total phenolic and flavonoid contents, and sensory characteristics of mung bean sprouts. These data indicated that PAW can be used as a promising nonthermal technology for reducing microbial populations on sprouts.

Effects of combined treatment with ultraviolet-C irradiation and grape seed extract followed by supercooled storage on microbial inactivation and quality of dongchimi

Dongchimi is a watery variety of kimchi prepared using firm radish and condiments. Over-ripening is the most undesirable outcome of dongchimi fermentation, resulting in softening of texture and an undesirable taste. Herein, the effects of combined treatment with ultraviolet-C (UV-C) irradiation and grape seed extract (GSE) supplementation, followed by supercooled storage, on the quality of dongchimi were investigated. Microbial inactivation tests showed that 6 kJ/m2 UV-C irradiation and 0.1% GSE supplementation before storage significantly reduced the populations of total aerobic bacteria, fungi, and lactic acid bacteria in dongchimi. Supercooled storage (−3 °C) delayed microbial growth in dongchimi compared to refrigeration (4 °C and 10 °C). Supercooled storage also suppressed changes in pH and titratable acidity in dongchimi. The hardness and colour of the radish slices did not vary with the treatments. Sensory evaluation results indicated that the qualities of dongchimi treated with the combination of UV-C and GSE followed by storage at −3 °C were better than those with other treatments. Thus, UV-C irradiation and GSE supplementation improved the final quality and extended dongchimi shelf life under supercooled storage at −3 °C without ice crystal nucleation and formation.

Application of gelatin film and coating prepared from dried alaska pollock by-product in quality maintanance of grape berries

In this study, gelatin extracted from dried Alaska pollock by-product (DAPG) was used as an edible film and coating source. Rosewood essential oil (RO) or pine needle extract (PE) was incorporated into the DAPG film and coating to provide antioxidant and antimicrobial activities. The DAPG film containing 1.0% PE had desirable physical properties as well as superior functional activities compared with the DAPG film containing 1.0% RO. The DAPG film and coating containing PE were then applied to “Kyoho” grape berries. Grape berries treated with the DAPG coating had lower populations of total aerobic bacteria and yeast and molds compared with the control after 20 days of storage and these differences were 3.62 and 1.46 log CFU g−1, respectively. Furthermore, the grape berries exhibited lesser weight loss and changes in anthocyanin content than the control, suggesting that DAPG coating is effective for the quality maintenance of grape berries during storage. Practical application The quality maintenance of “Kyoho” grape berries is needed due to postharvest spoilage during storage. Conventional methods such as modified atmosphere packaging and sulfur dioxide treatment may have inefficient effect and sulfite residue problems. Therefore, development of edible film and coating prepared from fish gelatin and the incorporation of essential oil or plant extract as an antioxidant or antimicrobial agent in this study can be a new approach to prevent postharvest loss of “Kyoho” grape berries during storage.

Disinfection effect of slightly acidic electrolyzed water on celery and cilantro

This study was designed to evaluate the efficacy of slightly acidic electrolyzed water (SAEW) to reduce natural microbiota on celery and cilantro at different available chlorine concentrations (ACC), different treatment time and temperatures. Additionally, SAEW treated celery and cilantro were stored at 4 and 20 °C for 6 days and population of total aerobic bacteria and yeast and mold were also determined at day 0, 2, 4 and 6, separately. Results showed that log reduction of total aerobic bacteria and yeast and mold significantly increased with increasing ACC and treatment time, respectively (p < 0.05). Celery and cilantro treated with SAEW at 30 mg/L ACC for 5 min and 25 mg/L for 7 min reduced yeast and mold to non-detectable level. No significant difference was observed for disinfection efficacy of SAEW on celery and cilantro at different temperatures (4, 20 and 37 °C) (p > 0.05). The microbial population on celery and cilantro maintained at a low level during storage at 4 and 20 °C after SAEW treatment (total aerobic bacteria: 3.3–4.1 log CFU/g, yeast and mold: 2.2–3.5 log CFU/g). The microbial inactivation effect as well as the absence of any sensory alterations on treated celery and cilantro rendered SAEW a promising disinfectant, which can be applied in fresh produce wash to control natural microbiota.

Fumaric acid와 mild heat의 병합 처리에 따른 시금치의 저장 중 미생물 제어 효과

The objective of this study was to examine the combined effect of fumaric acid with mild heat on the inactivation of microorganisms on spinach. Spinach leaves were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes. Based on the results of single treatment of fumaric acid (0.1, 0.3, and 0.5%) or mild heat (40, 50, and 60 o C) regarding the inactivation of the inoculated bacteria, the optimal condition for the combined treatment was suggested to be 0.5% fumaric acid and mild heat treatment at 50 o C for 5 min. The combined treatment of fumaric acid with mild heat caused 2.53 and 2.62 log reductions of the populations of L. monocytogenes and E. coli O157:H7, respectively. In addition, during storage of fresh spinach at 4 o C for 12 d, the combined treatment reduced initially the populations of total aerobic bacteria by 2.77 log CFU/g compared with the control. In particular, after 12 d of storage, the population of total aerobic bacteria for the combined treatment sample was 4.84 log CFU/g, whereas the control sample had 6.66 log CFU/g. Color and vitamin C content of spinach samples were not altered significantly by the combined treatment during storage. These results indicate that the combined treatment of fumaric acid with mild heat is an effective method to control microorganisms on spinach during storage.

Comparison of the murine norovirus-1 inactivation in cabbage Kimchi with two different salinities during storage

Enteric noroviruses are occasionally detected in Kimchi, which is a traditional dish made of fermented vegetables. This study was aimed at examining the effects of two levels of salt concentrations on the survival of murine norovirus-1 (MNV-1), a human norovirus surrogate, in experimentally contaminated cabbage Kimchi stored at 5°C for 10weeks. The number of total aerobic bacteria (TAB) and lactic acid bacteria (LAB), MNV-1 titer pH, and acidity were measured every week. The titers of MNV-1 in both low (1.17%) and normal (2.22%) salinity cabbage Kimchi were significantly (P<0.05) decreased with increase in storage time. The overall reduction was 1.75log10plaque-forming unit (PFU)/mL in normal salinity cabbage Kimchi and 1.24log10PFU/mL in low salinity cabbage Kimchi. The time required to reduce the titer by >1log10PFU/mL in normal and low salinity cabbage Kimchi were 4 and 8weeks, respectively. The pH value under both salinities significantly (P<0.05) decreased until 4weeks. The maximum acidity was 0.83% and 0.79% in normal and low salinity cabbage Kimchi, respectively, during the 10weeks. The population of TAB and LAB reached up to 7.33log10colony-forming unit (CFU)/g as a maximum population during the storage period of 3weeks in normal salinity cabbage Kimchi. However, the population of TAB and LAB in low salinity cabbage Kimchi reached to 6.99 and 7.04 log10CFU/g at 5 and 4weeks, respectively. Through these findings, fermentation factors such as TAB, LAB, pH, and acidity of cabbage Kimchi were influenced by salt concentration. The inactivation of MNV-1 in normal salinity cabbage Kimchi was much faster than that in low salinity cabbage Kimchi because the fermentation in normal salinity cabbage Kimchi progressed more quickly than that in low salinity cabbage Kimchi. However, both salinity cabbage Kimchi were able to infect cells for 70days even though the MNV-1 was reduced over 1 log10 during fermentation. Therefore, the way to protect cabbage Kimchi from norovirus must be considered.

Application of electrolyzed oxidizing water in production of radish sprouts to reduce natural microbiota

The objective of this study was to determine the efficacy of electrolyzed oxidizing (EO) water in reducing natural microbiota on radish seed and sprout during seed soaking and sprouting. EO water with different available chlorine concentrations (ACC, 15, 20, 28, 33 and 40 mg/L) and different pH (2.5, 3.5, 4.5, 5.5 and 6.5) were used to soak radish seeds for 12 h and the surviving population of total aerobic bacteria, yeast and mold, and germination rate were determined. On the other hand, EO water with ACC of 30 and 50 mg/L was applied to spray sprouts during seed sprouting and the antimicrobial efficacy of EO water, as well as length, gross weight and dry weight of sprout were evaluated. The results showed that the population of natural microbiota decreased with increasing ACC of EO water, while no significant difference was observed among EO waters with different pH levels that were applied while soaking the seeds. EO water with higher ACC and lower pH slightly reduced the germination percentage of radish seed during seed soaking. EO waters with ACC of 30 and 50 mg/L sprayed during seed sprouting resulted in 1.39 and 1.58 log reductions of total aerobic bacteria, yeast and mold, respectively, and improved the length, gross weight and dry weight of the sprouts. Therefore, EO water with low ACC and near neutral pH could be used to soak seeds and water sprouts throughout seed germination and sprouting to control the population of natural microbiota on seeds and sprouts.

수확 후 산채류의 미생물 제어를 위한 이산화염소수와 유기산 및 Blanching 병합 처리

To improve the microbiological safety of wild vegetables after harvest, Aster scaber and Cirsium setidens Nakai were treated with combinations of 50 ppm aqueous chlorine dioxide (ClO2)/0.5% citric acid or fumaric acid, and 50 ppm ClO2/0.5% fumaric acid/blanching at 90°C for 2 min. Combined treatment of 50 ppm ClO2 and 0.5% citric acid reduced populations of total aerobic bacteria, yeast, and molds in Aster scaber and Cirsium setidens Nakai by 2.80∼3.64 and 2.02∼2.67 log CFU/g, respectively, compared to those of the control. Combined treatment of 50 ppm ClO2 and 0.5% fumaric acid reduced total aerobic bacteria, yeast and molds populations by 3.62∼3.82 and 2.47∼3.02 log CFU/g, respectively. Based on the results, combined treatment of ClO2 and fumaric acid was more effective in controlling microorganisms in the wild vegetables than either ClO2 or citric acid. In addition, combined treatment of ClO2/fumaric acid/blanching reduced the populations of total aerobic bacteria by 4.59∼5.12 log CFU/g, and populations of yeast and molds were not detected by treatment. These results suggest that combined treatment of ClO2/fumaric acid/blanching is the most effective method for improving microbiological safety of wild vegetables after harvest.

한우육의 냉동 및 해동 조건에 따른 품질 변화

본 연구는 공기를 이용한 송풍식과 초저온 에탄올을 이용한 침지식 냉동방법 및 저온 송풍식과 유수식 해동방법을 조합하고 저장 중 냉동-해동 반복에 따른 한우 설도의 품질에 미치는 영향을 살펴보았다. 송풍식 냉동은 냉동이 완료되는데 약 800분이 소요됐지만 침지식 냉동방법은 8분에 한우 시료를 급속하게 동결시켰다. 한편 송풍식 해동은 한우 시료가 해동이 완료되는 데 약 350분 소요되었지만, 유수식 해동은 약 70분으로 해동시간이 280분 단축되었다. 송풍식 냉동시료는 송풍식 해동과 유수식 해동에 의해 4.05와 4.54%의 드립 감량이 발생했지만 침지식 냉동시료는 송풍식 해동과 유수식 해동에 의한 드립 감량이 2.59와 2.09%로 냉동방법에 따라 유의적(P0.05) 차이를 보였다. 냉동과 해동 처리로 한우 설도의 보수력은 64.40~66.05%로 감소하였지만 냉동과 해동 조건에 따른 차이가 거의 나타나지 않았다. 송풍식 냉동-송풍식 해동과 침지식 냉동-송풍식 해동 처리구의 TBARS 값은 각각 1.12와 1.18 mg MDA/kg으로 송풍식냉동-유수식 해동 처리구와 침지식 냉동-유수식 해동 처리구의 0.82와 0.77 mg MDA/kg과 비교하여 높은 값을 나타냈다. 휘발성 염기질소 함량은 TBARS 결과와 유사하게 송풍식 해동 처리구가 유수식 해동 처리구보다 높은 값을 보였다. 냉동과 해동이 조합된 모든 처리구의 총 호기성 세균수는 4.45~4.67 log CFU/g으로 냉동 및 해동 방법에 따라 유의적(P0.05) 차이는 나타나지 않았다. 송풍식 냉동된 한우육은 해동 후 근섬유 조직이 불균일하게 찢어지거나 근섬유 간의 간격이 더 넓어졌지만, 침지식 냉동된 한우육은 송풍식 해동 또는 유수식 해동 후 조직의 구조적 손상이나 변화가 훨씬 적은 것으로 나타났다. 한편 저장 중 냉동-해동의 3반복 처리로 드립 감량 증가, 보수력 감소, TBARS 값 및 휘발성 염기질소 함량 증가, 근섬유 조직 손상 등 품질 저하가 발생하였다. 앞으로 고품질 냉동 한우육의 생산 및 유통을 위한 부위별, 포장단위별 중량에 따른 냉동 및 해동 방법에 따른 이화학적 품질에 미치는 영향, 관능평가 등의 추가 연구가 필요할 것으로 사료된다.

저온 저장 중 절임배추의 미생물학적 품질 향상을 위한 혼합 살균제재와 항균성 얼음 병합처리 효과

본 연구는 절임배추의 미생물학적 안전성 확보에 따른 품질유지 및 저장성 향상을 위해 혼합 살균제재(50 ppm 이산화염소수+0.5% citric acid) 세척처리와 항균성 얼음(20 ppm 이산화염소수) 냉온살균기술을 병합하여 저장 중 절임배추의 미생물학적 및 이화학적 품질 변화를 분석하였다. 혼합살균제재 세척 처리된 절임배추는 대조구와 비교하여 총 호기성 세균, 대장균군, 효모 및 곰팡이, 그리고 젖산균 수가 2.20, 0.38, 1.28과 0.75 log CFU/g 각각 감소하였다. 저장온도 10°C와 비교하여 4°C 저온 저장에서 혼합 살균제재 세척/항균성 얼음 처리에 의한 미생물 감균 효과가 일정하게 유지됨을 보였으며, pH 감소와 적정산도 증가가 적은 것으로 나타났다. 한편 절임배추의 염도, 경도, 색도의 결과에 있어서 저장 중 대조구와 처리구 간에 유의적 차이는 보이지 않았다. 따라서 본 연구 결과 혼합 살균제재 처리는 절임배추의 초기 미생물 오염농도를 감소시키고 항균성 얼음처리와 4°C 저온 저장은 저장 중 미생물 생육 억제에 효과적인 것으로 나타나 절임배추의 미생물학적 품질 유지 및 shelf life 연장을 위한 효과적인 hurdle 기술이라고 판단된다.

Changes in nutritional value and application of thyme (Thymus vulgaris) essential oil on microbial and organoleptic markers of Persian clover (Trifolium resupinatum) sprouts

In this study, effect of the 4-day germination on the chemical composition, antioxidant activity and fatty acids profile of Persian clover seeds (Trifolium resupinatum) was investigated. In addition, clover sprouts was immersed in 0.5, 1 and 2% thyme (Thymus vulgaris) essential oil (EO) solutions, packaged in polyethylene containers and stored at refrigerated temperature (4 °C) for 10 days. As seedling progressed, the moisture, protein, crude fibre and ash content increased, whilst fat and carbohydrate reduced. After 4-day germination, ascorbic acid, total phenolic content and antioxidant activity indicated 1.3, 2 and 1.5 fold increase, respectively. Sprouting caused significantly (p < 0.05) increase in measured organic acids and minerals (except K). Moreover, oleic acid showed an increase of 3.4% compared to raw seed. In respect to microbial quality, the treated clover sprout demonstrated a significant reduction in the population of total aerobic bacteria, coliforms, molds and yeast count followed by increasing EO concentration compared to the control. Total aerobic bacteria, total coliforms, molds and yeast count of clover sprouts with 2% thyme EO showed 3.2, 2.3 and 2.2 log10 unit reduction, just after treatment. During storage, the population of natural microflora increased significantly (p < 0.05) in all treatments.

Effects of electron beam irradiation on microbial inactivation and quality of kimchi paste during storage

SummaryThe effects of electron beam irradiation on microbial inactivation and quality of noninoculated and inoculated (Listeria monocytogenes) kimchi pastes were examined. Kimchi paste samples were irradiated at doses of 2, 4, 6, 8 and 10 kGy and stored for 21 days at 4 °C. Irradiation (10 kGy) reduced the populations of total aerobic bacteria, lactic acid bacteria, and yeast and moulds in the samples by 1.72, 2.24 and 0.86 log CFU g−1, respectively, compared to the control. In particular, coliforms were not detected at 8 and 10 kGy, and the population of L. monocytogenes in inoculated samples was significantly decreased by 2.67 log CFU g−1. Electron beam irradiation delayed the changes in O2 and CO2 concentrations, pH, acidity and reducing sugar content observed in kimchi paste during storage. These results suggest that electron beam irradiation can be used to improve the microbiological safety and shelf life of kimchi paste.

고품질 수출용 파프리카 생산을 위한 이산화염소 가스 훈증 처리

ABSTRACT To maintain high quality and microbiological safety of paprika during storage for export, paprika samples after harvest were treated with 75 ppmv chlorine dioxide (ClO 2 ) gas and stored at 8°C, which is the optimal storage temperature, for 30 days. ClO 2 gas treatment reduced initial populations of total aerobic bacteria in samples by 1.62 log CFU/g as well as yeast and molds by 1.45 log CFU/g compared to those of the control. During storage, weight loss of all samples increased, and samples treated with ClO 2 gas showed lower weight loss than the control. In addition, total soluble solid and total phenolic contents were not significantly different between the samples during storage, whereas vitamin C content and hardness of all samples decreased. Hunter L, a, and b values of paprika samples were not significantly different between the treatments. These results suggest that ClO 2 gas treatment can be effective for improving microbiological safety and maintaining high quality of paprika during storage.