工厂中环境和海产品加工前后的微生物学检验

检测了2个海产品加工厂的环境及加工前后海产品样品的菌落总数(个/cm2,个/g或个/mL)、李斯特氏菌和单核细胞增生李氏菌数(每100cm2,100g或100mL样品的MPN数),其结果如下:2个工厂对应样品的菌落总数及其分布规律相接近,但李斯特氏菌和单核细胞增生李氏菌的出现率和数量却相差很大;单核细胞增生李氏菌数都低于或远低于李斯特氏菌,且单核细胞增生李氏菌与李斯特氏菌的数量和分布呈正相关;加工后海产品中的李斯特氏菌和单核细胞增生李氏菌可能来自原料和加工过程;环境中李斯特氏菌和单核细胞增生李氏菌主要来自原料.     

Effects of Low-dose Gamma Irradiation and Conventional Treatments on Shelf Life and Quality Characteristics of Diced Celery

ABSTRACT: The effects of 0.5 and 1.0 kGy gamma irradiation on microbial and sensory characteristics of diced celery were compared to conventional treatments such as acidification, blanching, and chlorination. Aerobic plate counts for the irradiated celery did not exceed 10⁷ CFU/g, in contrast, the acidified, blanched, chlorinated, and control samples surpassed aerobic microbial counts of 10⁸ CFU/g in 22, 19, 12, and 8 d, respectively. Importantly, the 1.0-kGy treatment eliminated inoculated Listeria monocytogenes and E. coli. While the acidified and blanched samples had significantly different sensory profiles compared to the other treatments, the irradiated samples maintained their color, texture, and aroma longer and were preferred in the sensory tests. The sensory shelf life of the 1.0-kGy-treated celery was 29 d compared to 22 d for the control, chlorinated, and 0.5 kGy, and 15 d for the acidified and blanched celery.     

Effect of Salts of Organic Acids on Listeria monocytogenes,Shelf Life,Meat Quality,and Consumer Acceptability of Beef Frankfurters

The objective of this study was to evaluate anti‐listerial efficacy of salts of organic acids, and their impact on the quality of frankfurters. Beef frankfurters were manufactured by incorporating organic acids in 5 different combinations: (1) control (no marinade addition; C); (2) sodium lactate (2% wt/wt; SL); (3) potassium lactate (2% wt/wt; PL); (4) sodium citrate (0.75% wt/wt; SC); and (5) sodium lactate (2% wt/wt)/sodium diacetate (0.25% wt/wt; SL/SD). Cooked frankfurters were inoculated with streptomycin‐resistant (1500 μg/mL) L. monocytogenes (7 log₁₀ CFU/frank). Inoculated and noninoculated frankfurters were vacuum packaged and stored at 4 °C. Samples were taken weekly up to 10 wk for estimation of L. monocytogenes as well as aerobic plate count (APC) and psychrotrophs (PSY), respectively. Total of 2 independent trials of the entire experiment were conducted. Noninoculated beef frankfurters were evaluated weekly by untrained sensory panelists for 7 wk. SL, PL, and SC treatments did not (P > 0.05) adversely affect consumer acceptability through 8 wk although, SL/SD treatment was significantly (P ≤ 0.05) less preferred across all sensory attributes. SL/SD treatment negatively affected product quality, but was able to control APC, PSY, and L. monocytogenes levels. SC performed similar to the control throughout the 8, 9, and 10 wk storage periods, providing no benefit for inhibiting L. monocytogenes (increasing from 7 logs CFU/frank to 10 logs CFU/frank throughout storage) or extending shelf life of the beef frankfurters. In conclusion, 2% SL and PL, and 2% SL/0.25% SD may be effective L. monocytogenes inhibitors (maintaining inoculation levels of 7 logs CFU/frank during storage), but changes in SL/SD treatment formulation should be studied to improve product quality.     

猪血亚硝基血红蛋白亚基色素的保存期限及其应用研究

以猪血和亚硝酸钠合成的亚硝基血红蛋白亚基色素为对象,通过光谱扫描、菌落总数测定和肉制品发色试验,研究色素在不同保存状态下的稳定性,以确定其保质期限。另外通过色差计测定该色素所制肉制品在贮藏期内的颜色变化,来判断色素发色的稳定性。结果表明:在-29℃冷冻条件下和采用真空冷冻干燥手段保存亚硝基血红蛋白亚基色素较为理想,保质期为6个月之久。而在肉制品贮藏期内,其色泽同样保持稳定,证实该色素添加到灌肠肉制品中是可行的。     

X射线辐照对冷鲜猪肉品质和货架期的影响

为研究X射线辐照对冷鲜猪肉品质的影响。该实验用0.1~1.0 kGy梯度的辐照剂量对纯培养细菌、冷鲜猪肉进行处理,评估不同辐照剂量和贮藏时间下微生物、理化指标和感官特性的变化。结果表明：微生物菌落数随辐照剂量的增加而减少。纯培养大肠杆菌和单核细胞增生李斯特氏菌的D10值分别为0.177 kGy和0.180 kGy。0.6 kGy X射线辐照处理时,纯培养细菌菌落数显著（p<0.05）减少3.0 log值以上;人工接种细菌菌落数显著（p<0.05）减少2.0 log值以上。1.0 kGy辐照处理冷鲜猪肉,固有微生物菌落数显著（p<0.05）减少2.0 log值以上;货架期从原来的4 d延长到9 d;贮藏前期感官评分无显著（p>0.05）差异,后期感官评分下降缓慢;与对照相比TVB-N和pH值的上升速率在贮藏期内显著降低（p<0.05）;辐照后冷鲜猪肉TBA值有所增加,但在贮藏中对照组TBA值上升速率大于辐照组。综合考虑,1.0 kGy X射线辐照处理冷鲜猪肉,在保证冷鲜猪肉符合国家食品安全标准规定的同时将货架期延长了 4~5 d,为冷鲜猪肉的辐照保鲜技术提供科学依据。     

Microbiological quality of fresh fruit and vegetable products in Catalonia (Spain) using normalised plate‐counting methods and real time polymerase chain reaction (QPCR)

BACKGROUND: Commercially available fruits and raw and ready‐to‐eat vegetables (n = 445) were examined for aerobic, coliform, and yeast and mould counts using normalised methods. Listeria spp., Listeria monocytogenes and Salmonella spp. were detected by real time polymerase chain reaction (QPCR) after enrichment. RESULTS: Aerobic plate counts ranged from < 10 to > 10⁹ colony‐forming units (CFU) g^?1, with the lowest and highest counts recorded for fruits and sprouts respectively. The highest incidence level of coliforms was found in ready‐to‐eat vegetables, with up to 65.7% of samples containing from 5 to 9 log₁₀CFU g^?1. Yeasts and moulds showed their highest incidence level between 5 and 6 log₁₀ CFU g^?1, with an overall range from < 2 to 9 log₁₀ CFU g^?1. Salmonella spp., Listeria spp. and L. monocytogenes were detected in 0.67, 2.7 and 0.9% respectively of the total samples examined. CONCLUSION: The samples analysed can be gathered into two main groups, one showing low microbial counts (fruits) and a second group (raw whole leaves and roots and packed ready‐to‐eat vegetables) with higher microbial contamination. Although incidence levels of pathogenic bacteria reported here are in the lower range of those reported elsewhere, positive detections highlight the importance of good hygienic measures throughout the whole food chain. Copyright © 2007 Society of Chemical Industry     

Extending the Shelf Life of Edible Flowers with Controlled Release of 1‐Methylcyclopropene and Modified Atmosphere Packaging

Abstract: Edible flowers have great sensory appeal, but their extremely short shelf life limits their commercial usage. Postharvest 1‐methylcyclopropene (1‐MCP) treatment is used to counter ethylene activity and delay senescence in fresh produce; however, its potential application in edible flowers has not been tested. The objective of this study was to investigate the effect of 1‐MCP treatment with modified atmosphere packaging (MAP) on the shelf life of edible flowers. Freshly harvested carnations and snapdragons were packaged in trays with or without 0.5 μL/L of 1‐MCP, sealed with a gas permeable film, and stored at 5 °C. Package atmospheres, tissue electrolyte leakage, and flower quality were evaluated on days 0, 7, and 14. Treatment with 1‐MCP resulted in significantly slower changes in package headspace O₂, CO₂, and C₂H₄ partial pressures, maintained higher overall quality of both flower species and reduced electrolyte leakage and abscission in snapdragon. All samples prepared with MAP had significantly reduced dehydration and higher overall quality compared to flowers packaged commercially in plastic clamshell containers. Treatments with controlled release of 1‐MCP and MAP significantly extended storage life of edible carnation and snapdragon flowers. Practical Application: Edible flowers are currently shipped via air cargo due to their extremely short shelf life. The technology developed in our research significantly extended the storage life of edible flowers, making it possible to ship the edible flowers via ground transportation with significant cost savings.     

Nondestructive and Continuous Monitoring of Oxygen Levels in Modified Atmosphere Packaged Ready‐to‐Eat Mixed Salad Products Using Optical Oxygen Sensors,and Its Effects on Sensory and Microbiological Counts during Storage

The objective of this study was to determine the percentage oxygen consumption of fresh, respiring ready‐to‐eat (RTE) mixed leaf salad products (Iceberg salad leaf, Caesar salad leaf, and Italian salad leaf). These were held under different modified atmosphere packaging (MAP) conditions (5% O₂, 5% CO₂, 90% N₂ (MAPC—commercial control), 21% O₂, 5% CO₂, 74% N₂ (MAP 1), 45% O₂, 5% CO₂, 50% N₂ (MAP 2), and 60% O₂, 5% CO₂, 35% N₂ (MAP 3)) and 4 °C for up to 10 d. The quality and shelf‐life stability of all packaged salad products were evaluated using sensory, physiochemical, and microbial assessment. Oxygen levels in all MAP packs were measured on each day of analysis using optical oxygen sensors allowing for nondestructive assessment of packs. Analysis showed that with the exception of control packs, oxygen levels for all MAP treatments decreased by approximately 10% after 7 d of storage. Oxygen levels in control packs were depleted after 7 d of storage. This appears to have had no detrimental effect on either the sensory quality or shelf‐life stability of any of the salad products investigated. Additionally, the presence of higher levels of oxygen in modified atmosphere packs did not significantly improve product quality or shelf‐life stability; however, these additional levels of oxygen were freely available to fresh respiring produce if required. This study shows that the application of optical sensors in MAP packs was successful in nondestructively monitoring oxygen level, or changes in oxygen level, during refrigerated storage of RTE salad products.     

Combined Application of Antibrowning,Heat Treatment and Modified‐Atmosphere Packaging to Extend the Shelf Life of Fresh‐Cut Lotus Root

This work aimed to determine the effects of different concentrations of antibrowning treatments (that is, distilled water [DW], 1% ascorbic acid [AA], 0.5% chamomile [CM], and 1% AA + 0.5% CM) and heat‐treatment (55 °C for 45 s) combined with packaging under 4 different modified‐atmosphere gas compositions (that is, air, vacuum, 100% CO₂, 50% CO₂/50% N₂) on the quality and microbiological characteristics of fresh‐cut lotus root. The quality characteristics (that is, color, weight loss, texture, pH, polyphenoloxidase activity, and total phenolic content) of the AA + CM‐dipped sample in 100% CO₂ packaging were maintained significantly better than those of the other samples (P < 0.05). The microbiological counts observed in the DW‐dipped sample during storage were higher than those of the AA, CM, and AA + CM samples, and heat‐treatment retarded the microbiological deterioration of fresh‐cut lotus root. Therefore, the results revealed that dipping in an antibrowning treatment (AA + CM), and 100% CO₂ MAP with heat treatment effectively extend the shelf life of fresh‐cut lotus root to 21 d at 5 °C.