馒头的微生物指标与安全性

贮存实验证明，馒头的菌落总数超过106cfu／g时出现感官品质劣变；保温贮存馒头。12h内菌落总数在104cfu／g以下，霉菌数不超过60cfu／g：4℃贮存5天馒头感官品质没有变化。菌落总数可以保证在106cfu／g以下；冷馒头复热后菌落数从不超过106cfu／g可以降低到103cfu／g以下。市场馒头检验结果显示。商品馒头菌落总数多在800～5000cfu／g之间，过严的要求企业难以实现。     

鲫鱼生鱼片不同温度贮藏特性研究

以活鲫鱼为试材,研究了0、4、-3、-18℃条件下生鱼片的品质变化。实验结果表明,不同温度冷藏处理均有一定的效应。其中-18℃温度最好,贮藏初期,鲫鱼生鱼片的TBA是0.715 mg/100 g,贮藏20 d,鲫鱼生鱼片的TBA、持水力、p H值、菌落总数分别为3.162 mg/100 g、0.6785、6.67、5.5 lg(cfu/g),弹性为0.627,回复性为0.3524。4℃的贮藏效果较差,贮藏10 d,鲫鱼生鱼片的TBA、持水力、p H值、菌落总数分别为5.515 mg/100 g、0.6465、5.215、7.5 lg(cfu/g),弹性和回复性下降很快。0℃和-3℃无显著差异。通过研究不同温度下,鲫鱼生鱼片各种品质的变化,可以突破鲫鱼生鱼片在贮藏过程中的难题,确定鲫鱼生鱼片的货架期,开发鲫鱼生鱼片保鲜新方法。     

冻藏时间对速冻水饺品质影响的试验研究

主要考查冷冻保藏时间对于速冻水饺的理化性质、微生物指标及感官性状的影响。结果表明,随保藏时间延长,饺皮的水分含量呈线性规律下降,从最初的（37．25±0．44）％降至试验末期的（32．5±0．92）％。而对于样品的酸价,随保藏时间延长,酸价升高,从初始的（2．01±0．01）mg KOH／g升至试验末期的（2．38±0．02）mgKOH／g。菌落总数及嗜冷菌菌落总数结果相似,都随保藏时间延长而增加,菌落总数从（1．27±0．09）×10^5 cfu／g升至（3．26±0．08）×10^5 cfu／g,而嗜冷菌菌落总数从（2．44±0．06）×10^5 cfu／g升至（3．73±0．15）×10^5 cfu／g。结合对水饺饺皮和饺馅的感官评价表明,速冻水饺的食用品质随保藏时间呈下降趋势,相对来讲,保藏时间越短,样品的食用品质越好。     

浅谈成品糖菌落总数的控制方法

GBl3104—2005《食糖卫生标准》于2005年1月25日发布,2005年10月1日开始实施。在新标准中增加了酵母菌和霉菌两个项目。规定酵母菌≤10cfu／kg,霉菌≤25cfu／kg。成品白砂糖、成品绵白糖的菌落总数指标从350个／g修订到100cfu／g。也就是说,新标准对成品糖的菌落总数的要求更加严格。对我国制糖企业尤其是那些以绵白糖生产为主的制糖企业而言,成品糖菌落总数指标的提高势必会对制糖生产过程的控制条件提出更加严格的要求。     

馒头的微生物指标与安全性

贮存实验证明,馒头的菌落总数超过106 cfu/g时出现感观品质劣变;保温贮存馒头,12h内菌落总数在104 cfu/g以下,霉菌数不超过60 cfu/g;4℃贮存5天馒头感官品质没有变化,菌落总数可以保证在106 cfu/g以下;冷馒头复热后菌落数从不超过106 cfu/g可以降低到103 cfu/g以下.市场馒头检验结果显示,商品馒头菌落总数多在800～5000 cfu/g之间,过严的要求企业难以实现.     

火腿肠中菌落总数的测定

对火腿肠中菌落总数进行了测定,结果表明,所测样品中菌落总数﹤10cfu/g,该方法简单、准确度高,适用于火腿肠中菌落总数的测定。     

肥育猪浓缩料中霉菌总数及霉菌毒素含量变化的研究

采用模拟饲料标准贮存条件及高温高湿贮存条件的方法,比较其霉菌总数、主要产毒菌的种类、黄曲霉毒素含量的变化情况。结果表明：肥育猪用浓缩料在相对湿度小于67％、温度（22±2）℃的标准贮存条件下,两个月内霉菌总数及毒素含量变化较小。在相对湿度为（80±2）％、温度为（30±2）℃的高温高湿条件下存放15d,霉菌总数为7．7×10^5cfu／g,超过国家饲料卫生标准1×10^5cfu／g,主要产毒菌种类有黄曲霉、寄生曲霉、绿青霉和镰刀菌等;存放32d,黄曲霉毒素含量为20．8μg／kg,超过浓缩料毒素限量标准20μg／kg;存放56d,玉米赤霉烯酮含量为18．3μg/kg,来超过标准限量500μg/kg。     

花生奶的超高压杀菌工艺研究

研究了花生奶超高压处理与微生物存活量之间的关系。考察了菌落总数、霉菌、酵母菌数和大肠菌群数的变化。实验结果表明：在室温下，花生奶中大肠菌群对压力非常敏感，霉菌和酵母菌较大肠菌群耐压，经500MPa，保压10min处理，菌落总数可降至20cfu／mL，达到了国家相应卫生标准。     

高温高湿条件腐竹防潮防霉包装技术研究

在40℃、湿度95%的高温高湿环境下,试验研究了空心圆支干腐竹防潮阻隔包装膜＋复合型防霉护色保鲜剂的新工艺。结果表明：腐竹保鲜剂用量6.67g/kg,于0.08mm厚OPP小包装和0.05mm厚LDPE小包装货架贮藏3个月,霉菌总数分别为91cfu/g和135cfu/g、菌落总数分别为50cfu/g和185cfu/g。腐竹内SO2残留量仅3.56×10-2g/kg,符合国家标准。     

自然发酵黄豆酱的微生物安全性的分析

对从11份农家和7份市场上销售的自然发酵黄豆酱样品进行了微生物的安全性检验和部分理化指标的测定，检验的项目包括细菌落总数、芽孢杆菌总数、大肠杆菌、沙门氏菌、志贺氏菌、腊样芽孢杆菌、金黄色葡萄球菌和肉毒梭菌。实验结果表明，所分析样品中菌落总数超过10^4个/g的样品有89％，腊样芽孢杆菌的检出率为30％，但含量不高，豆酱中的细菌总数除了与生产环境有关外，与产品的水分活度的相关性很大。     

Effects of retort conditions on ATP-related compounds in pouched fish muscle

To examine the usefulness of high-temperature short time (HTST) process on quality of retorted fish products, adenosine triphosphate (ATP)-related compounds in raw fishes and retorted fish models (10 g/pouch) heated at 115 °C for 90 min (common retort (CR) process) or 125 °C for 9 min (HTST process) were analyzed by HPLC method. The raw materials used in this study were fresh chub mackerel Scomber japonicus for sashimi (raw eating), frozen-thawed yellowfin tuna Thunnus albacares for sashimi, frozen-thawed pink salmon Oncorhynchus gorbuscha for cooking and frozen-thawed pink shrimp Pandalus borealis for sashimi. In all the fish samples, the level of inosine monophosphate (IMP), an umami-taste compound, was higher in HTST fishes than in CR fishes. On the other hand, inosine (HxR) and hypoxanthine (Hx), no-taste and bitter taste compounds, was high in CR fishes. K-value, an index of fish freshness defined as the ratio of the sum of HxR and Hx to the sum of ATP-related compounds, was high in CR fishes. In sensory test of pink salmon by the paired difference test, umami and sweetness in the HTST fish were stronger than the ones of the CR fish. The bitterness was stronger in the CR fish rather than in the HTST fish. These results indicated that HTST is a favorable process for retorted fish product and measurement of ATP-related compounds is useful for the quality check of retorted fishes.     

The Microbial and Sensory Quality of Mackerel Hot Smoked in Mild Conditions

The quality indices of Atlantic mackerel, hot smoked at core temperature not exceeding 60°C, containing 14-27 g salt and 580-670 g water per kg meat, was determined just after smoking and during storage. The aerobic plate count after smoking, chilling and packing in cardboard boxes was 0-12 cfu/25 cm²of the skin of the smoked fish and 10-240 cfu/g of flesh. It was 1.9 log cycle lower than that in the frozen raw material. At 2°C, the bacterial count on the fish surface and in the meat remained unchanged for at least 3 wk. At 8°C after 14 d, the cfu in the meat of smoked fish ranged from 1.8×10²to 1.6×10⁷/g. The total count on the skin and just under the skin did not increase up to 21 d at 2 and 8°C. There was no statistically significant difference between the mean values of all evaluated sensory attributes of the smoked fish stored up to 2 wk at 2 and 8°C. These results regard products from a smoking plant of very high hygienic standard, fulfilling all EC requirements, with quality assurance system based on HACCP.     

EFFECT OF PROCESSING ON BACTERIAL POPULATION OF CUTTLE FISH AND CRAB AND DETERMINATION OF BACTERIAL SPOILAGE AND RANCIDITY DEVELOPING ON FROZEN STORAGE

Processing techniques like cooking and freezing exhibited significant (P < 0.001) reduction in the bacterial load of cuttlefish, Sepia pharaonis, and marine crab, Portunus pelagicus. Raw cuttle fish had 2.4 × 10⁷ cfu/g which on cooking reduced to 9.7 × 10⁶ cfu/g. Freezing reduced the bacterial load further as cooked frozen product had only 9.9 × 10⁴ cfu/g. Similarly, raw crab had 2.6 × 10⁷ cfu/g which on cooking reduced to 6.5 × 10⁶ cfu/g. A further reduction in bacterial load was seen after freezing as cooked frozen crab exhibited only 7.3 × 10⁴ cfu/g. Escherichia coli and Staphylococcus aureus were present in the limit of acceptability for fish and fish products. Salmonella typhimurium and Vibrio cholerae were absent even in raw stage. Biochemical analysis performed on stored frozen products of cuttle fish and crab exhibited a significant (P ≤ 0.05) increase in bacterial spoilage and rancidity with increasing days of storage. Total volatile base nitrogen, trimethylamine, thiobarbituric acid and free fatty acid contents in frozen products of cuttle fish and crab increased significantly with 120 days of frozen storage.     

醋渍小鲥鱼生鱼片制作工艺研究

研究利用醋渍的方法将小鲥鱼制成生食制品。醋渍不但能起到杀灭微生物的作用,还能使蛋白质发生变性,使鱼片口感柔韧适中,适合生食。通过正交试验确定了小鲥鱼的最佳醋渍条件:醋与鱼的质量比为1:2,醋渍时间9h,温度5℃。醋渍产品色白而亮,口感佳,且细菌总数低于3000个/g(鱼肉)。     

Textural and biochemical properties of cobia (Rachycentron canadum) sashimi tenderised with the ultrasonic water bath

The present study investigated the tenderisation effects ultrasound processing (UT) on farmed cobia sashimi. Age-treated cobia trunk muscles (AT) were used as the control. The pH, total volatile base nitrogen, trimethylamine nitrogen, thiobarbituric acid reactive substances, ATP catabolism components, K₁ value, and texture were evaluated. The texture of AT sashimi reached the optimal firmness range with 8.53 N at day 7. However, AT samples could not be served raw after day 7 because of their poor freshness indexes, including a TVBN value of 18.53 g/100 g, a TMAN value of 3.25 mg/100 g, and a TBARS value 0.983 MDA mg/100 g. Moreover, the K₁ value of AT sashimi was 20.21% at day 5. UT was employed to efficiently tenderise cobia sashimi with an initial firmness of 9.70-7.82 N after 90 min of treatment. The results of this study indicate that UT accelerates the biochemical reaction rate, as evidenced by the increases in the TVBN, TMAN, and TBARS contents; however, these values were very low. The results of this study could provide basic information for the development of a novel ultrasonic tenderisation technique in raw seafood designed for restaurants and consumers.     

Listeria monocytogenes in foods in Norway

Three-hundred-and-eighty-two samples of different retail food items in Norway (imported soft cheese, raw chicken, minced meat, fermented sausages, vacuum-packed processed meat products, smoked salmon, peeled shrimps, raw minced fish) and 78 carcass samples (sheep, pig, cattle), were screened for Listeria monocytogenes. Of the 460 samples investigated, 78 were found to contain L. monocytogenes. Five of these contained greater than 10(3) cfu/g, four greater than 10(2) cfu/g, while the remainder were shown to contain L. monocytogenes only after enrichment. L. monocytogenes was isolated most frequently from raw chicken, sporadically from soft cheese, shrimps, processed meat products and smoked salmon, and not at all from carcasses and fermented sausages.     

High hydrostatic pressure treatment of finfish to inactivate Anisakis simplex

High hydrostatic pressure has been demonstrated to be a useful technique for treating food to reduce the number of pathogenic organisms and to extend shelf life. Most research in this area has focused on bacteria. However, a concern in the sashimi (raw fish) industry is that nematode worms such as Anisakis simplex occur naturally in cold-water marine fish. The objectives of this research were to perform a pilot study to determine the effect of high hydrostatic pressure on the viability of Anisakis simplex larvae, commonly found in king salmon and arrowtooth flounder, and to evaluate the effects of high hydrostatic pressure on the color and texture of the fish fillets. Pieces of fish (ca. 100 g per bag) containing 13 to 118 larvae were exposed to pressures of up to 80,000 lb/in2 (552 MPa) for up to 180 s. The times and pressures required to kill 100% of the larvae were as follows: 30 to 60 s at 60,000 lb/in2 (414 MPa), 90 to 180 s at 40,000 lb/in2 (276 MPa), and 180 s at 30,000 lb/in2 (207 MPa). For all salmon treatments that killed 100% of the larvae, a significant increase in the whiteness of the flesh was observed. Although high hydrostatic pressure was effective in killing A. simplex larvae in raw fish fillets, its significant effect on the color and overall appearance of the fillet may limit its application to the processing of fish for raw-fish markets.     

Biogenic amines in cold-smoked fish fermented with lactic acid bacteria

 It has been proved in previous studies that fish can be fermented by lactic acid bacteria (LAB). Added glucose must be at concentrations of almost 1% to reduce the pH to <5.3, a level which corresponds to the safe pH values for meat products. Because some LAB and some contaminating microbes form biogenic amines, this study was conducted to examine the possible formation of biogenic amines during the fish fermentation process. Other parameters under study were sensory quality, pH value, titrated acid content, weight loss, a _w value, redox potential and microbiological counts. Three groups of fish (rainbow trout) with three different LAB inocula and a group without any inoculum were made. The fermentation of the products made with LAB succeeded. The products were sensorially accepted, the inoculated LAB grew to >8 log cfu/g, the pH reduced to 5.0–5.3 and a _w to 0.927 and the pseudomonads, the predominant flora of fish raw material, disappeared. The fish raw material and the products contained low amounts of biogenic amines with one exception: cadaverine, histamine and tyramine increased in all product groups in one experimental series (II) out of three. The highest concentrations of these amines were in the control products without any LAB inoculation. The LAB used and the contaminants isolated from the products were unable to produce cadaverine, histamine or tyramine. The appearance of these amines could therefore be caused by the non-isolated contaminants of fish raw material. Received: 18 June 1999     

A case of sporadic ovine mastitis caused by Listeria monocytogenes and its effect on contamination of raw milk and raw-milk cheeses produced in the on-farm dairy

We describe a case of listerial mastitis in a flock of 130 sheep. The animals were housed at a farm where the bulk raw ewe milk was processed to produce raw milk soft cheese. List. monocytogenes was shed from the right mammary complex. Shedding was observed over a period of 99 d. A mean level of 4-56 x 10(4) cfu (colony forming units) Listeria monocytogenes/ml was recovered from the raw milk originating from the infected udder. The numbers ranged from 9 x10(1) to 2.95 x 10(5). The bulk milk was contaminated by approx. 5.7 x 10(3) cfu/ml. In the cheese product, 2.0 x 10(2) cfu List. monocytogenes/g were constantly detectable for a period of 7 d post manufacture. The starter culture used for coagulation had a pivotal influence on the behaviour of List. monocytogenes during cheesemaking. Using the same mesophilic buttermilk culture as used by the farmer allowed numbers of Listeria to increase 60-fold within 12 h owing to a delayed acidification of the bulk milk. Addition of a thermophilic yogurt culture reduced the numbers of Listeria within 8 h of incubation.     

Effect of nisin and its combination with sodium chloride on the survival of Listeria monocytogenes added to raw buffalo meat mince

Antilisterial activity of nisin (Nisaplin), alone at concentrations of 400 and 800 IU/g and in combination with 2% sodium chloride was incorporated in raw buffalo meat mince. Samples of the raw meat mince were inoculated with 10(3) colony forming units (cfu)/g of L. monocytogenes and stored at 4°C for 16 days and at 37°C for 36 h. Initial estimates of pH, extract release volume, mesophilic and psychrophilic counts were found to be 5.74, 48 ml, 3.5×10(5) and 1.0×10(5) cfu/g of meat, respectively. The growth of L. monocytogenes in the treated groups was significantly (P<0.05) inhibited compared to the control group. The degree of inhibition increased with increasing concentration of nisin and decreasing storage temperature. Addition of 2% sodium chloride in combination with nisin increased the efficacy of nisin at both storage temperatures. The pH in the treated groups remained significantly lower (P<0.01) than in the control groups at both 4 and 37°C.