低盐腊肉在加工过程中的菌相变化初探

为了解低盐腊肉在加工过程中的微生物变化,采用选择性培养基对低盐腊肉加工过程中的主要微生物菌相进行分离和计数。结果发现,在低盐腊肉中的微生物总数为2.58×103cfu/g,优势菌群是葡萄球菌和微球菌,它们的数量较之其它微生物的数量高了一个数量级。     

锌铜法加工无铅皮蛋技术

以新鲜鸭蛋为试材,采用浸泡法工艺,研究NaOH浓度及金属盐种类与用量对皮蛋加工品质的影响,探讨锌法、铜法和锌铜混合法加工皮蛋的可行性.结果表明:单独使用Zn<,2+>、Cu<,2+>,时,浸液NaOH浓度对皮蛋加工具有重大影响,其中最适浓度为4.5%;锌法和铜法都能加工成各具特点的合格皮蛋,锌铜盐混合能产生协同效应,一定程度缩短加工时间,且加工品质优良;选用腌制液 NaOH 浓度4.5%,Zn<'2+>添加量0.3%,Cu<'2+>添加量0.05%～0.075%腌制25 d左右出缸,皮蛋具有较好品质.     

Effect of curing salt and phosphate on the activity of porcine muscle proteases

The effect of curing salt on the activity of porcine muscle proteases was evaluated, within the salt concentration range found in the manufacturing process of Spanish cured ham. Salt (NaCl) acts as a strong inhibitor of proteolytic activity; sodium nitrate and potassium nitrate do not affect cathepsin D activity; cathepsin L is inhibited at levels of the salts not found in cured ham, and Ca-dependent proteolytic activity is enhanced by nitrate concentrations below 800 ppm.

The appearance of phosphate precipitates in several areas of ham has led to the study of phosphate effect on enzymatic activity. Results show that phosphate is an inhibitor of proteolytic activity.     

浅谈非洲猪瘟的流行现状及防控措施

非洲猪瘟(ASF)是由非洲猪瘟病毒引起的一种急性烈性高接触性传染病,其发病过程从急性、亚急性、慢性发病不等,其临诊特征是高热、皮肤发绀,各内脏器官出血,同时伴有呼吸障碍和神经症状,发病率和死亡率几乎可高达100％.该病在临床上与其他败血性、出血性疾病极其类似其死亡的几率都相对较高;非洲猪瘟的出现严重的影响了生猪行业的发...     

Inactivation of avian influenza virus by heat and high hydrostatic pressure

Avian influenza viruses threaten the life of domestic terrestrial poultry and contaminate poultry meat and eggs. Recently, these viruses rarely infected humans but had a high mortality rate in Southeast Asia, the Middle East, and Egypt. Thereby, these viruses caused high economic costs for production of poultry and health protection. We inactivated a highly pathogenic avian influenza A virus of subtype H7N7 in cell culture medium and chicken meat by heat and high hydrostatic pressure. Because heat and pressure inactivation curves of the H7N7 virus showed deviations from first-order kinetics, a reaction order of 1.1 had to be selected. A mathematical inactivation model has been developed that is valid between 10 and 60 degrees C and up to 500 MPa, allowing the prediction of the reduction in virus titer in response to pressure, temperature, and treatment time. Incubation at 63 degrees C for 2 min and 500 MPa at 15 degrees C for 15 s inactivated more than 10(5) PFU/ml, respectively. Thus, we suggest high-pressure treatment of poultry and its products to avoid the possible health threat by highly pathogenic avian influenza viruses.     

Inactivation of glucocorticoids by 11beta-hydroxysteroid dehydrogenase enzymes increases during the meiotic maturation of porcine oocytes

Recent reports have shown that glucocorticoids can modulate oocyte maturation in both teleost fish and mammals. Within potential target cells, the actions of physiological glucocorticoids are modulated by 11beta-hydroxysteroid dehydrogenase (HSD11B) isoenzymes that catalyse the interconversion of cortisol and cortisone. Hence, the objective of this study was to establish whether HSD11B enzymes mediate cortisol-cortisone metabolism in porcine oocytes and, if so, whether the rate of glucocorticoid metabolism changes during oocyte maturation. Enzyme activities were measured in cumulus-oocyte complexes (COCs) and denuded oocytes (DOs) using radiometric conversion assays. While COCs and DOs oxidised cortisol to inert cortisone, there was no detectable regeneration of cortisol from cortisone. The rate of cortisol oxidation was higher in expanded COCs than in compact COCs containing germinal vesicle (GV) stage oocytes (111+/-6 vs 2041+/-115 fmol cortisone/oocyte.24 h; P<0.001). Likewise, HSD11B activities were 17+/-1 fold higher in DOs from expanded COCs than in those from compact COCs (P<0.001). When GV stage oocytes were subject to a 48 h in vitro maturation protocol, the enzyme activities were significantly increased from 146+/-18 to 1857+/-276 fmol cortisone/oocyte.24 h in GV versus MII stage oocytes respectively (P<0.001). Cortisol metabolism was inhibited by established pharmacological inhibitors of HSD11B (glycyrrhetinic acid and carbenoxolone), and by porcine follicular and ovarian cyst fluid. We conclude that an HSD11B enzyme (or enzymes) functions within porcine oocytes to oxidise cortisol, and that this enzymatic inactivation of cortisol increases during oocyte maturation.     

Inactivation of hepatitis A virus and a calicivirus by high hydrostatic pressure

Potential application of high hydrostatic pressure processing (HPP) as a method for virus inactivation was evaluated. A 7-log10 PFU/ml hepatitis A virus (HAV) stock, in tissue culture medium, was reduced to nondetectable levels after exposure to more than 450 MPa of pressure for 5 min. Titers of HAV were reduced in a time- and pressure-dependent manner between 300 and 450 MPa. In contrast, poliovirus titer was unaffected by a 5-min treatment at 600 MPa. Dilution of HAV in seawater increased the pressure resistance of HAV, suggesting a protective effect of salts on virus inactivation. RNase protection experiments indicated that viral capsids may remain intact during pressure treatment, suggesting that inactivation was due to subtle alterations of viral capsid proteins. A 7-log10 tissue culture infectious dose for 50% of the cultures per ml of feline calicivirus, a Norwalk virus surrogate, was completely inactivated after 5-min treatments with 275 MPa or more. These data show that HAV and a Norwalk virus surrogate can be inactivated by HPP and suggest that HPP may be capable of rendering potentially contaminated raw shellfish free of infectious viruses.     

胶原肠衣在灌装过程中的应用

通过分析胶原肠衣两种加工工艺的优缺点,针对湿法制造的胶原肠衣在灌装过程中出现的问题,从胶原肠衣的加工工艺入手,深入的分析造成这些现象或问题的具体原因,经过一系列的实验验证,提出通过改变部分加工工艺,调整胶原肠衣使用时相匹配设备的工艺参数和操作条件,达到提高胶原肠衣在中国肉制品工业中应用的目的.     

Chemistry of swine liver and products of liver processing. 3. The Maillard reaction of a model and of preserved liverwurst

The storage life of industrial-made tinned liver sausage has more effect on the decrease in glucose and total carbohydrate content than the corresponding sterilisation program. The addition of glucose and casein shows greater effect as respects the Maillard-reaction on tinned model than on minced liver.     

Presence of hepatitis E virus in a naturally infected swine herd from nursery to slaughter

Hepatitis E virus has recently been recognized as having zoonotic potential and could be transmitted from pig to human. Pigs are identified as a potential animal reservoir and HEV is highly prevalent in the swine population around the world. In this study, the presence of HEV was investigated in 51 subjects reared on a simulated commercial farm setting from the age of 2 weeks up to slaughter. Samples were collected on four occasions: at 2, 8, and 18 weeks and between 22-29 weeks of age. Anti-HEV IgG in plasma samples, presence of HEV RNA in plasma samples and feces were monitored. At 2 weeks of age, HEV RNA was detected in feces of 6 subjects (11.8%) but not in their plasma. At 8 weeks, HEV was detected in feces of 27 subjects (52.9%) and in plasma of one subject. At 18 weeks, HEV was detected in feces of 44 subjects (86.2%) and in plasma of 24 subjects (47.1%). At slaughter time (22-29 weeks), HEV was present in plasma of 6 subjects (11.8%) and in stools of 21 subjects (41.2%). Spread of the virus inside the population was evaluated by comparison of means (paired t-test, P<0.05) of anti-HEV IgG ELISA results from the 4 bleedings. Significant differences were noted between the results of populations at 8 and 18 weeks and also between 18 and 22 to 29 weeks indicating an immune response to the virus. Based on the comparison of a 304 nucleotides sequence of the 5' ORF 2 gene, all amplified fragments clustered in genotype 3a.     

Inactivation of foot-and-mouth disease virus in various bovine tissues used for the production of natural sausage casings

Bovine intestines, bladders and oesophagus are used for the production of natural casings ("beef casings") as edible sausage containers. Derived from cattle experimentally infected with FMDV (initial dosage 10(4) TCID(50)/mL, strain A Iran 97), these beef casings were treated with sodium chloride (NaCl) or phosphate supplemented salt (P-salt). In addition, different in-vitro experiments using beef casings were done on a small scale with other FMDV strains (A Turkey 06, C-Oberbayern and O(1) Manisa) as "proof of principle". Based on the combined results of the in-vivo and in-vitro experiments, it can be concluded that the storage period of 30 days at 20 °C in NaCl is sufficiently effective to inactivate a possible contamination with FMDV in beef casings and that the usage of P-salt does not clearly enhance the inactivation of FMDV infectivity. Storage of salted beef casings at about 20 °C for 30 days is already part of the Standard Operating Procedures (included in HACCP) of the international casing industry and can therefore be considered as a protective measure for the international trade in natural casings.     

卷烟加料中1,2-丙二醇的快速测定方法

为快速评价卷烟加料均匀性,依据标记物1,2-丙二醇近红外光谱信息的特征,建立了基于1,2-丙二醇近红外预测模型的卷烟加料均匀性快速测定方法.研究表明:模型的决定系数R2 ＞0.95,对盲样预测相对误差基本小于5％;测定了3个牌号卷烟,其加料均匀性系数分别为87.9％、89.1％和90.9％,RSD＜ 3％.     

Inactivation and degradation of O Taiwan97 foot-and-mouth disease virus in pork sausage processing

This study was to investigate the levels of inactivation and degradation of a field-isolated foot-and-mouth disease virus (FMDV)-strain O Taiwan97 in pork sausage processing. FMDV antibody-free pigs were inoculated with virus suspensions and slaughtered after developing observable symptoms. Lymph nodes (LN), blood clots (BC), and muscle were collected for the evaluation of inactivation during chilling, curing, drying and steaming processes. Viable virus was assessed by the TCID₅₀ technique and RT-PCR was used to detect viral genomes. Cell culture results revealed that viruses could be detected from LN and BC, but not from muscle. Ninety percent of FMDV was inactivated after each of the chilling, curing and steaming processes as compared to <80% inactivation after the drying process. The FMDV genome was detectable in 88% of the muscle, and was found in 100% of the serum, BC and LN. After processing, a majority of the genomes were not degraded more than 60%, with the exception of the thermal-steaming process. These findings indicated that the FMDV genome was detectable after each processing step, indicating a potential infectious risk. Thus, apart from regular surveillance in the field, monitoring of meat product pH and heat treatments are essential for FMDV inactivation.     

Inactivation of hepatitis A virus,poliovirus and a norovirus surrogate by high pressure processing

Hepatitis A virus (HAV), feline calicivirus (FCV, a surrogate for non-culturable norovirus), and poliovirus (PV), suspended in buffered cell culture media, were treated with pressures ranging from 200 to 600 MPa at ambient temperature for between 30 and 600 s. HAV was inactivated by > 1-log₁₀ tissue culture infectious dose 50% mL^− 1 (TCID₅₀ mL^− 1) and > 2-log₁₀ TCID₅₀ mL^− 1 after 600 s treatment with 300 and 400 MPa, respectively, and was undetectable (> 3.5-log₁₀ TCID₅₀ mL^− 1 reduction) within 300 s treatment with 500 MPa. FCV was inactivated by 3.6-log₁₀ TCID₅₀ mL^− 1 after 120 s treatment with 300 MPa, and was undetectable after 180 s treatment with 300 MPa. PV was the most resistant with little or no substantial reduction in titre after 300 s treatment with 600 MPa. The studies were designed to determine the efficacy of using high pressure to inactivate enteric viruses and generate inactivation data to assist in determining appropriate process criteria for safe shellfish production.Industrial relevanceThe high pressure treatment of raw oysters has proved commercially successful, due in part to a marked increase in the product’s shelf life, yet little alteration of its organoleptic properties. Illnesses from human enteric viruses such as hepatitis A virus and norovirus have traditionally been associated with shellfish consumption, and for this reason, studies have examined the stability of enteric viruses under high pressure. However, kinetic data on enteric virus stability under pressure is needed by processors to better understand the response of viruses throughout the entire treatment time. The kinetic data obtained in this study may be useful for processors wishing to alter high pressure processing conditions to ensure a high quality product in terms of organoleptic and microbiological properties.     

Effects of microbial transglutaminase and sodium alginate on cold-set gelation of porcine myofibrillar protein with various salt levels

The effects of microbial transglutaminase (TG) and sodium alginate (SA) systems on cold-set gelation of myofibrillar protein (MP) at various salt levels were investigated. The gelation kinetics data showed that both TG and SA had optimal but different salt levels to form an acceptable cold-set MP gel. Although their gelling characteristics were altered with different salt levels, the combination of TG and SA showed a rapid cold-set MP gel formation, regardless of salt levels. The effect of TG and SA on gel strength was reversed by increasing the salt level, while the cold-set MP gel strength of the TG and SA combination was not affected by salt levels. Furthermore, the SA system contributed to improved water-binding ability and cold-set MP gel formation, while the TG system enhanced the gel strength of the MP after cooking at low-salt levels. In addition, TG's effects on gel strength of MP increased at higher salt levels, the SA system prevented the moisture loss induced by the TG reaction. There was no evidence of any interaction between SA and MP in the thermogram and gel electrophoresis data. Results from this study suggested that a system combining TG with SA had the potential advantage of improving the water-binding ability and producing cold-set MP gelation at an even lower salt level than TG alone.     

Inactivation of hepatitis A virus by high-pressure processing: the role of temperature and pressure oscillation

Inactivation of hepatitis A virus (HAV) in Dulbecco's modified Eagle medium with 10% fetal bovine serum was studied at pressures of 300, 350, and 400 MPa and initial sample temperatures of -10, 0, 5, 10, 20, 30, 40, and 50 degrees C. Sample temperature during pressure application strongly influenced the efficiency of HAV inactivation. Elevated temperature (> 30 degrees C) enhanced pressure inactivation of HAV, while lower temperatures resulted in less inactivation. For example, 1-min treatments of 400 MPa at -10, 20, and 50 degrees C reduced titers of HAV by 1.0, 2.5, and 4.7 log PFU/ml, respectively. Pressure inactivation curves of HAV were obtained at 400 MPa and three temperatures (-10, 20, and 50 degrees C). With increasing treatment time, all three temperatures showed a rapid initial drop in virus titer with a diminishing inactivation rate (or tailing effect). Analysis of inactivation data indicated that the Weibull model more adequately fitted the inactivation curves than the linear model. Oscillatory high-pressure processing for 2, 4, 6, and 8 cycles at 400 MPa and temperatures of 20 and 50 degrees C did not considerably enhance pressure inactivation of HAV as compared with continuous high-pressure application. These results indicate that HAV exhibits, unlike other viruses examined to date, a reduced sensitivity to high pressure observed at cooler treatment temperatures. This work suggested that slightly elevated temperatures are advantageous for pressure inactivation of HAV within foods.     

Inactivation of infectious hepatitis E virus present in commercial pig livers sold in local grocery stores in the United States

Hepatitis E virus (HEV) is a zoonotic pathogen and pigs are a known reservoir. Recently we showed that approximately 11% of commercial pig livers sold in local U.S. grocery stores for food consumptions are contaminated by infectious HEV. In this study, a swine bioassay was used to determine if the infectious HEV in contaminated commercial pig livers could be inactivated by traditional cooking methods. Group 1 pigs (n=5) were each inoculated intravenously (i.v.) with a HEV-negative liver homogenate as negative controls, group 2 pigs (n=5) were each inoculated i.v. with a pool of two HEV-positive pig liver homogenates as positive controls, groups 3, 4 and 5 pigs (n=5, each group) were each inoculated i.v. with a pool of homogenates of two HEV-positive livers incubated at 56 degrees C for 1 h, stir-fried at 191 degrees C (internal temperature of 71 degrees C) for 5 min or boiled in water for 5 min, respectively. As expected, the group 2 positive control pigs all became infected whereas the group 1 negative control pigs remained negative. Four of the five pigs inoculated with HEV-positive liver homogenates incubated at 56 degrees C for 1 h also became infected. However, pigs in groups 4 and 5 did not become infected. The results indicated that HEV in contaminated commercial pig livers can be effectively inactivated if cooked properly, although incubation at 56 degrees C for 1 h cannot inactivate the virus. Thus, to reduce the risk of food-borne HEV transmission, pig livers must be thoroughly cooked.     

高静压对桃汁的杀菌效果及动力学模型

为了描述及预测高静压对桃汁的杀菌效果,研究了压力300,400,500,600MPa条件下保压3,5,10,15,20,25min的高压处理对桃汁中菌落总数、霉菌、酵母数的影响,并对不同压力条件下的杀菌效果进行动力学分析。研究结果表明,压力越高,保压时间越长,杀菌效果越好。霉菌、酵母对压力较为敏感,500 MPa以上的压力即可将其完全杀灭。Weibull模型在压力300～600 MPa时具有很好的拟合性(相关系数R~2>0.9)。尺度参数b随压力增大而增大,形状参数n则随压力的增大而减小。     

腐乳生产中香辛料的作用

通过分析细菌型腐乳中常用的9种香辛料：白芷、高良姜、肉桂、甘草、陈皮、丁香、砂仁、樟脑和龙脑等的主要成分,阐述了香辛料使用过程的浸出机理,对提取香辛料有效成分提出了新的建议,并说明了香辛料保管中应注意的问题。