生乳中金黄色葡萄球菌产肠毒素特性及耐药性分析

了解生乳中金黄色葡萄球菌污染状况、产肠毒素特性及耐药性，为乳及乳制品的生产及制定HACCP以保证食品安全提供依据。采集省内20个奶牛场共209份生乳样品进行金黄色葡萄球菌的分离、产肠毒素（SEA—SEE）试验及耐药性试验。共检出金黄色葡萄球菌34株，检出率为16．27％，21株产肠毒素试验阳性，阳性率为61．76％，对青霉素、缸霉素、四环素、苯唑西林凝固酶阴性耐药性分别达88．24％、41．48％、35．29％、35．29％，并出现21种耐药谱。生乳中金黄色葡萄球菌的污染率及产肠毒素率较高，耐药性结果对人及畜的安全用药有指导性作用。控制生乳中金黄色葡萄球菌的污染对奶及奶制品食用安全有意义。     

INCIDENCE OF STAPHYLOCOCCUS AUREUS IN MEALS FROM CAFETERIAS

A study to determine the incidence of Staphylococccus aureus in 705 meals from several cafeterias in Valencia, Spain was undertaken. Out of the 705 studied meals, 81 samples (11.1%) had coagulase positive staphylococci with a range of S. aureus from 100 to 53000 cfu/g. The four highest values (> 10,000 S. aureus cfu/g) were obtained with Russian type salad, meatballs, chicken croquettes and salad. These products involved more handling stages. These data show that food handlers may contribute to food poisoning and that there are some handling practices that require more attention.     

GROWTH OF STAPHYLOCOCCUS AUREUS AND ENTEROTOXIN A PRODUCTION IN FOODS CONTAINING POLYPHOSPHATES

Effects of pyro-, tripoly- and hexametaphosphates (0.5 and 1%, w/w) on growth of Staphylococcus aureus strain 196E and enterotoxin A (SEA) production were studied in cooked custard and beef at 22 and 30°C. No effect was observed in custard, where cell numbers/g increased from 10³ to 10⁸ and SEA reached 4.2 ng/g after 48 h at 22°C, irrespective of treatment. Cell numbers in cooked beef were ca. 10⁹/g after 48 h, and reduced numbers (by 1.5–2 log cycles) were found in samples containing 0.5 and 1% pyrophosphate during incubation at 22%, but not at 30°C. SEA concentrations in beef were 28 ng/g after 48 h at 22°C, and 93 and 184 ng/g after 24 and 48 h, respectively, at 30°C. SEA concentration correlated with amount of growth, and was nondetectable when cell numbers were ± 10⁶/g. Reduction of the meat pH by sodium acid pyrophosphate contributed to the observed inhibitory effect.     

INHIBITION OF AEROBIC AND ANAEROBIC GROWTH OF STAPHYLOCOCCUS AUREUS IN A MODEL SAUSAGE SYSTEM

Sodium nitrite, potassium sorbate, and glycerol monolaurate all inhibited anaerobic growth of Staphylococcus aureus more than its aerobic growth in an agar-meat model sausage system, and all were more inhibitory when lactic acid was added. Whereas anaerobic growth of S. aureus was inhibited by concentrations of 100, 2500, and 2500 ppm, respectively, of nitrite, potassium sorbate, and glycerol monolaurate, corresponding concentrations of 150, 5000, and 5000 ppm were required to inhibit aerobic growth ((20 meq lactic acid added).
Sorbic acid, a 3:1 mixture of sorbic acid and glycerol monolaurate by weight, and butylated hydroxyanisole (BHA), however, did not show differential inhibitory effects toward aerobic and anaerobic growth of S. aureus and also were more effective inhibitors with addition of lactic acid. Sorbic acid suppressed staphylococcal growth in the model sausage system at 500 ppm, the mixture of sorbic acid and glycerol monolaurate at 750 ppm, and BHA at 10,000 ppm (20 meq lactic acid added).     

EFFECT OF WATER ACTIVITY ON THE GROWTH OF STAPHYLOCOCCUS AUREUS AT MEAT-CHEESE INTERFACES

There is increased marketing of ready-to-eat nonrefrigerated snack foods which consist of meat or sausage products with low or intermediate moisture levels combined with high moisture food products, i.e., cheese products. Packaging the intermediate moisture meat in direct contact with a high moisture food might change the water activity (a_w) of the products sufficiently to support growth of Staphylococcus aureus at contaminated interfaces. To evaluate this possibility, sterile sausage slices (a_w= 0.60 to 0.82) were surface inoculated with log 2-3 CFU/g of S. aureus, interfaced with processed cheese slices (a_w= 0.94), vacuum packaged, and incubated at 19, 28, 37C and at cyclic temperature of 19–37–19C. S. aureus levels and water activities were determined weekly for 0 to 9 weeks. The a_w at the interface changed rapidly and reached an a_w that supported S. aureus growth. Growth of S. aureus occurred under all test conditions when the samples were stored at 28 and 37C. At 19C storage S. aureus remained viable for the length of the study.     

DETECTION OF STAPHYLOCOCCUS AUREUS PRODUCTS IN FOODS USING ENZYME LINKED IMMUNOSORBENT ASSAY AND SPECTROPHOTOMETRIC THERMONUCLEASE ASSAY

The comparative sensitivity of an enzyme linked immunosorbent assay (ELISA) using four different antistaphylococcal antisera and a spectrophotometric assay for thermonuclease were determined using cheese and ravioli samples seeded with strains of Staphylococcus aureus and S. epidermidis. The ELISA used antisera to enterotoxin A, enterotoxin B, S. aureus strains 14609 (human), and UNH-570 (bovine). The 570 ELISA and spectrophotometric thermonuclease assay were of comparable sensitivity and detected seeded culture in concentrations as low as 2 × 10⁷ CFU/g of cheese. A simple two hour method for extracting thermonuclease from foods was 50% efficient when as little as 50 ng of purified enzyme was seeded per g of cheese. Analyses of 43 commercial cheeses for viable S. aureus found five (12%) positive with 3 × 10⁴ CFU/g of cheese being the highest counts detected. All samples were negative by ELISA and thermonuclease assay. A simple screening procedure for demonstration of S. aureus contamination of foods is discussed.     

THE EFFECT OF EEC REGULATIONS ON THE MARKETING OF MILK AND MILK PRODUCTS IN THE UK

The effect on the dairy industry of membership of the EEC and the distinction between its regulations and directives as set out in the Treaty of Rome are described. Over 3,000 regulations were issued in 1974, 250 of which dealt with milk and dairy products and a list of the main regulations is given in an appendix. The advantages of price reviews more than once a year and possible seasonal milk pricing are discussed. The marketing field is described and the need for products with the greatest earning potential stressed. Developments in liquid milk markets are shown and their importance in the United Kingdom emphasized. Possible standardization in the liquid milk market, and the difficulties involved in the operation of milk marketing boards is considered. {Editor's summary).     

RELEASE OF ENTEROTOXIN A AND THERMONUCLEASE FROM GROWING AND NON-GROWING CELLS OF STAPHYLOCOCCUS AUREUS

Enterotoxin A and thermonuclease were produced by Staphylococcus aureus cell populations in all growth phases. Synthesis of entero-toxin was more rapid than that of thermonuclease early in the exponential phase, whereas later in the exponential phase the thermonuclease synthesis was more rapid than that of enterotoxin. The optimum temperature for enterotoxin production was 42°C, while that for thermonuclease production was in the range 27–33°C. Small amounts of enterotoxin and thermonuclease were released at temperatures up to 45°C.
During heat treatment of staphylococcal cells, enterotoxin production was not observed at temperatures in excess of those permitting growth, although small amounts of thermonuclease were produced. Intracellular enterotoxin was not detected after disintegration of cells under pressure at –30°C. Enterotoxin at detectable concentration, was not bound to the cell membranes. All the results obtained indicate that the synthesis of enterotoxin by S. aureus is intimately associated with cell growth.     

ULTRAVIOLET SPECTROPHOTOMETRIC DETERMINATION OF PROTEIN IN SOME FOOD PRODUCTS

SUMMARY— The spectrophotometric method of estimating the protein content of whole milk at wavelength 280 nm (Nakai and Le, 1970) was modifed for corned beef, flour, bean and egg yolk. A clear solution was obtained by adding 50% sulfuric acid or 2N sodium hydroxide with and without 7–8M urea depending on solubility of the food products. The protein content was calculated from the absorbance at 280, 243 or 215 nm on o spectrophotometer. The correlation coefficient between the absorbance and the protein by Kjeldahl method was 0.99, 0.99, 0.99 and 0.99 with the coefficient of variability of Kjeldahl protein for absorbance of 1.8, 4.1, 3.8 and 4.1% for bean, corned beef, egg yolk and flour, respectively.     

THE FUTURE OF UHT MILK AND MILK PRODUCTS IN EUROPE

The development of packed milk relative to total milk consumption in Switzerland from 1958-76 is illustrated and the future of the industry in Continental Europe considered. Decrease in milk consumption in both Switzerland and Germany and the limitations of climatic conditions and transport are discussed and the advantages of UHT long-life milk evaluated. The potential in an increasing market for UHT milk products and in aseptic filling machines is assessed. ( Editor's summary ).     

决明子活性成分对四氯化碳肝损伤的保护作用

研究决明子不同活性成分蒽醌（SCI）和多糖（SCII）对CCh肝损伤小鼠的保护作用。随机将小鼠分为四组：对照组。模型组，SCI治疗组和SCII治疗组，分别给不同药物，连续处理4周。之后处死取血，测定血清谷丙转氨酶（ALT），谷草转氨酶（AsT）和碱性磷酸酶（ALP）的活性；取肝脏，测定肝匀浆丙二醛（MDA）、超氧化物歧化酶（SOD）和肝糖原（CHO）的含量及肝脏指数，并通过HE染色观察肝细胞的组织形态。结果表明决明子SCI和SCII均能显著地抑制CCl4引起的小鼠血清ALT、AST、ALP及肝匀浆MDA含量、肝脏指数的升高，显著增加肝匀浆SOD、CHO的含量，并能显著地减轻CCh引起的肝脏组织病理损伤。     

TRANS FATTY ACID CONTENT OF SOME FOOD PRODUCTS IN POLAND

The fatty acid composition of chips, cakes and ice creams was determined with particular attention to their trans fatty acid content. The trans C18:1 content was determined by a combined capillary gas-liquid chromatography (GLC) and silver thin-layer chromatography (Ag-TLC). Six of ten types of chips examined contained more than 10% trans C18:1 (in the range of 10.3 to 17.3% of the total fatty acids), and the other four had below 0.5%. In the lipids of cakes trans C18:1 isomers occurred at 1.49 to 41.44% and only four types of cakes contained less than 5% of trans C18:1. The cis-trans and trans-cis C18:2 isomers were present among the fatty acids of the majority of chips and cakes investigated. Six types of chips contained trans-trans C18:2 in the 1.2–1.6% range. Trans fatty acids were absent in the lipids of 6 types of ice cream, but two types contained 11.3 and 19.4% trans C18:1.