SUPERCRITICAL CARBON DIOXIDE TREATMENT TO INACTIVATE AEROBIC MICROORGANISMS ON ALFALFA SEEDS

The supercritical carbon dioxide (SC-CO₂) process involves pressurizing CO₂ in a chamber which generates liquid phase of carbon dioxide. Pressurized liquid CO₂ has a strong extraction capability of organic and inorganic compounds. The recent studies have also demonstrated that antimicrobial effect of SC-CO₂ due extraction some cellular components of microorganisms. The efficacy of a supercritical carbon dioxide treatment on alfalfa seeds contaminated with Escherichia coli K12 was tested at 2000, 3000, and 4000 psi at 50C. Samples were treated for 15, 30, and 60 min at each pressure. After pummeling the seed samples in 0.1% peptone water, the initial and final Escherichia coli and total aerobic bacteria on the seeds were determined by plating on 3M Petri Films. After 48 h of incubation at 37 C, the colonies were enumerated. Treated seeds were evaluated in terms of germination characteristics. For aerobic plate count, the effect of pressure in the range of 2000–4000 psi was not statistically significant (p > 0.05) even though 85.6% inactivation was achieved at 4000 psi for 60 min. For E. coli, the reductions for 2000, 3000, and 4000 psi treatments for 15 min were 26.6, 68.1, and 81.3%, respectively. As the time was increased from 15 to 60 min at 4000 psi, the percent E. coli reduction increased from 81.3% to 92.8%. The percent germination for all treatments was over 90%. There was no significant difference (p > 0.05) in the germination rate of treated and untreated seeds. Supercritical carbon dioxide treatments demonstrated a reduction of E. coli K12 and total aerobic counts without affecting the germination characteristics of alfalfa seeds (p < 0.05). This study was a step in the direction of improving safety of alfalfa seeds used to produce fresh sprouts, which have been the cause of several outbreaks.     

ABILITY OF VARIOUS CHEMICALS TO REDUCE COPPER AND TO INACTIVATE MUSHROOM TYROSINASE1

Treatment of mushroom tyrosinase with reducing agents such as hydrogen peroxide, ascorbic acid, phenylhydrazine, gallic acid, ferrocyanide and NH₂OH resulted in inactivation of the enzyme. Under the conditions tested, 50% inactivation of the enzyme was obtained with 4 μM H₂O₂, 20 μM ascorbic acid, 40μM phenylhydrazine, 6 mM gallic acid, 12 mM ferrocyanide and 22 mM NH₂OH. The ability of the reducing agents to reduce Cu²⁺ in a chemical model system was determined and it was found that gallic acid, phenylhydrazine, ascorbic acid and NH₂OH are relatively good reductants of Cu²⁺ while H₂O₂ and ferrocyanide are relatively poor ones. The copper content of mushroom tyrosinase before and after inactivation by each of the reducing agents was determined. The copper content of the enzyme inactivated by H₂O₂, NH₂OH, phenylhydrazine, ferrocyanide, gallic acid and ascorbic acid was 100%, 90%, 90%, 85%, 85% and 76% compared to that of the control (enzyme not treated). It was concluded that the degree of inactivation of mushroom tyrosinase by the reducing agents was not correlated with the decrease in the copper content of the enzyme nor with their ability to reduce Cu²⁺ in a chemical model system.     

清洗剂对生菜贮藏保鲜效果的影响

以臭氧、次氯酸钠处理生菜，进行生菜贮藏保鲜试验。结果表明，臭氧水处理有利于降低生菜中还原糖、叶绿素、抗坏血酸的损失和降低其呼吸强度、电导率，从而表明经臭氧处理的生菜比次氯酸钠处理的生菜贮藏保鲜效果好。     

ASSESSMENT OF A WASH TREATMENT WITH WARM CHLORINATED WATER TO EXTEND THE SHELF–LIFE OF READY–TO–USE LETTUCE

Abstract The influence of a warm chlorine wash on the microbiological quality and shelf–life of ready–to–use (RTU) shredded iceberg lettuce was examined using the electronic nose (EN) and culture methods. There was a significant difference in psychrotrophic counts (P<0.0001) of warm chlorine (100 ppm) washed lettuce at 47 ± 2C for 30 s, 60 s, and 180 s exposure from days 1 to 10 of storage at 4C compared with cold chlorine (100 ppm) washed lettuce at 4 ± 1C for 30 s. There were no significant differences in psychrotrophic counts between wash treatments of 30 s and 60 s during 17 days storage (P < 0.05). The EN detected initially high levels of volatiles in this group compared with cold treatment. Lettuce samples treated with cold or warm chlorine wash water showed no differences in the presence/absence or levels of Listeria monocytogenes. The warm chlorine washed lettuce samples were rated acceptable upon sensory evaluation up to day 14.     

PHYSICOCHEMICAL AND SENSORY ANALYSES ON EGG POWDER IRRADIATED TO INACTIVATE SALMONELLA AND REDUCE MICROBIAL LOAD

Egg powder was treated with 0, 2, 5 and 10 kGy of gamma radiation at 20C to inactivate Salmonella and to stabilize its microbial load. Microbial, physicochemical and sensory determinations were performed during 4 months of storage to select the optimal radiation dose to attain the objective without significantly reducing egg quality. Microbial results show that 2.0 kGy inactivated Salmonella and reduced microbial load to levels below those stipulated by the Argentine regulations. Physicochemical determinations of egg powder extracts for peroxide number, spectrophotometric measurements in the visible and ultraviolet regions, functional properties on sponge cakes made with egg powder (height, comprssion-relaxiation cycle parameters), foam stability and viscosity showed that gamma radiation at the dose of 2 kGy, did not cause significant changes in these parameters. Higher radiation doses (5 and 10 kGy) did increase rancidity, pigment loss and protein chain scission. Sensory determinations performed on egg powder, and on cakes manufactured with it, agreed with the physicochemical results. After 110 storage days, 2 kGy was the most suitable of the tested doses .     

USE OF IRRADIATION TO KILL ENTERIC PATHOGENS ON MEAT AND POULTRY1

Ionizing radiation can be an effective step in a HACCP program to kill enteric pathogens associated with meat and poultry products. The populations of most common enteric pathogens such as Campylobacter jejuni, Escherichia coli O157:H7, Staphylococcus aureus, Salmonella spp., Listeria monocytogenes, and Aeromonas hydrophila can be significantly decreased or eliminated by low-dose (< 3.0 kGy) treatments with ionizing radiation. Only the enteric viruses and the endospores of the genera Clostridium and Bacillus are highly resistant to ionizing radiation, and even these are affected to some degree. Temperature effects must be carefully considered, as reduced irradiation temperatures not only result in fewer adverse changes in the sensorial properties of meat and poultry products, but they also may demand that greater radiation doses be used to inactivate the foodborne pathogen. Equations have been developed that predict the effects of low-dose ionizing radiation treatments on several enteric pathogens associated with meat and poultry. In some cases substrate-specific differences in radiation resistance have been found. Irradiation in combination with vacuum packaging or modified-atmosphere packaging has increased both safety and shelf-life for some types of refrigerated products. High-dose irradiation treatments of enzyme-inactivated meat or poultry products in vacuo at subfreezing temperatures can be used to prepare sterile, shelf-stable products with excellent sensorial properties. Such products have been used extensively by military organizations, NASA during space flights, yachtsman, and hospitals. Contemporary research will be reviewed.     

USE OF SONIC AND ULTRASONIC MEASUREMENTS ON BOVINE BONE TO ESTIMATE CHRONOLOGICAL AGE

SUMMARY– Sonic and ultrasonic measurements were made on bovine bone to explore their possible value in objectively determining chronological age of a beef animal carcass. The sonic resonant frequency of the bone and the transmission rate of an ultrasonic pulse through the bone were measured on the right large metacarpal bone of slaughtered beef animals of different ages of the same breed. Thirty-four bones from animals approximately 6, 12, 18, 24, and 30 months of age were measured. The simple correlation coefficient between animal age and the sonic resonance parameter, (FLP was 0.875 and between age and the ultrasonic velocity parameter, (cm/μsec)² was 0.866.     

USE OF THE FRIABILIMETER TO ASSESS HOMOGENEITY OF MALT

A method has been developed for assessing the homogeneity of a sample of malt using the Friabilimeter. Material retained by the Friabilimeter sieve is further fractionated using a sieve with slits 2·2mm wide by 23mm long, as recommended by the EBC for assessing corn size. Material composed of unmodified grains and large pieces of endosperm is collected from the sieve and weighed. This gives a rapid and reproducible estimate of the proportion of unmodified material in the sample. The technique readily detects small quantities of unmodified grain added to a sample of malt. Staining half corns with Calcofluor gives similar scores for homogeneity but with poorer reproducibility and the technique is much slower. Staining with methylene blue gives much lower figures for homogeneity and is also slower and less reproducible than the Friabilimeter method.     

乳糖在莴苣干制中的应用研究

脱水蔬菜是将新鲜蔬菜经过干制(热风或冷冻干燥),使其水分降至可长期安全储藏的程度(5%～8%),并保持新鲜蔬菜的色泽、风味及营养成分的干制品.莴苣的最佳的干制工艺为漂烫的温度为100℃,漂烫时间为3 min,食盐溶液的浓度为0.5%,乳糖溶液的浓度为6%,烘烤的工艺条件为先用80℃烘4 h,再用70℃烘4 h.乳糖在莴苣干制中的作用有增加固体含量,改善产品质构而不至于使产品过甜的作用;乳糖在莴苣干制加工及贮藏过程中比较稳定,与其它糖类比较,溶解度低,受环境湿度的影响较小,可以较好地保持产品的色泽,对提高产品的复水效果也有较好的作用.乳糖在脱水蔬菜(尤其是出口蔬菜)中将进一步得到广泛的应用.     

荷露酿酒

对于五百年前的明人来说,假如拥有很大一片荷塘,那么,就可以从事一等最风雅的享受:收集荷叶上的雨水和露水,代替泉水来酿酒.晚明散文大家张岱在其《品山堂鱼》-文中如此回忆他早年的生活经历:远离城市的喧嚣,在远山映影的湖边建起一所私家园林.