基于混料设计优化超高温灭菌乳复配乳化剂

微生物腐败引起的变质不是超高温灭菌乳货架期的限制因素,其货架期主要取决于组织状态的保持。为了延长超高温灭菌乳的货架期,以目前使用的复配稳定剂BD 0027为对照,选取蔗糖酯SE-15、分子蒸馏单甘酯(DMG)及羟基化改性大豆磷脂(SHP)为原料,采用混料设计的原理进行配方设计并基于布朗粒子的Boltzmann分布定律构建稳定动力学参数（SI）与超高温灭菌乳体系近红外光背散射光随时间的变化率的均值（ΔBS）之间模型,作为超高温灭菌乳货架期的预测值。通过回归分析得到SI与SE-15、DMG、SHP配比之间的回归方程,方差分析以及验证试验结果表明该模型高度显著。因此,SI与ΔBS和SE-15、DMG、SHP配比比例之间的两个模型可以用于评价超高温灭菌乳稳定性并预测其货架期。     

Microbiological quality of home-made cheese produced in Costa Rica

The microbiological quality of 205 samples of home-made cheese prepared from raw milk in six rural zones of Costa Rica was studied. In addition to determining their microbiological quality, recommendations are also issued for reducing to a minimum, the deficient sanitary conditions under which they are produced. Collection of samples was done directly at the producing farms. The following microbiological analyses were then undertaken: Staphylococcus aureus, thermonuclease (TNase) positive. Determination of most probable number (MPN) of coliform organisms of fecal origin. Total count of molds and yeasts, and Enumeration of mesophilic aerobic bacteria. As the data revealed, all samples contained high counts of the four microorganisms investigated, therefore demonstrating the deficient microbiological quality of the home-made cheese. On the basis of results obtained, a series of practical recommendations are suggested to improve the poor sanitary conditions under which they are now prepared.     

Microbiological controls and control points in a hake fillets manufacturing process for exportation

Indicator and foodborne pathogen microorganisms in the "for export" hake fillets manufacturing were investigated in this study. Critical control points were identified and prevention activities and control were proposed during seafood elaboration process. 45 samples of hake from sequential processing operation stages, 15 ice samples and 12 water samples from utensil washing, were collected. The samples were analyzed for their content of aerobic mesophilic bacteria, psychrotrophic bacteria, enterobacteria, total and fecal coliform bacteria, Staphylococcus aureus and the presence of Escherichia coli, Salmonella and Shigella. The analysis of the samples collected from the factory revealed that the amounts of aerobic mesophile bacteria increased during manual filleting and packaging, in comparison with raw material. Psychrotrophic bacteria were the predominant microorganisms, specially in hake samples. In addition, high levels of enterobacteria, which do not occur normally in fish, were detected in raw hake samples. Staphylococcus aureus, Escherichia coli, Salmonella and Shigella, were not isolated from any samples in this study. The goal of this work is to establish microbiological risks in the hake fillets manufacturing process and, therefore to make possible corrective and control actions to assure the quality and safety of seafood.     

Laboratory bioremediation experiments with soil from a diesel-oil contaminated site—significant role of cold-adapted microorganisms and fertilizers

Laboratory bioremediation experiments were performed with soil from a diesel-oil contaminated waste disposal site; contamination was 5580 mg hydrocarbons per kg soil dry mass. The effects of incubation temperatures (10°C and 25°C), of the addition of an inorganic fertilizer at C: N ratios of 10:1 and 50:1, of the indigenous soil microorganisms and of a psychrotrophic and a mesophilic inoculum capable of degrading diesel-oil were investigated. The highest diesel-oil decontamination rates were 43% at 10°C and 55% at 25°C after 30 days. The biodegradation activity of the indigenous soil microorganisms was highly increased by the use of fertilizers. The diesel-oil degradation activity of the added inocula was highest when no fertilizer was present and was inhibited by nutrient supply. Abiotic processes did not contribute to diesel-oil elimination. ©1997 SCI     

Sanitary and technologic evaluation of the rural processing of fresh goat cheese in Chile

A sanitary and technological diagnosis of the goat cheese rural process was carried out. The purpose was to obtain more information for the planning of a program aimed to the improvement of this small agroindustry. Samples of milk, curdle, dry abomasum, rennet, water and cheese of 10% of the small industries of two rural villages in two agricultural seasons, were taken. Moreover, dilutions of the utensils and goat udders were prepared. The samples were subjected to microbiological analysis of mesophilic aerobic bacteria count, most probable number of total and fecal coliforms, and detection of Staphylococcus aureus coagulase (+), Salmonella typhi and Brucella melitensis. Proximate chemical analysis and determinations of sodium chloride and titratible acidity in milk, cheese, dry abomasum and rennet, were carried out. Goat milk was also subjected to analysis of density. It was found that significant sanitary failures are present during th whole goat cheese process, although the highest bacteria contamination occurred at the milking, curdling and filling stages. These are characterized by excessive handling and absolute lack of hygiene. The pathogen B. melitensis was absent; therefore the causes of poisoning were attributed to the toxin produced by S. aureus and to the significant count of fecal coliforms found in the goat cheese. Even though the goats are fed under a poor feeding system, the milk presented a normal physical and chemical composition. Nevertheless, protein and fat matter losses occur during cheese preparation, as a result of handling practices and lack of process control.     

UHT脱脂纯牛奶感官评价和电子鼻分析相关性研究

选取四种市售不同品牌的UHT脱脂纯牛奶作为研究对象,通过感官描述性分析和电子鼻技术对其风味属性进行评价。采用主成分分析(PCA)和聚类分析(CA)结合偏最小二乘回归法(PLSR)法将电子鼻传感器性能和感官属性进行相关性分析。结果表明样品奶油味及脂质感评分均较低;电子鼻的十个传感器对四个样品的区分效果良好;基于感官属性和传感器响应值的PLSR分析建立的相关性模型,能够很好地解释感官属性和传感器响应值的相关性,反映脱脂纯牛奶样品的整体信息。本文结合两种技术方法,弥补了人工感官评价存在的主观性与智能感官分析的局限性影响,旨在为后续改善脱脂纯牛奶风味提供技术参考。     

Evaluation of commercial UHT milk and optimization of industrial process

From the nutrition al point of view milk is one of the most complete food in the diet of mammals. It contains nearly all the nutrients necessary to sustain life, but milk can deteriorate very easily, either by microbiological contamination or by biochemical reactions during processing and/or storage. The objective of this research study was to design a modified UHT treatment to achieve commercial sterilization and maximize the stabilization of the heat-treated product during storage. To search for a modified UHT process, a mathematical model coupled with an optimization routine (complex method) was developed. The mathematical model considers Kinetics for the inactivation of Bacillus stearothermophilus and several quality factors. To attain the objective function, several commercial UHT milk were analyzed and for the computer search the minimization of hydroxy methyl furfural (HMF) formation was considered and also including constraints for protease and lipase inactivation. The complex optimization procedure was implemented to search for the optimum modified UHT treatment.. One of the optimum modified UHT treatments was the combination of two pre-treatment (3.16 minutes at 62.30 degrees C and 6 minutes at 75 degrees C) in addition with a UHT treatment (0.75 s at 148.8 degrees C). This treatment attains the maximum product stability with a negligible effect on composition and color formation in the treated milk (HMF formation less than 3 mg/mL).     

Sequence and homology model of 3-isopropylmalate dehydrogenase from the psychrotrophic bacterium Vibrio sp. I5 suggest reasons for thermal instability

The leuB gene from the psychrotrophic strain Vibrio sp. I5 has been cloned and sequenced. The gene codes for 3-isopropylmalate dehydrogenase, a 360-residue, dimeric enzyme involved in the biosynthesis of leucine. Three recently solved homologous isopropylmalate dehydrogenase (IPMDH) crystal structures from thermophilic and mesophilic organisms have been used to build a homology model for the psychrotrophic IPMDH and to deduce the possible structural reasons for its decreased thermostability. According to our model the psychrotrophic IPMDH contains fewer stabilizing interactions than its mesophilic and thermophilic counterparts. Elements that have been identified as destabilizing in the comparison of the psychrotrophic, mesophilic and thermophilic IPMDHs are a smaller number of salt-bridges, a reduction in aromatic-aromatic interactions, fewer proline residues and longer surface loops. In addition, there are a number of substitutions of otherwise strictly conserved residues that can be linked to thermostability.      

Vegetable food resources with agroindustrial potential from Guatemala. Manufacture of vegetable milk from the seed of morro fruit (Crescentia alata)

The objective of the present study was to establish the conditions for the preparation of vegetable milk from the morro or jicara seed, and to characterize the products, the milk and the residue for their partial chemical composition and acceptability. From the ripe fruit, the seeds were obtained by maceration in water for 3.5 hrs, obtaining seed yields of 80%. This seed contained 38% fat and 26% protein on a dry weight basis. The harvested seed was then dehydrated to 9-12% moisture by exposure to solar energy. A similar lot was lightly roasted by heating on a hot surface for 10 min at 90-110 degrees C. The seed was used for the extraction of solubles or the vegetable milk. Water extraction with up to 10 minutes of mechanical blending gave low yields of soluble solids (4.66 +/- 0.10 to 4.98 +/- 0.07%) and low contents of fat, protein and ash in the extract with sun dried seed and significantly lower with the lightly roasted seed (3.0 +/- 0.05 to 3.4 +/- 0.03%). Due to the low yields of total soluble solids and to the low nutrient content by aqueous extraction, new extractants were used consisting of buffer solutions at pH 7.8, or 8.5 with and without saline solution at 0.5% concentration. With these solutions greater amounts of solids were extracted with a higher content of nutrients. The milk prepared from the sun dried seed and extracted with buffer at pH 8.5 and saline solution (0.5%) gave an extract with 9.85% of total solids, 3.37% protein, 4.44% fat. The extraction with roasted seed gave significantly lower yields. The residue of the extraction contained 21.47% fat and 14.72% protein. With the use of buffers and saline solution the extracts had better acceptability, with the milk produced from sun dried seed having better organoleptic characteristics in comparison with soy milk (5.84 vrs 3.76), however it was of lower acceptability when tested against cows milk (5.7 vrs 7.7). The isoelectric point of the extracted protein was between 4 4.45.     

Recent Studies on Nonspecific Aspects of Intraoral Adhesion

There is usually a high number of microorganisms present in the oral cavity, yet it takes some time for the first microorganisms to attach in vivo on clean solid surfaces. Similar patterns of microbiological adhesion can be observed in vitro and, conversely, in vivo attachment of non-biological colloidal particles occurs readily. This indicates that primary physical forces rather than biological specificities are responsible for initial adhesion of microorganisms and similarly shaped particles to teeth and restorations. Under physiological conditions, oral adhesive events are probably based on general types of physico-chemical interactions, and might be mainly controlled by the properties of the spontaneously adsorbed biological films that precede particle attachment. A variety of surface physico-chemical techniques, monitoring formation of biological films and attachment of biological, as well as nonbiological particles of colloidal dimensions both in vivo and in vitro on various solid surfaces, indicated that the formation of oral biological films proceeds at high speed and precedes particle attachment. Further, when different surfaces were clinically exposed to saliva and covered with such biological films, their significant original differences in surface properties could no longer be detected. Continuing differences in strength of particle adhesion to these surfaces must result, therefore, from differences in binding of the initial salivary films.     

虎杖根提取物及分离组分对黄瓜白粉病的作用效果

在实验室内进行了虎杖（Polygonum cuspidatum Sieb.etZucc.）根提取物及其活性组分分离研究,并且对黄瓜白粉病进行了活性测定及温室小区试验。结果表明,无论提取率还是作用效果,乙醇较适合于做为虎杖根提取物的提取溶剂。虎杖根乙醇提取物和乙醚提取物对黄瓜白粉病的EC90值分别为537.85、35.38mg/L,而乙醚提取后残留物的活性很弱,说明乙醇提取物中具有杀菌作用的成分主要存在于乙醚提取物中。用pH梯度分离法对乙醚提取物进行分离,得到3个不同组分,其中以氢氧化钠分离得到的组分对黄瓜白粉病显示了极高的杀菌活性。在温室条件下虎杖乙醇提取物在800～1600mg/L下对黄瓜白粉病的防效相当或优于对照药剂三唑酮。     

Type and amount of dietary fat affect relative concentration of cholesterol in blood and other tissues of calves

Sixteen male Holstein calves consumed by nipple a reconstituted milk containing nonfat dry milk and either soybean oil or tallow for 24 weeks. Calves fed milk in this manner (with no dry feed) are functionally nonruminants because the milk bypasses the ruminoreticulum. The fat in these diets contributed about 30% of total dietary calories. The calves consuming soybean oil milk had significantly greater amounts of cholesterol in blood plasma and adipose tissue than did the calves consuming tallow milk.     

Quality of soybeans in export

Soybean quality is of concern to processors throughout the world, as deterioration during storage, handling and shipment can result in crude oil which is difficult to process and has high refining losses. Little information is available comparing the relative quality of soybeans in export shipment based on crop year and origin. Shipments of soybeans originating from the United States, Brazil, Paraguay, and Argentina were sampled in Europe and Asia during a four-year period. Soybean samples were graded, protein and oil contents determined, and oil quality characteristics assessed by laboratory procedures. Results of these analyses present, for the first time, direct comparisons of the quality of soybeans exported from the principal producing countries. The data suggests that United States (U.S.) farmers and exporters must continue their efforts to improve the physical characteristics of soybeans in export shipment; the emphasis of breeding and genetic engineering research should be to increase the protein content of soybeans grown in the U.S.; and that the high quality of crude oil recovered from U.S. soybeans should prove an advantage to the processor using soybeans imported from the United States.     

Application of enzyme-assisted aqueous fat extraction to cocoa fat

An enzyme-assisted aqueous fat extraction method was used to extract fat from dry cocoa beans. The beans were dehulled and finely ground. Samples were mixed with water in predetermined ratios. A protease and an enzyme with high activities of both cellulase and hemicellulase were added at 1% of the sample weight, mixed, and incubated for about 6 h at 37°C. The treated samples were then extracted by a water flotation technique. The preextraction treatment with enzymes effectively increased fat yield by about 26%. The observation suggests that the enzyme-assisted aqueous fat extraction method could improve the efficiency of rural fats and oils technologies currently in use in many developing countries.     

Properties of Brazilian gasoline mixed with hydrated ethanol for flex-fuel technology

In the present work, samples of Brazilian gasoline type C previously mixed with hydrated ethanol at concentrations of 20, 40, 60 and 80 vol.% were analyzed by distillation, octane number, specific mass, pH and conductivity, in order to evaluate the physico-chemical properties for a better comprehension of the effects caused by the flex-fuel technology. The obtained results were compared with the specifications of the ANP – Agência Nacional de Petróleo Gás Natural e Biocombustíveis – that is the federal regulatory agency for monitoring of the quality of fuels in Brazil. It was observed that there exists an ideal concentration of hydrated ethanol for addition in gasoline type C in order to obtain good properties for application in the flex-fuel technology.     

超高温灭菌乳货架期加速试验的研究

In order to estimate the shelf-life of cow milk sterilized by instant treated with Ultra Heat Temperature(UHT) in a relatively short time, the accelerated shelf-life testing (ASLT) was designed and conducted, selecting the histological change of the sterilized milk caused by fat droplets creaming as its criteria.The stability index (SI) and the viscosity variation of the sterilized milk were determined at preservation conditions of 20, 25, 30, 35, 40 and 45℃, using Turbiscan technology.The result showed that the SI was slightly higher for 25℃ than for 20℃, elevating linearly for temperature from 25℃ to 40℃, and decreased for 40℃ to 45℃.The SI data for 25℃ to 40℃ were fitted well with equation SI_t=0.062t-1.382 (R²=0.990).If a ratio SI_t/SI_25℃ called as accelerated ratio (AR) was defined, the AR values calculated from the equation were 3.6,4.3 and 5.0 for 35, 37.5 and 40℃, respectively, which were agreement with the data from ASLT.So, the model could be used for the prediction of the shelf-life of sterilized milk by UHT process.     

The fatty acid composition of small and large naturally occurring milk fat globules

Native milk fat globules of various mean diameters, ranging from d₄₃ = 1.5 to 7.3 μm, were obtained using microfiltration of raw whole milk acquired in winter and spring. After total lipid extraction, fatty acid composition was characterized by methyl and butyl ester analysis using gas chromatography. The oleic and linoleic acid content of milk obtained in winter increased with fat globule size, whereas myristic and palmitic acid decreased. There was significantly more lauric, myristic and palmitoleic acid, and less stearic acid in small fat globules compared to large fat globules in milk obtained in both winter and spring. The relative content of oleic and linoleic acids were found to depend on fat globule size and season. Results are interpreted on the basis of the relative content of milk fat globule membrane depending on fat globule size, and on consequences of compositional variations on milk fat globule melting behavior.     

Evaluation of the antimicrobial action of honey against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, Salmonella enteritidis, Listeria monocytogenes and Aspergillus niger. Evaluation of its microbiological charge

The evaluation of the microbiological charge present in Costa Rican samples as the evaluation of its antimicrobial activity over different microorganisms, including those associated to wound infections, will allow to emit criteria referred to its use in therapeutic treatments, specially as alternative therapy for cases involving antibiotic resistant bacteria. The microbiological charge of 25 honey samples, acquired in Costa Rican markets was evaluated through several indicators including total plate aerobic count, total plate anaerobic count, total aerobic spore count, total anaerobic spore count and molds and yeast count. Also, samples were inoculated in tubes with chopped meat media and plated in egg yolk agar in order to determine the presence of Clostridium botulinum. For the antimicrobial activity evaluation, the diffusion method in Muller Hinton agar was performed, testing different honey concentrations (100, 75, 50, 25, 12,5 and 6,25 % v/v) against Staphylococcus aureus (ATCC 25923), Staphylococcus epidermidis (UCR 2902), Pseudomonas aeruginosa (ATCC 9027), Escherichia coli (ATCC25922), Salmonella enteritidis (ATCC 13076), Listeria monocytogenes (ATCC 19116) and Aspergillus niger. The results obtained for the microbiological characterization of honey show that 91% of samples had counts equal or lower than 1,0 x 10(1) CFU/g. No positive result was obtained for the isolation of C. botulinum. 24 of the samples analyzed inhibited the growth of S. aureus even in a 25% v/v concentration, nevertheless, A. niger was no inhibited by any of the samples tested.     

Characterization of microbial population present in the edible seaweed, Monostroma undulatum, Wittrock

The microbiological quality of Monostroma undulatum, Wittrock from the Southern Argentinean coast, was studied for its application for human food. Also the diversity and function of the native bacterial population to this green seaweed was analyzed. Samples were collected in Puerto Deseado, province of Santa Cruz, Southern Argentina (47 degrees 45'L.S., 65 degrees 55'L.W). The samples were analyzed for the presence of psycotrophic heterotrophic bacteria, marine heterotrophic bacteria, low nutritional request bacteria (LNRB), marine low nutritional request bacteria (LNRB marine), Vibrio spp, total and thermotolerant colifom bacteria, anaerobic sulfite reducing bacteria, yeasts and moulds. The isolates were identified using standard techniques based on morphologic, physiologic and metabolic characteristics. Among the gram-negative bacteria isolated, the predominant genera belonged to Vibrio (20%), E. coli inactiva (18%), Flavobacterium (11%), Flexibacter (9%), Moraxella (9%), Alcaligenes/Pseudomonas group (9%), Aeromonas (2%), Acinetobacter (2%). Cotophaga (2%), Photobacterium (2%), Ps/Caulobacter/Alteromonas/Spirillum group (2), The main genus of gram-positive bacteria was Staphylococcus. Human pathogenic bacteria were not detected. Fecal contamination indicator bacteria were not isolated from fresh seaweed and seawater. These results showed an adequate microbiological quality of seaweed acceptable for human food. The bacterial population associated to Monostroma undulatum, consisted of gram-negative, marine and psycotrophic microorganisms, including vibrios and enterobacteria as their main components. Also the identified bacteria showed a great capacity to hydrolyze different substrates and so they might contribute to the balance of this marine ecosystem.     

The fractionation of milk fat from a solvent at low temperatures

Summary A procedure for fractionating milk fat from a solvent at low temperatures has been developed. This procedure consists of freezing out fractions of the fat from solvent (Skelly Solve A) at progressively lower temperatures —7°, —13°, —23°, —53°C., with the remaining filtrate taken as a final fraction. In physical appearance these fractions vary from a dry white powder to a reddish-yellow oil; in melting point from 53°C. to —10.6°C.; in iodine number from 8.29 to 58.37; and in saponification equivalent from 262.8 to 235.2. The saponification equivalents do not change in the same order as the other properties mentioned. This fat fractionation effects a simplification of milk fat and makes available less complex portions of the natural glyceride mixtures for detailed study of the composition, configuration, and other properties. Some of these studies are now being carried out and will be reported later.