The influence of moisture content and cooking on the screw pressing and prepressing of corn oil from corn germ

Samples of corn germ were obtained from a commercial corn wet mill (factory dried to about 3% moisture) and a commerical corn dry mill (undried, produced in the mill with about 13% moisture). The germ samples (200 g each) were cooked for various times in either a conventional oven at 180°C or a microwave oven at 1500 W. Bench-scale single screw pressing was then performed. With the dry milled corn germ, no oil was obtained from the uncooked germ. A maximal yield of about 5% oil [26% of total oil recovery (TOR), relative to hexane extraction] was obtained by cooking the dry-milled germ for 6.5 min in a conventional oven at 180°C before pressing. A maximal yield of about 7% oil (37% TOR) was obtained by cooking the dry-milled germ for 4.5 min in a microwave oven at 1500 W before pressing. With the wet-milled germ, yields of about 7% oil (18% TOR) were obtained with the uncooked germ and yields increased to a maximum of about 22% oil (56% TOR) by cooking in a conventional oven at 180°C for 5 min or a maximum of about 17% oil (44% TOR) by cooking for 4 min in a microwave oven at 1500 W. These results indicate that microwave and conventional oven cooking are both effective pretreatments before pressing. Microwave preheating resulted in higher oil yields with dry-milled germ, and conventional oven pretreatment resulted in higher oil yields with factory-dried wet-milled corn germ.     

Evaluation of the effect of Lactobacillus rhamnosus probiotic culture added to yogurt over Staphylococcus aureus, Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enteritidis populations

The effect of different types of probiotics present in yogurt over known populations of Staphylococcus aureus, Escherichia coli O157:H7, Listeria monocytogenes and Salmonella enteritidis was evaluated. The three types of yogurt used were: without added probiotics, with added probiotics (Lactobacillus casei CRL_431 and L. acidophilus CRL_730 CHR HANSEN) and another one with the same probiotics mentioned above and Lactobacillus rhamnosus (LR-35) culture. About 10(9) CFU/ mL of each potentially pathogenic bacteria was added to each type of yogurt tested, and kept in refrigeration at 4 degrees C during its shelf life, about 30 days. Bacterial count was done the initial day and every four days. Results obtained show that there is a difference in the inhibition between yogurts without added probiotics and the commercial yogurt with added probiotics; there is a clear inhibitory effect of the last one over S. aureus, E. coli O157:H7 and Listeria monocytogenes. The yogurt with added probiotics and L. rhamnosus did not show any additional inhibitory effect over the bacteria tested when compared with the yogurt with added probiotics. S. enteritidis could not be evaluated because it was not detectable in any yogurt samples evaluated four days after its inoculation. This study confirms the antagonic effect of probiotic cultures over potentially pathogenic bacteria for human beings and animals that may be present in food. Nevertheless, the use of L. rhamnosus did not produce any additional inhibitory effect.     

Evaluation of the effect of probiotic cultures added to commercial yogurt over a known population of Listeria monocytogenes and Escherichia coli O157:H7

The effect of probiotic cultures over Listeria monocytogenes and Escherichia coli O157:H7 during yogurt storage was evaluated. Two different yogurt brands, one with additional probiotic cultures (Lactobacillus casei and L. acidophilus) were inoculated with known populations (106 UFC/g) of either L. monocytogenes or E. coli O157:H7 in three different times and stored for 32 days at 5 degrees C. Every four days the count of lactic bacteria, the added pathogens and pH was evaluated, according to the methodology described in the Bacteriological Analytical Manual. The pH and lactic bacteria population were constant during the testing period. Yogurt with additional probiotic cultures reduced the population of L. monocytogenes in 8 days, the population of E. coli O157:H7 in 16; yogurt with no additional probiotics took 20 days to reduce L. monocytogenes to non-detectable levels and even after 28 days of storage, E. coli O157:H7 was cultured. In this work, the beneficial effects of additional probiotic cultures in yogurt is confirmed again.     

Presence of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella spp. in food from animal origin in Costa Rica

The presence of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella spp was analyzed in two kinds of food from animal origin in Costa Rica. 100 samples of non pasteurized milk, from the principal producing zones of the country, and 100 samples of chicken giblets, purchased in retail markets, were analyzed according to the methodology described by Food and Drug Administration, 1995. Escherichia coli O157:H7 was analyzed in both kinds of food, while L. monocytogenes was evaluated in raw milk and Salmonella spp. in chicken giblets. Five strains of E. coli O157:H7 were isolated, three of them coming from chicken giblets and the other two from raw milk. 15% positivity for Salmonella spp. was found in chicken giblet samples and 3% positivity for L. monocytogenes in raw milk samples. The results obtained show the importance of the adequate processing of food from animal origin in order to decrease the potential transmission of pathogenic agents. The introduction of Hazard Analysis Critical Control Points system (HACCP) and Good Manufacturing practices in food industry keep on being the principal control measures and inocuity warranty.     

N-Halamine-Based Antimicrobial Additives for Polymers: Preparation, Characterization and Antimicrobial Activity

A series of 3-alkyl-5,5-dimethylhydantoin derivatives were prepared by reacting 5,5-dimethylhydantoin with alkyl bromides with different alkyl chain length (C-2 to C-22). Upon chlorination, the hydration derivatives were transformed into 1-chloro-3-alkyl-5,5-dimethylhydantoins (CADMH). The structures of the samples were fully characterized with FT-IR, (1)H NMR, UV, and DSC analyses. The antimicrobial functions of CADMH were challenged with 10(8-9) CFU/mL of Escherichia coli (gram-negative bacteria) and Staphylococcus aureus (gram-positive bacteria). All the samples provided a total kill of the gram-negative and gram-positive bacteria in less than 30 min. CADMH were used as antimicrobial additives for polymeric materials. It was found that the presence of as low as 1% of CADMH could provide the samples with potent antimicrobial functions. The structure-antimicrobial efficacy relationships of the CADMH were further discussed.     

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.     

Evaluation of the effect of probiotic cultures on two different yogurt brands over a known population of Staphylococcus aureus and the production of thermonuclease

The effect of probiotic cultures over known populations of Staphylococcus aureus inoculated in yogurt was studied; also the production and stability of its thermonuclease during yogurt storage was evaluated. In three different occasions, two different yogurt brands, one with additional probiotic cultures (Lactobacillus casei and L. acidophilus), were inoculated with known populations of S. aureus in high and low concentration (10(9) CFU/g and 10(7) CFU/g), respectively. These samples were stored for 28 days at 5 degrees C. Every four days the count of lactic bacteria, S. aureus and pH were evaluated, according to the methodology described in the Compendium of Methods for the Microbiological Examination of Foods, Vanderzant & Splittstoesser. The presence of thermonuclease was determined using petrifilm for S. aureus from 3M company. The pH and lactic bacteria population were constant during the testing period. Yogurt with additional probiotic cultures (high and low concentration) lowered the population of S. aureus to non detectable levels in 8 days; but, S. aureus could be cultured from yogurt without probiotics even after 24 days of incubation. Same time, the presence of thermonuclease was positive in all tests; it was not affected by probiotics. The presence of thermonuclease is related to the production of S. aureus enterotoxin. This work emphasizes again the beneficial effects of probiotic cultures in yogurt over bacteria and the importance of keeping hygienic practices in order to avoid the contamination of food with S. aureus and the eventual production of its enterotoxin, since it is not affected by probiotics.     

Chromium content in foods and dietary intake estimation in the Northwest of Mexico

Chromium is an indispensable nutrient for the carbohydrates and lipids metabolism. In this study the chromium content in the twenty main foods of the diet from Northwestern Mexico was determined, as well as the daily mean intake which was estimated based on the food intake basket of this region. Chromium content was analyzed by atomic absorption spectrophotometry using the graphite furnace technique and previous digestion of foods in microwave oven. The chromium mean intake was estimated considering the chromium daily mean intake for person per day and the chromium content of the foods analyzed in this study. The range chromium content in the foods analyzed was between 0.0004 and 0.1641 microgram/g dry weight. White cheese showed the highest chromium content followed by pasta soup, wheat tortilla, bread and meat. The main foods chromium contributors in the diet were: wheat tortilla (20%), white cheese (11%), corn tortilla (11%), pasta soup (10%), milk (10%), meat (9%) and white bread (8%). The daily chromium intake was 30.43 +/- 1.6 micrograms/d. Chromium values obtained in the food analyzed are considered low. Moreover, chromium intake obtained from the diet is not enough to meet the safety and adequate daily chromium intake. Therefore, the population from the Northwestern Mexico has a suboptimal dietary chromium intake.     

A sandwich-type assay based on quantum dot/aptamer bioconjugates for analysis of E. Coli O157:H7 in microtiter plate format

An optical assay based on CdSe/ZnS quantum dots (QD)/NH₂-Apt bioconjugates for the pathogen detection was presented. QDs with carboxyl functional groups and 72-mer aptamer (against E. coli outer membrane proteins) were used as probes and sensing element. E. coli O157:H7 was selected as a model pathogen and 96-well plate assay in the sandwich hybridization format was constructed. Poly-L-lysine-coated 96-well plate surfaces were used as support material where thiol functionalized aptamers were immobilized by 4-(N-Maleimidomethyl)cyclohexane-1-carboxylic acid 3-sulfo-N-hydroxysuccinimide (sulfo-SMCC). After incubation with the bacteria, CdSe/ZnS QDs/aptamer bioconjugates were added. The fluorescence signals were followed before and after addition of bioconjugates. Probe concentrations, incubation time with E. coli O157:H7 were also optimized. The bioassay could detect the pathogen down to 10² CFU/mL with high selectivity. The detection system was successfully employed in samples, in the presence of interfering compounds.     

Presence of Clostridium perfringens in meat-based preparations in public food services in central San Jose, Costa Rica

In Costa Rica there are a large number of public food services distributed along the country, where a considerable number of people eat daily. Clostridium perfringens is a bacteria associated with foodborne illness related, especially, to meat products kept for long time at temperatures under 70 degrees C. The aim of this study was to evaluate the public food services that use water baths for keeping food hot in order to establish the presence of C. perfringens in cooked bovine meat dishes and to evaluate the enterotoxigenic capacity of the strains isolated. 81 samples of cooked bovine meat plates coming from 27 public food services, located in the Central County of San José were analyzed. The methodology described by Labbe & Harmon for the isolation of C. perfringens was used in 10 g of sample. Also, the enterotoxigenic capacity of the strains was evaluated using the passive-reverse-latex-agglutination assay from Oxoid. From the 27 public food services analyzed, eight (30%) were positive in the three samplings done, nine (33%) were positive in one or two occasions, and ten (37%) were negative all times. This implies that in 17 (63%) of the establishments studied, the bacteria was isolated at least once. From the 81 preparations studied, 37 (46%) were positive for the bacteria. The temperatures at which food was kept varied from 56 to 82 degrees C, with an average of 68.7 degrees C. From the 37 strains identified as C. perfringens, 12 (32%) were positive for enterotoxin. In conclusion, the presence of C. perfringens in bovine meat dishes, maintained in water baths, represents an important risk for public health, and the temperature at which the preparation is kept is critical for the multiplication of the bacteria.     

油酸和十二烷二酸的氨基酸酯的合成及其生物抗菌性

以L-丙氨酸乙酯盐酸盐、甘氨酸乙酯盐酸盐、L-蛋氨酸甲酯盐酸盐、L-亮氨酸乙酯盐酸盐和L-酪氨酸甲酯盐酸盐在1-乙基-(3-二甲基氨基丙基)碳酰二亚胺盐酸盐和1-羟基苯并三唑(HOBt)的作用下分别与油酸进行反应，生成了5种油酸的氨基酸衍生物；将L-丙氨酸乙酯盐酸盐和甘氨酸乙酯盐酸盐分别与十二烷二酸进行反应，生成了两种十二烷二酸的氨基酸衍生物，7种产物的收率均≥75%。利用FTIR、TGA、¹HNMR和LC-MS对产物进行了表征，测试了产物的水油分散性，考察了产物对金黄色葡萄球菌和大肠杆菌的抑菌性。结果表明，所合成的脂肪酰氨基酸酯均能在水油体系中分散，且具有较强的生物抗菌性，其中，0.01 mg油酸酰亮氨酸乙酯能有效地抑制金黄色葡萄球菌(菌数由2.0×10⁹ CFU/mL降至1.4×10⁷ CFU/mL)，而相同质量油酸酰酪氨酸甲酯则能抑制大肠杆菌(菌数由2.0×10⁹ CFU/mL降至1.8×10⁷ CFU/mL)。     

无硫膨胀石墨的制备及性能表征

针对传统方法制得的膨胀石墨含硫量高和膨胀容积不稳定的问题,以0.28 mm的鳞片石墨为原料,KMnO4为氧化剂,HClO4和H3PO4为插层剂,经微波炉和马弗炉两种膨胀方式对可膨胀石墨的膨胀容积进行测试,采用正交实验法确定了最佳工艺条件.结果表明:在石墨(g)∶混酸(mL)∶高锰酸钾(g)=1∶4.5 mL(3.6 mL高氯酸∶0.9 mL磷酸)∶0.3,反应温度30 ℃,反应时间60 min,抽滤洗涤至pH值为5~7,80 ℃干燥,于微波炉中高温膨胀,膨胀容积最大,可达350 mL/g.     

微波提取苹果渣中总黄酮的工艺研究

采用微波辐射技术,以乙醇提取苹果渣中黄酮类化合物。考察了乙醇浓度、微波功率、处理时间、料液比和浸泡时间对总黄酮提取率的影响。结果表明,最佳工艺条件为:70%乙醇,微波萃取2 min,微波功率为350 W,料液比1∶30(g/mL),总黄酮1次提取率0.683 7%。     

Aptasensors for rapid detection of Escherichia coli O157:H7 and Salmonella typhimurium

Herein we reported the development of aptamer-based biosensors (aptasensors) based on label-free aptamers and gold nanoparticles (AuNPs) for detection of Escherichia coli (E. coli) O157:H7 and Salmonella typhimurium. Target bacteria binding aptamers are adsorbed on the surface of unmodified AuNPs to capture target bacteria, and the detection was accomplished by target bacteria-induced aggregation of the aptasensor which is associated as red-to-purple color change upon high-salt conditions. By employing anti-E. coli O157:H7 aptamer and anti-S. typhimurium aptamer, we developed a convenient and rapid approach that could selectively detect bacteria without specialized instrumentation and pretreatment steps such as cell lysis. The aptasensor could detect as low as 10⁵colony-forming units (CFU)/ml target bacteria within 20 min or less and its specificity was 100%. This novel method has a great potential application in rapid detection of bacteria in the near future.     

Clostridium perfringens in raw and cooked meats and its relation with the environment in Costa Rica

The presence of Clostridium perfringens in eight slaughter houses from Costa Rica was analyzed using the Most Probable Number (MPN) technique, in order to assess the risk of acquiring a food borne intoxication due to consumption of contaminated meat. C. perfringens was detected in 29 (88%) out of 33 soil samples collected from the slaughter house surroundings (average 6.7 x 10(2) MPN/g), as well as in 70 (93%) out of 75 intestinal contents of slaughtered animals (average 3 x 10(4) MPN/g), in 42 (55%) out of 76 samples of slaughtered meat (average 2.2 x 10(4) MPN/g) and in 30 (61%) out of 49 retail meats (average 8 x 10(3) MPN/g). In addition, the presence of this bacterium was evaluated in ten retail meat markets located in the Metropolitan Area of Costa Rica, where it was isolated from 15 (75%) out of 20 samples of ground meat and from 28 (36%) de 78 stew meat samples (average 1.9 x 10(3) and 7.5 x 10(2) MPN/g, respectively). Only one out of 35 samples of cooked meat obtained from 32 restaurants that utilize heated water baths (average temperature of 82 degrees C) was positive for C. perfringens (4 MPN/g, temperature 72 degrees C). Out of 1121 bacterial isolates obtained, 250 were evaluated for enterotoxigenicity. Only 3 (1.2%) of these tested positive for enterotoxin production, probably because most wild strains are not toxin producers, even though they can be induced to produce it as a result of repeated thermal shocks. The present results urge the adoption of adequate preventive measures and high sanitary standards in the meat processing industry in Costa Rica, in order to minimize the risk of food-borne intoxications caused by C. perfringens, due to its widespread distribution and potential human health hazard.     

Stability of anthocyanins in pasteurized juice of blackberry ((Rubus glaucus benth

In this research the chemical stability of total anthocyanins in three pasteurized juices elaborated from 12% of blackberry (Rubus glaucus Benth) pulp, and addition of ascorbic acid (Formulation A: 0.1%, Formulation B: 0.05% and Formulation C: 0.01%), was evaluated by means of absorption visible spectra (400-580 nm). Physicol-chemical characterization (acidity, soluble solids content in degree Brix, pH), and count of mesophilic microorganism, fungi, yeasts, fecal coliforms (PMN/mL) and Escherichia coli, were evaluated. Sensorial parameters (color, smell, flavor) were investigated by means of un-trained panel using a hedonic scale (Fridman, P < 0.05). The study was performed during storage for 9 days. The total anthocyanins were reported as pelargonidin-3-glycoside g/L, and no significant differences were founded among the evaluated in each formulation during storage (P > 0.05). Bactocromic effect due to oxidation as not observed. Acidity (6.0-7.2 mL NaOH 0.079 N), soluble solids content (9.0-9.8 degrees Brix) and pH (3.4) did not show significant differences (P > 0.05). The microbiological evaluation showed minimum values for pasturized products (fungi CFU/mL < 10, yeast CFU/mL < 10, fecal coliforms CFU/mL < 10 and mesophilic microorganism CFU/mL between 120-140 on first day in storage). Sensorial analysis did not show significant differences (Fridman, P > 0.05).     

微波萃取鸢尾的研究

用经改造的家用微波炉作主要设备 ,对微波萃取鸢尾过程的影响因素进行了考察。 6 0～90℃石油醚是微波萃取鸢尾的合适溶剂 ,鸢尾根的粉碎度对提取率的影响很大 ,直径为 0 .2 8～0 .45mm时 ,结果较好。微波萃取、索氏提取和超临界二氧化碳萃取鸢尾的比较结果表明 ,微波萃取法具有萃取时间短 (约 12 0s) ,提取率高 (约 10 % ) ,溶剂用量少 (约 16 0mL 40g原料 ) ,产品香气纯正等优点。     

反硝化抑制油田采出水中SRB的效果研究

以硫酸去除率及硫酸盐还原菌(sulfate reducing bacteria,SRB)的数量为指标,研究硝酸盐和反硝化细菌(denitrifying bacteria,DNB)对油田采出水中SRB的抑制作用。结果表明:在单独接种DNB (5%,体积分数)或投加硝酸盐浓度为100mg/L条件下,采出水中SRB的生长均受到有效抑制,其数量从104个/mL可降至10个/mL,硫酸盐去除率从25.5%分别降至6.8%和7.8%;当DNB (12.5%,体积分数)和硝酸盐(100mg/L)共同作用于采出水可使SRB的数量降至10个/mL以下,其硫酸盐去除率降至2.4%,两者对SRB的抑制作用具有协同作用。     

Corrosion and wear behavior of alumina‐polyester nanocomposite coatings

The corrosion and wear behavior of powder coatings fabricated by the electrostatic method was investigated in this study. Pure polyester coating and fabricated nanocomposite powder coating with 10 and 20 mass.% alumina nanoparticles were coated with electrostatic spraying method on the surfaces of carbon steel substrate. Coatings were cured in two regimes by oven and microwave for the appropriate time. The effects of alumina nanoparticles on the corrosion resistance of coated samples were studied by immersion and electrochemical impedance spectroscopy (EIS) tests. Also, pin‐on‐disk test was applied to evaluate the wear properties and coefficient of friction (COF) of the coatings. The results of the corrosion test reveal that the samples with 10 mass.% alumina show the best corrosion resistance and cause a reduction in corrosion rates which is about 36 times to that of the pure sample. The wear rate of nanocomposite coatings is 10 times lower than that of pure ones and also the coefficient of friction of nanocomposite samples is almost half of the pure samples. Furthermore, the nanocomposite coatings cured in the microwave show better protection properties and wear resistance than that of ones cured in an oven. POLYM. ENG. SCI., 57:846–856, 2017. © 2016 Society of Plastics Engineers     

Effects of Ozone Treatment on Microbiological Quality and Physicochemical Properties of Turkey Breast Meat

ABSTRACT

The effects of ozone treatment (1 × 10^?2 kg m^?3, for up to 8 h) on quality parameters of turkey meat were investigated. Ozone was effective in inactivating microorganisms. Approximately 2.9, 2.3 and 1.9 log reductions were achieved in the counts of total aerobic mesophilic bacteria, Enterobacteriaceae and yeast-mold, respectively. Ozone caused significant changes in carbonyl contents, thiobarbituric acid reactive substances, color and pH values of the samples. Water holding capacity and cooking yield of treated samples increased significantly (p < .05). This is the first report demonstrating that quality parameters of turkey breast meat are markedly affected by ozone treatment.