Interaction of barley β-glucan and tea polyphenols on glucose metabolism in streptozotocin-induced diabetic rats

Soluble dietary fiber and antioxidants have received much attention as most important components of functional foods. However, few data are available on the effects of the combination of tea polyphenols (TP) and β-glucan (BG) on blood glucose in a diabetic rat. The effects of administration of barley BG and TP or their combination (TP + BG) on blood glucose, lipid profiles, and antioxidant parameters on streptozotocin-induced diabetic rats were investigated. Significant improvements on the blood glucose level, serum lipid parameters (decreases in triglyceride, total cholesterol, LDL-C, and increase in HDL-C), lipid peroxidation (decrease in malondiadehyde content), and serum antioxidant status (increases in superoxide dismutase, glutathione peroxidase, and total antioxidant capacity) resulted in diabetic rats after administering TP + BG. This study, therefore, demonstrated that the intake of TP + BG has beneficial effects on glucose tolerance, lipid metabolism, and serum antioxidant status. It also revealed that TP + BG is better than TP or BG alone in improving glucose metabolism and antioxidant status in diabetic rats. Practically, the present study suggested that polyphenols-rich cereal foods are help for type 2 diabetes. PRACTICAL APPLICATION: Although TP or BG was definitely helpful in the treatment and management of diabetes mellitus, synthetic anti-hyperglycemic effects were found between TP and BG. The fortification of a BG-rich cereal diet with TP could be used as a strategy to maintain health of diabetic subjects.     

β-Hydroxybutyrate (BHB) and glucose concentrations in the blood of dairy calves as influenced by age,vaccination stress,weaning, and starter intake including evaluation of BHB and glucose markers of starter intake

The objective of this research was to determine how blood β-hydroxybutyrate (BHB) and glucose are affected by age, time of day, stress, weaning, forced intake restriction, and voluntary starter intake in calves between 1 and 9 wk of age, and to evaluate if either is an acceptable proxy for starter intake. Holstein calves were fed a 27% crude protein, 17% fat milk replacer at 660 g of dry matter daily along with free-choice starter and water. Calves were weaned on d 42. Jugular blood was sampled at 0800, 1200, and 1600 h, and within 5 min of sampling BHB, and glucose concentrations were estimated using test strips (Nova Max Plus meter, Nova Biomedical Corporation, Waltham, MA). Age effects and time of day were estimated by sampling blood weekly (d 6, 13, 20, 27, 34, 41, and 48). To determine vaccination stress, a Pasteurella vaccine was administered after blood sampling at 0800 h on d 36. Effect of voluntary starter intake was tested by selecting calves for low and high intakes (d 35 to 39) and sampling on d 40, 41, 43, and 44. Starter intake restriction was tested by restricting intake in half of the calves and sampling on d 60 and 61. Data were analyzed with repeated measurements in a mixed model procedure with either within-calf effect (day or week) or within-calf effects (hour, and day or week) included in the model. Time of day did not affect blood BHB and glucose in the first 6 wk. Blood BHB was greater in wk 7 versus wk 1 to 6. Blood glucose was greater in the first 5 wk compared with wk 6 and 7. Blood BHB increased and glucose decreased with increasing starter intake. Blood BHB declined due to vaccination, but glucose was unaffected. Starter intake restriction reduced BHB for 3 d and glucose for 2 d after restriction. Both were affected by time of day. Around weaning (d 40 to 44), BHB and glucose increased with increasing starter intake. In this research, neither blood BHB nor glucose was a good proxy for starter intake. Blood BHB was positively and glucose negatively related to starter intake; however, relationships were weak, variable, and affected by time of day, stress, and intake restriction. Over 30% of calves tested ≤0.2 mmol/L BHB when consuming >1,250 g/d of starter, and test strip increments were 0.1 mmol/L, which represented >25% of the mean blood BHB concentration. In this study, neither blood BHB nor glucose was an acceptable proxy for estimating starter intake.     

The kinetics of acrylamide formation/elimination in asparagine–glucose systems at different initial reactant concentrations and ratios

The effect of initial reactant concentration and ratio on the kinetics of acrylamide formation and elimination was studied using diluted asparagine–glucose model systems, heated at temperatures between 120 and 200 °C. By means of single response modelling, acrylamide concentrations measured could be modelled using a simplified kinetic model, in which acrylamide formation and elimination reactions were included. Changing the reactant concentration in equimolar systems did not affect significantly the kinetic parameters (k_Fref and E_aF) for acrylamide formation, whereas the rate constant for acrylamide elimination increased with increasing reactant concentration, in the range from 0.01 M to 0.125 M. Modifying the reactant ratio, while keeping one of the reactants at a fixed concentration (0.125 M), did not affect the estimated parameters as compared to the equimolar system. In addition, multiresponse modelling was applied on three model systems with a different initial reactant ratio. Besides acrylamide, the concentration of the reactants and fructose and the level of browning were quantified. By means of deduction, a mechanistic model was proposed which was able to model all responses simultaneously in an adequate way. It appeared that caramelisation has a predominant role in browning, however, only in the system with an excess of sugar. The corresponding kinetic parameters estimated were in some cases significantly different, but in the same order of magnitude.     

Survival and growth of foodborne pathogens in minimally processed vegetables at 4 and 15 °C

Abstract: We conducted this study to investigate the survival and growth of pathogens on fresh vegetables stored at 4 and 15 °C. Vegetables (romaine lettuce, iceberg lettuce, perilla leaves, and sprouts) were inoculated with 4 pathogens (Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli O157:H7) and stored at 2 different temperatures for different periods of time (3, 6, 9, 12, and 15 d at 4 °C and 1, 2, 3, 5, and 7 d at 15 °C). Populations of the 4 pathogens tended to increase on all vegetables stored at 15 °C for 7 d. Populations of E. coli O157:H7 and S. Typhimurium increased significantly, by approximately 2 log₁₀CFU/g, on loose and head lettuce stored at 15 °C for 1 d. No significant differences were observed in the growth of different pathogens on vegetables stored at 4 °C for 15 d. E. coli O157:H7 did not survive on sprouts stored at 15 or 4 °C. The survival and growth of food pathogens on fresh vegetables were very different depending on the pathogen type and storage temperature. Practical Application: Survivals and growth of pathogens on various vegetables at 4 and 15 °C were observed in this study. Survivals and growth of pathogens on vegetables were different depending on the pathogen type and storage temperature. Therefore, vegetables should be stored under refrigerated conditions (below 4 °C) prior to consumption. This recommendation may vary depending on the type of vegetable.     

Continuous separation of α-cyclodextrin and glucose using a simulated moving-bed adsorber

α-Cyclodextrin and glucose were continuously separated by a simulated moving-bed adsorber made up of four or 12 columns packed with the sodium ion form of a cation exchanger. In both cases, the components were successfully separated. The effect of the number of columns constituting the adsorber on the recovery of α-cyclodextrin was examined theoretically. The use of more than eight columns resulted in almost the same recovery.     

Histamine stability in Rihaakuru at -80, 4 and 30°C

Rihaakuru is a shelf stable fish paste product formed from a fish soup prepared from tuna. Histamine contamination is a food safety issue with this product that is manufactured from tuna fish that has been temperature abused. Histamine concentrations decreased between 31% and 73% in Rihaakuru stored for 10months at either -80, 4 or 30°C. This appears to be a property of the product as histamine solutions are reported to be stable, at least under frozen storage. The risk of histamine food poisoning due to Rihaakuru may reduce during the storage of the product.     

Physical changes induced by the Maillard reaction in a glucose–glycine solution

Some physical changes associated with the development of Maillard reaction in a glucose–glycine aqueous solution were detected by means of thermal and rheological analysis as well as by more conventional determinations. The increase in water content, water activity (A_w) and enthalpy of ice melting (ΔHm) during the reaction reflects both the formation of new water molecules and the consumption of low molecular weight species. The concomitant arrangement of more complex molecular structures was indicated by changes in the glass transition temperature of the maximally freeze-concentrated solution (Tg′) and of the freeze-dried solution (Tg _(dry)) as well as in the estimated unfrozen water (UFW). After fractionation of the samples by solid phase extraction, the non-polar fractions exhibited much higher Tg_(dry) than the non-fractionated samples. The Tgs_(dry) of samples at increasing heating time were treated with the Gordon–Taylor equation and results were discussed. The expected increase in viscosity due to polymerisation was compensated by the formation of water, but it could be detected when viscosities were measured on samples equilibrated at a same A_w     

Effect of supplementation with vitamin D₃ on glucose production pathways in human subjects

Scope: Research reports suggest that vitamin D affects glucose and insulin metabolism; however, the exact mechanisms are unclear. ²H NMR analysis of monoacetone glucose (MAG) after tracer administration provides a non‐invasive method of profiling hepatic glucose metabolism. This study examined the effects of supplementation with vitamin D₃ on contribution of glycogenolysis to glucose production. Methods and results: Tracer administration and biofluid collections were performed with eight healthy females before and following a 4‐wk vitamin D₃ administration period. Following an overnight fast subjects ingested deuterated water and acetaminophen. Full void urine samples were collected after 4 h. ²H NMR spectra of urinary monoacetone glucose were acquired to determine the contribution of glycogenolysis to glucose production. The mean contribution of glycogenolysis to glucose production was 60±13%. Supplementation with vitamin D₃ had no effect on hepatic glucose production. Regression analysis revealed a significant relationship between carbohydrate intake and the contribution of glycogenolysis (β=0.914, p=0.004). Conclusion: In conclusion, we saw no changes in the percentage contribution of glycogenolysis following supplementation with vitamin D₃. The reproducibility of our results and the non‐invasive nature of the method highlight the potential for this method in assessing mechanistic modes of action in future nutritional interventions.     

Ochratoxin A and Aspergillus section Nigri in peanut seeds at different months of storage in Córdoba, Argentina

Peanut is an important food commodity in Argentina. Last year Córdoba Province accounted for approximately 96% of the total Argentinian production. Few surveys of peanuts for the natural occurrence of ochratoxins and ochratoxin-producing fungi have been reported. The objectives of this study were to investigate the occurrence of Aspergillus section Nigri and ochratoxin A (OTA) in storage peanuts during a three-month-period. The capacity to produce OTA by Aspergillus section Nigri was also studied. A total of 100 samples were collected from May to July 2004. The frequency of contaminating fungi were determined by surface-disinfection the seeds and plating onto several agar types. Detection of OTA in seed samples was performed using an HPLC method. Strains belonging to Aspergillus section Nigri or Flavi were detected in all seeds samples. From the section Nigri, the species belonging to A. niger aggregate were isolated in 100% of the samples. The main ochratoxigenic specie, A. carbonarius, was present at low levels throughout the study period. OTA was found in 50% of the peanut samples, with mean levels ranging from 5.6 to 130 ng g(-1). The mean value of OTA obtained after the first month of storage (30 ng g(-1)) was significantly higher from those obtained after the second (6.5 ng g(-1)) and third (13 ng g(-1)) month (p<0.0001). One hundred and four (32%) of 322 strains of Aspergillus section Nigri, were OTA producers. The levels of toxin produced ranged from 2 to 24 ng ml(-1) of culture medium (mean level: 12.7 ng ml(-1)). These results indicate that humans and animals being may be frequently exposed to OTA in Argentina through the ingestion of peanut seed and foods based on peanuts. The presence of this toxin in peanuts might be an appropriate focus for future studies to estimate exposure through normal consumption of this commodity. These data are important in formulating guidelines for quality control of peanuts in Argentina.     

Spores of Bacillus cereus strain KBAB4 produced at 10 °C and 30 °C display variations in their properties

Spores of the psychrotrophic Bacillus cereus KBAB4 strain were produced at 10 °C and 30 °C in fermentors. Spores produced at 30 °C were more resistant to wet heat at 85 °C, 1 % glutaraldehyde, 5 % hydrogen peroxide, 1 M NaOH and pulsed light at fluences between 0.5 and 1.75 J cm⁻² and to a lesser extent to monochromatic UV-C at 254 nm. No difference in resistance to 0.25 mM formaldehyde, 1 M nitrous acid and 0.025 g l⁻¹ calcium hypochlorite was observed. Spores produced at 10 °C germinated more efficiently with 10 mM and 100 mM l-alanine than spores produced at 30 °C, while no difference in germination was observed with inosine. Dipicolinic acid (DPA) content in the spore was significantly higher for spores prepared at 30 °C. Composition of certain fatty acids varied significantly between spores produced at 10 °C and 30 °C.     

Structure and antioxidant activity of high molecular weight Maillard reaction products from casein–glucose

Maillard reaction products (MRPs) were prepared from a casein–glucose reaction and ultrafiltrated to provide six fractions. The high molecular weight glycated proteins (melanoprotein) were further purified with a Sephadex G-75 column. Two fractions were obtained and analysed for their reducing power and Fe²⁺ chelating activity. Results obtained from the first fraction, analysed by Fourier transform infrared spectroscopy (FT-IR) indicated that the amide I, II and III bands of casein were changed by the Maillard reaction. The obtained samples were also hydrolysed with pepsin and trypsin in vitro, and the proteolytic hydrolysates were evaluated for their antioxidant activities. Non-hydrolysed melanoproteins exhibited the highest reducing power, but peptic hydrolysates of different MRPs were more efficient in radical-scavenging activity.     

Recovery of heat-stressed E. coli O157:H7 from ground beef and survival of E. coli O157:H7 in refrigerated and frozen ground beef and in fermented sausage kept at 7°C and 22°C

A study was undertaken to obtain information on survival of Escherichia coli O157:H7 in ground beef subjected to heat treatment, refrigeration and freezing and on survival of E. coli O157:H7 in fermented sausage kept at 7°C and 22°C. For the challenge test, a mixture of E. coli O157:H7 strains (EH 321, EH 385, EH 302) was used and enumeration was performed on an isolation medium suitable for recovery of stressed organisms: modified Levine's eosin methylene blue agar (mEMB). Heat resistance of E. coli O157:H7 decreased after pre-incubation at a reduced temperature.Escherichia coli O157:H7 was more susceptible to heat inactivation after storage at 7°C and die-off was even more enhanced if cultures were frozen prior to heat inactivation. The enhanced reduction of the pathogen at 56°C after prior storage under refrigeration was confirmed in a test with inoculated ground beef.Escherichia coli O157:H7 was able to survive in ground beef at 7°C for 11 days and at −18°C for 35 days showing maximal one log reduction during the storage period. Thus, ground beef contaminated with E. coli O157:H7 will remain a hazard even if the ground beef is held at low or freezing temperatures. At both 7°C and 22°C, a gradual reduction of E. coli O157:H7 was noticed in fermented sausage over the 35 days storage period resulting in a 2 log decrease of the high inoculum (10⁶cfu 25 g⁻¹). For the low inoculum (10³cfu 25 g⁻¹) a 2·5 log reduction was obtained in 7 and 28 days storage at respectively 22 and 7°C. Application of good hygienic practices and implementation of HACCP in the beef industry are important tools in the control of E. coli O157:H7.     

Determination of biogenic amines in fresh unpacked and vacuum-packed beef during storage at 4°C

Biogenic amines, putrescine, cadaverine, and histamine were determined in unpacked and vacuum-packed beef; during storage at 4°C for 12 and 35 days, respectively, under the same conditions. Analysis by High Performance Liquid Chromatography in both kind of samples, showed variation of cadaverine and histamine with an increasing tendency to a definite increase of putrescine. In unpacked samples, maximum mean contents for each amine reached 10.4, 5.2 μg/g for putrescine and cadaverine, respectively (12th day) and 2.2 μg/g for histamine (5th day). The total amine content reached 16.5 μg/g (12th day). After 8 days of storage, organoleptic fall-off began and, on the 12th day, all samples were disqualified. In vacuum packs, amine levels increased after 19 days. Maximum levels were determined for putrescine on the 35th day (36.3 μg/g), for cadaverine on the 26th day (28.9 μg/g) and for histamine on the 35th day (19.0 μg/g). Although the vacuum-packed beef was organoleptically acceptable up to 35 days, the total amine levels were greater than 5 μg/g after the 12th day, indicating a leveling off of quality.     

Determination of volatile compounds formed in a glucose–selenomethionine model system by gas chromatography–atomic emission detector and gas chromatography–mass spectrometry

In order to gain a better understanding of the formation of organoselenium compounds in food system, the Maillard reaction of selenomethionine and glucose was studied in a model system. The effects of heating time and pH on the volatile compounds formed in a glucose–selenomethionine reaction were also investigated. Nine organoselenium compounds were identified. Pyrazines and dimethyldiselenide are major volatile compounds generated from the glucose–selenomethionine model system. A high pH level favours the formation of pyrazine and dimethyldiselenide. In unbuffered systems, a pH change of three or more pH units may occur, and this may significantly affect the formation of Maillard reaction products.