Bacterial Growth and Histamine Production on Vacuum Packaged Tuna

Vacuum and nonvacuum packaged samples of tuna or tuna spiked with Klebsiella oxytoca T₂, Morganella morganii JM or Hafnia alvei T₈ were stored at 2°C and 10°C and examined for bacterial growth and histamine production on day 3, 6, 10 and 15. Unlike those stored at 2°C, tuna samples stored at 100°C showed significant bacterial growth over time and had high levels of histamine (>200 mg/100g tuna on day 15). Vacuum packaging did not show any beneficial effect in controlling bacterial growth and histamine production on tuna samples at these two temperatures. Low temperature storage was more effective than vacuum packaging in controlling histamine production by the bacteria tested.     

Histamine, Putrescine and Cadaverine Formation in Spanish Semipreserved Anchovies as Affected by Time/Temperature

We studied the changes in counts of mesophilic, psychrotrophic, entera-bacteria, sulphite-reducing and Vibrio microorganisms in commercial samples of Spanish semipreserved anchovies. The influence of NaCl, oxygen concentration and pH on bacterial growth and histamine, putrescine and cadaverine formation were also studied. Notable histamine formation was detected in samples incubated at 20°C and preserved in olive oil (443.68 ppm-3012.13 ppm). This accumulation was probably caused by the conditions of the product, pH 5–6, relatively low NaCl (< 15%), and permissive temperature (product not refrigerated). Correlation between the microorganisms and histamine formation was not clear. Histamine was produced by too high storage temperatures but not by the ripening process.     

Stability of Apple Polyphenols as a Function of Temperature and pH

The effect of heat treatment on apple polyphenols was investigated at six different temperatures over three different lengths of time. Apple polyphenols, after heat treatment, maintained similar concentrations in solution compared to the control (at room temperature). The effect of pH on apple polyphenols was investigated at 11 different pH levels and at 2 different temperatures. The pH-optimum for apple polyphenols proved to be 5.0. Two apple polyphenol concentrations, three vitamin C concentrations, two sugar concentrations, and two different temperatures were chosen to investigate the effect of apple polyphenols on vitamin C. Apple polyphenols showed good stability and can be used in many types of food products.     

Inactivation and Injury of Listeria monocytogenes in a Minimal Medium as Affected by Benzoic Acid and Incubation Temperature

The population of Listeria monocytogenes in a minimal medium (lacking a nitrogen source) at pH 5.5 decreased logarithmically during incubation. Rate of death of the pathogen, indicated by D-values, was greatly affected by changes in the temperature of incubation (4–35°C), but to a much lesser extent by the presence of benzoic acid (3000 ppm). Injury of L. monocytogenes during incubation was equally detectable on tryptose agar containing 6% salt and McBride Listeria Agar containing 0.5% lithium chloride. A greater degree of injury was detected at the lower than the higher temperatures of incubation, but presence of benzoic acid (3000 ppm) did not seem to affect the extent of injury.     

Glucose Production from Maltohexaose as a Substrate by the Bacterial Alpha-amylase-catalyzed Reaction. Its Time Courses Obtained by a Theoretical and an Experimental Approaches

Based on the subsite structure of an α-amylase from Bacillus subtilis, production of glucose from a substrate maltohexaose in the amylase-catalyzed reaction was theoretically predicted as a function of time. The theoretical time course was found consistent with the experimental results, which were obtained by the determination of a product glucose with a commercial assay-kit. Hence, glucose, product from a substrate maltohexaose, will be a useful probe for the amylase-catalyzed reaction.     

Compositional Changes in Brewed Coffee as a Function of Brewing Time

Variations in the composition of brewed coffee as a function of brewing time were monitored using gas chromatography-mass spectrometry. Batches of coffee were produced using flow rates of 50-500 mL/min, which resulted in brewtimes of 4.42-31.07 min. While most components increased in concentration with longer brewing times, several showed significant losses beyond 8 min, indicating an optimum brewtime of 7-9 min.     

Thermophysical Properties of Clarified Apple Juice as a Function of Concentration and Temperature

Effect of concentration and temperature on thermophysical properties of clarified apple juice was studied. Density, viscosity, specific heat, and thermal conductivity were measured at different conditions, ranging from 20 to 90^oC and 12 to 70^oBrix. Experimental data were related to the corresponding properties of water and compared with the behavior of sugar solutions. The results obtained were used to derive mathematical models and correlations for predicting these properties as a function of both concentration and temperature.     

Kinetics of Ascorbic Acid Autoxidation as a Function of Dissolved Oxygen Concentration and Temperature

The kinetics of ascorbic acid autoxidation was studied at pH 6.1 (μ= 0.08) using a buffered model system. Oxygen replenishment in the solution was accomplished by shaking the reaction vessel in a shaker water bath or by bubbling oxygen-nitrogen gas mixtures through the solution. Using the former system, a second order rate constant of 58.19 ± 11.92 min^?1 M^?1 was calculated (45°C), Since the shaker bath did not assure oxygen replenishment and dissolved oxygen levels could not be varied, the latter system was developed. The second order rate constants in the gas mixture experiments ranged from 20.80 ± 2.28 min^?1 M^?1 (30°C) to 176 ± 6.93 min^?1 M^?1 (55°C). Activation energies measured under different conditions ranged from 9.47 to 16.43 kcal mole^?1.     

Acceptability of Water, Selected Beverages and Foods as a Function of Serving Temperature

In Experiment 1 the consumer acceptability of water, four fruit-flavored beverages and tea was examined at five serving temperatures (38°, 52°, 74°, 97° and 120°F). Results showed significant main effects of beverage and temperature on acceptability ratings and a significant beverage × temperature interaction. Pure water, which was moderately acceptable at low serving temperatures, was the most unacceptable of all samples at high temperatures. In Experiment 2 the acceptability of three beverages and ten solid foods was examined at five serving temperatures (40°, 55°, 70°, 100° and 135°F). Results showed that the acceptability of each food item was greatest in the temperature range at which the food is normally served; except for foods normally served at ambient temperatures. The importance of temperature/acceptability functions for food and beverage selection under conditions where heating and/or cooling is not feasible, and the relationship of the present data to data on temperature/intensity functions in taste were discussed.     

适当延长制曲中挺温度时间对制酒生产的影响

曲药培养过程中适当延长中挺温度时间,对曲药酶活力有适当的抑制作用,从而减小白酒中因酶活力过高而给生产和产酒质量带来的不利影响。适当延长中挺温度时间,有利于对曲药中微生物的驯化,增加微生物对生产环境的适应性;控制曲药的酶活和发酵力,更加有益于生产;增加曲药的复合香。(孙悟)     

Content and Profile of Isoflavones in Soy-Based Foods as a Function of the Production Process

Soy has been traditionally incorporated in diet as processed foods, such as soymilk, tofu, miso, tempeh, etc., and the consumption is commonly associated with a reduction of the development of chronic diseases due to their antioxidant, anti-inflammatory, and anti-allergic properties, among others. Many of the health benefits of soy have been attributed to isoflavones. They comprise a group of naturally occurring flavonoids consisting of heterocyclic phenols. Soy contains three types of isoflavones in four chemical forms: the aglycones daidzein, genistein, and glycitein; the β-glucosides daidzin, genistin, and glycitin; their 6″-O-malonyl-β-glucosides (6OMalGlc); and their 6″-O-acetyl-β-glucosides (6OAcGlc) conjugates. Industrial processing methods of soy-based food products commonly lead to the loss of isoflavones through removal of undesirable fractions. On the other hand, isoflavones can be transformed into different conjugates, which may have significant effects on the food texture and on the bioavailability and pharmacokinetics of the isoflavones. This article reviews the effect of a number of soybean processing treatments on the isoflavone content and profile. The preparation and manufacturing of different soy-based food and food ingredients, fermented and non-fermented, has been analyzed in terms of content and distribution of the three major isoflavone derivatives, daidzein, genistein, and glycitein, and their respective conjugates.     

Temperature, pH and Bacterial Populations of Meat as Influenced by Home Freezer Failure

Consumers are concerned about the fate of frozen meat products in home freezers when electrical power is interrupted. We investigated this concern by using an upright home freezer. Fourteen trials were conducted with packages of either beef or pork with varying trial load weights (Range = 43–128 kg). Meat samples were frozen, power was disconnected, and packages within each lot were analyzed daily for 9 days for temperature, microbial count, and pH. After about 36 hr without electrical power, bacterial populations reached log 6 and the meat product's wholesomeness for consumption or possible refreeze became questionable.     

Dielectric Properties of Pea Puree at 915 MHz and 2450 MHz as a Function of Temperature

Dielectric properties [dielectric constant (e′) and loss factor (e″)] of 20% (w/w) pea puree with and without fortification of 3.5 mg thiamin/ 100g pea puree at 915 MHz and 2450 MHz were measured from 25 to 125°C by the cavity perturbation techniaue. Thiamin did not affect dielectric properties at ihe concentration studied. The dielectric constant decreased as frequency and temperature increased. The loss factor increased as temperature increased at 915 MHz. However, the relationship between loss factor and temperature was not direct at 2450 MHz due to the contributions of dipolar and ionic losses.     

Effects of Electrical Stimulation, Temperature of Boning and Storage Time on Bacterial Counts and Shelf-Life Characteristics of Beef Cuts

Strip loins and eye of rounds from 16 beef carcasses were used to study the effects of electrical stimulation (ES), no stimulation (NS), hot-boning (HB), and cold-boning (CB) on bacteriological and shelf-life evaluations. Following 7 days of vacuum-packaged storage, coliform counts were higher in the drip fluid from strip loins and lean surfaces of eye of rounds from ES compared to NS carcasses. A major advantage for HB in this study was the additional time required in retail display before the occurrence of lean surface discoloration. A previously identified benefit of lighter lean color with ES beef in carcass and primal cut form was also found in this study during display of retail cuts.     

Low Temperature Growth of Type E Clostridium botulinum Spores. 2. Effects of Solutes and Incubation Temperature

SUMMARY— The inhibition of outgrowth of spores of Clostridium botulinum Type E by the addition of different concentrations of various solutes to a trypticase-peptone-sucrose-yeast extract medium (TPSY) was studied at different incubation temperatures. Solutes added to TPSY medium were sodium chloride (NaCl), sodium formate (NaCOOH), potassium chloride (KCI), sucrose and glucose. Incubation was at 30, 21.1, 15.6, 10 and 7.2°C, and growth was confirmed by mouse toxin assay. The effect of the solutes on the equilibrium relative humidities (ERHI of the various media was measured using the graphical interpolation method and expressed as water activity (a_w). The possibility of an osmotic effect was also investigated. The molar (M) concentrations and osmotic pressures of the different solutes were calculated and related to the approximate inhibitory concentrations of 5.0% NaCl (a_w 0.975), 6.0% KCI (a_w 0.974), 5.5% NeCOOH (a_w 0.9711, 38.5% sucrose (a_w 0.976) and 22.5%. glucose (a_w 0.970).
The inhibitory salt concentrations were approximately 0.80 M and produced osmotic pressures of about 36.0 atmospheres. The approximate osmotic pressure of the inhibitory 1.12 and 1.24 M sucrose and glucose solutions were 25.08 and 27.97 atmospheres respectively.
Growth response decreased as the incubation temperature decreased as measured by delayed outgrowth times and in decreased amount of cellular material produced by the Type E strains tested.     

Inactivation Kinetics of Peach Pulp Pectin Methylesterase as a Function of High Hydrostatic Pressure and Temperature Process Conditions

A kinetic study of the inactivation of endogenous pectin methylesterase (PME) in Greek commercial peach pulp under high hydrostatic pressure (HHP; 100–800 MPa) combined with moderate temperature (30–70 °C) was conducted. Thermal inactivation of the enzyme at ambient pressure conditions was also studied. PME inactivation was modeled by first order kinetics at all conditions tested. High pressure and temperature acted synergistically on PME inactivation, except at the high temperature of 70 °C at the middle pressure range (100–600 MPa), where an antagonistic effect of pressure and temperature was observed. At this specific middle pressure range, an increase of pressure processing led to increased inactivation rate constants of peach PME. A multiparameter model was developed to express the PME inactivation rate constant as a function of temperature and pressure process conditions, taking into account the dependence of both activation energy and activation volume on pressure and temperature, respectively. A good correlation between experimental and predicted values of inactivation rate constants was established. This modeling approach enables the quantitative estimation of the HHP–temperature conditions needed to achieve a targeted PME inactivation in the peach pulp.     

Time and Temperature Parameters of Corn Popping

High quality commercial popcorn containing 14.0% moisture was processed in a continuous hot air domestic corn popper. The time required to pop individual kernels ranged from 35 − 120 sec, with 43% of the corn being cooked between 60 and 75 sec. The temperature of the popping chamber ranged from 196 − 277°C. The average temperature at the center of the kernels when they burst was 187°C. The empirical parameters, f and j values for heat transfer were determined.