Further Characterization of a Caffeine-Resistant Mutant of Aspergillus parasiticus

Studies were performed to characterize further Aspergillus parasiticus BCR1, a caffeine-resistant mutant of A. parasiticus NRRL 2999, particularly in regard to its caffeine-dependent production of aflatoxins. The enhanced synthesis of aflatoxins by caffeine was highly specific since neither dimethylxanthines nor purines could substitute for the trimethylxanthine. Caffeine's effects were phase dependent and only increased toxin formation if added early in the microorganism's life cycle. The ability of BCR1 to exclude caffeine appeared dependent on the initial levels of caffeine in the growth medium. Respiration and glucose utilization in the wild type strain were inhibited strongly by caffeine, but BCR1 was resistant to these effects. Comparison of glucose uptake kinetics in the wild type and mutant strains indicated that caffeine inhibition of aflatoxin synthesis in the wild type was not due to a disruption of glucose transport.     

BARLEY β-AMYLASE HYDROLYSIS of STARCH DURING TWIN SCREW EXTRUSION

Effect of moisture content, screw rpm and β-amylase dose on the rate of maltose production in a Baker-Perkins twin screw food extruder has been studied. Fifteen experiments were conducted using a fixed screw configuration at a fixed mass flow rate of 15 kg/h, under isothermal conditions (t=57°C) and a pH of 5.5. Each of the three variables was found to have a significant effect (P<. 05) on maltose production. Using response surface regression analysis on the experimental data, a quadratic objective function was derived. the function was optimized, subjecting it to three explicit boundary conditions, using the adaptive complex method. the optimization process yielded a maximum maltose production of 34% at 54% moisture content, 30 rpm screw speed and 157 units of enzyme/g of starch. the extent of saccharification was about 30%.     

CONSUMER ACCEPTANCE OF "FARM RAISED" PRECOOKED ROAST BEEF

A store intercept consumer survey was used to examine consumer willingness to pay for a marinated, precooked roast beef product produced from “farm raised” cattle fed a predominantly forage‐based diet. Consumers were asked to participate and, if they agreed, were provided with a sample of the precooked product. They were asked to compare this product with an existing similar product at various price levels. The data collected suggest there is a consumer willingness to pay premium prices for “farm raised” precooked roast beef. Therefore, creative retail positioning of value‐added, convenient, precooked beef products from forage‐fed cattle could result in increased consumer awareness of the easy convenience of these products, capitalize on the apparent emerging market for forage‐fed beef and potentially increase the overall demand for beef.     

Isolation of a Caffeine-Resistant Mutant of Aspergillus parasiticus

A caffeine-resistant mutant of Aspergillus parasiticus NRRL 2999 was isolated and subsequently designated strain BCR1. The mutant strain grew in the presence of > 8 mg/mL caffeine, while growth of the parent strain was delayed by 1 mg/mL and inhibited by 2 mg/mL. Strain BCR1 produced abundant amounts of aflatoxin only when cultured in media containing caffeine. Residual caffeine analyses indicated that caffeine-resistance in BCR1 was not due to the metabolic elimination of caffeine.     

Effect of Handling and Packaging on the Quality of Frozen Whitefish

Individually frozen, scaled whitefish (Coregonus clupeaformis) rapidly developed oxidative off-flavors when stored without packaging at ?12°C, but both vacuum-packaging in barrier films and ice-glazing significantly suppressed the development of oxidized flavors through 24 wk of storage. Removal of scales prior to freezing significantly enhanced the development of oxidized flavors over unscaled whitefish when both were held unprotected at ?12°C. Loose-packaging of individual, well-washed whitefish in closed polyethylene pouches significantly improved oxidative stability compared to those stored unprotected. However, vacuum, barrier-film packaging gave significantly better protection than polyethylene at both ?12°C and ?25°C through 24 wk and 72 wk, respectively.     

DILUTION AND SOLIDS ADULTERATION OF APPLE JUICE

The adulteration of apple juice with pear juice and corn drived syrups has been practiced in many countries. The sorbitol/sucrose ratios and the sorbitol/total sugar ratios were determined for the juices of 14 apple varieties and 3 pear varieties. A multivariate normal test was applied to develop an equation for the detection of apple juice adulteration with sugar solutions or pear juice. Adulteration of apple juice with more than 10% sugar solution or pear juice were detectable with this method.     

Reassessment of Some Fruit and Vegetable Pectin Levels

Several reviews of pectin as a soluble fiber have included unreliable tables of pectin content for fruits and vegetables. Values given for ranges of pectin content in the fresh, edible portion are actually presented in original reports variously as peel pectin content, dry weight values, soluble rather than total pectins, and some values have been for unripe fruit. This has resulted in reporting pectin levels for some products that may be 2-10 times higher than other published data on the same product. This report examines the original sources and errors of such data and, when available, provides other more substantiated published values.     

COMPARISON OF IN-LINE CONSISTENCY MEASUREMENT OF TOMATO CONCENTRATES USING ULTRASONICS AND CAPILLARY METHODS

This study focuses on the development of a noninvasive, in‐line rheometer using ultrasonics and its comparison with data from a traditional capillary viscometer. The ultrasonic based pointwise viscosity measurement technique combines a measurement of the velocity profile and the pressure drop to determine the shear rate and the shear stress distributions, respectively in a pipe. The experiments were carried out using tomato concentrates at 8.75%, 12.75%, and 17.10% total solids content. The flow system consisted of a 53.2 mm diameter acrylic tube, a positive displacement pump and two pressure transducers. Multiple shear viscosity‐shear rate data were recorded under actual pipeline conditions from a single combined measurement of the velocity profiles using ultrasonics and the pressure gradient, using the pressure transducers. The samples showed shear thinning behavior and a yield stress. Power law and Casson models were used to fit the data and both obtained R² values higher than 0.99. The yield stress was also directly determined from the velocity profiles. Shear viscosity versus shear rate data of the 12.75% total solids sample were obtained by capillary rheometry at four different flow rates. These showed very‐good agreement with those obtained using the velocity profile technique.     

Enzymatic Browning Inhibited in Fresh and Dried Apple Rings by Pineapple Juice

Sliced apple rings were treated with water (control), canned pineapple juice, frozen pineapple juice, ion-exchanged pineapple juice, frozen orange juice, ascorbic acid, a commercial antibrowning preparation or sodium bisulfite. The rings were either left exposed to air, vacuum packaged, or dehydrated. Browning was measured calorimetrically and by visual examination over extended periods of time. Pineapple juice was an effective browning inhibitor in both fresh and dried apples. Pineapple juice was fractionated using various size and charge separation procedures. All fractions inhibited enzymatic browning of crude apple extracts by at least 26%. Results indicate that the inhibitor is a neutral compound of low molecular weight.     

Growth Conditions Affecting Proteolytic Enzyme and Extracellular Vesicle Production by Pseudomonas fragi ATCC 4973

Pseudomonas fragi ATCC 4973 was grown in liquid culture (trypticase soy broth) and on a solid surface (tryticase soy broth + 1.5% agar). Pseudomonas fragi grown in liquid culture started extracellular proteolytic enzyme production at 24 hr, during the late exponential early stationary growth phase. Pseudomonas fragi, grown on solid surfaces, initiated proteinase production at 4 hr, 20 hr earlier than in liquid medium. Proteinase production was greatest during periods when the cells were not actively growing. Electron micrographs of P. fragi grown on solid surfaces revealed extracellular vesicles ca. 20 nm in diameter “blebbing” off the surface of the cells. The greatest number of vesicles coincided with maximum proteinase production. These vesicles were absent from the surface of P. fragi cells grown in liquid culture.