ESTIMATION of HEAT of MOISTURE SORPTION and IMPROVED CRITERIA FOR EVALUATING MOISTURE SORPTION ISOTHERM EQUATIONS FOR FOODS

Heat of sorption of moisture on foods can be estimated from sorption isotherm equations having both moisture and temperature as independent variables. Sorption thermodynamics dictate that the heat of moisture sorption should decrease with increased moisture concentration, or increased temperature of food, provided no biological, chemical or other changes occur during sorption. This fact, and the Clausius-Clapeyron equation were used to derive two analytical formulae to evaluate the reliability of moisture sorption equations in the calculation of heat of sorption. As examples, Chung and Pfost, modified Harkins and Jura, modified Henderson, and Guggenheim-Anderson-De Boer equations at specified conditions were analyzed.     

BACTERIAL ADHERENCE AND VIABILITY ON CUTTING BOARD SURFACES

The adherence and viability of Escherichia coli inoculated onto the surfaces of plastic cutting boards and new and used wood cutting boards were evaluated. Most of the inoculum was recovered from all surfaces after resident drying times of 5 min and from plastic surfaces at 24 h. When the exposure time was extended to 2 h, > 90% of the cells placed on new and used dry wood surfaces were not recovered after vigorous rinsing. Scanning electron microscopy showed that the bacteria resided within the structural xylem fibers and vegetative elements of the wood. After resident drying times of up to 2 h, almost 75% of the adherent bacteria on the wood surfaces were viable, as defined by a nalidixic acid direct viable count procedure. Microcosm studies showed no intrinsic growth-supporting or toxic properties of the cutting board materials. Bacteria that adhered to plastic surfaces were more easily removed by low-temperature washing than were cells that adhered to wood surfaces. These studies demonstrated that bacteria adhering to wood surfaces resided within the structural and vegetative elements of the wood's xylem tissues and were viable; wood was more retentive than plastic; penetration of the inoculum liquid promoted cell adherence to the wood matrix; and conditioning of wood with water before inoculation interfered with bacterial adherence.     

Differentiation of Australian wine isolates of Oenococcus oeni using random amplified polymorphic DNA (RAPD)

Intraspecific variation of Oenococcus oeni , the preferred lactic acid bacteria species for inducing malolactic fermentation in wine, was studied using the randomly amplified polymorphic DNA (RAPD) strain fingerprinting technique. Ten of fifteen isolates of O. oeni from Australian wineries situated in different wine regions could be distinguished by the RAPD technique. Strains of O. oeni which originated from the same winery were either indistinguishable or closely related to each other. Six different commercially available O. oeni strains could be differentiated with the four RAPD primers used and their genetic similarity determined. Analysis of O. oeni present in wines from a single source of fruit (Cabernet Sauvignon, vintage 2002) that underwent spontaneous malolactic fermentation revealed wide genetic variation amongst the isolates. Each fermentor contained several different O. oeni strains, which were present throughout alcoholic and malolactic fermentation. These data highlight the sensitivity of RAPDs when suitable primers are applied to O. oeni of unknown genetic origin, thus enabling O. oeni strains with desirable sensory and fermentation properties to be genetically analysed.     

Shelf-Life Enhancement of Lamb Meat under Refrigeration by Gamma Irradiation

Influence of low dose gamma irradiation on the storage stability of fresh lamb meat (prepacked chunks and mince) at 0-3°C was examined by sensory, microbiological and chemical criteria. The meat chunks irradiated at 1.0 kGy and 2.5 kGy remained in acceptable condition for 3 and 5 weeks respectively, whereas the corresponding shelf life for irradiated (1.0 kGy and 2.5 kGy) mince were 2 and 4 weeks respectively. In contrast, unirradiated meat chunks and mince spoiled within one week of storage at 0-3°C.     

Inhibition of rennets by blood serum

Incubation of calf chymosin with the serum from blood of various mammalian species before addition to milk reduced its milk‐clotting activity at 30°C; the inhibitory potency of the sera was in the order horse > goat > cattle > donkey = human. For all species, inhibition of calf chymosin increased on increasing both the incubation time and the level of blood serum. Horse blood serum inhibited other milk coagulants in the order porcine pepsin > Cryphonectria parasitica proteinase = calf chymosin > Rhizomucor miehei proteinase = bovine pepsin. Methylamine‐treated blood serum did not inhibit calf chymosin, suggesting that α₂‐macroglobulin may be the principal inhibitor of rennet in blood serum.     

Teaching Multi‐Disciplinary Design: Solar Car Design

Multi‐disciplinary design can be taught in a very general way focusing on methods and procedures that work for any multi‐disciplinary design project or in a very specific way focusing on a specific multi‐disciplinary design project. The general approach teaches students the principles of how to approach any multi‐disciplinary design project but often lacks meaningful examples of how the principles are applied. Focusing on a specific multi‐disciplinary design project gives the students a meaningful example of how to apply design principles but they may have difficulty generalizing what they have learned and how it can be applied to other projects. To get a good background in engineering design, engineering students should have educational experiences that are both general and specific. This paper describes a course developed at the University of Missouri‐Rolla (UMR) to teach multi‐disciplinary design by focusing on the design of a solar racing car. The purpose of the course is to teach the aspects of a multi‐disciplinary design project utilizing a specific example for student comprehension.     

Calcitriol induces post-thawed bovine sperm capacitation

Background: Capacitation is a set of physiological changes sperms undergo to acquire fertilizing capacity. In vivo, this process is directly associated with high calcium levels in sperm cytoplasm. Calcitriol, the vitamin D hypercalcemic metabolite, is related to human sperm motility, capacitation, and acrosome reaction. This work aimed to study the effect of calcitriol on bull sperm quality parameters and capacitation. Methods: One million freeze-thawed spermatozoa were obtained from different bulls and treated with 20 nM of calcitriol for 30 min. Untreated cells (negative control) and treated ones with calcitriol or heparin (100 µg/mL, positive capacitation control) were evaluated for motility, viability, and functional parameters. Menadione (70 µM, 30 min) treatment was included as a reactive oxygen species (ROS) positive sperm agent. Results: The results elucidated that sperm exposed to 20 nM calcitriol showed higher viability, vigor, and capacitation than their positive and negative controls. The percentage of sperm with intact plasma and acrosome membranes, mitochondrial membrane potential (ΔΨm), and phosphatidylserine externalization was similar in all the conditions evaluated, while ROS production was higher with heparin and menadione-treated groups than the calcitriol group or negative control. Conclusion: Our results indicate that calcitriol induces the capacitation of thawed bull spermatozoa and maintains acceptable values of progressive motility, viability, and vigor without altering key biological parameters such as redox status, ΔΨm, and cell death.