Nutrition & Food Science

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1987 - 19902

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Start date: 1980End date: 1999

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    Age, Nutrition, and Bone Metabolism: Analyses of Effects Using a Short-Term In Vivo Bone Model
    (1987) Sinha, Rashmi; Soares, Jos; Nutritional Sciences Program; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    The preventative effects of dietary calcium, zinc, and vitamin D metabolites on the net loss of bone were assessed using rats of different ages. Biochemical changes were monitored in femurs, humeri, mandibles, scapulas, and tibias. In addition femora were sectioned into epiphyses-metaphyses and diaphyses to evaluate nutritional influences on the trabecular and cortical type bone. since measurable bone degradation due to aging and nutritional status requires long period of time, a short-term in vivo system was developed to simultaneously examine bone formation and resorption. The system consisted of subcutaneous implantation of demineralized (DB) and mineralized (MB) bone powders. There was evidence of bone formation and resorption in the DB and MB implants respectively, as assessed by marker enzyme (formation-alkaline phosphatase; resorption-acid phosphatase) activities, mineral concentrations, radioisotope incorporation, and histological studies. The results indicated that several different bone samples are required to adequately predict changes occurring in the skeletal system. The epiphysesmetaphyses of long bone is a useful sample site examining changes occurring in trabecular bone while the diaphysis can assess cortical bone status. There was decreased bone formation and resorption as assessed by alkaline and acid phosphatase activity in the MB and DB implants in the 24 month-old rats as compared to 2 month-old rats. Dietary calcium and zinc levels did not affect the overall status of the bones and implants in the aged rats. Conversely, in 2 month-old rats dietary calcium at 1.0% stimulated bone formation in the DB implant, whereas 0.2% calcium increased bone resorption in the MB implants. Furthermore, 75 ng dietary 1,25-dihydroxycholecalciferol (l,25(OH) 2 D) per day increased resorption in MB implant and inhibited mineralization of DB implants in the young rats. Dietary zinc at 300 ppm reduced bone calcification in 2 month-old. The results of these studies indicated that neither high levels of dietary calcium, nor zinc, act as prophylaxes to counteract bone loss due to aging. The dietary use of l,25(OH) 2 D in old animals needs to be investigated further, since results in young animals are contradictory with reports in older rats.
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    THE EFFICACY OF A BOILING WATER BLANCH ON THE INACTIVATION OF LISTERIA MONOCYTOGENES IN DICED CELERY
    (1990) Losikoff, Mary Bohrer; Westhoff, Dennis C.; Nutrition & Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)
    The effect of a boiling water blanch on the thermal inactivation of Listeria monocytogenes in raw diced celery was investigated. L. monocytogenes, Scott A was heated in Tryptic Soy Broth with 0.6% yeast extract, pH 5.3, at 52, 54, 56, 58, and 59°C. D values were 13.33, 7.75, 1.29, 0.792, and 0.701 min, respectively. A predicted D value at 60°C = 0.36 min was obtained using a z value of 5. These thermal inactivation characteristics were subsequently used to evaluate the L. monocytogenes was recovered from inoculated (1 X 10^7 cells/g) diced raw celery after heating for 0.25 min in a laboratory boiling water blanch. Viable cells were not recovered after 0.5 min of heating. Heat penetration data for diced raw celery during a boiling water blanch were obtained in a commercial setting. These data were analyzed by the general method to determine the cumulative lethality at reference temperatures of 60°C using a z of 5 and, 70 and 71.7°C using a z of 10. It was determined that a recommended process of 2 min at 70 °C was reached in 80 sec during the blanch. Based on the findings of this study, a boiling water blanch could be used as part of the hurdles approach to eliminate L. monocytogenes from raw diced celery.