ENZYME KINETICS AT LOW TEMPERATURE AND REDUCED WATER ACTIVITY

1978 ◽  
pp. 297-322 ◽  
Author(s):  
O. Fennema
Keyword(s):  
Low Temperature ◽  
Enzyme Kinetics ◽  
Water Activity ◽  
Reduced Water

scholarly journals Nitrogen utilisation and growth at reduced water activity by mucoralean fungi present in soil

1999 ◽  
Vol 65 (5-6) ◽  
pp. 407-413 ◽  
Author(s):  
B.O. Seabi ◽  
B.C. Viljoen ◽  
C. Roux ◽  
A. Botha
Keyword(s):  
Water Activity ◽  
Nitrogen Utilisation ◽  
Reduced Water

Effect of Gamma Irradiation on the Survival of Pathogens in Kwamegi, a Traditional Korean Semidried Seafood

2003 ◽  
Vol 66 (11) ◽  
pp. 2093-2096 ◽  
Author(s):  
S. P. CHAWLA ◽  
D. H. KIM ◽  
C. JO ◽  
J. W. LEE ◽  
H. P. SONG ◽  
...  
Keyword(s):  
Low Temperature ◽  
Salmonella Typhimurium ◽  
Water Activity ◽  
Pathogenic Bacteria ◽  
Radiation Sensitivity ◽  
E Coli ◽  
Public Health Significance ◽  
Irradiation Treatment ◽  
Test Organisms ◽  
Health Significance

Kwamegi (semidried raw Pacific saury) is traditional seafood available in Korea. It has water activity in the range of 0.90 to 0.95. Spoilage and the growth of most pathogenic bacteria is retarded because of low water activity, low temperature, and packaging. However, it is contaminated with bacteria of public health significance and poses a hazard to the consumer because it is consumed raw without any cooking. The effectiveness of these hurdles in preventing the growth of Staphylococcus aureus, Bacillus cereus, Salmonella Typhimurium, and Escherichia coli and the efficacy of irradiation treatment in eliminating these bacteria from kwamegi using inoculated pack studies was examined. Radiation sensitivity of S. aureus, B. cereus, Salmonella Typhimurium, and E. coli in kwamegi was investigated. D10-values of these organisms in kwamegi were 590 ± 13.6, 640 ± 14.9, 560 ± 45.4, and 550 ± 8.6 Gy, respectively. The growth of all four test organisms inoculated into these foods during 4 weeks of storage at an ambient winter temperature (ranging from −5°C to +5°C) was recorded. All four pathogens (inoculated at 106 CFU/g) were eliminated by irradiation at 4 kGy. These studies unequivocally demonstrate that irradiation, with a combination of low water activity and low temperature, results in microbiologically safe kwamegi.

Effects of potassium sorbate on growth patterns, morphology, and heat resistance of Zygosaccharomyces rouxii at reduced water activity

1992 ◽  
Vol 38 (12) ◽  
pp. 1252-1259 ◽  
Author(s):  
David A. Golden ◽  
Larry R. Beuchat
Keyword(s):  
Heat Resistance ◽  
Water Activity ◽  
Growth Patterns ◽  
Potassium Sorbate ◽  
Heat Sensitivity ◽  
Growth Morphology ◽  
Zygosaccharomyces Rouxii ◽  
Inhibition Of Growth ◽  
Reduced Water ◽  
Sorbate Concentration

A study was made of the effects of potassium sorbate on growth, morphology, and heat sensitivity of an osmotolerant yeast, Zygosaccharomyces rouxii, grown in media (water activity (aw) 0.93) supplemented with glucose and sucrose. Growth patterns of Z. rouxii in YM broth supplemented with glucose (YMBG) and sucrose (YMBS) were similar, although increased potassium sorbate concentration in both media resulted in decreased growth rates. Growth in YMBS containing potassium sorbate was not as prolific as that in YMBG containing potassium sorbate. Inhibition of growth was indicated by decreased absorbance (at 600 nm) of cells grown in YMBS and in YMBG and YMBS supplemented with potassium sorbate at 600 or 1000 μg/mL. Slight decreases in cell size and alteration of cellular morphology were associated with increased potassium sorbate concentration. Plasmolysis increased as potassium sorbate concentration was elevated in YMBS but not in YMBG. Tolerance of Z. rouxii to potassium sorbate was enhanced by previous adaptation of cells in media with elevated potassium sorbate concentrations. Heat resistance of cells unadapted to potassium sorbate showed little or no increase regardless of culture age, but increased substantially in cells grown in media containing potassium sorbate, particularly YMBS. Key words: Zygosaccharomyces rouxii, potassium sorbate, glucose, sucrose, heat resistance.

Influence of Water Activity on Foodborne Bacteria — A Review1

1983 ◽  
Vol 46 (2) ◽  
pp. 142-150 ◽  
Author(s):  
WILLIAM H. SPERBER
Keyword(s):  
Glutamic Acid ◽  
Water Activity ◽  
Bacterial Growth ◽  
Food Systems ◽  
New Technologies ◽  
Compatible Solutes ◽  
Food Products ◽  
Influence Of Water ◽  
Chemical Preservatives ◽  
Reduced Water

The influence of water activity on some characteristics of bacterial growth is presented. Bacteria are able to overcome the plasmolytic effect of reduced water activity by intracellularly accumulating compatible solutes such as glutamic acid or proline. In food systems, water activity is one of several preservative factors which interact to form a preservative system. Other preservative factors considered in this review are temperature, pH, O/R potential and chemical preservatives. Control of water activity in foods is receiving more attention as new food products and new technologies are developed.

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