The rationale for this study lies in the upsurge of home food preservation which has occurred as a result of the unprecedented rise in food prices and, concommitantly, the danger and economic loss entailed in the use of faulty methods. A sample of 200 non-urban homemakers in the province of Alberta who do food preservation were examined on their practices and knowledge with regard to canning, drying, making sauerkraut, pickling, smoking and root cellar storage. The demographic characteristics of the sample population were delineated as to age, education, income, and size of family still living at home. These general demographic differences were not reflected in the food preservation methods used, in general. Cookbooks, some of which may have been government bulletins, were the most important source of information followed by family and district home economists. Unsafe practices followed by these homemakers were the use by 12% of the open kettle method for processing foods other than jams and jellies and the use by 76% of the boiling water bath rather than pressure processing for the low acid foods. These unsafe practices were made more serious by incorrectly evaluating the safety of food and the inability of the respondents to relate acidity classification of the food with its safety. The recommendation is made that canning publications provide the rationale for approved methods. More effective communication methods to reach homemakers are needed. / Graduation date: 1980

No description available.

Traditional African foods are often rich in nutrients and play an important role in increasing variety in diets of people in rural areas. Tshidzimba is popular amongst the Vhavenda of South Africa. It is made from maize samp, milled peanuts and salt. However, it has a very short shelf life when stored at ambient temperature. Canning, drying and fermentation of Tshidzimba were investigated to increase shelf-life. Factors investigated were microbiological quality, nutrient content (in terms of fat and protein content), levels of essential amino acids, water activity and sensory acceptability. Unpreserved Tshidzimba had very high total plate counts, yeasts and moulds after 3 days of storage at 25°C. Fermentation reduced the yeasts and moulds by 102 and total plate counts by 103 after 21 days of storage at 25°C from those of unpreserved Tshidzimba. Drying reduced the yeasts and moulds by 104 and total plate counts by 105 after 21 days of storage at 25°C. Anaerobic spore formers were not detected in canned Tshidzimba after 21 days of storage at 25°C. Drying reduced the fat content probably due to fat oxidation at the elevated drying temperature (50°C). However, in general the preservation methods had little effect on the general nutrient content of Tshidzimba. Tshidzimba protein showed low lysine value compared to the estimates of amino acid requirements for infants. For Tshidzimba to be a good source of nutrients for infants, fortification with a higher proportion of legume grains is recommended. Drying seemed to increase lysine (2.61 g/100 g protein) compared to that of unpreserved Tshidzimba (2.28 g/100 g protein), while canning reduced lysine (1.97 g/l00 g protein), probably due to its participation in Maillard reaction at the high canning temperature (116°C/70 min). Fermentation increased methionine content probably due to fermentative microorganisms, which are known to produce some amino acids while fermenting food products. Canning seemed to have reduced the methionine content possibly due to Maillard reaction. Consumer panellists indicated that of the preserved Tshidzimba, dried Tshidzimba had high acceptance compared to canned and fermented Tshidzimba. Some panellists disliked the sour taste of fermented Tshidzimba. Dried Tshidzimba was perceived to have a firmer texture compared to unpreserved Tshidzimba. Further research could help to determine the appropriate temperature/time combination that can least affect the texture of dried Tshidzimba. / Dissertation (M Inst Agrar ( Food Processing))--University of Pretoria, 2006. / Food Science / unrestricted

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This study was undertaken to determine the sensory differences in high pressure vs. heat processed food systems after storage at ambient and refrigerated temperatures as determined by a trained sensory panel. Spanish rice and spaghetti with meat sauce were prepared and treated with heat and with high pressure processing (HHP). A citrus fruit mix consisting of pieces of orange, grapefruit, and pineapple was processed by mild heat and HHP, and heat alone. One day after processing, treated products were tested along with untreated controls. Products were stored at either 22°C or 3°C, and tested at 10, 30, 60, 90, and 120 days. Sensory testing was done by a panel trained in a QDA-type method, and data was analyzed by univariate and multivariate methods. For spaghetti with meat sauce, significant differences (p>0.05) were found between processing methods stored at the same temperature in appearance and texture attributes, with the high pressure processed samples closer to unstored product than those treated by heat. Differences in treatments first appeared in 'dry appearance' at 10 days, and by 120 days there were differences in 'tomato integrity', 'pasta integrity', 'brightness of color', and 'firmness of pasta' as well. Most of these differences were due to the stickiness caused by the extra amylose leaking out of the heat treated pasta over time. For Spanish rice, there were no statistically significant differences between samples processed by the two methods and stored at the same temperature. The Spanish rice was formulated with parboiled rice, which allows very little amylose leakage, so it did not show amylose-related effects as the spaghetti with meat sauce did. The fruit mix processed with HPP and mild heat had significantly higher ratings in appearance attributes 'brightness of color' and piece integrity', and lower ratings in 'cooked' descriptors than product treated with heat alone stored at the same temperature. / Graduation date: 2000

Microgard, a commercially-available pasteurized fermented milk, was found inhibitory to gram negative bacteria such as Pseudomonas putida, some well-known foodborne pathogens (e.g. Salmonella, Yersinia and Aeromonas) and some fungi as revealed by an agar incorporation assay method. Gram positive bacteria, however, were not inhibited. Rather, some bacteria in this group were stimulated by Microgard. The inhibitory activity of Microgard was optimum at pH 5.3 and below. Thermal stability and protease sensitivity were characteristic of Microgard. Addition of albumin or some emulsifying substances antagonized Microgard whereas treatment with proteases at an initial pH of 11.0 enhanced its inhibitory ability. Purified eluates of Microgard from a Sephadex Column (gel filtration) exhibited thermal stability and maximum UV absorbance. Furthermore, they gave positive results with the Biuret test, indicating the presence of protein type substance(s). Diacetyl, known to be inhibitory for psychotrophic bacteria, was present in Microgard as well as several organic acids. Filter-sterilized fermentation growth metabolites of Pediococcus spp., Propionibacterium spp., Bifidobacterium longum, Lactobacillus plantarum and a black-pigmented yeast were tested for antimicrobial activity as Microgard had been tested. Results revealed that some of these metabolites were inhibitory to Pseudomonas putida and Listeria monocytogenes, which represented food spoilage and pathogenic bacteria, respectively. / Graduation date: 1989

No description available.

No description available.

Weak acids are commonly used in the food industry as food preservatives however a complete understanding of their mode of action is not available. This study aimed to gain an understanding of the inhibitory mechanisms of two weak acids: sodium acetate and sodium benzoate. The ability of these weak acids to perturb the internal pH of cells was determined, a phenomenon previously shown as a mode of action of weak acids. However, changes in pHi alone were not sufficient in explaining the growth inhibition observed with sodium acetate, suggesting that the weak acid anion may also contribute to growth inhibition. The effect of the accumulation of was weak acid anions was found to be a reduction of cellular amino acid pools, mainly glutamate. When cells were transferred from medium containing weak acid to acid-free medium, recovery of internal pH was shown to be dependent on glutamate synthesis. The relieving effects of methionine on weak acid inhibition were also investigated. The aim of this section of the study was to identify the mechanism by which methionine resulted in relief of weak acid inhibition. It was found that addition of weak acid resulted in a 16-fold increase of the intracellular concentrations of homocysteine. This methionine precursor has been shown to act as a competitive inhibitor of methionine for methyl-tRNA-synthetase. Addition of methionine is therefore proposed to reduce weak acid inhibition by reducing homocysteine pools by feedback inhibition and by out-competing the intermediate.

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