Thesis (M.S. in food science)--Washington State University, August 2007. / Includes bibliographical references (p. 72-85).

No description available.

Thesis (Ph.D.)--University of Massachusetts Amherst, 2008. / Adviser: Kalidas Shetty. Includes bibliographical references.

No description available.

A method was developed for monitoring the growth of a range of bacteria and fungi in the Bactometer 32 impedimeter. 195 yeast strains, 74 strains of mould and 20 strains of bacteria were screened for sensitivity to 1 mug ml[-1] of T-2 toxin. Growth inhibition was assessed impedimetrically. Twelve bacteria, 20 moulds and 38 yeast strains were tested against roridin A, verrucarin A, deoxynivalenol, and diacetoxyscirpenol each at 1 mum ml[-1] . Deoxynivalenol was found to be only slightly toxic. Roridin A and verrucarin A were markedly more toxic than the others to the fungi, but not to the bacteria. Four microorganisms (Bacillus subtilis, Candida albicans. Hansenula fabianii and Pichia burtonii)were selected for further study. No obvious pattern of response could be discerned for the effects of different carbohydrates on microbial sensitivity to T-2 toxin. The effects of T-2 toxin on B. subtilis and C. albicans were greater if chloroform rather than dichloromethane and methanol (95:5, v/v) was used as the toxin carrying solvent, the reverse was true for H. fabianii and P. burtonii. Dose-response curves were constructed, based on impedimetric responses, and no-effect levels were determined for each species. For B. subtilis the no-effect level was 0.35 mum ml[-1], for C. albicans it was 0.40 mum ml[-1], for H. fabianii it was 0.012 mum ml[-1] and for P. burtonii it was 0.018 mum ml[-1]. H. fabianii was selected for further studies. This strain was found to be auxotrophic for proline. The effect of T-2 toxin and verrucarin A on the uptake of radiolabelled proline in H. fabianii cultures was studied. Dose-response curves were constructed for each toxin. It was found that both toxins reduced proline uptake in a dose dependent manner, the no-effect levels were 0.025 mum ml[-1] for T-2 toxin and 0.0125 mum ml[-1] for verrucarin A.

beta-Carbolines are tricyclic compounds deriving from the condensation of indoleamines or tryptophan with fairly electrophilic carbonylic compounds to form a fused benzene-pyrrole-pyridine ring system (Pictet-Spengler reaction). Previous investigation carried out with model systems proved the facile formation of various tetrahydro-beta-carboline-3-carboxylic acids (beta-CCA) from tryptophan and reactive carbonyls present in wood smoke, under conditions simulating those of foods during their smoking process. The present work has been undertaken to investigate and confirm the actual occurence of such compounds in real smoked foodstuffs of animal origin. Five representative beta-CCA were selected taking into account the high content of their precursor aldehydes in smoke (formaldehyde, acetaldehyde, glycolaldehyde) and/or the facility of their formation during the model system experiments (benzaldehyde and salicylaldehyde derivatives). They were synthesized following methods based on the Pictet-Spengler reaction as they were described in the literature, or by slightly modifying and altering them. The structure of the synthesised products was confirmed using spot tests, melting points, elemental analysis and spectrometric methods such as fluorescence, UV, 1HNMR, MS and 13CNMR spectroscopy. A method was developed for the isolation of these compounds from smoked solid foods. The samples were extracted with an aqueous acidic medium containing semicarbazide to prevent artifactual formation of beta-CCA. The extract was purified on an XAD-4 resin containing, clean-up column. The eluate was concentrated, further purified by extraction with CHaCla and analysed by high performance liquid chromatography on a Spherisorb ODS1 reversed phase column with gradient elution and fluorescence detection. The quantitation was based on calculating the ratio of the peek area of each compound to the peak area of the internal standard (serotonin creatinine sulphate). The mean recovery of the method was about 76% for the more hydrophilic derivatives of formaldehyde, acetaldehyde and glycol aldehyde and 11% for the more hydrophobic derivatives of benzaldehyde and salicylaldehyde. Higher concentrations of analytes in the samples led to decreased recoveries. The detection limit was lower than 25 mug/kg for the more hydrophilic and 2 mg/kg for the more hydrophobic group of compounds. Thirty four samples of miscellaneous smoked food products such as dry salamis, heat processed comminuted meat products, cured meats (heat processed or not), raw or heat processed fish, hard cheese, were analysed. The beta-CCA concentration in them was variable depending on many factors such as pH value, heavy or light smoking and maturation time. Dry, fermented comminuted meat products contained the higher concentrations. Tetrahydro-beta-carboline-3-carboxylic acid prevailed in all samples examined and was detected at a level of 0.86 up to 22.63 mg/kg in dry salamis, whereas in other samples it ranged from 16 to 680 mug/kg. The levels of 1-methyl- and 1- hydroxymethyl-tetrahydro-beta-carboline-3-carboxylic acids were much lower (0-881 mug/kg and 0-444 mug/kg respectively). The occurence of benzaldehyde and salicylaldehyde derivatives was not definitely proved. The synthesised beta-CCA were tried for mutagenicity using the Ames test. None of them was mutagenic to Salmonella typhimurium TA-100, TA-98, TA-97 strains with and without metabolic activation, end without preincubation. At concentrations higher than 100 mug/plate, 1-hydroxymethyl- and unsubstituted tetrahydro-beta-carboline-3-carboxylic acids were toxic to strains TA-98 and TA-100. B-Carbolines are biologically active compounds and their detection in smoked foods might help to prevent potential implications to the consumers' health.

Traditional fermented food, especially fermented maize and sorghum represents an important part of the diet of peri-urban and rural communities in South Africa. In this study a survey was conducted to determine the popularity and utilization of “Ting” in the Limpopo Province of South Africa. The following areas were selected for the study: Venda, Giyani, Bolobedu and Polokwane. Ting samples were collected from different areas and from different local families. Gram positive, catalase-negative, oxidase negative, non-motile cells were presumptively identified as lactobacilli. Isolates were assigned to a genus on the basis of key characteristics. Growth at 10, 15 and 45oC in MRS broth wase evaluated visually after 72h of incubation. Tests for the catalase reaction, production of gas from glucose and growth at 7 and 10% NaCl concentrations were performed. API 50CHL medium and API 50CH strips were used to identify all the isolates to species level. Microorganisms from “Ting” fermented from both sorghum and maize were bacteria, which belong to the genus Lactobacillus, Leuconostoc and Pediococcus. Lactobacillus pentosaceus, and Lactobacillus plantarum, Lactobacillus pentosaceus were dominant in the fermentation of maize, while Lactobacillus cellobisus, Leuconostoc mesenteroides, Lactobacillus collinoides, Lactobacillus brevis, Lactobacillus fermentum and Lactobacillus curvatus were identified as bacteria from fermented “Ting” sorghum. The use of polyacrylamide gel electrophoresis (PAGE) of total soluble proteins, together with computer analysis was used to analyse the resultant protein profiles. L. plantarum, L. pentosus and P. pediococcus were the most dominant isolates. / Dissertation (MSc (Microbiology))--University of Pretoria, 2007. / Microbiology and Plant Pathology / unrestricted

The effect of gamma irradiation on the emulsifying capacity of turkey light meat was studied in a model system. A change of emulsifying capacity due to the changes of functional capabilities of salt-soluble proteins were studied on the irradiated salt-soluble-protein extract by disc electrophoresis, viscometry, fluorescence spectroscopy and measurement of pH. The formed emulsions were taken for examination of the particle size under the microscope, measurement of the viscosity with a Haake Rotovisco Viscometer, and for the determination of the stability by a method of centrifugation and cooking. Irradiation of turkey meat at doses of 1 or 3 Mrad increased the emulsifying capacity of the tissue but doses of 2 or 4 Mrad decreased capacity relative to an unirradiated control. Irradiation had no effect on the extractability of salt-soluble proteins. The emulsifying capacity of irradiated salt-soluble-protein extract increased significantly ( p≤0.05 ) and viscosity decreased significantly ( p≤0.05 ) with increasing dose of irradiation from 0 to 2 Mrad. Doses of 3 or 4 Mrad failed to produce further significant change in either variable. Irradiation of the salt-soluble-protein extract also resulted in a decrease in particle size of the emulsion; an increase in viscosity of the emulsion; an increase of hydrophobic effect in the salt-soluble-protein molecule; an increase in the electrophoretic mobility of the two main protein fractions on polyacrylamide gel; an increase in pH; and an increase in the stability of emulsions judged on the basis of volume of oil in the supernatant after centrifugation and cooking. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.