The thermal, oxidative, and hydrolytic stability of several frying shortenings were studied via chemical, physical and sensory analyses. Corn, cottonseed and peanut oils, and cottonseed and soybean liquid shortenings were tested under static heating conditions, while peanut oil, and cottonseed and soybean oil liquid shortenings were evaluated under commercial frying conditions. The research had two objectives: to evaluate the relative stability of the various shortenings under both heating condition; and to evaluate new or modified quality assessment methods which would provide early prediction of heat abuse for the fast-food industry. Six of the conducted analyses were conventional or modified: free fatty acids; polar components; gas chromatograph volatile profiles; viscosity; FoodOil-Sensor; and sensory. Three were new: contact angle; high temperature; and high-temperature gas chromatographic analysis of triglyceride; and polar component % as determined by high-performance thin-layer chromatography (HPTLC). Under static heating conditions, varying heating periods or shortening types had significant (P<0.000l) effects on the resulting data of the following tests: free fatty acids; polar component; total volatiles; dielectric constant; viscosity; polar component % measured by HPTLC; contact angle; and sensory analysis; but heating time had no significant effect on triglyceride profiles Under commercial frying conditions of chicken nuggets and filets, heating time had significant effects on changes in the dielectric constant; free fatty acid %; viscosity; contact angle; and sensory rating; also it had a significant effect on the polar component % under chicken nugget frying conditions only. Furthermore, heating time had no significant effect on polar component % under chicken filet frying conditions and on polar component % by HPTLC under both frying conditions Cottonseed oil liquid shortening had sensory scores equal to peanut oil under static and commercial frying conditions even though peanut oil exhibited a greater chemical and physical stability. Soybean oil liquid shortening had an objective quality identical to peanut oil, however, its subjective quality was lower. Cottonseed oil liquid shortening had better flavor but less objective stability than soybean oil liquid shortening The cut-off quality level for the shortenings was not reached, because all the shortenings were discarded after seven days of use which was before the onset of significant-quality deterioration. The best on-site index of shortening stability was the FoodOil-Sensor reading (dielectric constant) which was followed by the free fatty acid test. / Ph. D.

The demand for deep fried chips by public and the number of people entering the fast food industry in the form of fast food outlets has increased tremendously. Frying oils are very expensive and are the most important ingredient used in the preparation of fried foods. Due to high oil costs and lack of knowledge, frying oils are used to their maximum. This has resulted in the abuse of deep fried chip cooking oils. The overall quality of the deep fried chip cooking oil used in the South Central Operational Entity of the eThekwini Municipality is not known but abused cooking oils have been identified by Environmental Health Practitioners (EHP's) during routine inspections of fast food outlets. Considering all of the above, the objectives of the proposed research were: (l) Determine the overall prevalence of the use of abused deep fried chip cooking oils at fast food outlets in the South Central Operational Entity of the eThekwini Municipality. (2) Determine in which supervision areas in the South Central Operational Entity the use of abused cooking oil is most prevalent. (3) Determine current/reported practices in preserving the quality of chip oil. (4) Make appropriate recommendations to owner/managers of the fast food outlets and to Environmental Health Practitioners. The study design was observational utilizing a Rapid Epidemiological Assessment (REA) technique, with both a descriptive and analytical component. All fast food outlets making deep fried chips in the South Central Operational Entity registered with the eThekwini Health Department at the time of the study were included in the study population. The Lot Quality Assurance Sampling (LQAS) method was used to determine the overall prevalence of the use of abused oil and to determine supervision areas reached the predetermined service target. A total of 100 fast food outlets were sampled. An oil sample from each fast food outlet, which was taken and sent to a laboratory where an Oxifrit Test was done on every oil sample taken. The Oxifrit Test was the benchmark in this study. EHP's of eThekwini Municipality collected further data by means of an observational checklist and a closed-ended questionnaire, which aimed to establish cooking oil preservation practices. The study revealed that 60 of the outlets had oil that was acceptable whereas 40 had oil that was unacceptable (abused oil). In the multivariate analysis the only factors significantly associated with abused oil were the condition of the fryer and frequency of oil change. Supervision Areas 6, and 4 had more abused deep fried chip cooking oil than average in the South Central Operational Entity. For further prioritization, Supervision Areas 6 and 4 fell below the decision rule for majority of acceptable oil preservation practices, thus Supervision Areas 6 and 4 will be targeted for intervention. Intervention will include education, monitoring and ultimately enforcing the law by EHP's to ensure safe use of deep fried chip cooking oil in the South Central Operational Entity within eThekwini Municipality. / Thesis (M.P.H.)-University of KwaZulu-Natal, 2006.