Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 64-77). Also available via the Internet.

Thesis (MSc Food Sc )--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The oxidative stability of crude, cold-pressed mango kernel fat (MKF) was determined over a period of 240 days using the peroxide value (PV), conjugated diene value (CD) and p-anisidine value (AV) tests. The changes in fatty acid profile were monitored with gas chromatography and the oxidative status of MKF effectively predicted by FT-NIR spectroscopy. Results obtained from the different methods complemented each other and indicated the stable character of mango kernel fat against oxidative deterioration. The fatty acid profile constituted palmitic acid (CI6:0; 8.43%), stearic acid (CI8:0; 34.98%), oleic acid (CI8:1 cis; 48.05%), linoleic acid (CI8:2; 6.60%) and arachidic acid (C20:0; 1.73%). Trace amounts of C16:1 (0.56%), C18:1 trans (0.25%), C18:3 (0.43%), C20:1 (0.25%) and C22:0 (0.40%) were also found. The freshly pressed MKF had a peroxide value of 2.7 meq.kg", CD value of 0.07% and an AV of 2.2 mmol.kg", After 40 days of storage, the peroxide values of MKF stored with and without exposure to a limited amount of oxygen at 5, 15,25 and 40°C increased to 5 meq.kg" and 4 meq.kg" respectively. Emulsification of MKF had a stabilising effect (maximum PV = 2.8 meq.kg'), while exposure to UV light had a catalysing effect (maximum PV = 5 meq.kg'). These maximum values, decreased after 40 days. The CD values of MKF samples stored with and without exposure to oxygen at 5, 15,25 and 40°C increased to 0.18% and 0.16%, respectively at day 40. The CD values of samples exposed to light increased to 0_20% and the emulsified samples showed similar values to that of the MKF samples not exposed to oxygen. The conjugated diene values remained stable after day 40. The p-anisidine values of the MKF samples both stored with and without exposure to oxygen at 5, 15, 25 and 40°C varied between 0.5 and 5 mmol.kg". The weak correlation to the measurement of nonanal, as well as the low levels of 2-alkenals produced by the MKF, resulted in these low and sometimes non-linear values. The peroxide, conjugated diene and p-anisidine values obtained for MKF stored at 25°C over 240 days were low due to the low content of polyunsaturated fatty acids in MKF. This compared favourably with the higher values attained for sunflower, canola and olive oil, which are all rich in polyunsaturated fatty acids. The minimal changes observed in the fatty acid profile of mango kernel fat indicated the stability of the saturated fatty acids (CI6:0 and CI8:0) and oleic acid. In addition, the instability of linoleic and linolenic acids was evident due to oxidative deterioration. A decrease of 7.41% and 12.80% was observed between day 0 and 240 for the C18:2/C16:0 and C18:2/C18:0 ratios respectively. The prediction of the oxidative status of the MKF samples by near infrared spectroscopy were possible after the development of calibration models from a total data set of 300 samples of which one-third was used for independent validation. Principle component analysis (PCA) indicated classification at 0, 40 and the remaining (80 - 240) days. The best calibration model for PV yielded a SEP (standard error of prediction) of 0.46 meq.kg", correlation coefficient (r) of 0.95, bias of 0.02 and a root mean square error of prediction (RMSEP) of 0.46 meq.kg". The CD calibration model had a correlation coefficient of 0.89, SEP of 0.01 %, bias of 0.001 and RMSEP of 0.01% when developed on a data set with no pre-processing applied. The AV calibration had a SEP of 0.32 mmol.kg", bias of 0.03, RMSEP of 0.32 mmol.kg" and rof 0.93. The C18:2 and C18:3 models were built using partial least squares (PLS) regression and the values obtained for SEP were 0.31% and 0.054%, RMSEP 0.32% and 0.05%, bias 0.05 and 0.01 and correlation coefficcients were 0.82 and 0.54 respectively. The calibrations for CI8:1, C18:0 and C16:0 yielded weaker correlations. Good correlations were obtained when calibrating the CI8:2/CI6:0 and C18:2/CI8:0 ratios. / AFRIKAANSE OPSOMMING: Die oksidatiewe stabiliteit van ru, koud-geperste mango kern vet (MKV) (Mangifera indica L.) is oor 'n periode van 240 dae bepaal deur gebruik te maak van die peroksiedwaarde (PV), gekonjugeerde dieen waarde (CD) en p-anisidien waarde (AV) toetse. Die veranderinge in die vetsuurprofiel is gemonitor deur gaschromatografie en die oksidatiewe status van MKV is akkuraat voorspel word deur Fourier transformasie naby infrarooi (FT-NIR) spektroskopie. Die resultate van die verskillende toetsmetodes komplementeer mekaar goed en dui die stabiliteit van mango kern vet teen oksidatiewe verval aan. Die vetsuurprofiel is saamgestel uit palimitiensuur (C16:0; 8.43%), steariensuur (C18:0; 34.98%), oleïensuur (C18:1 cis; 48.05%), linoleïensuur (C18:2; 6.60%) en aragiedsuur (20:0; 1.73%). Spoorhoeveelhede C16:1 (0.56%), C18:1 trans (0.25%), C18:3 (0.43%), C20:1 (0.25%) en C22:0 (0.40%) is ook geïdentifiseer. Die vars geperste MKF het 'n peroksiedwaarde van 2.7 meq.kg", 'n CD waarde van 0.07% en 'n AV waarde van 2.2 mmol.kg" getoon. Na afloop van 40 dae opbergingsperiode by 5, 15, 25 en 40°C het die PV van MKV met 'n beperkte blootstelling aan suurstof na 5 meq.kg" vermeerder, terwyl die waardes van monsters sonder suurstofblootstelling na 4 meq.kg" vermeerder het. Emulsifisering van MKV het 'n stabiliserende effek (maksimum PV = 2.8 meq.kg") terwyl blootstelling aan ultraviolet (UV) lig 'n kataliserende effek (maksimum PV = meq.kgl ) op oksidasie gehad het. Hierdie maksimum waardes het na 40 dae afgeneem. Die CD waardes van MKF monsters opgeberg by 5, 15, 25 en 40°C en met beperkte blootstelling aan suurstof het vermeerder tot 0.18% terwyl die monsters sonder suurstofblootstelling by bogenoemde temperature vermeerder het tot 0.16% na 40 dae. Die gekonjugeerde dieen waardes van die monsters blootgestel aan UV lig het vermeerder tot 0.20%; terwyl die geëmulsifiseerde monsters waardes soortgelyk aan die MKV monsters sonder blootstelling aan suurstof getoon het. Gekonjugeerde dieen waardes het gestabiliseer vanaf dag 40. Die p-anisidienwaardes van MKV monsters opgeberg by temperature van 5,15, 25 en 40°C, met en sonder blootstelling aan suurstof, het varieer tussen 0.5 en 5 mmol.kg". Die swak korrellasie tussen nonanal produksie en p-anisidienwaardes, sowel as die klein hoeveelhede 2-alkenale geproduseer, was verantwoordelik vir hierdie lae en nie linêere waardes. Die peroksied, gekonjugeerde dieen en p-anisidienwaardes wat verkry is nadat MKV by 25°C in 240 opgeberg is, was laag weens die klein persentasie poli-onversadigde vetsure teenwoordig in die vet. Dit vergelyk goed met die hoë waardes wat verkry is vir sonneblom-, canola- en olyfolie wat almal ryk aan poli-onversadigde vetsure is. Die minimale veranderinge in die vetsuurprofiel van MKF dui op die stabiliserende invloed van versadigde vetsure (C16:0 en C18:0) en oleïensuur. Die onstabiliteit van linoleïen- en lineensuur duidelik uit hierdie vetsure se oksidatiewe verval. 'n Afname van 7.41% en 12.80% is waargeneem tussen dae 0 en 240 vir die C18:2/C16:0 en C18:2/C18:0 verhoudings, onderskeidelik. Die voorspelling van die oksidatiewe status van die MKF monsters met behulp van FT-NIR spektroskopie was moontlik deur die ontwikkeling van kalibrasie modelle. 'n Totale datastel van 300 monsters, waarvan ongeveer 'n derde vir validasie aangewend is, is gebruik vir die kalibrasiemodelle. Met behulp van PCA (hoojkomponent analise) kon drie klassifiseerbare groepe by 0, 40 en 80-240 dae onderskei word. Die beste kalibrasiemodel vir PV het 'n standaardfout van voorspelling (SEP) van 0.46 meq.kg", 'n korrellasiekoëffisient (r) van 0.95, 'n oorhelling van 0.02 en 'n standaardfout van voorspelling (RMSEP) van 0.46 meq.kg" gehad. Die CD kalibrasiemodel (geen voorafverwerking) het 'n r van 0.89, SEP van 0.01% oorhelling van 0.001 en RMSEP van 0.01% gehad. Die AV kalibrasie het 'n SEP van 0.32 mmol.kg', oorhelling van 0.03, RMSEP van 0.32 mmol.kg" en r van 0.93 gehad. Die C18:2 en C18:3 modelle is saamgestel deur PLS (partial least squares) regressie. Waardes verkry vir C18:2 en C18:3 was onderskeidelik: SEP 0.32% en 0.05%, RMSEP, 0.32% en 0.05%, oorhelling 0.05 en 0.01 en r 0.82 en 0.54. In die geval van C18:1, C18:0 en C16:0, het die kalibrasies swakker statistiek korrellasies getoon. Goeie korrellasies is verkry tydens kalibrasie vir die C18:2/C16:0 en C18:2/C18:0 verhoudings.

Muitas famílias não têm tempo de preparar bolos caseiros e acabam optando pela praticidade de comprar produtos prontos. A atitude dos consumidores, em relação aos problemas de saúde que podem advir do consumo de alimentos com alto teor de gorduras, é de consumir alimentos formulados de maneira que apresentem menores teores, mas com as mesmas características sensoriais dos produtos originais. O objetivo deste estudo foi determinar o efeito da substituição de gordura vegetal hidrogenada por outros lipídeos (gordura de palma, óleo de soja, óleo de castanha do Brasil, óleo de coco) e por extrato de aveia em formulações de bolos. Foram elaboradas nove formulações contendo farinha de trigo, açúcar, ovo em pó, gordura, água, leite em pó integral, emulsificante, fermento químico e sal, substituindo-se a gordura vegetal hidrogenada pelos diferentes tipos de lipídeos e extrato de aveia. Formulações: (controle) gordura vegetal hidrogenada (GVH) - 100%; (1): gordura de palma - 100%; (2): óleo de soja - 100%; (3): óleo de castanha do Brasil - 100%; (4): óleo de coco - 100%; (5): extrato de aveia - 100%; (6): GVH - 50% + óleo de castanha do Brasil - 50%; (7): GVH - 50% + óleo de coco - 50%; (8): GVH - 50% + extrato de aveia - 50%. Através das análises de textura com probes back extrusion e de compressão (TPA-análise do perfil de textura) pode-se avaliar, respectivamente, o comportamento das massas de bolos e o shelf-life dos produtos finais durante seis dias de armazenamento. Foram feitas avaliações de volume específico, densidade, porosidade, composição centesimal e atividade de água - aw. A análise sensorial com 60 provadores foi realizada utilizando-se as formulações controle, óleo de coco, óleo de castanha do Brasil e extrato de aveia de acordo com a escala hedônica (9 pontos) e intenção de compra. A análise de textura (back extrusion) apontou diferentes comportamentos reológicos, embora todas as formulações caracterizaram-se como fluido dilatante (n>1). O resultado do shelf-life mostrou que o bolo produzido com extrato de aveia obteve melhores características de qualidade. O bolo produzido com GVH apresentou maior volume (2,65 mL/g), menor densidade (0,39 g/mL)e maior incorporação de ar (16,45 mm2). A análise de cor apontou que o bolo elaborado com GVH + óleo de coco apresentou-se mais amarelado (35,94) e o bolo com GVH + extrato de aveia com maior brilho (75,27). A composição centesimal mostrou as variações obtidas de acordo com a substituição de gordura por extrato de aveia e o menor valor calórico (257,62 kcal) para este produto. O resultado de aw mostrou maior valor para a formulação com extrato de aveia (0,94), sendo esperado devido ao maior conteúdo de água da formulação. A análise sensorial, através da avaliação de painel não treinado, indicou que o bolo elaborado com óleo de coco obteve a maior aceitação e, consequentemente, a maior intenção de compra, entretanto, apresentou pouca diferença em relação ao bolo controle. Em geral, os resultados mostraram ótimo padrão de qualidade dos bolos elaborados com a substituição da gordura vegetal hidrogenada, podendo-se assim, obter produtos com outras opções de ingredientes e com agregação de valor nutricional. / Many families do not have time to prepare homemade cakes and usually opt for the convenience of buying ready products. Consumer\'s attitudes regarding health issues, that may arise from the consumption of foods high in fat, is to consume foods that have formulated so low in fat, but with the same sensory characteristics of the original products. The purpose of this study was to determine the effect of replacing hydrogenated vegetable fat for other lipids (fat palm, soybean oil, Brazil nut oil, coconut oil) and oat extract in cake formulations. Nine formulations containing flour, sugar, egg powder, fat, water, whole milk powder, emulsifier, baking powder, and salt were elaborated by replacing the hydrogenated vegetable fat for different types of lipids and oat extract. Formulations: (control) hydrogenated vegetable fat (GVH) - 100%; (1): palm fat - 100%; (2) soybean oil - 100%; (3): Brazil nut oil - 100%; (4) coconut oil - 100%; (5): oat extract - 100%; (6): GVH - 50% + nut oil from Brazil - 50%; (7) GVH - 50% Coconut oil + - 50%; (8): GVH - 50% + oat extract - 50%. The behavior of cakes batters and shelf life of the final product during six days of storage were assessed through the texture analysis with probes back extrusion and compression (TPA-texture profile analysis), respectively. The evaluation of specific volume, density, porosity, chemical composition and water activity - aw was made. Sensory analysis was performed with 60 tasters using the control formulations, coconut oil, Brazil nut oil l and oat extract according to the hedonic scale (9 points) and purchase intent. Texture analysis (back extrusion) showed different rheological behaviors, although all formulations were characterized as a dilatant fluid (n> 1). The result of the shelf-life showed that the cake made with oat extract produced better quality characteristics. The cake produced with GVH showed higher volume (2,65 mL/g), lower density (0,39 g/mL) and greater incorporation of air (16,45 mm2). The color analysis showed that the cake made with coconut oil + GVH presented more yellowness (35,94) and cake with GVH + oat extract presented higher brightness (75,27). The chemical composition showed variations obtained in accordance with the substitution of fat for oat extract and lower caloric value (257,62 kcal) for this product. The result showed higher aw value (0,94) for the formulation with oat extract, it is expected due to the higher water content of the formulation. The sensory analysis, through evaluating untrained panel, indicated that the cake prepared with coconut oil had the highest acceptance and, consequently, the higher purchase intention, although it presented little difference from the control cake. In general, the results showed great standard of quality cakes prepared by replacing the hydrogenated vegetable fat, leading to products with other options of ingredients and with added nutritional value.

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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.

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Biscuits were prepared from eighteen different recipe formulations. The biscuits were made from flour containing 7.53%, 8.99%, and 10.05% protein with 30, 40, and 50 grams of shortening and 0 or 2.2 grams of microcrystalline cellulose (MCC). Biscuit quality was assessed by objective and sensory evaluation. The caloric content of the biscuits was also determined by bomb calorimetry. No significant differences were detected in biscuit volume, crumb and crust color, or tenderness. The biscuits prepared with lower levels of shortening were moister than the biscuits prepared with higher levels of shortening. Wo significant differences were found by sensory panelists with regard to evenness of exterior color, aroma, evenness of cell structure, size of cell structure, interior color, center moistness, tenderness, biscuit flavor, or aftertaste. Flakiness and exterior color were found to be significantly different. Biscuits with added MCC were detected to be less flaky. Biscuits prepared from medium protein level flour and low-shortening with MCC were darker than high-shortening biscuits without MCC. High-protein, high-shortening biscuits with MCC were darker than medium-protein, high-shortening biscuits without MCC. The caloric content of the biscuits prepared with lower amounts of shortening was found to be significantly less than biscuits prepared with the higher levels of shortening. In conclusion, high quality biscuits can be produced from flour of varying protein content with less shortening and without the incorporation of MCC. / Master of Science