Sub-threshold effects were studied in binary and tertiary mixtures comprising a panel-recognition-concentration odorant and sub-threshold odorant(s). Sub-threshold condition was maintained by controlling the sub-threshold concentration as percentages of subjects' individual detection threshold. The perceived intensities (overall intensity and several descriptors) of recognizable odorants were rated using magnitude estimation. Sub-threshold suppression was common and concentration independent in mixtures comprising odorants with different functional groups. Suppression was observed at the lowest sub-threshold concentration tested (30% level). At sub-threshold concentrations, acetic acid suppressed the perceived intensity of acetaldehyde and ethanol but not vice versa. Acetaldehyde and ethanol, however, suppressed each other when one was at sub-threshold concentrations in binary mixtures. Enhancement was observed in tertiary mixtures containing acetaldehyde at panel recognition concentration and was dependent on sub-threshold concentrations of acetic acid and ethanol. In mixtures that contained aliphatic acids with different carbon chain lengths (acetic acid, propanoic acid and n-butanoic acid), sub-threshold enhancement and suppression depended on concentrations and molecular similarity of mixture components. Sub-threshold effects were not observed when the acids were two carbon-atoms different. 50% and 70% sub-threshold levels caused sub-threshold enhancement; however, higher concentrations caused decrease in intensity. Sub-threshold suppression was observed in mixtures containing n-butanoic acid as a recognizable odorants with propanoic acid at a 10% level in a binary mixture and acetic acid and propanoic acid in a 30%-30% combination in the tertiary mixture. / Graduation date: 2003

This thesis describes a series of experiments concerned with the production of aromatised rice. The end product showed no visible difference from untreated rice, and the cooked product had a perceivable aroma. The aromatisation process used liquid carbon dioxide as a vehicle to deliver the aroma, and eugenol, isoeugenol, methyl eugenol, cinnamyl alcohol and cinnamaldehyde were used as the principle model aroma components. The aromas penetrated the cores of the rice grains, providing a longer period for the aroma compounds to migrate toward the surface and be lost to the open air. The stability of the injected compounds in aromatised rice was investigated, showing that aroma loss was a first-order process, although some model compounds showed evidence of two binding models, with two distinct phases of aroma loss. The strength of aroma binding to rice was further assessed by means of gas-chromatography columns, and the model aroma compounds interacted best with the rice-flour column. Shelf-life studies demonstrated that eugenol and cinnamaldehyde in aromatised rice showed no significant changes after being stored for 6 months in sealed vacuum aroma-barrier plastic bags, and the aromas could be detected by the human olfactory system after the rice had been cooked by boiling and steaming / Doctor of Philosophy (PhD)

published_or_final_version / Zoology / Master / Master of Philosophy

Passive (static) and dynamic studies have shown aroma to be an important aspect of food quality, which can be used to differentiate, classify, and grade foodstuffs, and in some cases it can be used to predict other quality characteristics. Monitoring and control of food aroma changes during food processing can significantly improve the quality of the final product in terms of flavour, color, taste, and overall appearance. Hence, it is a prominent and urgent field of study in the post production systems. / Passive aroma detection of unprocessed foods and dynamic aroma detection during food processing was undertaken using a fast GC analyzer -- zNose. During the study on the passive aroma detection, the aroma of Chinese spirits (Fenjiu) and mango (Mangifera indica L.) fruits, (i.e., liquid and solid states, respectively) was analyzed. In the study of Chinese spirits, aroma profiles of Fenjiu liquor samples of different quality levels were acquired and used for quality classification and prediction. Measurements of dielectric properties of the samples were also conducted to estimate alcohol concentration. In the study of mango fruits, aroma changes of mango samples were monitored during their shelf life and used to evaluate mango quality. Ripening and rots were detected with 80% and 93% accuracy, respectively. / During the study of dynamic aroma detection, a real-time aroma monitoring and control system was developed for use during microwave drying. Aroma signals of a processed food item were detected with zNose and analyzed with a fuzzy logic algorithm to determine the optimal food drying temperature. Phase control was used to adjust the microwave power level to meet temperature requirements. Carrot (Daucus carota L.) and apple (Malus domestica Borkh) were selected as representatives of vegetables and fruits. In carrot drying, samples could be dried in a short time at high temperatures but the interior of some sample cubes was burnt. Drying at a lower temperature extended the drying process, but led to a great loss of aroma in the finished product.' The best results were obtained at 60°C. Based on these results, a fuzzy logic controller was designed and employed to control the drying process according to carrot aroma changes. To investigate the possibility of aroma improvement without zNose assistance, a linear control method was developed whereby a temperature control profile imitated the fuzzy logic control, but aroma control was not included. With these new control strategies, the carrot color and flavour were significantly improved and less time and power were consumed. Similar results were achieved when apple was microwave-dried. Apple aroma was monitored online during microwave drying processes and controlled with similar fuzzy and linear control strategies. Apple color, aroma, and overall appearance remained intact with the new strategies and less time and power were consumed. In contrast to the carrot drying, a different linear temperature profile was required for apple drying in terms of aroma retention.

Animals can associate orosensory characteristics from food with postingestive effects and adjust meal size to prevent energy deficit. By using odor-fasting duration conditioning, two studies were conducted to test the above hypothesis. In the first study, thirteen male and eleven female adult Wistar rats were given 1.5 hours to ingest a casein-based test-meal odorized by either vanilla or chicken flavor prior to a 4-hour short-fast or a 12-hour long-fast. Rats went through the training phase with a pseudo-random sequence of six duplicates of each odor-fasting pairing over four experimental days, followed by an odor preference test. Gender differences may exist regarding hunger perception because only females were capable of adjusting meal size according to the postprandial fast duration. A second study was conducted to examine whether a sugar-rich meal can improve acquisition of anticipatory satiety through memory enhancement. Thirty-two female Sprague-Dawley rats were given either a sugar-rich or a protein-rich test-meal prior to the post-prandial fasts. Rats were conditioned in a similar fashion to the first study except that different odors were used, postprandial fasts were shortened to 3 and 10 hours, whereas training phase was elongated to eleven duplicates and followed by an extinction phase. Both dietary groups acquired the anticipatory satiety. However, probably due to the carbohydrate-induced overeating, the sugar-rich group in contrast to the protein-rich group, exhibited a delayed learning in meal-size adjustment prior to a short fast. The above studies demonstrated the existence of gender and macronutrient differences in food intake regulation.

The responses of the saw-toothed grain beetle, 0ryzaephilus surinamensis to food odours and pheromones were investigated at both sensory and behavioural levels to give an integrated picture of olfaction, and the importance of odours in this species. The sensory capability of the antenna was assessed by a study of the structure, distribution and function of sensilla using SEM and TEM. Seven different sensilla types, including 3 with an olfactory function, were identified, although the total number of olfactory sensilla was low compared with those for mechanoreception. Antennal responses to odours were studied using both the electroantennogram (EAG) technique and single-cell recordings, whilst a 2-choice pitfall assay and a single-insect arena test were used to investigate behavioural responses. Food-produced volatiles from carob pods were found to produce large amplitude antennal responses and attraction in behavioural assays. Analysis of such volatiles by coupled gas chromatography-electroantennography (GC-EAG) demonstrated at least 3 active components, of which one was identified as hexanoic acid. Attraction to food odour was found to vary with insect age, and this correlated with similar variation in the EAG response, suggesting a role for peripheral receptor sensitivity in modulating insect behaviour. Beetle-produced volatiles also caused antennal responses and attraction of conspecific individuals of both sexes, thus acting as an aggregation pheromone. The active components were identified by GC-EAG as (Z,Z)-3,6-dodecadien-11-olide, (Z,Z)-3,6-dodecadienolide and (Z,Z)-5,8-tetradecadien-13-olide. These act as a multicomponent pheromone, with separate antennal receptors for each component. Although no sexual differences in antennal responses were found, consistently more females than males were attracted to the pheromone. This suggested a partial sex pheromone function, as the pheromone was shown to be male-produced. However, the ratio of females:males attracted was found to vary with the blend ratio tested. Thus if males are able to alter the blend they produce, the pheromone may act at different times as either a sex pheromone or an aggregation pheromone. Finally, the functional and evolutionary importance of odours to this insect are discussed.

Capes; CNPq / O aroma de café é constituído por uma mistura de componentes voláteis, os quais podem ser encontrados no óleo obtido na torração do café. O café solúvel, em função das condições de processamento, perde parte do seu aroma que, a princípio, poderia ser reincorporado ao produto pela adição do óleo de café diretamente sobre o produto final. Contudo, alguns trabalhos apontam para dificuldades de se obter bons resultados quando se trabalha com o óleo in natura devido à sua volatilidade e à degradação dos aromas. A incorporação de nanocápsulas contendo o óleo de café pode ser uma alternativa para minimizar estas perdas, pois o polímero encapsulante pode agir como barreira de proteção e promover sua liberação de forma controlada. A proposta do trabalho é a obtenção de nanocápsulas de poli(L-ácido lático)(PLLA), contendo o óleo de café torrado pela técnica de miniemulsificação/evaporação do solvente e validar o método para quantificação do óleo de café por espectrofotometria UV-Vis. Os estudos de validação possibilitaram garantir a qualidade dos resultados obtidos. Formulações com diferentes concentrações de PLLA, óleo e tipos de surfactantes foram valiadas quanto ao tamanho e índice de polidispersão frente à recuperação de óleo. Todas as formulações testadas apresentaram valores de recuperação de óleo acima de 80% mostrando que a técnica é adequada e pode ser considerada uma alternativa promissora para produzir nanocápsulas contendo óleo de café. As análises da composição do aroma das nanocápsulas, que indica a qualidade da porção de óleo encapsulada, mostraram que as nanocápsulas contêm frações de todos os compostos encontrados no óleo. / Coffee flavor is a mixture of volatile components found in the oil obtained from the roasted coffee. Soluble coffee loses part of its aroma due to processing conditions which could be reintroduced to the product by the direct addition of the coffee oil. However, some studies point out difficulties in obtaining good results when working with in natura oil because of the high volatility and the flavor degradation. The incorporation of nanocapsules containing coffee oil could be an alternative to minimize these losses, because the encapsulating polymer could act as a protecting barrier and promote its controlled release. The aim of this work is obtain PLLA nanocapsules containing roasted coffee oil by the miniemulsification/solvent evaporation technique. The spectrophometric UV- Vis method used to quantify the coffee oil was validated. Formulations with different PLLA and oil concentrations and kind of surfactant were evaluated in respect to the average nanocapsules size and polydispersion index and oil recovery. All formulations demonstrated oil recovery values above 80 % demonstrating that the technique is adequate and can be consider a promising alternative to coffee oil nanocapsules production. Flavor analysis nanocapsules composition, which indicates the quality of the encapsulated oil, showed that the nanocapsules contain fractions of all the substances found on the in natura oil.

Capes; CNPq / O aroma de café é constituído por uma mistura de componentes voláteis, os quais podem ser encontrados no óleo obtido na torração do café. O café solúvel, em função das condições de processamento, perde parte do seu aroma que, a princípio, poderia ser reincorporado ao produto pela adição do óleo de café diretamente sobre o produto final. Contudo, alguns trabalhos apontam para dificuldades de se obter bons resultados quando se trabalha com o óleo in natura devido à sua volatilidade e à degradação dos aromas. A incorporação de nanocápsulas contendo o óleo de café pode ser uma alternativa para minimizar estas perdas, pois o polímero encapsulante pode agir como barreira de proteção e promover sua liberação de forma controlada. A proposta do trabalho é a obtenção de nanocápsulas de poli(L-ácido lático)(PLLA), contendo o óleo de café torrado pela técnica de miniemulsificação/evaporação do solvente e validar o método para quantificação do óleo de café por espectrofotometria UV-Vis. Os estudos de validação possibilitaram garantir a qualidade dos resultados obtidos. Formulações com diferentes concentrações de PLLA, óleo e tipos de surfactantes foram valiadas quanto ao tamanho e índice de polidispersão frente à recuperação de óleo. Todas as formulações testadas apresentaram valores de recuperação de óleo acima de 80% mostrando que a técnica é adequada e pode ser considerada uma alternativa promissora para produzir nanocápsulas contendo óleo de café. As análises da composição do aroma das nanocápsulas, que indica a qualidade da porção de óleo encapsulada, mostraram que as nanocápsulas contêm frações de todos os compostos encontrados no óleo. / Coffee flavor is a mixture of volatile components found in the oil obtained from the roasted coffee. Soluble coffee loses part of its aroma due to processing conditions which could be reintroduced to the product by the direct addition of the coffee oil. However, some studies point out difficulties in obtaining good results when working with in natura oil because of the high volatility and the flavor degradation. The incorporation of nanocapsules containing coffee oil could be an alternative to minimize these losses, because the encapsulating polymer could act as a protecting barrier and promote its controlled release. The aim of this work is obtain PLLA nanocapsules containing roasted coffee oil by the miniemulsification/solvent evaporation technique. The spectrophometric UV- Vis method used to quantify the coffee oil was validated. Formulations with different PLLA and oil concentrations and kind of surfactant were evaluated in respect to the average nanocapsules size and polydispersion index and oil recovery. All formulations demonstrated oil recovery values above 80 % demonstrating that the technique is adequate and can be consider a promising alternative to coffee oil nanocapsules production. Flavor analysis nanocapsules composition, which indicates the quality of the encapsulated oil, showed that the nanocapsules contain fractions of all the substances found on the in natura oil.

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