Both consumer and descriptive analyses were used to study the shelf-life of packaged, roasted and ground coffee in order to evaluate the utility of using sensory data in a shelf life model, and to examine the ability of consumers to detect a difference between treated and control samples. Two types of coffee, which differed in bean roast, blend and origin, were evaluated and were referred to as moderate roast and high roast. Samples were packaged under <2%, 9%, or 21% oxygen in airtight laminated foil packages. Over the course of 84 days, the samples were stored in 20��C, 30��C, or 40��C conditions and samples for all treatments were removed throughout the storage. The control samples were packaged at <2% oxygen and stored at -35��C for the duration of the study. Descriptive results illustrated a time trend in the moderate roast coffee along Factor 1, characterized by changes in the attributes of paper aroma, paper flavor, paper aftertaste, wood flavor, body, and oily mouthfeel. This trend resulted in significant differences between the control and the 40��C high oxygen 7 day stored samples in paper aroma (p=0.000) and paper flavor (p=0.000), as well as significant differences between the control and the 40��C high oxygen 49 day stored samples in paper aroma (p=0.002), paper flavor (p=0.000), paper aftertaste (p=0.000), body (p=0.000), and wood flavor (p=0.002). Factor I data from the 40��C high oxygen, moderate roast coffee were utilized in an Arrhenius shelf-life model. A second order model was fit to the data, indicating curvature in relationship for the rate of change over temperature for Factor 1 attributes. The model successfully generated a predictive curve for storage at 40��C. Consumers evaluated 30��C stored samples packaged under high oxygen and stored for either 4 or 7 days, and packaged under low oxygen and stored for 42 and 84 days. Consumer results indicated that it was difficult for consumers to detect differences between the moderate roast coffees. Consumers were readily able to tell significant differences between the high roast coffee treatments and the control sample (p<0.05). / Graduation date: 2000

Read the abstract in the section 00front of this document. / Dissertation (MSc (Agric) Food Science and Technology)--University of Pretoria, 2006. / Food Science / unrestricted

O café solúvel aglomerado é produto da aglomeração do café solúvel em pó. A sua produção envolve etapas de processo cujas variações térmicas modificam qualitativamente e quantitativamente a fração de compostos voláteis responsáveis pelo aroma e sabor do produto acabado. A indústria de bebidas de café considera o sabor e aroma de cereal como um defeito na produção de café solúvel aglomerado. Desta forma, este trabalho objetivou aplicar o planejamento experimental para avaliação dos parâmetros de processo da produção de café solúvel aglomerado em escala industrial. Os efeitos destes parâmetros nos componentes voláteis do café e na intensidade do gosto de cereal foram avaliados através do planejamento fracionário 24-1 com resolução IV. As variáveis independentes estudadas foram temperatura do queimador (TQ), fluxo de ar de processo (FA), temperatura da seção quente do leito (TL) e pressão de vapor (PV). Os resultados do planejamento experimental deram-se pela utilização de análise sensorial conduzida por equipe treinada para a detecção do aroma e sabor indesejado. Adicionalmente, os compostos voláteis foram extraídos pela técnica microextração em fase sólida com amostragem no headspace (HS-MFES), identificados e quantificados por cromatografia gasosa acoplada a espectrometria de massa (CG-EM). O efeito dos fatores estudados foi avaliado mediante análise de variância (ANOVA) com nível de significância de 90% e os resultados expressos por gráficos de pareto. A análise de componentes principais (ACP) foi realizada com o intuito de identificar dentre os compostos que podem conferir sabor e aroma de cereais aqueles tem a maior contribuição e quais as condições de processo ideias para evitar a formação do sabor e aroma de cereal. De acordo com ACP foi constatado que piridina, 2-metoxi-4-vinilfenol, 2,3-dimetilpirazina, 2,5-dimetilpirazina, 2,6-dimetilpirazina, 4-metiltiazol, pirazina, 2-metoxifenol, 4,5-dimetiltiazol contribuem para formação do sabor e aroma de cereal. Também indicou que a aglomeração deve ocorrer conforme TQ=215ºC, FA=250rpm, TL=120ºC e PV=1,2 x100KPa. / The agglomerated instant coffee is the product of the powder instant coffee agglomeration. Its production involves stages of processes whose thermal variations change qualitatively and quantitatively the volatile compounds fractions responsible for the aroma and flavor of the finished product. The coffee beverage industry considers the cereal like flavor and aroma as a fault in the production of the agglomerated instant coffee. In this way, this study had as the aim to apply experimental plan to evaluate the parameters of the processes of the agglomerated instant coffee production on an industrial scale. The effects of those parameters in the coffee volatile components and in the intensity of the cereal taste were evaluated through the fractional 24-1 with resolution IV. The independent variables studied were the burner temperature (BT), the process air flow (AF), the temperature of the fluidized bed hot section (LT) and the steam pressure (SP). The results of the experimental plan were made by the use of sensory analysis performed by a trained team for the detection of the undesired aroma and flavor. Additionally, the volatile compounds were extracted by solid-phase microextractiontechniquewithsampling in theheadspace (HS-SPME), identified and quantified by gas chromatography coupled to mass spectrometry (GC-MS). The effect of the factors studied was evaluated by variance analysis (ANOVA) with significance level of 90% and the results showed by Pareto charts. The principal components analysis (PCA) was made with the aim to identify, among several compounds, those that implies on more cereal flavor and aroma, those which major contribution and which ideal process conditions could be used to reduce the cereal flavor and aroma development. According to PCA, it was found that pyridine, 2-metoxi-4-vinylphenol, 2,3-dimethylpyrazine, 2,5-dimetylpyrazine, 2,6-dimethylpyrazine, 4-methyltiazol, pyrazine, 2-methoxyphenol, 4,5-dimethylthiazol contribute to the development of the cereal flavor and aroma. It was also found that the agglomeration must be according to TQ = 215°C, AF=250 rpm, LT=120°C and EPV = 1,2 x 100 KPa.