Masters Degrees (Food Science)

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Browsing Masters Degrees (Food Science) by browse.metadata.advisor "Colling, Janine"

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    Evaluating the influence of germination as a post-harvest treatment on green and roasted South African coffee beans (Coffea arabica)
    (Stellenbosch : Stellenbosch University, 2021-12) Phelps, Stephanie Leigh; Williams, Paul James; Colling, Janine; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Coffee is popular worldwide for its diversity in flavour as well as its beneficial health factors. The coffee bean is produced from Coffea species, of which there are 103 different species. The chosen method for post-harvest processing plays an essential role in the development of the coffee bean’s flavour and aroma. Aside from the hybrid “semi-washed” process, no other processing has been commercially established in the last few decades. Germination has been proposed as a novel, post-harvest treatment for coffee bean processing, specifically for South African coffee beans. Although research has focused on germination and its effects in terms of sprouting seeds, no research has been conducted regarding intentional germination during coffee processing. In this research, liquid chromatography coupled to a mass spectrometer (LCMS) was used to analyze the various chemical components of South African coffee beans (C. arabica, Catuai). For the first study, caffeine, chlorogenic acid, trigonelline, and nicotinic acid were identified as key compounds that play a role in coffee’s flavour profile. These compounds were therefore evaluated to determine if germination influenced their concentration levels. Analysis of Variance (ANOVA) results revealed that the interaction effect of production stage and treatment were not significant (p < 0.05) for all the compounds studied. The main effect of treatment also did not reveal significant differences (p < 0.05) for all the compounds (caffeine (p = 0.48), chlorogenic acid (p = 0.27), trigonelline (p = 0.28), and nicotinic acid (p = 0.44)). The low p-values of chlorogenic acid and trigonelline suggest that perhaps some significance could be observed. However, further sampling a second population would be required to support this since the current research had a sampling size of 24 and only one coffee variety. The influence of germination on the key compounds was not observed for either green or roasted coffees and therefore it is assumed that the flavour profile would remain the same between control and germinated coffee. The second study focused on the entire phenolic profile of the coffee beans to determine if other compounds were being influenced. Principal Component Analysis (PCA) and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) were the chosen chemometric techniques to analyze the data matrices. Normalization, pareto scaling, and automated minor peak-shift alignments were applied as pre-processing techniques to eliminate unwanted variations. However, neither PCA nor OPLS-DA could distinguish significant differences (p < 0.05) between the control and germinated coffee samples. Although the sampling size was sufficient for statistical analysis, the small sample set, from only two harvest years, impacted the reproducibility of the multivariate data analysis. Thus, it is recommended to gain more samples from different harvest years to determine if germination influences chemical composition. The results observed in this study reveal the first evaluation of a South African origin coffee bean and the first study of germination as novel, post-harvest treatment. Although the results suggest that germination has no influence on coffee’s flavour profile, more research should be conducted to include samples from different origins, different species, and different harvest years.