Doctoral Degrees (Food Science)

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Browsing Doctoral Degrees (Food Science) by Subject "Apples -- Sensory evaluation"

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    Quantification of genotypic variation and consumer segmentation related to fruit quality attributes in apple (Malus x domestica Borkh.)
    (Stellenbosch : Stellenbosch University, 2013-03) Van der Merwe, Anreza; Steyn, Willem J.; Muller, M.; Labuschagne, I. F.; Naes, T.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Limited information is available on the apple preferences of the South African consumer market, which is characterised by diverse consumers from different age and ethnic groups with different food preferences. White, coloured and black consumers from different age groups were selected from the Stellenbosch area, Western Cape, South Africa. Consumer preference analysis for apple eating quality and appearance, and descriptive sensory analysis (DSA) were performed on nine commercial apple cultivars. Analysis of variance (ANOVA) conducted on mean preference scores for each age and ethnic group showed that preference generally differed between these groups. However, Ward’s statistical clustering that was applied to the same data set showed that the sociodemographic composition of consumer groups with similar apple preferences is not homogenous. Three consumer clusters were identified with similar preferences for apple eating quality (E1-3) and appearance (A1-3): E1 liked firmness and therefore tolerated sour taste and disliked mealiness. Although E1 liked sweet fruit, they indicated lower preference for sweet fruit compared to E2 and E3. E2 liked sour taste and apple flavour more compared to the other clusters while E3 disliked sour taste and had the highest preference for sweetness. Although coloured and black consumers generally disliked sour taste and E3 constituted a larger proportion of these consumers, the coloured and black consumers who liked or tolerated sour taste constituted approximately 41% of the total consumer population in the Western Cape. White and younger (<26 years) consumers were mostly in cluster E1 liking firm fruit. Peel colour preferred by the appearance preference clusters were: Green and pink bi-colour (A1), green/yellow and red-striped (A2); and red peel colour (A3). Consumers preferred the appearance of cultivars that associated with the eating quality attributes that they liked. When consumers’ preference for the eating quality of five cultivars were analysed during presentation with different levels of visual pictorial information (no, correct and incorrect photograph), mismatches between expected and actual eating quality preference resulted in lower preference scores. Apple breeding is time-consuming and expensive. Comprehensive knowledge of fruit quality parameters that drive consumer preference is required to streamline the breeding process. Eating quality and appearance attributes of four apple breeding families were subjected to instrumental and individual assessment by a trained assessor and DSA by a trained panel. Instrumental measurements could not predict the sensory attributes analysed by the individual assessor. Sensory textural attributes, apple flavour and sweet taste as quantified by DSA and instrumental measurement of titratable acidity (TA) and total soluble solids (TSS)/TA, but not TSS, could predict consumer preference. The assessor responsible for individual assessment could not predict the preference of the total consumer group. A quantitative genetic analysis of the data was carried out to quantify within- and between-family variation using ANOVA, variance components and heritability estimates. Variation between families was shown for attributes relating to colour and acidity, but not for sweet taste, TSS and apple flavour. Strong genetic control that was generally shown for colour attributes predicts a rapid selection response. Most attributes were inherited quantitatively, but TA showed complicated inheritance mechanisms.