Masters Degrees (Microbial, Biochemical and Food Biotechnology)

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Browsing Masters Degrees (Microbial, Biochemical and Food Biotechnology) by Author "Bothma, C."

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    Fruit quality of South African cactus pear cultivars
    (University of the Free State, 2010-06) Rothman, Anna Maria Petronella; De Wit, M.; Bothma, C.
    English: The cultivation of cactus pears requires low input and it has been grown widely in drier areas of South-Africa as fodder crop, particularly for times of serious drought. Cactus pears also serve as a source of inexpensive nutritious food for lower income groups Sugar is the main determent of taste of the cactus pear cultivar and content value range from 10 °Brix to 17 °Brix. Glucose is the predominant sugar with fructose as the second sugar, thus the fruit pulp is very sweet. The pulp of the cactus pear cultivar consists of a high pH value (> 4.5) and low acidity level (0.03-0.12 % ), (SaenzHernandez, 1985; Brutch, 1993; Piga, 2004; Salim, 2009). The aim of this study was to determine the fruit quality of cactus pear fruit. Physical/chemical and sensory quality attributes were evaluated for two agricultural seasons ( 2007 and 2008). The influence of factors such as rainfall and temperature on quality was determined. Furthermore, sensory analysis was used to distinguish among the available 33 cultivars, not only for their taste, but also to establish the cultivar most stable to varying environmental conditions. This study determined whether sensory quality of cactus pear fruit was influenced by the physical/chemical parameters by correlating the physical/chemical data with the sensory analysis. There were highly significant differences observed in terms of physical/chemical composition (p < 0.001) among 33 different cactus pear cultivars in South Africa, for seasons 2007 and 2008. This finding indicated that genetic differences among cultivars as well as seasonal changes have a significant influence on fruit quality. It was evident from this study that not only the cultivar and agricultural season, but also the interaction between the cultivar and season had significant influences on fruit quality. The best preferred cultivar, regarding physical/chemical fruit quality attributes, was Nudosa, performing the best regarding fruit mass and pulp glucose. Messina performed the best regarding 0 Bx. Nudosa and Messina performed the best regarding pulp fructose content, while Blue Motto had the best acidity levels (pH and TA). Sensory analysis, used to determine whether the consumer could distinguish among the available 33 cultivars was done by using the FCP technique and it was clear that the consumers could only successfully distinguish between the two seasons (77.72 %) , but not among the 33 different cactus pear cultivars. The fodder cultivar, Robusta, was an exemption and could be clearly distinguished from the other 32 cultivars. The sensory quality of cactus pear fruit obtained from the consumers was indeed influenced by the physical/chemical parameters. Cultivars like Robusta, Fresno and Nudosa had been significantly influenced by seasonal differences. The physical/chemical data and the sensory attributes were correlated.
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    The relationship between consumer acceptability and descriptive sensory attributes of cheddar cheese, with special reference to free choice profiling
    (University of the Free State, 2009-09-17) Prinsloo, Annelize; Bothma, C.; Hugo, A.; Osthoff, G.
    English: The main aim of this study was to determine whether data, obtained from FCP and using semi-naïve panellists (experienced in descriptive techniques, but no previous experience with cheese), could express the perceptions of South African consumers on Cheddar cheese attributes. Firstly a panel of 220 consumers was asked to indicate their level of acceptance on a nine-point hedonic scale for overall acceptance of 15 Cheddar cheese products, in two locations in South Africa. The 15 Cheddar cheese samples included five retail Cheddar cheeses from four dairy companies, four cheese samples from two culture houses and six experimental cheeses. The ageing period of the 15 cheeses ranged from 60 to 180 days, all being mild Cheddars, except one mature Cheddar cheese. Significant differences (p < 0.05) occurred amongst consumer demographics for consumer acceptability. The number of cheeses showing a significant difference for the different main effects was: gender (two); income (one); population group (three); age (eight); and location (five). For the overall liking attribute, there was a significant difference in acceptance (p < 0.05) between the 15 Cheeses. Fisher’s Least Significant Difference test at a 5% significance level was performed to determine which cheeses differed significantly from one another for overall liking/acceptance. The most liked cheese sample had the highest mean value of 7.16, was aged for 60 days and yellow in colour. The least acceptable cheese had a mean value of 4.75, was aged for 180 days and was white. Free choice profiling (FCP) was carried out in order to investigate how semi-naïve consumers (who had experience in descriptive work and received minimal training on Cheddar cheese) described and perceived different Cheddar cheese samples. This method allowed participants to use their own attributes to describe and quantify the food product. The study used 15 different Cheddar cheeses available in South Africa, analyzed by ten consumers in three replications. The data were analyzed by using generalized Procrustes analysis. The FCP procedure generated between 21 and 42 attributes, with an average of 35, including 16 descriptors on the attribute aroma, 14 descriptors on the attribute texture/appearance, 15 descriptors on the attribute mouthfeel, 20 descriptors on the attribute taste, 18 descriptors on the attribute aftertaste and nine descriptors on the attribute afterfeel. Rubbery texture and sweet, buttery and Gouda taste and aftertaste attributes were some of the important attributes that separated the cheeses in the study. The results from the descriptive profiling method suggested that the FCP method, which is less expensive and time consuming, is an appropriate technique when used with semi-naïve assessors. The relationship between consumer acceptability and descriptive sensory attributes of cheddar cheese were determined by using preference mapping (PM). The results from the PM indicated that two major (but very similar) consumer clusters, showed higher acceptance for cheeses with more ‘young/undeveloped’ attributes. The ‘ideal’ Cheddar cheese, for the South African consumer, can therefore be described as having the following attributes: an aroma characterized by ‘sweetmilk’, ‘Gouda-like’ and ‘buttery’ attributes; a ‘shiny’ appearance and ‘rubbery’ texture; a mouthfeel characterized by ‘rubbery’, ‘fatty’, ‘tacky’ and ‘soft- and/or hardness’ attributes; a ‘Gouda’, ‘buttery’, ‘sweet’ taste; a ‘Gouda’, ‘buttery’, ‘sweet’ aftertaste; and an afterfeel that can be described as ‘fatty coating’ and ‘oily/fatty’. Results from this study seem to support and confirm speculations of some cheese specialists in the dairy industry who have perceived that Cheddar cheese, manufactured and available in the last few years, have showed/exerted more Gouda-like sensory attributes than typical known Cheddar-like attributes. Therefore, the results from the study indicated that data, obtained from FCP and using semi-naïve panellists, successfully expressed the perceptions of South African consumers on Cheddar cheese attributes.