Theses and Dissertations (Consumer and Food Sciences)

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    South African consumer knowledge of the current paediatric food-based dietary guidelines
    (University of Pretoria, 2024-02-16) Hoffman, Marinel; Pretorius, Adeline; Marx-Pienaar, Nadene J.M.M.; rochellevanvei@gmail.com; Van Veijeren, Rochelle
    The co-existence of undernutrition, overnutrition, and micronutrient deficiencies constitutes what is known as the Triple Burden of Malnutrition. While the perception may persist that this phenomenon predominantly affects lower-income communities within developing nations, it is crucial to acknowledge its impact on consumers across all settings. Contributing factors extend beyond resource scarcity, often related to lower-income groups, and also encompass a lack of awareness of proactive measures. Within the framework of the United Nation’s second Sustainable Development Goal (SDG) the “Zero Hunger” initiative strives to reduce the Triple Burden of Malnutrition by 2023. However, this goal will largely be missed if current consumer ignorance toward proactive measures endures. The Paediatric Food-based Dietary Guidelines (PFBDGs) are available to caregivers as an educational tool that has the potential to make targets, such as the second SDG, more realistic. Among the most vulnerable to the Triple Burden of Malnutrition are young children aged 0-5 years, whose nourishment directly depends on their caregiver’s competence toward feeding. Although there are various proactive measures in place, such as the abovementioned guidelines, caregivers often put the health of young children at risk due to overestimating their abilities. The situation is described by the Dunning-Kruger Effect (DKE), which is a cognitive bias whereby people with low capability regarding a certain domain tend to overestimate their abilities or knowledge. The DKE theory suggests that overconfidence gradually decreases as one’s accurate knowledge of a specific topic of interest increases. A threshold is eventually reached, where confidence and competence increase in a favourable direction and limitations are recognised and admitted. DKEs can be harmful, especially in the light of young, vulnerable children. Such occurrences will consequently contribute to the country’s prevalence of the Triple Burden of Malnutrition. This study therefore aims to investigate the possibility of DKEs amongst South African caregivers when it comes to young child feeding by comparing their subjective knowledge with objective knowledge (i.e. the PFBDGs). If the subjective evaluation surpasses objective criteria, a DKE is recognised, which underscores the need for consumer education of proactive measures, such as the PFBDGs, in this context. A structured, self-administered questionnaire was designed and distributed to consumers electronically through a link that could be accessed on an internet-connected device. Data was conveniently collected throughout Gauteng by strategically focusing on areas with a significant concentration of participants meeting the predefined inclusion criteria. The inclusion of the sample was driven by the prerequisites of being a caregiver of one or more children under the age of five, residing in Gauteng, and being over 18 years old. Overall findings indicate that the vast majority of consumers were largely unaware of the PFBDGs. A significant 61% of consumers reported their unfamiliarity with the PFBDGs, highlighting a crucial requirement for heightened awareness efforts. It is essential to make this proactive approach better available to ensure all consumers can fully capitalise on its benefits. Retailers bear a corporate responsibility of assisting consumers in making well-informed decisions. An effective strategy is to enhance the accessibility of the PFBDGs to consumers by incorporating direct links to the guidelines on the packaging of food intended for young children. Subjective knowledge scores were collected with a 5-point Likert scale, and consumers were asked to rate their level of knowledge out of five for each dimension of the PFBDGs. The objective knowledge of the PFBDGs was tested with a 5-point ‘true’ or ‘false’ questionnaire. This approach enabled the calculation of total mean scores i.e. subjective knowledge and percentage scores i.e. objective knowledge which received a rating ranging from poor to excellent. The outcomes facilitated a comprehensive comparison to determine whether an overall DKE existed. The investigation delved into each dimension of the PFBDGs, allowing for a detailed comparison between subjective and objective knowledge to pinpoint specific areas where DKEs may be present. Interferential statistics strengthened these results through ANOVAs and Multiple Comparison tests. This analytic approach not only facilitated the identification of possible influential factors or predictors of consumers’ subjective and objective knowledge but also enabled the precise identification of demographic groups with a heightened requirement for education on proactive measures. Overall, the subjective knowledge outcome (M = 3.2) was aligned with the objective criteria (58.9%), and both knowledge fields across all dimensions were of average quality. The key findings from the subjective knowledge assessment indicated that a significant number of respondents held an inflated perception of their knowledge. Respondents seemed to rate their knowledge of the Feeding Practices (M = 3.26) and Hygiene (M = 3.6) dimensions of the PFBDGs as higher than average. Nonetheless, a contrast emerged when comparing the subjective evaluations with the objective knowledge scores. The latter provided an accurate reflection of the consumers’ actual knowledge which was of poor quality for Feeding Practices (46.23%) and average quality for Hygiene (52.08%), suggesting DKEs within these fields. In essence, even though an overall DKE was not determined, an overestimation of knowledge was particularly identified within the Feeding Practices and Hygiene fields. The study’s outcomes inspired focus toward policymakers to adhere to their corporate responsibility by focusing education on the identified fields most in need of intervention. By tackling concern areas in young child feeding, targets such as the Zero Hunger SDG can significantly be amplified. This can lead to a reduction in the harsh effects of the Triple Burden of Malnutrition among South Africa’s youngest and most vulnerable generation. Keywords • Dunning-Kruger Effect • Objective Knowledge • Subjective knowledge • Sustainable Development Goals (SDGs) • The Paediatric Food-based Dietary Guidelines (PFBDGs) • Triple Burden of Malnutrition
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    Survival of oxidative stress-adapted Bifidobacterium spp. in yoghurt
    (University of Pretoria, 2024-07-12) Buys, E.M. (Elna Maria); Sibanda, Thulani; ursulathomashoff@icloud.com; Thomashoff, Ursula Louise
    Bifidobacterium species are prominent constituents of the gut microbiota of healthy humans whose presence in the gut is linked with several health benefits. The supplementation of Bifi- dobacterium spp. as a probiotic through foods such as yoghurt is considered to be an effective way of sustaining a healthy gut microbiome and preventing gut dysbiosis. However, the ability to maintain the viability of Bifidobacterium spp. above the recommended therapeutic dose during the production and storage of yoghurt remains challenging due to its susceptibility to oxidative stress. This study aimed to investigate the effect of oxidative stress adaptation treatments on the physiological responses of three Bifidobacterium species, B. bifidum, B. breve and B. animalis subsp. animalis. The study also sought to isolate stress-adapted Bifidobacterium spp. variants and subsequently investigated their survival and viability during yoghurt manufacturing and storage shelf-life. Cultures of B. bifidum, B. breve and B. animalis were subjected to a sublethal (0.4 mM) hydrogen peroxide (H2O2) treatment followed by exposure to lethal (1 mM) H2O2 treatments across three successive generations. Membrane integrity and intracellular oxidation states of the H2O2-treated cells were evaluated using flow cytometry (FC) and fluorescent staining with SYTO 9 (S9) coupled with propidium iodide (PI), and CellROX® Green (CRG), respectively. The H2O2 treatments improved membrane integrity in B. breve and B. animalis, but increased intracellular oxidation states in all three Bifidobacterium species. Furthermore, the H2O2-treated cells were subjected to a lethal H2O2 challenge(30 min; 1 mM H2O2) before combined FC analysis of membrane integrity and intracellular oxidation states using CRG with PI. Results showed that the H2O2 treatment had no effect on B. breve while improving the membrane integrity retention of B. bifidum, indicating potential adaptive changes that mitigated oxidative damage. B. animalis had the most distinct response in maintaining membrane integrity in an oxidised intracellular state, potentially reflecting the species’ intrinsic oxidative stress tolerance. The morphological and ultrastructural characteristics and stress responses of stress-adapted Bifidobacterium cells were examined us- ing scanning and transmission electron microscopy (SEM and TEM). B. bifidum consistently expressed extracellular vesicles (EVs), affecting the cell surface texture and possibly indicating disrupted cell division and granule formation – features that were enhanced following the lethal H2O2 challenge. Further adaptations and responses observed in Bifidobacterium spp. included cellular elongation, compaction of intracellular components, thinning of its cell envelope and surface texturing. B. breve also underwent cytoplasmic compaction for protection, whereas prominent circumferential rings observed on B. animalis enhanced cell aggregation and stress resistance. Finally, the adapted Bifidobacterium spp. were evaluated for their viability during yoghurt fermentation and storage, and their storage was compared to that of unadapted cells over 28 days. Although the viability of B. bifidum and B. breve declined during yoghurt storage, the stress adaptation resulted in better survival for both species during fermentation, suggesting that the stress adaptation may not be sufficient to protect the species against the combined effects of oxidative and acid stress during yoghurt shelf-life. Consistent with its known intrinsic stress tolerance, B. animalis maintained stable viability counts during yoghurt fermentation and storage. Bacterial viability was also determined using a novel propidium monoazide-quantitative polymerase chain reaction (PMAxx-qPCR) method. Interestingly, this culture-independent technique showed that all three Bifidobacterium spp. remained above the probiotic minimum level (6 log CFU/g) throughout storage. The results suggested a significant loss of culturability for some Bifidobacterium species and the potential transition into a viable but non-culturable (VBNC) state. Thus, the PMAxx-qPCR method may be a feasible option for accurate probiotic viability quantification that can account for cells in a VBNC state. The study shows that exposing B. bifidum, B. breve, and B. animalis subspp. animalis to sublethal- and subsequent lethal H2O2 treatments result in variants that are less susceptible to ROS-induced damage. Furthermore, the study confirms that stress adaptation is a promising method to enhance the viability of Bifidobacterium spp. during yoghurt manufacturing and storage, maintaining recommended probiotic levels throughout the product’s shelf life. This enhanced survival, attributed to an active oxidative stress response induced by adaptation treatments, suggests that oxidative stress adaptation is a feasible method to improve the survivability and functional stability of some probiotic Bifidobacterium spp. in yoghurt. This approach not only supports the maintenance of the minimum recommended probiotic levels (6 log CFU/g viable cells) throughout production and storage but also potentially extends the probiotic shelf-life of the yoghurt.