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Investigating the Temporal Sensory Characteristics, Liking and Consumer Sensory Perception of Sugar Reduced Yoghurts

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Thesis is embargoed until 1 August 2027(12.65 MB)

Date

2024

Authors

Supervisor

Hamid, Nazimah
Kantono, Kevin

Item type

Thesis

Degree name

Doctor of Philosophy

Journal Title

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Publisher

Auckland University of Technology

Abstract

The present research explores the effect of natural sweetener and fruit puree addition in yoghurts on the temporal sensory characteristics, liking, and consumer perception. The first study focused on assessing the impact of natural sweetener addition in yoghurts in terms of sensory profile, liking, satiety, and post-consumption attributes. Yoghurt samples were prepared using sucrose, xylitol, stevia, and monk fruit that had same sweetness levels. The temporal sensory profile of yoghurts was evaluated using multiple-intake Temporal Dominance of Sensations (TDS). Additionally, measures of dynamic liking, satiety (hunger, thirst, fullness) and post-consumption attributes (perceived healthiness, satisfaction, purchase intent) were also investigated. Results showed that the temporal xylitol-sweetened yoghurt closely resembled sucrose-sweetened yoghurt, without any onset of negative sensory characteristics throughout consumption. In contrast, the yoghurt sweetened with stevia exhibited increased astringency dominance, while the monk fruit-sweetened yoghurt showed increased bitterness and astringency dominance over successive intakes. Panellists liked xylitol-sweetened yoghurt the most, followed by stevia and monk fruit. Sweet attribute positively influenced liking in monk fruit-sweetened yoghurt, while mouthcoating, sweet and sour attributes had negative effects on liking in sucrose, xylitol, and stevia-sweetened yoghurts, respectively. In terms of perceived healthiness, satisfaction, and purchase intent, sucrose-sweetened yoghurt received the highest scores, followed by xylitol-sweetened yoghurt. In addition, the consumption of yoghurts sweetened with xylitol, stevia, or monk fruit significantly reduced feelings of hunger compared to sucrose-sweetened yoghurt. The second study investigated the impact of incorporating puree and natural sweeteners (sucrose, xylitol, and stevia) on the temporal sensory profile of yoghurts. The multiple-intake temporal check-all-that-apply (TCATA) approach was used to assess the sensory characteristics, with the goal of minimising the negative sensory characteristics associated with natural sugar substitutes. The TCATA results were analysed using Aligned Rank Transformation (ART)-ANOVA for the first time to identify significant differences in sensory attributes. The findings revealed that as fruit puree concentration increased, especially at lower sucrose levels, attributes like sweetness and fruitiness decreased. Yoghurts formulated with varying concentrations of fruit puree and xylitol displayed more consistent sensory profiles compared to those with sucrose. Increasing the concentration of fruit puree in yoghurts sweetened with low concentration of stevia increased fruity and decreased mouthcoating attributes. Across successive intakes, sweet, sour, creamy, and fruity significantly decreased in yoghurts sweetened with sucrose, xylitol, and stevia. Correspondence analysis showed that sucrose-sweetened yoghurts were associated with fruity, creamy, and mouthcoating attributes, xylitol-sweetened yoghurts with sweet, sour, and astringent attributes, and stevia-sweetened yoghurts with liquorice and bitterness. Yoghurts with lower sucrose or xylitol concentrations and fruit puree had the highest levels of liking. However, the liking for stevia-sweetened yoghurts did not significantly differ, regardless of sweetener and puree concentrations. In the third study, the effect of different concentrations of fruit puree and sweetener (sucrose, xylitol or stevia) in yoghurt was investigated using Response surface methodology (RSM). Multiple-intake TCATA was used to examine the temporal sensory characteristics of the yoghurts. The results provided a comprehensive understanding on how different combinations of puree and sweetener influenced the dynamic sensory profiles of yoghurts. The results indicated that in sucrose and xylitol-sweetened yoghurts, sweetness increased with increasing concentrations of puree (15 to 20%), sucrose (6.75 to 9%) and xylitol (7.5 to 8.75%). However, in stevia sweetened yoghurts, sweetness decreased with increasing puree (10 to 19%) and sweetener (0.15 to 0.18%) concentrations. Increasing concentration of fruit puree in yoghurts sweetened with sucrose (18.5 to 20%), xylitol (15 to 20%) and stevia (10 to 15%) decreased the bitterness of yoghurts sweetened with sucrose (4.5 to 5.5%), xylitol (8.75 to 10%), and stevia (0.15 to 0.20%). Creaminess increased in xylitol and stevia-sweetened yoghurts with increasing puree concentration (15 to 20%), irrespective of the amount of sweetener added. In stevia-sweetened yoghurts (0.15 to 0.20%), astringency decreased and fruitiness increased with increasing puree concentration (15 to 20%). Partial least squares path modelling (PLS-PM) was further applied to investigate the correlation of sensory attributes with liking. Sweet, creamy, or fruity attributes showed a positive correlation with liking in sucrose, xylitol and stevia sweetened yoghurts. These attributes were further used in the optimisation of yoghurts formulated with fruit puree and sweetener. The final study investigated the socio-cultural factors that influenced sugar consumption patterns in three diverse countries: New Zealand, France, and Singapore using the Theory of Planned Behaviour (TPB) framework. In addition, consumer perception and acceptance constructs (sugar consciousness, product label and claims, substitution of sugar with sweeteners, and perceived flavour) were used to further understand participants’ consumption and purchase behaviour towards sugar-sweetened, sugar-reduced, artificially sweetened and naturally sweetened yoghurts. Data for the study was collected using three web surveys conducted in New Zealand, France, and Singapore. The data obtained was analysed using Partial Least Squares – Confirmatory Factor Analysis (PLS-CFA) to develop a unique conceptual framework specific to each country. These models were further validated and measured using Partial least Squares-Path Modelling (PLS-PM) to understand the correlation between the TPB, and consumer perception and acceptance constructs within each country. PLS-PM results showed that perceived behavioural control had a significantly positive effect on behavioural intentions among participants from New Zealand and Singapore. Moreover, the substitution of sugar with sweeteners had a significantly positive effect on the behavioural intentions among participants from France and Singapore. Furthermore, sugar-consciousness was positively correlated with behavioural intentions across all three countries, suggesting that individuals who are more aware of their sugar intake are more motivated to reduce sugar consumption. Notably, the presence of labels and claims showed a trade-off with perceived flavour, among the participants from New Zealand and France. This indicates that the presence of nutritional claims may create the expectation of more negative hedonic attributes. Therefore, researchers skillfully navigate this delicate balance to successfully design and market products that not only meet nutritional demands but also satisfy consumer acceptance of food. Partial Least Squares-Multigroup Analysis (PLS-MGA) was further applied to examine the differences in consumption and purchase behaviour across the different countries. In terms of subjective norms, most participants from Singapore indicated that eating less than recommended portion size of sugar-sweetened yoghurt was strongly approved by people whose opinions they value. In contrast, participants from New Zealand and France had a more neutral stance towards this. A higher percentage of participants from Singapore found it easier to limit their intake of sugar-sweetened yoghurt, even if it was more expensive than yoghurt sweetened with sweeteners, compared to participants from France. Both Singapore and New Zealand participants agreed that they pay special attention to types of sweeteners when making food selection. In conclusion, the findings of this research emphasised the importance of considering both sweetener and puree concentrations when developing products with alternative sweeteners. Overall, the findings from the study offered valuable insights into the complex interplay of fruit puree, sweeteners, and sensory attributes of yoghurts. The socio-cultural factors influencing sugar consumption patterns provides insights into the correlations between various factors and consumer behavioural intentions in different countries. The findings revealed the importance of considering both nutritional and sensory properties when designing and marketing sugar reduced products, as well as recognising the differences in consumer preferences and norms across different countries.

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http://hdl.handle.net/10292/17844

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