Abstract
Many older adults fail to meet their daily protein requirements, potentially due to social, physical and medical factors, including sensory and appetite changes. Additionally, our previous research has identified potential sulfurous off-flavours, originating from heat-treatment of protein ingredients, which could play a role in consumer acceptance. This study aims to determine the hedonic impact of these potential off-flavours when added to a dairy beverage, identify the specific off-flavour concentrations which cause rejection by consumers, and lastly investigate difference in acceptance between older and younger consumers. A rejection threshold (RjT) protocol was used, in combination with Best Estimate Thresholds (BET), whereby sulfurous flavours (dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide), and diacetyl were added to create a range of concentrations. 95 participants (younger n = 49, 18–38 years; older n = 46, 60–79 years) tasted 7 pairs of samples (one blank and one with ascending off-flavour concentration) and selected their preferred samples. Sulfurous flavours negatively impacted consumer acceptance, however, the extent to which they impart a negative effect differs between age groups. Younger adults rejected samples containing low concentrations of sulfurous off-flavours (1.55 ppb), however, older adults rejected samples with concentrations over 3 times higher (5.08 ppb). When combined with sulfurous flavours, diacetyl increased the rejection threshold for both groups. In conclusion, these observations imply that a greater quantity of off-flavour may be present before acceptance is reduced in the older consumer group. Moreover, diacetyl demonstrates partial masking abilities of sulfurous off-flavours, and BET gave a more conservative estimate of acceptability. This knowledge will help guide sensory innovation of high-protein beverages for older consumers to support product acceptance and optimal intake.
Highlights
Protein recommendations for healthy adults range from 0.75 g protein/kg body weight/day in the United Kingdom (Department of Health, 1991) to 0.8 g protein/kg body weight/day in Europe and The United States (EFSA Panel on Dietetic Products Nutrition and Allergies, 2012)
When combined into a single group, the group rejection threshold (RjT50) was 2.47 ppb, when participants were separated into the respective age categories, younger adults reached rejection at 1.55 ppb and older adults reached rejection at 5.08 ppb
This study firstly aimed to examine the hedonic impact of potential off-flavour compounds, when added in increasing concentrations to a dairy beverage
Summary
Protein recommendations for healthy adults range from 0.75 g protein/kg body weight/day in the United Kingdom (Department of Health, 1991) to 0.8 g protein/kg body weight/day in Europe and The United States (EFSA Panel on Dietetic Products Nutrition and Allergies, 2012). These recommendations are set irrespective of age, there is strong consensus amongst international bodies and researchers that daily protein requirements for healthy adults aged 65 years and above rise to 1.0–1.2 g protein/kg body weight/day (Bauer et al, 2013; Deutz et al, 2014). Protein-energy undernutrition (PEM), defined as an inadequate intake of energy and protein compared to requirements, is associated with delayed recovery from disease, poorer life quality and increased risk of morbidity and mortality (LeijHalfwerk et al, 2019)
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