Sensory characteristics of plain yogurt before and beyond the best before date

Autoren:Majchrzak, Dorota; Rudolph, Charlotte
Abstrakt:To predict the shelf life for a product’s quality accurately, the sensory characteristics during storage should be evaluated. Our senses are usually the most reliable instruments to tell if the product has gone bad. The aim of the present work was to investigate the sensory changes of refrigerated (5ºC) plain yogurt with 1% and 3.6% fat content, over the 42 days of storage, by a trained panel and by a consumer panel. A trained panel assessed the intensity of 26 sensory attributes using Quantitative Descriptive Analysis (QDA) on four specific appointments (before the best before date (BBD), on the BBD as well as 3 and 7 days beyond the BBD). To evaluate the degree of liking of both kinds of yogurt 7 days after the BBD, 117 consumers rated the product’s acceptance with and without information about expiration on a 9-point hedonic scale. In relation to storage time the results of the QDA showed for both yogurts, with a fat content of 1% and 3.6% significant changes (p<0.05) in the intensity of the following attributes: colour, syneresis, sweet odour, creamy odour and flavour, cooked milk flavour, sour, sweet and bitter taste, firmness, mouth coating, astringent and overall aftertaste. The acceptance test indicates that the information about the product’s expiration influenced the consumer’s acceptance negatively but the yogurt was still enjoyed after the “best before date.” Additionally, the low fat yogurt (1%) was rated significant lower (p<0.01) than the product with 3.6% fat. Despite of the changes in the sensory characteristics of plain yoghurt over the storage period, until 7 days after the BBD, both yogurts, with 1% and 3.6% fat content, were still good to eat. Furthermore the results showed that the fat content and the knowledge about the product’s expiration influenced significantly (p<0.01) the consumer’s acceptability.