STORAGE AND TEMPERATURE EFFECTS ON APPEARANCE AND TEXTURAL CHARACTERISTICS OF CONVENTIONAL MILK YOGURT

ABSTRACT The effects of storage days (0–56) and temperature (4.4, 7 or 10C) on appearance and textural sensory characteristics of conventional milk yogurt were evaluated. Covariate analysis determined the effects of storage days, temperature and their interaction on 20 sensory variables. Time–temperature interaction and temperature effects were not significant for any sensory response. The sensory variables significantly affected by time were: five of 10 appearance attributes (color description, brightness, evenness, particle intensity, distribution) and six of 10 texture attributes (hand‐felt [HF]: slipperiness, ropiness, firmness; mouthfelt [MF]: viscosity, slipperiness, firmness). Color, particles and distribution increased in intensity over storage and temperature. Slipperiness and firmness increased for both HF and MF textures. Ropiness HF and viscosity MF increased over time. Correlation analyses within each of the two sensory groupings included only those significantly affected by time. Principal component analysis was moderately effective at reducing dimensionality. PRACTICAL APPLICATIONS Appearance and textural attributes of conventional milk yogurt and the effects of storage time and temperature can be monitored using descriptive analysis. Measurement of yogurt's textural attributes includes both mouthfelt and hand‐felt attributes that are equally important to the overall quality of yogurt. This research adds dimensionality to the descriptive textural attributes of yogurt by evaluating both sensory categories. The changing pace of food and dairy science demonstrates the need for descriptive knowledge that can be transferred easily into predictive knowledge. Dairy manufacturers can refer to descriptive studies to characterize the sensory attributes of yogurt at a specific age or storage time to determine marketability of the stored product. Consumers can be critical of the perceived sensory characteristics of foods, thus making it additionally important for the dairy industry to monitor the quality and acceptability of conventional milk yogurt.