An Aroma Precursor-Based Approach to Improving the Sensory Quality of Thermally Treated Watermelon Juice

Watermelon juice (WJ) is not widely consumed commercially in most countries due to the change in its sensory properties after thermal treatment, despite its attractive color and high lycopene content. To reveal the effect of heat on WJ, the sensory properties, aroma compounds, amino acids, fatty acids, hydroxymethyl furfural (HMF), lycopene content, and microbiological load analyses were carried out. Among them, HMF-(-0.576), leucine-(0.500), lycopene-(0.539), nonenal-(0.524), and nonadienol-(0.506) were correlated with the aroma and/or overall acceptance scores obtained during sensory evaluation. The mathematical models describing the changes in watermelon juice components as a function of thermal processing parameters were established and validated (error ≤ 8.7%). The optimum pasteurization conditions were determined to be 84°C and 1 min to obtain WJ (desirability: 0.844), which have a higher acceptability, better aroma, and sufficient microbial reduction. The concentrations of nonenal, hexanal, and 6-methyl-5-hepten-2-one, 2-decenal decreased with increasing temperature and duration of pasteurization, unlike those of dimethyl disulfide. The variations in 6-methyl-5-hepten-2-one and 2-decenal concentrations as a function of thermal treatment conditions exhibited similar trends. Leucine concentration was influenced to a greater extent by processing time compared to temperature. HMF formation in WJ was more pronounced than that of pasteurization time. Additionally, intensifying the pasteurization conditions led to an unfavorable change in all sensory attributes, contrasting with its effects on HMF and linolenic acid levels.