Freshness indicator selection and monitoring of red paprika (Capsicum annuum L.) based on volatile organic compounds (VOCs) analysis using an electronic nose

Red paprika (Capsicum annuum L.) quality maintenance during storage and distribution is crucial, with storage temperature significantly impacting physiological changes and freshness. This study evaluated the effects of two storage temperatures (10 °C and 20 °C) on red paprika quality attributes and aimed to identify freshness indicators through volatile organic compounds (VOCs) analysis using a non-destructive electronic nose (E-nose) system. Among the quality changes, color (a* value), firmness, and microbial growth progressed more rapidly at 20 °C. During ripening, total polyphenol and carotenoid content increased, while vitamin C decreased with storage. E-nose analysis identified 14 major VOCs, including alcohols, aldehydes, esters, ketones, and sulfur-containing compounds, showing distinct volatile profile changes. Freshness-related VOCs (e.g., pent-1-en-3-ol, 1-hexen-3-one, L-carvone) were predominant in the early storage stage. As ripening progressed, related indicators emerged sequentially for ripening (e.g., 1-hexanol, hexanal), overripeness (e.g., 2-methylbutane, 5-methylfurfural), and spoilage (e.g., methanethiol). Multivariate and correlation analyses revealed that as storage duration increased, quality attributes such as a* value, total polyphenols, and carotenoids, as well as spoilage-related VOCs (methanethiol, 2-methylbutane), showed positive correlations. Conversely, b* value, firmness, vitamin C, and freshness-related VOCs (pent-1-en-3-ol, 1-hexen-3-one, L-carvone) exhibited negative correlations. These findings demonstrate that specific VOCs detected by E-nose technology can serve as effective indicators for assessing red paprika freshness and storage condition. This can be utilized for real-time quality control of paprikas during storage and distribution.