Quality change of minimally processed carrots during the shelf-life by aroma compounds, carotenoids and sensory analysis

In the recent years the market of ready-to-use fresh vegetables have grown rapidly as a result of changes in consumer habits especially referred to the consumption of fresh-cut lettuce and carrots. In general, fresh-cut vegetables are considered to be food items with nutritional and sensory characteristics equivalent to unprocessed products.[1] Really, washing, peeling and cutting operations promote physiological, biochemical, and microbiological changes that can accelerate the process of deterioration and reduce nutritional and sensory value, and thus the quality and the shelf-life, of the products.[2] The aim of this study was to evaluate the changes in chemical and sensory parameters in fresh-cut carrots during their shelf-life. All samples, purchesed at a local market, were from the same production batch . They were kept in their original packaging until analysis that were performed at 0, 1, 3, 6 and 9 days of refrigerated (+ 4 °C) storage since the production. At each day, carotenoid levels and volatile profiles were determined using HPLC-DAD and HS-SPME-GC-MS, respectively, and qualitative descriptive sensory analysis was performed according to ISO 13299:2003(E) using a trained sensory panel. α-, β- and ζ-Carotene, lutein and phytofluene were identified and quantified, with β-carotene (27.32-64.34 mg/kg of fresh weight) and α-carotene (12.90-39.80 mg/kg of fresh weight) accounting for almost the total carotenoid content of carrot samples. The volatile profile were characterized by a prevalence of monoterpenes and sesquiterpenes; other classes of substances, such as alcohols, aldehydes, acids and C13-norisoprenoids, were also identified. The main volatiles were (E)-β-caryophyllene (terpene-like, spicy, woody), (E)-γ-bisabolene (fatty, woody) and γ-cadinene, the latter identified for the first time in carrots. Twelve sensory descriptors referred to visual appearance, texture, taste and odour were evaluated. Statistically significant variations were observed during the nine day of shelf-life in both chemical and sensory parameters. In particular, it was observed a decrease of carotenes after 3 days and, among volatiles, an increase of C13-norisoprenoids deriving from the degradation of carotenoids and a decrease of terpenes and sesquiterpenes responsible of fresh carrot odor. At the same time the sensory attributes “color”, “carrot odor”, “sweet taste” and “fruity taste” decreased, whereas “browning”, “earthy odor” and “earthy taste” increased. Results obtained showed that the variations of sensory scores are in agreement with the changes of chemical compounds responsible of aroma and colour. These alterations should be taken into account for the evaluation of the shelf-life of fresh-cut products.