Sensory vs instrumental analysis for the shelf-life definition of minimally processed vegetables

Minimally processed vegetables are fresh vegetables processed to increase their functionality without greatly changing their fresh-like properties. The type of process is dependent on the type of produce and includes all the operations necessary to obtain fresh cut ready-to-use and ready-to-eat vegetables, such as washing, peeling, cutting, mixing, packaging etc. In the recent years the market of minimally processed vegetables has grown rapidly because of new lifestyles, increasing purchasing power and growing consumer demand for foods that are healthy, nutritious, convenient to prepare and yet maintain a fresh-like quality. Really the mechanical stresses caused by processing operations promote physiological, biochemical and microbiological changes that can accelerate the process of deterioration and reduce safety, nutritional value and sensory quality of the products even during their shelf-life. The aim of this research was to evaluate the changes in sensory features and, as a consequence, the consumer's acceptability of minimally processed carrots during the shelf-life and to correlate these data with microbial levels and chemical parameters. A basic storage design approach was used. The samples, purchased at a local market, 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. For the microbial analysis total bacteria, total coliforms, lactic acid bacteria, yeasts and molds were counted. Chemical analyses included determination of carotenoid content (HPLC-DAD) and volatile profile (SPME-GC-MS). Finally, sensory analyses involved Descriptive tests and a consumer study coupled to Survival Analysis. Results obtained showed that even if the product safety is guaranteed till the end of the shelf-life, sensory parameters significantly changed during the shelf-life in agreement to chemical modifications. These changes were perceived by the consumers that judged the product quality below the acceptance limit before the end of the labeled shelf-life.