Quality changes of green vegetable smoothies during shelf-life

Abstract

The health-promoting benefits of the Mediterranean diet are related to consumption of fruits and vegetables, which are important sources of phytochemicals such as phenolics, carotenoids and vitamin C. Smoothies are an excellent solution to ingest these health-promoting compounds in an easy way and increase fruit and vegetable consumption. Two different fresh green vegetable smoothies, V1 (tomato, carrot, broccoli and spinach, making up 90% of the composition) and V2 (90% cucumber and broccoli), were lightly processed with a mild heat treatment. Fresh blended unheated smoothies were used as controls. Physicochemical, sensory, microbial and nutritional/bioactive (vitamin C, phenolics, antioxidant capacity, carotenoids and chlorophylls) and quality analyses were studied during 7 days at 5 or 20°C. Generally, soluble solids content, pH and titratable acidity did not change greatly after 7 days at 5°C. Initial total phenolics content [305.5/292.7 mg gallic acid equivalent kg-1 f.w.] was generally preserved throughout storage. Initial total vitamin C contents (79/155 mg kg-1 f.w.) showed 58-56% reduction even after the heat treatment, while a progressive decrease was generally observed, which was remarked in fresh blended smoothies. In conclusion, fresh blended green vegetable smoothies can preserve good quality for a week at low temperature, while a mild thermal treatment may extend the shelf-life, but will influence some quality attributes. Further studies should enhance smoothie composition and time-temperature heat treatment parameters for optimized minimal processing and extended shelf-life.