Effects of new packaging solutions on the shelf-life of fresh raspberries

Red raspberries (Rubus idaeus L.) are highly appreciated for their aromatic taste and healthy nutrient components. Post harvest life of raspberries is limited due to their high respiration rate, loss of firmness and freshness and susceptibility to fruit rot. The aim of this research was to evaluate the effects of various packaging solutions on physico-chemical (firmness, color, soluble solids, weight loss, pH), nutritional (ascorbic acid, total phenolics, anthocyanins and antioxidant activity), aromatic (e-nose) and visual (damaged berries) characteristics during storage at +4°C up to 7 days. A mother-bag system containing multiple PET tray units of red raspberries was tested. Plastic materials with low (LDPE) and high (LDPE/EVOH/LDPE) gas barrier and a biopolimeric film (PLA) with medium gas barrier were used. Again, a micro perforated stretch film (PVC) was used to wrap the tray unit. All the trials were compared to the control sample stored in rigid macro-perforated PET tray with lid. Results show that the most sensitive parameters for the assessment of raspberry decay are percentage of damaged berries, weight loss, fruit softening and the aromatic profile evolution. Soluble solids, pH and color did not change significantly and did not depend on the packaging. Ascorbic acid, total phenolics and anthocyanins increased in the first 2-4 days of storage, then subsequently decreased, with no influence of the packaging. All samples showed a clear loss of firmness after 4 days of storage, which was maximally reduced in the case of LDPE/EVOH/LDPE and PLA package. The aromatic profile, evaluated by e-nose, changed in the course of storage and was influenced by the packaging used: raspberries stored in low barrier packaging materials (PVC and LDPE films) had an aromatic evolution similar to the control, whereas berries stored in the medium and high barrier materials (PLA and LDPE/EVOH/LDPE) evidenced important changes in the aromatic profile, related to the fermentative phenomena promoted by low O2 and high CO2 concentrations in the package.