Evaluation of the impact of molecular weight and concentration of chitosan on the quality and postharvest longevity of raspberry fruits

Chitosan is a biopolymer with antimicrobial and biostimulatory properties, widely utilised in plant protection and fruit quality enhancement. This research aimed to determine the effect of chitosan on raspberry fruit firmness and assess the relationship between its concentration and molecular weight with yield quality. The study was conducted on raspberries treated with chitosan, applied as a spray, varying in molecular weights (3.3, 5, 500, and 950 kDa) at two concentrations (0.2% and 0.4%). The results showed that chitosan significantly enhanced fruit firmness, with the highest values observed for high-molecular-weight chitosan (500 and 950 kDa). Moreover, low-molecular-weight chitosan (3.3 and 5 kDa) positively influenced fruit mass, whereas high-molecular-weight forms had a limiting effect. It was also found that a higher chitosan concentration (0.4%) led to increased fruit firmness. Previous studies indicated that raspberry fruit quality was most influenced by low-molecular-weight chitosan (3.3 and 5 kDa), while fruit health was most improved by high-molecular-weight chitosan (500 and 950 kDa). Therefore, these chitosan variants were selected for further investigation to determine whether the fruit’s response is primarily driven by molecular weight or if concentration also plays a crucial role. These findings indicate that chitosan may be an effective tool for improving raspberries' quality and postharvest longevity, with its efficacy depending on the appropriate choice of molecular weight and concentration. The application of chitosan may serve as an alternative to conventional fruit protection and preservation methods, contributing to prolonged fruit shelf life and enhanced commercial value.