Improving the Overall Quality and Safety of Fruit and Vegetable Smoothies During Refrigerated Storage Through Gamma Irradiation and Natural Antimicrobials

Abstract

As the market of natural fruits and vegetable (F&V) beverages constantly grows, there is a rising interest in alternative preservation methods, like non-thermal technologies and natural preservatives, to inactivate detrimental factors while providing fresh-like quality characteristics. This study aimed to evaluate and select a treatment combining gamma irradiation (GI: 0, 0.5, 1 kGy), nisin (0, 50,100 UI/mL) and green tea extract (GTE: 0, 0.2%) in order to improve and preserve the microbiological and nutritional quality of a mixed F&V smoothie, extending its shelf-life and ensuring its safety. A radioresistance study positioned Listeria innocua as the design microorganism. The combination of 1 kGy of GI with 50 or 100 IU/mL of nisin effectively reduced Listeria counts by over 5 log, maintaining their counts below the detection limit during 28 days of refrigerated storage. Irradiated samples showed significant reductions (p < 0.05) in deterioration enzymes, without altering the smoothie's physicochemical characteristics and color. Moreover, the combination of 1 kGy of GI and 100 UI/mL of nisin extended the microbiological shelf-life by 21 days. Although irradiation reduced betacyanin content, combining it with GTE (0.2%) achieved excellent stability for these compounds. GI caused increases (10%) in the content of total polyphenols (TPC), although the antioxidant capacity was similar to the control. Moreover, samples added with GTE exhibited TPC, DPPH, and FRAP values of 6.5, 11.5, and 8.5 higher than control, respectively. Therefore, the GI, nisin, and GTE combination produces a safe smoothie with outstanding microbiological, physical, chemical, and nutritional attributes.