Combined effect of UV-C light and mild heat on microbial quality and antioxidant capacity of grapefruit juice by flow continuous reactor

LA CAVA, ENZO L.; SGROPPO, SONIA C.

FOOD AND BIOPROCESS TECHNOLOGY

SPRINGER

Lugar: Berlin; Año: 2019 p. 1 - 9

1935-5130

The efficacy of combined UV-C radiation (39.6 J/L) and mild heat (65.0±3.0 ºC) on the inactivation of aerobic mesophilic and yeast/molds in grapefruit juice (GFJ) (pH: 3.12, °Brix: 9.6, 2500 NTU, absorption coefficient: 42.9 cm-1) using a flow continuous reactor was investigated. Changes in microbial load, ascorbic acid and total phenols content, antioxidant capacity, pH, acidity, °Brix and color were evaluated during 28 days at 4.0±1.0 °C. The spoilage microorganisms were inactivated due to the synergistic effect of both technologies, but the ascorbic acid (74%) and phenol (14%) contents were considerably reduced, with losses of antioxidant capacity (DPPH?=19% and ABTS?+=16%). During storage the ascorbic acid level and antioxidant capacity gradually decreased. On the other hand, the treated GFJ did not show microbial growth while the untreated GFJ reached more than 4 logs CFU/mL. Conversely, no changes (P < 0.05) in the physicochemical parameters were observed. Principal component analysis discriminated among the antioxidant compounds and physicochemical properties of the untreated and treated GFJ during storage. Application of UV-C in a Teflon-coil reactor combined with mild heat resulted in a longer microbial shelf-stability in the GFJ and was able to maintain the physicochemical properties of the juice unchanged during 28 days of storage. Hence, this process can be effectively applied as a combined method to ensure microbial quality.