Influence of block freeze concentration and evaporation on physicochemical properties, bioactive compounds and antioxidant activity in blueberry juice

Abstract This study investigated the impacts of centrifugal block freeze concentration (CBFC) and evaporation processes on physicochemical properties, bioactive compounds and antioxidant activity applied to fresh blueberry juice. After three concentration cycles, the solutes were approximately 3.6 times to the initial condition (12 °Brix) and the final color (ΔE*>4.7) was darker than the fresh juice. In all cycles, CBFC obtained higher bioactive compound concentration than evaporation, with values, in the last cycle, close to 610 mg GAE/100 mL, 57 mg M3G/100 mL and 279 mg CEQ/100 mL for total polyphenol, anthocyanin and flavonoid content, respectively, causing a retention over 70%. Similarly, as the cycles progressed, DPPH assay presented values from 1916 to 5700 μmol Trolox equivalents/L, which were higher than those reported by the treatment at high temperatures (1916 to 4600 μmol Trolox equivalents/L), resulting in good antioxidant activity in the cryoconcentrates achieved at low temperatures. Moreover, a significant correlations between CIELab parameters, bioactive compounds and antioxidant activity were observed. Thus, CBFC is an interesting and novel technique to preserve important quality properties from fresh fruit juices.

【摘要】本研究探究了离心式块冷冻浓缩（centrifugal block freeze concentration, CBFC）与蒸发工艺对新鲜蓝莓汁的理化特性、生物活性成分及抗氧化活性的影响。经3次浓缩循环后，果汁的溶质固形物含量约为初始状态（12°白利糖度）的3.6倍，最终色泽的CIE色差ΔE*>4.7，较鲜榨汁更深。各浓缩循环阶段中，CBFC组的生物活性成分含量均高于蒸发组；末次循环时，总多酚、花青素与类黄酮含量分别接近610 mg没食子酸当量/100 mL（gallic acid equivalent, GAE）、57 mg M3G/100 mL与279 mg儿茶素当量/100 mL（catechin equivalent, CEQ），保留率均超过70%。同理，随着循环次数增加，DPPH自由基清除法测得的抗氧化活性值从1916升至5700 μmol Trolox当量/L，高于高温蒸发处理组（1916至4600 μmol Trolox当量/L），低温制备的冷冻浓缩物展现出优异的抗氧化活性。此外，本研究还观察到CIE Lab颜色空间参数、生物活性成分与抗氧化活性之间存在显著相关性。综上，CBFC是一种颇具应用前景的新型技术，可有效保留鲜榨果汁的核心品质特性。