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

Nidia Casas-Forero,Guillermo Petzold,Patricio Orellana-Palma

doi:10.1590/fst.29819

Nidia Casas-Forero, Guillermo Petzold + Show 1 more

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https://doi.org/10.1590/fst.29819

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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.

Highlights

In general terms, the concentration process is an important unit operation due to reduce several production costs such as storage, transportation, packaging and distribution costs, since concentrated samples occupy less volume and weight, as well as increased product foods’ shelf-life
In centrifugal block freeze concentration (CBFC), the concentrate solutes increased progressively compared with the fresh sample (≈12 °Brix), with final values close to 22, 33, and 44 °Brix after the first, second, and third cycles, respectively
From a practical point of view, the cryoconcentrate results were slightly superior to those obtained previously in our laboratory with other fruit juice samples such as pineapple juice (Petzold et al, 2015) and orange juice (Orellana-Palma et al, 2017b) under comparable conditions, in which the final concentration values increased until 42 °Brix in the final cycle

Summary

Introduction

The concentration process is an important unit operation due to reduce several production costs such as storage, transportation, packaging and distribution costs, since concentrated samples occupy less volume and weight, as well as increased product foods’ shelf-life. The high temperatures applied produce undesirable effects in the final food products due to the degradation of important components, and leads to consumer dissatisfaction. It has some disadvantageous such as high amount of energy to remove water (2260 kJ/kg), high installation and operating costs, and long processing time (Ling et al, 2015). Various studies have shown the negative evaporation effects in thermolabile and thermostable components applied to pomegranate, black mulberry, sour cherry and blueberry juices (Dincer et al, 2016; Elik et al, 2016; Sabanci & Icier, 2017)

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