Impact of pulsed magnetic field treatment on enzymatic inactivation and quality of cloudy apple juice
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ORIGINAL ARTICLE
Impact of pulsed magnetic field treatment on enzymatic inactivation and quality of cloudy apple juice Jingya Qian1,2 • Shubei Chen1 • Shuhao Huo1,2 • Chunhua Dai1,2 Cunshan Zhou1,2 • Haile Ma1,2
•
Revised: 11 August 2020 / Accepted: 15 September 2020 Ó Association of Food Scientists & Technologists (India) 2020
Abstract The effects of PMF (5–7 T, 5–30 pulses) on enzyme activity, pH, titratable acidity, soluble solids, color, ascorbic acid, total phenols and antioxidant activity (DPPH radical scavenging activity) of cloudy apple juice were evaluated. PMF inhibited activities of polyphenoloxidase (PPO), peroxidase (POD) and pectinmethylesterase (PME), but PPO was more sensitive to PMF than POD and PME. At the intensity of 6 T with 15 pulses, PPO and POD both exhibited the lowest residual activity (53.22 and 92.96%), while PME showed the lowest residual activity (83.01%) at 7 T with 30 pulses. No significant effect on soluble solids was found under all processing parameters, whereas significant decreases of ascorbic acid were observed at the intensity of 7 T with 5–30 pulses. PMF did not change pH, titratable acidity, color, total phenols and DPPH radical scavenging activity severely. These results suggest PMF can be a potential technology for enzymatic inactivation in apple juice with high retention of quality. Keywords Pulsed magnetic field Apple juice Enzymatic inactivation Quality
& Haile Ma [email protected] 1
School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, Jiangsu, China
2
Institute of Food Physical Processing, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, Jiangsu, China
Introduction Apple juice is a very popular juice in the world, with high nutritional and medicinal value. Cloudy apple juice has a better market value than clarified juice since it is more beneficial to human health. It is a good resource of nutrients such as vitamins, minerals and sugars. It also contains several polyphenols which can prevent many diseases owing to its antioxidant ability. However, enzymatic browning has been addressed as the main challenge for apple juice that changes the color of fresh apple juice to brown, inducing the decline in quality (Sun et al. 2015). It is well known that enzymatic browning depends on oxidative enzymes including polyphenoloxidase (PPO) and peroxidase (POD), which cause browning by catalyzing oxidation of phenolic compounds. Other challenge is cloudy loss in apple juice, which is related to pectinmethylesterase (PME). PPO is an enzyme containing copper and can hydroxylate monophenols to o-diphenols which polymerize with endogenous amino acids or proteins and form brown or dark compounds (Gong et al. 2015). POD that carries a ‘b’type haem is another oxidoreductases and catalyzes many kinds of reactions (Marszałek et al. 2017). POD participates in enzymatic browning reaction when diphenols act as reducing substrate (Chisari et al. 2007). The contribution of POD to browning is not only influenced by hydrogen peroxide, the
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