Optimization of ohmicsonication conditions for production and evaluation of some processed not-from-concentrate fruit juices / Tarek Gamal Mohamed Abedelmaksoud ; Supervised Sobhy Mohamed Mohsen , Mohamed Mohamed Elnikeety , Aberham Hailu Feyissa

Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Food Science and Technology

In the present study processing of not-from-concentrate (NFC) orange, apple and mango juices by using sonication (S), Thermosonication (TS), ohmic heating (OH), ohmicsonication (OS) and compared to conventional heating (CH) was evaluated. The effect of these technologies on inactivation of polypheneoleoxidase (PPO) and pectinmethylesterase (PME) as the most causing problems in juice processing as well as microbial load (total plate count, mold, yeast and psychrophilic bacteria) were also studied. The effect of these treatments on quality parameters such as ascorbic acid, total phenolic, flavonoids and carotenoids as well as sugar content, electric conductivity and color values were evaluated. Response surface methodology (RSM) was used for optimization of OH and OS parameters, where the effect of OH and OS condtions on PPO and PME activity in the NFC orange, apple and mango juices were evaluated. The effect of storage under modified atmosphere condition (N2 gas instead of air inside the localized bottels) at 2±2{u00B0}C for 8 months on the quality properties of NFC orange, apple and mango juices processed by all treatments were studied. The results showed that the highest inactivation of PPO and PME in NFC orange, apple and mango juices were obtained by OS treatment. No microbial growth was detected for all treatments except for S. The highest ascorbic acid content was obtained with the OS compared to all other treatments except S (insufficient inactivation of both enzymes and microorganisms) being in the following order OS>OH>TS>CH

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