High pressure processing of carrot juice: Effect of static and multi-pulsed pressure on the polyphenolic profile, oxidoreductases activity and colour

Ultrasonication and thermosonication blanching treatments of carrot at varying frequencies: Effects on peroxidase inactivation mechanisms and quality characterization evaluation

The effects of ultrasonication (US) and thermosonication (TS) blanching at varying frequencies on the carrot peroxidase (POD) inactivation and potential mechanisms were studied. The physicochemical properties were evaluated. Hot water (HW) blanching was used as control. Thermosonication decreased the POD activity to a greater extent, with a dual-frequency of 22/40 kHz showing the most significant effect. The POD-related gene expression was down-regulated by TS, which was contrary to the thermally treated samples. Electron paramagnetic resonance (EPR) spectra revealed that ultrasound-induced radicals from water sonolysis might involve in the POD inactivation. Thermosonication substantially increased the total carotenoid content (TCC). The color analysis showed that thermosonicated samples with a dual-frequency (22/40 kHz) exhibited the maximum values of C* and ΔE, and the minimum value of the whiteness index (WI). The micrographs verified the alterations in TCC and relative electrolyte leakage (REL) of carrot treated by HW, US, and TS.

Thermal inactivation kinetics of peroxidase and polyphenol oxidase from pomegranate arils (Punica granatum L. cv. Wonderful)

Thermal inactivation of peroxidase (POD) and polyphenol oxidase (PPO) in both pomegranate arils crude enzyme extract and fresh juice was investigated. The optimum conditions for reactions were studied using a mixture of guaiacol and H2O2 as substrate for POD and pyrogallol for PPO. The experimental work indicated that optimum pH for both enzymes was 7.0; meanwhile optimum temperature was 30°C for POD and 25°C for PPO. Michaelis-Menten constant (Km) values for POD were 8.33 and 8.00 mM for guaiacol and H2O2, respectively. The Km value was 5.88 mM pyrogallol for PPO. Thermal inactivation results revealed that the inactivation kinetics followed a monophasic first-order model. Activation energies (Ea) were 74.68 and 112.97 kJ/mol for POD and PPO, respectively. Therefore, POD was more heat-stable than PPO. This result is very useful to optimize pomegranate processing (canning or freezing), which represents the most important food industries in many tropical and subtropical regions. PRACTICAL APPLICATIONS: Pomegranate has been attracted more interest due to its antioxidant and nutritional values. For industrial applications, there is a growing interest to obtain pomegranate products such as juice, jams, food supplements, etc. It is well established that the residual activities of endogenous enzymes in either raw materials or processed products may cause loss of quality during storage. Inhibition of enzymatic browning is an important factor to maintain pomegranate quality. This work offers a better insight of characterization of browning enzymes and their thermosatbility, which will be useful to control the possible browning of pomegranate arils during processing and storage. In addition, the results of this study is very important in pomegranate processing where it showed a higher temperature with shortened time can be applied.

Green Chemistry Extractions of Carotenoids from Daucus carota L.-Supercritical Carbon Dioxide and Enzyme-Assisted Methods

Multiple reviews have been published on various aspects of carotenoid extraction. Nevertheless, none of them focused on the discussion of recent green chemistry extraction protocols, especially for the carotenoids extraction from Daucus carota L. This group of bioactive compounds has been chosen for this review since most of the scientific papers proved their antioxidant properties relevant for inflammation, stress-related disorders, cancer, or neurological and neurodegenerative diseases, such as stroke and Alzheimer's Disease. Besides, carrots constitute one of the most popular sources of carotenoids. In the presented review emphasis has been placed on the supercritical carbon dioxide and enzyme-assisted extraction techniques for the relevant tetraterpenoids. The detailed descriptions of these methods, as well as practical examples, are provided. In addition, the pros and cons of each method and comparison with the standard solvent extraction have been discussed.