Ultrasound in orange sweet potato juice: Bioactive compounds, antioxidant activity, and enzymatic inactivation

Abstract

Orange flesh sweet potato contains bioactive compounds which have nutritional and health‐protective values. The aim of this investigation was to evaluate the impact of ultrasound treatment in orange sweet potato juice on physicochemical parameters, β‐carotene, total phenolic, antioxidant activity (ORAC and ferric thiocyanate), polyphenol oxidase, and peroxidase activity. The juice was sonicated for 2, 4, 6, 8, and 10 min, with ultrasonic intensity of 0.24 and 0.66 W cm−2. The sonicated juice showed an increase of β‐carotene content (57%) and a decrease in the percentage of total polyphenol content with values between 4.88 and 14.25%. The antioxidant activity by ORAC was 29.55 µmol TROLOX equivalent mL−1 and the inhibition of linoleic acid oxidation was higher than 94%. Ultrasound treatment showed inactivation of 28.38 and 46.28% for polyphenol oxidase and peroxidase, respectively. Ultrasound technology allowed the achievement of a sweet potato quality juice without compromising the retention of antioxidant compounds. Practical applications Orange fresh sweet potato has minimal industrialization in México. In general there is lack of knowledge about the functional properties that this product may have. This research presents a preprocessing option for the sweet potato that allows the greater extraction and conservation of its bioactive components, such as β‐carotene. Likewise, the potential benefit of sweet potato juice can be obtained by combining it with other juices to increase its palatability and to develop more functional and nutritious products. Once combined the juices they should be subjected to a thermal processing to inactivate enzymes and to extend the shelf life.

Effect of ultrasound and steam treatments on bioaccessibility of β-carotene and physicochemical parameters in orange-fleshed sweet potato juice

“…The antioxidant activity was mainly attributed to non-phenolic compounds, such as β-carotene, but also to the phenolic compounds present in the juice. In a previous study, Rios-Romero et al. (2018) reported the same tendency in sweet potato juice sonicated under different conditions.…”

“…México). The resulting juice immediately was processed and subjected to three types of treatment: (i) ultrasound waves, applied with an ultrasonic device (UP200Ht; Hielscher Ultrasound Technology, Germany) attached to 40 mm diameter probe (treatment time of 8 min, ultrasonic intensity of 0.66 W cm −2 , and a constant frequency of 26 kHz) ( Ríos-Romero et al., 2018 ); (ii) steam treatment, performed using a domestic steamer for 2 min; (iii) a combination of steam and ultrasound treatment. A sample of juice without treatment was physicochemically characterized and used as a control.…”

“…The β-carotene extraction from the treated samples was performed as reported by Rios-Romero et al. (2018) .…”

“…Enzyme inactivation, mainly of polyphenol oxidase, represents a quality parameter in the processing of fruits and vegetables. Previous reports have indicated that the inactivation of enzymes is difficult to achieve only through the use of ultrasound ( Bi et al., 2015 ; Cheng et al., 2007 ; Ríos-Romero et al., 2018 ). Nevertheless, blanching can also negatively affect the heat sensitive nutrients, texture, water soluble components, and the value and biological activity of the final products.…”

Valorisation of potato wastes

“…Huang et al () reported a polyethylene glycol‐based ultrasonic‐assisted extraction of anthocyanins and phenolics from purple sweet potato. Overall, the total phenolic compounds improvement extracted from potato peels, potato flesh or discarded potatoes using ultrasound assistance was reported for several authors (Samarin et al , ; Cai et al , ; Rios‐Romero et al , ).…”