Combined Effect of Microwave and Steam Cooking on Phytochemical Compounds and Antioxidant Activity of Purple Sweet Potatoes

Abstract

This study evaluates the effects of a microwave and steam cooking combination on the sugar composition, phytochemical compounds (total phenolics, total flavonoids, total anthocyanins and phenolic acids and anthocyanin compositions) and antioxidant capacity of purple sweet potatoes (PSPs). The combination of microwave and steam cooking could significantly decrease the cooking time. The results show an obvious increase in the quantity of total phenolics, flavonoids, and anthocyanins in PSPs after cooking. The microwave and steam cooking combination induced the greatest increase for the total flavonoids and total phenolics, with values of 22.2% and 26%, respectively. Among the phenolic acids in the PSP extract, chlorogenic acid was the major constituent, and phenolic acid concentrations increased after cooking, except for caffeic acid. An HPLC-MS analysis of anthocyanin showed that the cyanidin-3-(6"-caffeoyl-6"'-feruloylsophoroside) -5-glucoside and peonidin-3-(6"-caffeoyl-6"'-feruloylsophoroside)-5-glucoside contents in PSPs cooked with steaming for 10 min followed by microwaving for 3 min (S 10 _ M 3 ) were highest among the cyanidin and peonidin compounds. The PSPs exhibited a greater antioxidant capacity after cooking, and the S 10 _ M 3 cooking method produced the greatest antioxidant capacity. Therefore, an appropriate combination of microwave and steam cooking can better retain phytochemical compounds in PSPs and increase antioxidant capacity compared with only steaming or microwaving.Keywords: purple sweet potato, microwave, steaming, phytochemical compounds, antioxidant activity flavonoids and phenolic compounds (Blessington et al., 2010;Giusti et al., 2014;Tierno et al., 2015). Previous studies have shown that purple sweet potatoes (PSPs) exhibit strong antioxidant activity and an anti-mutagenic capacity, and they clearly decrease high blood pressure and liver injury (Kim et al., 2015;Truong et al., 2012). Considerable research on PSP has quantified the antioxidant activity as well as phenolic acid and anthocyanin compositions for various cultivars or after different cooking treatments (Kita et al., 2013;Lemos et al., 2015;Perla et al., 2012). A study performed by Lemos et al. (2015) showed the total phenolic and anthocyanin quantities as well as antioxidant activity in potatoes increased after steaming and microwaving. In addition, baking, frying and microwaving increase antioxidants as well as the carotenoid and total phenolic content in potato according to Blessington et al. (2010). However, Perla et al. (2012) reported that the total phenolics, flavonoids, anthocyanins and antioxidant activity in potatoes were significantly reduced by a microwave treatment.

Influence of Cooking Conditions on Nutritional Properties and Sensory Characteristics Interpreted by E-Senses: Case-Study on Selected Vegetables

“…The boiled sweet potatoes showed a lower AA, with a declining trend at longer boiling times. Conflicting data about the effect of cooking on the AA are found in the literature, with some studies observing an increase [7,37] and others a decrease [36]. Values and trends observed in our tests are consistent with the phenolic content.…”

“…The data concerning sweet potatoes are shown in Table 3. The nutritional constituents evaluated in this vegetable were β-C, which represents the main carotenoid in orange-fleshed sweet potatoes [36], and TP, mainly represented by the phenolic acids in the orange-flesh roots [7,37]. The solid content of the sweet potatoes used in this research was 18.3 and 19.2 g/100 g for the two lots, respectively, which is lower than what is reported in the literature [7,38].…”

“…For cooking times longer than 10 min, the steamed and microwaved products had similar and steady TP contents. An increase in TP as well as in individual phenolic acids in cooked sweet potatoes has been reported [7,37,42] and ascribed to various and concomitant factors: inactivation of polyphenoloxidases, hydrolysis of esterified products, release of bound phenolics from cell walls and insoluble fractions of the vegetable tissue, and the formation of Maillard reaction products that react with the Folin-Ciocalteau assay and thus contribute to overall quantification. The decrease observed in the sweet potatoes boiled for longer times can reasonably be ascribed to the dissolution of the soluble phenolic components (mainly phenolic acids) released by the above-mentioned modifications and favored by the water adsorption and softening of the cell walls.…”

Kualitas dan Aktivitas Antioksidan Selai Lembaran Kombinasi Ubi Jalar Ungu (Ipomoea batatas L.) dan Ekstrak Kelopak Bunga Rosella (Hibiscus sabdariffa L.)

“…Selai lembaran perlakuan (P) memiliki kandungan senyawa fenolik yang berasal dari ubi jalar ungu. Komponen fenolik yang terdapat dalam ubi jalar ungu yaitu asam fenolik dan antosianin (Chen et al, 2017). Semakin banyak penambahan ekstrak kelopak bunga rosella pada selai lembaran Q, R, S, maka total fenolik selai lembaran semakin meningkat.…”

Optimization of <i>Eucommia Ulmoides</i> Leaves Vinegar Process to Improve the Antioxidant Activity

“…At the same time, it was found that chlorogenic acid (CA) content in leaves (1 %~5.5 % in dried-leaves) was higher than that in barks. Studies also have proved that CA has strong oxidative resistance, bacteriological action, and inhibiting different free radicals (Hosoo et al, 2015;Chen et al, 2017). So, the application of functional components of Eucommia ulmoides leaves in foods has gained more and more interests.…”