Stability and Quality of Anthocyanin in Purple Sweet Potato Extracts

Chin-Chia Chen,Po-Yuan Chiang,Chi Lin,Min-Hung Chen

doi:10.3390/foods8090393

Chin-Chia Chen, Po-Yuan Chiang + Show 2 more

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https://doi.org/10.3390/foods8090393

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Abstract

Because of the high nutritional value of anthocyanin in purple sweet potatoes (TN57), the stability and quality of anthocyanin in purple sweet potatoes during and after the processing were investigated in this study. First of all, the extraction methods with different parameters, such as temperature, time, solid-liquid ratio, pH value, and solvent were employed to get better extraction efficiencies. After that, DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2,2′-azino-bis (3-ethylbenz thiazoline-6-sulphonic acid) were used to evaluate the anti-oxidation ability of the extracts. Lastly, the thermal degradation kinetics and photodegradation were used to obtain important degradation factors including the content of anthocyanin residue, degradation index (DI), color parameters, reaction rate (k), and chromatic aberration (ΔE). We found that the extraction condition as using 60% ethanol with 1% citric acid under 80 °C for 40 min was optimal for purple sweet potatoes, which obtained antioxidant capacity as 333 μM TE DPPH, 376 μM TE ABTS+, and 593.6 μM TE ferric ion reducing antioxidant power (FRAP). The results indicate that the most important parameter for the stability of anthocyanin in the purple sweet potato extract (PSPAE) was the pH value rather than temperature. In addition, there was no significant difference in chromatic aberration between the light and dark storage conditions under 37 °C. Thus, PSPAE has the potential to be developed as health foods and drinks rich in anthocyanin.

Highlights

Sweet potatoes (Ipomoea batatas L.) are widely cultivated in tropical and subtropical areas, since it has been introduced from the South America in the early 18th century [1]
The high content of anthocyanin in purple sweet potato has been verified in a previous study, which were 19.78 mg/100 g in water extract and 158 mg/100 g in acid-ethanol (HCl, 1.5 mM) [9,10], while cyanidin and peonidin are the major components of the purple sweet potato anthocyanin [11]
Because of the good water solubility of anthocyanin, the purple sweet potato was extracted with water at first, with 1:15 solid–liquid ratio under 70 ◦ C for 30 min

Summary

Introduction

Sweet potatoes (Ipomoea batatas L.) are widely cultivated in tropical and subtropical areas, since it has been introduced from the South America in the early 18th century [1]. The enrichment in starch, crude protein, dietary fibers, minerals, pigments, and polyphenols makes it one of the most important root crops in agricultural production as well as a major raw supply in the food industry nowadays [2,3]. The purple sweet potato (TN73) has distinctive prunosus peel and deep purple flesh with an inviting flavor and mouth feeling [4,5]. Because of these advantages, the purple sweet potato is served as various dishes, nutritional brewing dry powder, stuffing, sweetmeat etc., in food processing industry, and has become a popular cultivar in Asia [6]. Comparing to other anthocyanin enrichment foods, like black hawk raspberry (315.9 mg/100 g), black waxy rice (17.89–99.53 mg/100 g), and grape (1076 mg/100 g), Foods 2019, 8, 393; doi:10.3390/foods8090393 www.mdpi.com/journal/foods

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