**1. Introduction**

Natural pigments have attracted more and more attention owing to the rejection by consumers of synthetic colorants and their adverse effects [1]. Betalains are a type of natural pigments which are commercially obtained from red beet root. In addition, red dragon fruit and pitaya are also abundant sources of betalains, which can be explored as viable alternatives [2]. Betanin is a major betalain and a soluble pigment that is also present in the pitaya fruit [3]. Meanwhile, betanin is a nontoxic betalain approved for use in foods [4] that can be used as a food colorant. In addition, betalains, including betanin, have antioxidant properties [5]. However, previous research about applying betalains mainly concentrated on their stability, due to their sensitivity to thermal and photochemical decomposition. For example, betalains were applied in dairy products, such as cow milk [6] and ice-cream [7], because these products are commonly stored under chilled conditions and could maintain a higher pigment stability. In order to expand the application of this excellent resource, other functions of betalains remain to be explored in addition to being used as a colorant.

Starches serve as an important ingredient, which have been applied in many processed foods such as bakery products, noodles, instant foods and snacks [8]. The physicochemical properties of starches, such as pasting, rheological and retrogradation behaviors, are the main parameters that determine their technological properties and the qualities of their end products. Nevertheless, native starches have some disadvantages, such as weak shear

**Citation:** Dai, T.; He, X.; Xu, J.; Geng, Q.; Li, C.; Sun, J.; Liu, C.; Chen, J.; He, X. Effects of Betanin on Pasting, Rheology and Retrogradation Properties of Different Starches. *Foods* **2022**, *11*, 1600. https://doi.org/ 10.3390/foods11111600

Academic Editor: Alessandra Marti

Received: 11 May 2022 Accepted: 26 May 2022 Published: 29 May 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

resistance, undesired paste consistency and easy retrogradation. These insufficient characteristics of native starches limited their practical applications in the food industry to a certain extent [9]. Briefly, the retrogradation of starches profoundly affects the textural attributes, shelf life and acceptability of starch-based products [10]. In order to suit specific applications, modification methods, such as chemical, enzymatic and physical methods or some combination of these, were reported to regulate the properties of starches [11]. Recently, plant bioactive substances such as phenolics and plant extracts have been increasingly incorporated to adjust the physicochemical properties of starches. Yu et al. [10] investigated the influences of the selected phenolic acids (cinnamic acid, caffeic acid and ferulic acid) on the retrogradation of corn starch, and found that phenolic acids inhibited the retrogradation of corn starch via the interactions of hydrogen bonding or hydrophobic interaction. Wu et al. [12] suggested that green tea polyphenols reduced pasting attributes, gelatinization enthalpy and the retrogradation degree, as well as improved the freeze–thaw stability of rice starch. Wang et al. [13] reported on the inhibition effect of three common proanthocyanidins (grape seed proanthocyanidins, peanut skin proanthocyanidins and pine bark proanthocyanidins) on the retrogradation properties of maize starch, which was reflected by lowering the melting enthalpy and degree of relative crystallinity. Nevertheless, to our best knowledge, there is little information about the impacts of betanin on the physicochemical properties of starches. Therefore, the aim of this study was to investigate the effects of betanin on pasting, rheology and retrogradation behaviors of rice, potato and pea starches, and the co-gelatinization of betanin and starches was selected as the treatment condition. The results of the study probably provide some useful knowledge for improving the quality of starchy foods, and open up new ideas for the potential utilization of betanin.
