Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Stabilizing effect of montmorillonite on acerola juice anthocyanins Hálisson L. Ribeiro a , Ana Vitória de Oliveira a , Edy S. de Brito b , Paulo R.V. Ribeiro b , Men de sá M. Souza Filho b , Henriette M.C. Azeredo b,c, ⁎ a Federal University of Ceara, Campus Pici, Bloco 709, 60455-760 Fortaleza, CE, Brazil b Embrapa Agroindústria Tropical, R. Dra. Sara Mesquita, 2270, Pici, 60511-110 Fortaleza, CE, Brazil c Embrapa Instrumentação, R. 15 de Novembro, 1452, 13560-970 São Carlos, SP, Brazil ARTICLE INFO Keywords: Clays Silicates Cation exchange Natural pigments ABSTRACT This study was conducted to evaluate color and anthocyanin stability of clarified acerola juice (CAJ) as affected by montmorillonite (Mnt) at different concentrations (0–6 wt%, dry basis). While non-complexed CAJ suffered noticeable color degradation with time and pH variations, the presence of Mnt (especially at 4–6 wt%) not only changed the initial color of CAJ but also made it more stable with time and pH changes. CAJ/Mnt mixtures were ultracentrifuged in order to separate them into supernatants and anthocyanin-complexed Mnt precipitates. The supernatants presented decreasing anthocyanin contents with increasing Mnt concentrations, indicating pigment retention by the precipitates. X-ray diffraction of precipitates showed that Mnt interlayer spacing was increased by increasing anthocyanin/Mnt ratios, corroborating anthocyanin intercalation. FTIR revealed a band at 1530 cm −1 ascribed to formation of anthocyanin-Mnt complexes. Moreover, chromatograms indicated the se- lective adsorption of two compounds by Mnt, which were identified by LC-MS as cyanidin-3-O-rhamnoside and pelargonidin-3-O-rhamnoside. 1. Introduction Acerolas (Malpighia emarginata), also known as Barbados cherries, have been increasingly produced, because of their high vitamin C contents (from 700 to 1400 mg/100 g −1 , according to Cunha Neto, Rabelo, Bertini, Marques, & Miranda, 2012). They also contain antho- cyanins in contents ranging from 3.8 to 47.4 mg/100 g of fruit pulp, depending on the cultivar (Musser et al., 2004), the main anthocyanins being cyanidin-3-rhamnoside and pelargonidin-3-rhamnoside (Brito et al., 2007; De Rosso et al., 2008). Acerolas are mostly processed into pasteurized juices and frozen purees rather than consumed fresh, be- cause of their high perishability and high acidity (SEBRAE, 2016). However, their color is deeply affected by processing, due to antho- cyanin degradation, which impairs their consumer acceptability. Anthocyanins are glycosylated polyhydroxy or polymethoxy deri- vatives of 2-phenylbenzopyrylium, containing two benzoyl rings sepa- rated by a heterocyclic ring. Different anthocyanins are characterized by differences in: number and degree of methylation of hydroxyl groups; nature, number and position of sugar moieties attached to the phenolic molecule (aglycone); nature and number of aliphatic or aro- matic acids attached to the sugars (Mazza & Miniati, 1993). Antho- cyanins are very reactive and degradable; their stability is a function of properties of the product and processing conditions, including chemical structure of the anthocyanins present, light, oxygen, temperature, the presence of enzymes (particularly polyphenol oxidase), proteins, me- tallic ions, and especially pH (McGhie & Walton, 2007; Patras, Brunton, O’Donnell, & Tiwari, 2010). In aqueous solutions, four different mole- cular forms of anthocyanins exist in dynamic equilibrium: the red fla- vylium cation (the most abundant form at pH < 2), the blue quinoidal structure, and the colorless hemiketal and chalcone forms. Although the red flavylium is usually the predominant form in plants, other mole- cular forms will dominate at neutral pH (McGhie & Walton, 2007). Acerola anthocyanins are especially susceptible to degradation, which is a problem on storage of juices and purees. The low stability of acerola anthocyanins has been ascribed to the high concentration of ascorbic acid, the degradation occurring by direct condensation of as- corbic acid on C4 of anthocyanins, which results in losses of both components (De Rosso & Mercadante, 2007). Moreover, De Rosso et al. (2008) reported that the aglycones (anthocyanidins) cyanidin and pe- largonidin were present in acerolas along with their glycosylated counterparts, which may contribute to the low color stability of acerola products, since aglycones are less stable than glycosylated anthocyanins in weakly acidic medium (He & Giusti, 2010). Incorporation of organic dyes into inorganic host materials such as https://doi.org/10.1016/j.foodchem.2017.11.076 Received 24 July 2017; Received in revised form 17 November 2017; Accepted 20 November 2017 ⁎ Corresponding author at: Embrapa Instrumentação, R. 15 de Novembro, 1452, 13560-970 São Carlos, SP, Brazil. E-mail addresses: edy.brito@embrapa.br (E.S.d. Brito), paulo.riceli@embrapa.br (P.R.V. Ribeiro), men.souza@embrapa.br (M.d.s.M. Souza Filho), henriette.azeredo@embrapa.br (H.M.C. Azeredo). Food Chemistry 245 (2018) 966–973 Available online 22 November 2017 0308-8146/ © 2017 Elsevier Ltd. All rights reserved. T