Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Phenomenological study of the synthesis of pure anhydrous β-lactose in alcoholic solution Edgar Enrique Lara-Mota a , María Inés Nicolás–Vázquez b , Laura Araceli López-Martínez c , Vicente Espinosa-Solis d , Pedro Cruz-Alcantar a , Alberto Toxqui-Teran e , Maria Zenaida Saavedra-Leos a, ⁎ a Universidad Autónoma de San Luis Potosí, Coordinación Académica Región Altiplano, Matehuala, SLP 78700, Mexico b Universidad Nacional Autónoma de México, Departamento de Ciencias Químicas, Facultad de Estudios Superiores Cuautitlán, Cuautitlán Izcalli, Estado de México 54740, Mexico c Universidad Autónoma de San Luis Potosi, Coordinación Académica Región Altiplano Oeste, Salinas de Hidalgo, SLP 78600, Mexico d Universidad Autónoma de San Luis Potosí, Coordinación Académica Región Huasteca Sur, Tamazunchale, SLP 79960, Mexico e Centro de Investigación de Materiales Avanzados (CIMAV-Mty), Parque de Investigación e Innovación Tecnológica, Apodaca, Nuevo León 66600, Mexico ARTICLE INFO Keywords: Anhydrous β-lactose Monohydrate α-lactose MDSC FTIR SEM ABSTRACT Lactose is an important additive because of its food, pharmaceutical, and cosmetic applications. Among lactose polymorphs, anhydrous β-lactose stands out due to its thermodynamic stability. Thus, a simple method to produce the inter-conversion from monohydrate α-lactose to anhydrous β-lactose was investigated employing a methanolic solution and diferent reaction variables (catalyst type, temperature, and stirring). Pure β-lactose powders were synthesized in short reaction time (2–16 h), with a moderate temperature (refux: 65 °C), and low concentration (0.014 M) of catalysts (NaOH and KOH). The SEM analysis revealed a change in the morphology from fne needles to tomahawk shape, which is dependent on the content of β-lactose. The products were ap- propriately characterized using common analytic procedures (XRD, FTIR, and MDSC). In addition, an exhaustive discussion of the obtained results is provided. Finally, it seems to be the frst work, where the inter-conversion to pure β-lactose is reported successfully. 1. Introduction Lactose (β-D-galactopyranosyl-D-glucopyranose) is a milk dis- accharide, linked by a β-(1,4) glycosidic bond of galactose and glucose. Lactose is found in dairy products because it confers textural, taste and adhesive properties (Hobman, 1984). In the pharmaceutical industry, lactose is largely employed as an excipient in tablets. The lactose mo- lecule shows two isoforms difering only in the orientation of the hy- droxyl group (–OH) located in the glucose unit. The presence of an anomeric carbon in alcoholic media allows the formation of a hemi- acetal bond, providing a more stable cyclic structure. Through a mu- tarotation process in the chiral center, two isomers (enantiomers) α and β anomers are obtained (Fox, 2009). The inter-conversion process of α- lactose into β-lactose is important since the latter anomer is more thermally stable (Listiohadi, Hourigan, Sleigh & Steele, 2009) and may impart other properties to the fnal product. Consequently, β-lactose is sweeter and present higher solubility than α-lactose (Beebe & Gilpin, 1983). In addition, anhydrous β-lactose powders present higher compactibility attributed to better binding ability of anhydrous β-lac- tose particles compared to α-lactose monohydrate. Thus, this is pre- ferred for making stronger tablet in pharmaceutics (Lamešic, Planinšek, Lavric, & Ilic, 2017). Moreover, the α/β lactose ratio isomers present in a powder samples indirectly afects the fuidity and compaction beha- vior of the product due to changes in the surface morphology of the crystallized material (Dwivedi & Mitchell, 1989). It is important to note that the equilibrium between α-β isomers is strongly dependent of temperature, concentration, and the presence of other substances in the solution (Hartel & Shastry, 1991). In particular for an aqueous solution, the temperature efect can show great re- percussions in the crystallization phenomena (Hartel & Shastry, 1991), solubility (Wong & Hartel, 2014), the rate of nucleation or the mutar- otation process for inter-conversion (Shi, Liang & Hartel, 1990). Thus, when the temperature is increased, the β-lactose formation is improved, resulting in the change of shape of crystals, from tomahawk shape for α- lactose, with lower quantity of β-lactose, to uneven-sided diamond or curved-needle like prisms, with higher content of β-lactose (Raghavan https://doi.org/10.1016/j.foodchem.2020.128054 Received 27 March 2020; Received in revised form 4 September 2020; Accepted 7 September 2020 ⁎ Corresponding author. E-mail address: zenaida.saavedra@uaslp.mx (M.Z. Saavedra-Leos). Food Chemistry 340 (2021) 128054 Available online 28 September 2020 0308-8146/ © 2020 Elsevier Ltd. All rights reserved. T