ORIGINAL PAPER Effect of Sustainable Chemical Modifications on Pasting and Gel Properties of Sorghum and Cassava Starch Pablo Martín Palavecino 1,2 & María Cecilia Penci 2 & Pablo Daniel Ribotta 1,2 Received: 27 August 2019 /Accepted: 20 November 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Starch isolated from two different sorghum hybrids and a commercial cassava starch were modified in order to assess the improvement in rheological and thermal properties that could be produced by sustainable methods. Modifications were acety- lation with acetic anhydride, hydrolysis with acetic acid, and esterification with octanoyl chloride. All sorghum starch paste exhibited higher syneresis than cassava ones and acetylation slightly improved water retention. In general, pasting profiles were significantly altered throughout modifications and the paste textural properties and rheological results suggested a physical gel behavior. Cassava and white sorghum unmodified gels showed higher values of textural parameters than those of brown sorghum. The flow data were adequately fitted by the power-law model (R 2 > 0.96) with flow behavior index < 1. The acetyla- tion, acid treatment, and octanoyl esterification of cassava and sorghum starch resulted in significant changes in water interaction, indicating a wider range of properties. Keywords Sorghum starch . Cassava starch . Gel properties . Pasting properties . Modified starch Introduction Starch is the primary component of cereals and plays a main role in all cereal-based foods mostly due to water–starch in- teraction. Among them, the gelatinization process allows sev- eral food and non-food applications of starch and regulates phenomena such as gelation and retrogradation. The popular- ity of starch is attributed to its wide range of functional prop- erties which allows replacing other higher-cost ingredients (Barrera et al. 2012; Gençcelep et al. 2017). In fruit pie filling thickener, the starch gel needs to be transparent, but in salad dressing it had to be opaque; then starch paste clarity is fun- damental (Bello-Pérez et al. 1998). Likewise, paste syneresis should be low because in both cases products releasing water during storage is not desirable (Mbougueng et al. 2012). Starch is also commonly used to form or stabilize emulsions due to its capacity to interact with lipids (Gençcelep et al. 2017). Another technological aspect of starch that increases its importance is the rheological behavior that it could provide to a food system. Then, the viscosity properties of starch pastes and gels are fundamental for starch applications in the food industry (Ai and Jane 2015). Usually starch has been modified to reach a wider range of properties and to overcome some of the aforementioned prob- lems. Chemical modification involves the use of chemical compounds to change the chemical and physical structure of linked D-glucopyranosyl units which constitute starch chains, and then its technological properties. Starch esterification in- volves the acylation of its hydroxyl groups, for example, with acetyl groups (Golachowski et al. 2015; Colussi et al. 2015). Starch esterification with long-chain organic acid improves starch–oil interactions, turning it into a useful emulsifier agent and fat replacer (Dapčević Hadnađev et al. 2015). Acid treat- ment implies the hydrolysis of the starch molecules which consequently affects granule structure and changes some of its physicochemical characteristics, including gelatinization temperature and enthalpy, and retrogradation tendency. Such starch was used in jellies, sausages, and dressings. The re- agents frequently employed to perform acid modification were chlorhydric or sulfuric acid, which are dangerous to han- dle, generally expensive, and generate undesirable byproducts * Pablo Daniel Ribotta pdribotta@unc.edu.ar 1 Instituto de Ciencia y Tecnología de Alimentos Córdoba (ICYTAC), CONICET–UNC, Córdoba, Argentina 2 Facultad de Ciencias Exactas, Físicas y Naturales, Instituto de Ciencia y Tecnología de los Alimentos, Universidad Nacional de Córdoba, Córdoba, Argentina Food and Bioprocess Technology https://doi.org/10.1007/s11947-019-02381-0