Hydrothermal–Microwave Processing for Starch Extraction from Mexican Avocado Seeds: Operational Conditions and Characterization

Rafael G Araújo,Cristobal Noe Aguilar,Rosa M Rodríguez-Jasso,Héctor A Ruiz,Cynthia Luevanos,Walfred Rosas-Flores,Mayela Govea-Salas,Miguel Angel Aguilar-González,Manuela E Pintado,Claudia Lopez-Badillo

doi:10.3390/pr8070759

Abstract

Avocado seeds are an agroindustrial residue widely produced in Mexico that are causing various environmental problems due to their accumulation. The evaluation of avocado residues to recover biopolymers by microwave-assisted extraction (MAE) and the characterization of avocado starch properties were studied in the present work. A central-composite design was used to optimize the MAE process. Moreover, a comparison was performed between MAE non-isothermal mode (NO–ISO) and conventional extraction. Starch optimization by MAE was obtained at 161.09 °C for 56.23 min with an extraction yield of 49.52% ± 0.69%, while with NO–ISO at 161 °C was obtained 45.75% ± 2.18%. Conventional extraction was 39.04% ± 2.22%. Compared with conventional starch, MAE starch showed similar proprieties and molecular spectra. In contrast, MAE starch showed high solubility, low water absorption capacity, a non-granular structure with small particle size (<2 µm) and polydispersity of fragments at different sizes of polymers. Therefore, MAE is a viable technology to extract the starch, and avocado seed can be considered an excellent starch source for the development of novel functional foods, contributing to promoting sustainability across the food chain.

Highlights

IntroductionAvocado (Persea americana Mill) is a native fruit of Mexico and Central America that is nowadays consumed worldwide due to its very complete nutritional content and many positive health benefits [1,2]
Avocado (Persea americana Mill) is a native fruit of Mexico and Central America that is nowadays consumed worldwide due to its very complete nutritional content and many positive health benefits [1,2].In 2018, avocado production in Mexico was more than two million tons, valued at more than five billion dollars, and representing more than 34% of worldwide production [3,4].Processes 2020, 8, 759; doi:10.3390/pr8070759 www.mdpi.com/journal/processesThe avocado seed represents approximately 13–17% of the fruit
Lyophilization was used to be able to create a homogeneous batch of avocado seed to find the optimal conditions of extraction, which was not achieved using fresh seed since great variability was obtained in the same treatments, derived from variations of starch content between seeds. on the other hand, the convection drying method decreased the starch extraction yield perhaps because the heating caused Maillard reactions on the surface of the seed pieces which created a caramel-like layer

Summary

Introduction

Avocado (Persea americana Mill) is a native fruit of Mexico and Central America that is nowadays consumed worldwide due to its very complete nutritional content and many positive health benefits [1,2]. The avocado seed represents approximately 13–17% of the fruit. It is composed of many bioactive compounds, sugars, proteins and starches, which are the main compound of approximately 60% by dry weight [5,6,7]. Avocado waste—like many fruit wastes—is a growing concern worldwide, as it represents an environmental, social and economic problems [8]. For the modern sustainable food industry, waste generated is one of the main concerns. Its management is a crucial issue for the modern avocado industry

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