Expanded porous-starch matrix as an alternative to porous starch granule: Present status, challenges, and future prospects

Abstract

Exposing the hydrated-soft-starch matrix of intact grain or reconstituted flour dough to a high-temperature-short-time (HTST) leads to rapid vapor generation that facilitates high-pressure build-up in its elastic matrix linked to large deformation and expansion. The expanded starch matrix at high temperatures dries up quickly by flash vaporization of water, which causes loss of its structural flexibility and imparts a porous and rigid structure of the expanded porous starch matrix (EPSM). EPSM, with abundant pores in its construction, offers adsorptive effectiveness, solubility, swelling ability, mechanical strength, and thermal stability. It can be a sustainable and easy-to-construct alternative to porous starch (PS) in food and pharmaceutical applications. This review is a comparative study of PS and EPSM on their preparation methods, structure, and physicochemical properties, finding compatibility and addressing challenges in recommending EPSM as an alternative to PS in adsorbing, dispersing, stabilizing, and delivering active ingredients in a controlled and efficient way.

Introduction

Porous matrix has attracted considerable interest in the nutraceutical, functional food, and pharmaceutical sector due to its beneficial functions in protecting and allowing targeted and regulated release of bioactive components (Chen, Wang, Liu, & Xu, 2020). The bioactive delivery vehicle for human consumption should not only bear the ability to adsorb, encapsulate and protect the bioactive ingredients but also mandatorily be safe, edible, biodegradable, non-toxic, and economical (Mcclements, 2020). Porous starch (PS) having several pores (micrometer range) from the surface to the core of its granule increases its specific surface area and allows bioactive molecules to reside in the interstices of the granules, resulting in high adsorption and slow-release (Chen, Wang, Liu, & Xu, 2020). Owing to its surface area, biodegradability, and non-toxicity, PS has been extensively used as the delivery agent, texture modifier, emulsifier and fat substitute in the nutraceutical and pharmaceutical sector (Gonzalez and Wang, 2021, Latip et al., 2021).

PS can be prepared by the physical, chemical, enzymatic, or hybrid methods. Chemical methods involve the use of chemicals, which are not often recommended for food applications. Organic solvents in the solvent exchange method can increase the expense of the process, compromise stability, and add toxicity during PS manufacturing. A physical method such as ultrasonication is environment friendly but requires high energy consumption, with a long processing time. PS prepared through enzymatic hydrolysis is mostly used but requires starch matching enzymes and bears high cost, longer process time, and several other process complexities. Limitations associated with PS have led to the search for easy to process low-cost alternatives having similar functional characteristics.

High-temperature-short-time (HTST) food-processing technique is the process where food products are subjected to a temperature higher than 100 °C for a few seconds only (Sreyajit Saha and Roy, 2020a, Saha and Roy, 2020). Exposing starch rich matrix to high temperature for few seconds generates high pressure build up inside the matrix due to rapid evaporation of water to vapour. Instant vapour generation associated with large vapour pressure facilitates the large deformation in the flexible starch matrix and results in its large expansion. In its expanded state, the starch matrix stays at high temperatures and dries up quickly by flash vaporization of water that causes loss of structural flexibility and imparts a porous and rigid structure of expanded porous starch matrix (EPSM) (Gulati & Datta, 2016; Sreyajit Saha et al., 2023). EPSM, with abundant pores in its construction, offers adsorptive effectiveness, solubility, swelling ability, crystallinity, mechanical strength, and thermal stability and can be a sustainable and easy-to-construct alternative to PS. Recommending EPSM as an alternative to PS requires a comparative understanding of both of their preparation methods, structure, and associated physicochemical properties.

Over the last five years, several efforts in form of review and research articles have been made to describe the formation of PS with their commercial industrial applications (Chen et al., 2020, Gonzalez and Wang, 2021, Ju et al., 2020, Latip et al., 2021, Liu et al., 2018, Oliyaei et al., 2018, Sujka et al., 2018). There are limited reviews on EPSM, its production process, and physicochemical properties.

Therefore, current review focuses to draw a comparative study on the production process and physicochemical properties between PS and EPSM, points out the drawbacks of EPSM and suggests strategies to use of EPSM as a low-cost alternative to PS use.