Toward a Better Understanding of the Functional Prosperties of Flour and Starch

Starch is the most important functional polymer from plants, primarily due to its gelling, water-binding, and viscosifying properties (Sjöö & Nilsson, 2017). Starch is composed of two glucans: amylopectin and amylose, varies depending on the botanical variety (Sjöö & Nilsson, 2017). In standard wheat flour, starch is typically composed of 75% amylopectin and 25% amylose. Waxy wheat flour can contain up to 99% amylopectin, while high-amylose wheat varieties contains up to 70% amylose (Van Hung et al., 2006). In the industry, starches can be chemically modified to enhance their resistance during food processing and to be used as texturizers.

However, since the 2010s, consumers have become increasingly reluctant to purchase ultra-processed products with labels listing food additives identified by E-numbers, such as E1400-1499 for starch derivatives (FAO & WHO, 2023). The rise of movements such as ‘Clean Label’ and ‘Label Friendly’, which favour physical treatments (thermal or non-thermal), has attracted significant attention (Asioli et al., 2017). The goal of these methods is to improve functionality and use a clean-label ingredient rather that an additive. Physical treatments reorganize or alter the molecular arrangement of starch chains, particularly amylopectin (Stute, 1992). The primary objective is to stabilize and enhance the structure of amylopectin chains, thereby improving starch’s water retention by reorganizing the outer and inner helices (Gessler et al., 1999).

Indeed, for several decades, the behaviour of starch in the presence of water has generated growing interest due to its functional properties, thereby enhancing the understanding of structural interactions under various experimental conditions (Zhang et al., 2024). Laboratory research has extensively examined the influence of starch swelling in function of botanical source, and specific compositions, including high amylose wheat or waxy wheat varieties, for starches and flours (Whistler & BeMiller, 2009).

Researchers have particularly focused on the gelatinization, a critical process influencing the final texture of food products, especially the viscosity of starch pastes (Chakraborty et al., 2022). The swelling capacity of starch is also explored to optimize chemical and enzymatic processes, as well as physical modifications, aimed to develop starches with specific functional properties and ensure their quality control during production (Jia et al., 2023).

At an industrial level, starch swelling capacity offers interesting benefits, especially for optimizing the stability and consistency of functional ingredients used in food product formulations (Park & Kim, 2021). As a result, physically treated native flours, referred to as functional flours (FF), have been developed and are used as texturizing ingredients in food preparations, offering an alternative to chemically modified starches (CMS). The primary purpose of texturizers is to increase the viscosity of food preparations (Himashree et al., 2022).

The swelling power (SP) can be used as a performance indicator to quantify the amount of gelatinized starch. While the swelling power is a common metrics used to evaluate water absorption and granule expansion during gelatinization, while the solubility is based on amylose content, these characteristics do not provide a complete understanding of functional properties (Zhang et al., 2024).

Swelling power alone provides an incomplete assessment of ingredient functionality, and currently, there are no standardized methods to measure it. Consequently, a more comprehensive approach is needed. By incorporating additional data (density and actual starch content of the ingredient), it is possible to evaluate the performance of FF&CMS as a function of their concentration in food products. Relying solely on swelling power may therefore overlook critical aspects of ingredient behaviour in complex food systems. The main objective of this study is to better understand the functionality of the ingredients and establish a relevant performance indicator, the Water Holding Ratio, by identifying the concentration at which a clean-label flour can provide textural properties equivalent to those of a chemically modified starch in food product formulations.

The system under investigation is a food sauce model that corresponds to the main use of this type of ingredient and represents the main challenge for industrial application. It is therefore considered to be a fluid composed of a continuous phase (water and part of starch) and a functional phase, consisting of the ingredients in state of gelatinization (FF&CMS). To highlight the limitations of the “actual swelling power”, six samples were analysed in a model sauce made with water and ingredients, where functional flour, native flour and starches are used as thickening agents. To cover the viscosity range typically required for sauces at hot conditions to achieve the targeted texture, a concentration at 4% was selected as the standard concentration (Sarka, 2017). Four samples were formulated with 4% (g ingredients/g total sample) of FF, WxF, WxS and CMS. Two additional samples containing 6% and 8% (g ingredients/g total sample) of FF were prepared to evaluate the performance of this novel flour and compare it with the other ingredients.