Effect of high hydrostatic pressure on physicochemical properties of quinoa flour

Highlights

• High hydrostatic pressure (HHP) has potential to modify flour functionality.

• HHP reduced viscosity of quinoa flour during pasting event.

• HHP induced gelatinization of quinoa flour.

• HHP increased extractable phenolic content of quinoa flour.

• HHP decreased starch digestibility of quinoa flour.

Abstract

High hydrostatic pressure (HHP) has potential to modify physicochemical properties of food systems. Quinoa (Chenopodium quinoa) has attracted research focus for nutritional properties. Three different types of whole grain quinoa flour were processed using HHP up to 600 MPa. HHP of 500 and 600 MPa decreased the viscosity during pasting event (e.g., peak viscosity from 4.90 to 0.18 Pa⋅s), gel hardness (e.g., from 0.185 to 0.0343 N), enthalpy change (ΔH) of gelatinization (e.g., from 11.8 to 0 J/g), and in vitro starch digestibility of quinoa flour (e.g., from 954 to 862 g/kg), while increasing the water solubility (e.g., from 15.8 to 40.2% at 55 °C). The extents of these changes were seen to depend on the type of quinoa flour. Structural analysis showed that, to a large degree, the HHP induced changes in the physicochemical properties could be attributed to the gelatinization of the starch component, and to a smaller extent, to the changes in non-starch components. The physicochemical properties of the quinoa four were much less significantly affected by HHP of 200 and 400 MPa. HHP as a non-thermal processing technique has potential to modify grain flour properties.

Introduction

Quinoa (Chenopodium quinoa Willd.) has become more popular as a “novel” food item due to the attractive nutritional benefits (Wang & Zhu, 2016). Quinoa is a source of proteins well-balanced in essential amino acids. The lipids in quinoa are largely unsaturated (e.g., linoleic and linoleic acids). The grain contains relative high amounts of minerals, vitamins (e.g., tocopherols). It is a source of dietary fibers, polyphenols, and phytosterols with potential health benefits (Abugoch James, 2009; Tang et al., 2015). There has been increasing interest in developing quinoa based food products. A range of products such as bread, pasta, cookie, breakfast cereal, snack, edible film, and emulsion stabilizer have been developed from quinoa and its components (Wang & Zhu, 2016). As the global production of quinoa has kept increasing, there is a great opportunity to develop quinoa based food products using novel food processing techniques to expand the range of quinoa functionalities.

There has been increasing interest in minimally processed food for the retention of nutritional value, flavour, and aroma. Another trend is the demands for physically processed food products to replace chemically/enzymatically treated products (Knorr, 2018). High pressure technology has drawn attention for its potential in food preservation without much disruption of quality attributes. Pioneering work of high pressure processing was done by Hite (1899) for the pasteurisation of milk. At present, high pressure processing is increasingly used in food industry (Knorr, 2018). The processing can inactivate endogenous enzymes and microorganisms in food products, significantly increasing the shelf life. The covalent bonds of organoleptic and nutritional components are not affected by the processing (Sun, Kang, Chen, Liao, & Hu, 2019). The quality attributes of the processed products can be much better retained compared to conventional thermal processing (Knorr, 2018; Sun et al., 2019). High pressure processing can also modify the functionality of food components (Pérez-Andrés, Charoux, Cullen, & Tiwari, 2018; Yang, Chaib, Gu, & Hemar, 2017). For example, high pressure can induce gelatinization of starch. Compared to heat-gelatinized starch, pressure-gelatinized starch has different properties (e.g., better retained granular remnants) with potential novel applications (Li & Zhu, 2017). High pressure treated rice flour and corn starch could be used to improve the quality of gluten free bread to help people with celiac diseases (Cappa, Barbosa-Cánovas, Lucisano, & Mariotti, 2016a; Cappa, Lucisano, Barbosa-Canovas, & Mariotti, 2016b). HHP processing of wheat-oat flour blends improved the noodle making quality (Lee & Koo, 2019). Overall, application of high pressure to modify food functionality remains to be used on different food products, especially to include a range of cereal/grain foods which are staple foods. Novel properties of grain products may be obtained using HHP processing.

High hydrostatic pressure (HHP) up to 600 MPa was applied on 3 different types (white, red, and black) of whole grain quinoa flour samples. Different physicochemical properties including swelling, solubility, pasting, gel texture, gelatinization, retrogradation, in vitro starch digestibility, total phenolic content, and colour as affected by HHP were analysed. The structural properties were measured using particle size analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR). The results were compared to those of previous studies of HHP processing of other starch/flour systems. The results of this study will be of importance to expand the uses of quinoa for potential food applications such as in bakery, source, and beverage products.