Effect of the extrusion process and expansion by microwave heating on physicochemical, phytochemical, and antioxidant properties during the production of indirectly expanded snack foods

Abstract

The aim of this study was to evaluate the physicochemical, phytochemical, and antioxidant changes in different stages (unprocessed mixture [UM], extruded pellet [EP], and expanded product [EXP]) during the production of indirectly expanded snacks by microwave. Four mixtures (from corn starch/whole yellow corn flour), adding naranjita bagasse (NB) and/or skimmed milk powder, were used. Ash content, water absorption index (WAI), water solubility index (WSI), soluble dietary fiber (SDF), free phenolic compounds (FP), bound phenolic compounds (BP), and antioxidant activity (AOA) were higher in EP than in UM, whereas lipids, crude fiber, total carotenoids (TC), and total and insoluble dietary fiber (TDF and IDF) were lower. Also, WAI, WSI, color b*, FP, SDF, and AOA from FP were higher in EXP than in EP, while BP, TC, TDF, IDF, and AOA from BP were lower. The snacks with added NB presented acceptable sensory characteristics. Snacks with appropriate nutritional/nutraceutical properties from raw materials rich in bioactive compounds can be produced. Practical applications Based on the high demand of consumers for purchasing healthier products, the food industry has shown great interest in improving the nutritional properties of some products that are rich in calories, but very poor in nutrients. The incorporation of raw materials rich into bioactive compounds, such as cereals and by‐products of the citrus industry, as well as the addition of milk powder for the fortification of snack foods has been highly recommended. Several studies have shown increased nutritional properties and potential health benefits on humans by the addition of these materials. Furthermore, there is little information on the physicochemical, phytochemical, and antioxidant changes that are generated during the processing of indirectly expanded snack foods.

Characteristics of Newly Developed Extruded Products Supplemented with Plants in a Form of Microwave-Expanded Snacks

“…Reports exist in the literature about microwave-expanded corn pellets with orange and powdered milk additions, in which an increase in total polyphenols after microwave treatment at 1450 W has been described [ 26 ]. Hayat et al [ 23 ] also observed an increase in the content of polyphenols, and an enhancement of the antioxidant properties of extracts made from the citrus mandarin peel, after microwave treatment.…”

Effect of Composition and Processing Conditions on Selected Properties of Potato-Based Pellets and Microwave-Expanded Snacks Supplemented with Fresh Beetroot Pulp

“…The microwave power over 4 W/g led to the cooking of samples, resulting in a significant deterioration of their quality, therefore they selected this microwave power for further study. In turn, Ruiz-Armenta et al [2019] manufactured expanded snack products using a conventional microwave oven with a power of 1,450 W and a frequency of 2,450 MHz by selecting microwave heating for 20 s after testing different heating times (16,18,20,22,24,26, and 28 s). Given the above findings, it can be concluded that the application of a higher microwave power allows reducing heating time to obtain properly expanded products.…”

“…Researchers who experimented with expanding corn starch-based pellets supplemented with naranjita and milk powder observed an increase in WSI after extrusion and after microwave treatment [Ruiz-Armenta et al, 2019]. They concluded that this was linked to the loss of the semicrystalline form of native starch granules after processing.…”

“…Microwave treatment, as an alternative method of pellet expansion, reduces fat content in RTE products as compared to conventional expansion by frying in deep oil . It is also an easy and inexpensive process to execute either on an industrial scale or at household conditions [Ruiz-Armenta et al, 2019].…”

“…This study aimed to examine the changes that take place in RTE snacks after extrusion of pellets at various screw speeds and following microwave expansion, with regard to the effect of replacing potato starch with increasing amounts of vegetable pulp. The novelty of this study lies in the use of fresh beetroot pulp rather than dry powdered vegetables to produce pellets, as in the case of most research performed [Bhat et al, 2019;Ruiz-Armenta et al, 2019].…”