Elsevier

Journal of Food Engineering

Volume 120, January 2014, Pages 1-8
Journal of Food Engineering

Novel blasting extrusion processing improved the physicochemical properties of soluble dietary fiber from soybean residue and in vivo evaluation

https://doi.org/10.1016/j.jfoodeng.2013.07.011Get rights and content

Highlights

  • BEP treatment for the extraction of soluble dietary fiber was optimized.

  • BEP treatment improved the physicochemical properties of soluble dietary fiber.

  • BEP treatment significantly enhanced the yield of soluble dietary fiber.

  • BEP treated soluble dietary fiber with modified structural properties showed improved functionality.

Abstract

Soluble dietary fiber is a carbohydrate-based polymer with significant health benefits that is enriched in whole grains, nuts, fruits, and vegetables. Soybean residues are generally discarded in food industries during the production of soybean milk and tofu. This study investigated the effect of blasting extrusion processing (BEP) on the increase in soybean residue SDF content under optimal conditions (170 °C and an extrusion screw speed of 150 r/min). Compared with the control, the content of soluble dietary fiber from soybean residues treated by BEP (BEPSDF) was increased from 2.6 ± 0.3% to 30.1 ± 0.6%. In addition, BEPSDF showed improved water solubility, water retention capacity and swelling capacity. Furthermore, differential scanning calorimetry (DSC) experiments showed that SDF treated by BEP has a higher peak temperature (92.5 °C) than that of the control (86.6 °C). Scanning electron microscopy (SEM) images showed that the surface of BEPSDF was rough and collapsed. Moreover, in vivo experiment results indicated that BEPSDF significantly reduces the concentrations of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) while elevating the concentration of high-density lipoprotein cholesterol (HDL-C). This finding indicates that BEPSDF has beneficial physiological effects.

Introduction

Dietary fiber, a group of compounds containing carbohydrate polymers and non-carbohydrate components, is generally derived from certain cereals, legumes, fruits and vegetables. It is usually categorized as either water soluble or insoluble. Dietary fiber has gained considerable attention in recent years due to its potential role in improving human health. For instance, it has been shown to prevent heart disease, obesity, and cancers (Elleuch et al., 2011, Huang et al., 2013). In addition, it can be incorporated into other food products for enhancing textural properties and promoting favorable mouth-feel because the addition of dietary fiber is associated with certain food properties, including water and oil retention capacity (Elleuch et al., 2011).

Soybean residue, a readily available and inexpensive by-product from the soy milk and tofu manufacturing industry (Hayashi et al., 1992), is rich in dietary fiber. Approximately twenty million tons of soybean residue are produced annually in China. Unfortunately, most of this soybean residue is not fully utilized and is discarded as industry waste. This waste poses potential environmental problems because the large amounts of water and abundant nutrients that are found in soybean residues can promote the growth of microorganisms. (O’Toole, 1999). Therefore, a novel food processing technique is suggested to manufacture valuable additional products, such as dietary fiber, from soybean residues based on the aforementioned economic and environmental incentives.

Blasting extrusion processing (BEP) is a novel food processing technique that may potentially be used in the food industry. Compared with other traditional common processing approaches, such as the thermal or chemical modification of food materials, the extrusion processing technique shows high thermal dynamic efficiency, retention of heat sensitive nutritional components, low operating cost, and ease of the scale up. These properties arise because BEP treats raw materials with a combination of multiple physical phenomena that consist of high pressure, shear stress, torque, and high temperature. Furthermore, samples are treated quickly with high throughput (Kim et al., 2006). In addition, minor changes in the processing conditions readily yield food ingredients with different shapes, textures, and appearances. Furthermore, this process is environmentally friendly because it is relatively dry and reduces wastewater treatment costs. Numerous studies have attempted to take advantage of extrusion processing techniques to improve certain physicochemical properties of cereal-based food products, such as oat bran (Zhang et al., 2011), gluten-free teff flour cereal (Stojceska et al., 2010), okara–maize snack foods (Shi et al., 2011) and wheat bran (Robin et al., 2011). However, the literature provides little information about the effects of BEP on the extraction of soluble dietary fiber (SDF) from soybean residue.

The primary objective of this study was to assess the effect of BEP on the content of SDF from soybean residue under optimal conditions. In addition, the physicochemical properties of BEPSDF were investigated. Furthermore, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were used to analyze and characterize the structure of BEPSDF. Moreover, the physiological functions of BEPSDF were further studied in animal experiments.

Section snippets

Materials

Untreated raw soybean residue with a moisture content of 80 ± 2% (w/w, %) was obtained from Shanhaiguan Bean Products Co., Ltd. (Tianjin, China). All chemicals and reagents were of analytical grade and purchased from North Yayi Chemicals Co., Ltd. (Tianjin, China).

Sample preparation

A novel extrusion unit was recently developed by our group that consisted of an extruder barrel, feed port, heater, clockwise and anticlockwise screw, die with nozzle (∅2.5 mm), and transmission devices (Fig. 1a). In this study, raw

Effects of extrusion screw speed and temperature on SDF content

Compared to other extrusion processes, the unique device developed by our group contains a clockwise and anticlockwise screw and a die with a nozzle (∅2.5 mm). Using a clockwise and anticlockwise screw can extend the retention time of soybean residues for further thermal degradation. In addition, heat pretreatment, which is required for conventional extrusion processes, is no longer necessary because the retention time is extended. In other words, raw soybean residues with high a water content

Conclusions

In this study, BEP was applied to improve the recovery of SDF from soybean residues under optimal conditions. Our results illustrate that the recovery of SDF could be increased from 2.6 ± 0.3% to 30.1 ± 0.6% using the BEP process. In addition, the water solubility, water retention capacity and swelling capacity of treated soybean residues were improved compared to the control. The results of the SEM and thermal analyses indicated a high concentration of short-chain SDF with a tough, irregular

Acknowledgement

This research was kindly supported by the Key Projects of Tianjin Science and Technology Support Program (Number: 10ZCKNC01900).

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