Impact of Particle Size on the Rheological Properties and Amylolysis Kinetics of Ungelatinized Cassava Flour Suspensions

Tien Cuong Nguyen,Luc Fillaudeau,Dominique Anne-Archard,Thi Hoai Duc Nguyen,Thu Trang Vu,Son Chu-Ky,Van Hung Nguyen,Hong Nga Luong

doi:10.3390/pr9060989

Abstract

The effect of particle size on enzymatic hydrolysis of cassava flour at subgelatinization temperature was investigated. A multiscale physical metrology was developed to study the evolution of different physical-biochemical parameters: rheology, granulometry, and biochemistry. In this study, four fractions of cassava flour based on the particle sizes under 75 µm (CR075), 75–125 µm (CR125), 125–250 µm (CR250), and 250–500 µm (CR500) were screened for enzymatic hydrolysis effect. The results showed that all cassava flour suspensions exhibited a shear-thinning behavior, and the viscosity increased drastically with the increase of particle size. During hydrolysis, the viscosity reduced slightly and the non-Newtonian behavior became negligible beyond 4 h of the process. The particles size for CR075 and CR125 increased steadily in diameter mean. The samples of CR250 and CR500 showed more fluctuation by first decreasing, followed by increasing in particle sizes during the process. The highest hydrolysis yield was found for samples with particle size under 125 µm (89.5–90.7%), suggesting that mechanical treatment of cassava can enhance the bioconversion rate.

Highlights

This study investigates the impact of cassava flour granulometry on the suspension viscosity and hydrolysis yield at low-temperature by a multiscale approach combining in-situ physical and ex-situ biochemical analyses
The initial particle size distribution generally showed a bimodal distribution for all cassava flour samples (Figure 2), as reported by previous studies for other cereals and legumes in an aqueous medium [28,29]
This study investigated the rheo-granulo-biochemical changes during enzymatic hydrolysisofofungelatinized ungelatinizedcassava cassavaflour floursuspension

Summary

Introduction

The conventional starch-based sugar production technology requires a high energy consumption during liquefaction and saccharifications. This energy consumption can be reduced by decreasing the starch hydrolysis below gelatinization temperature [1]. This lowtemperature technology is activated by several amylolysis enzymes that attack native starch (granular form) and by-pass the liquefaction and cooking steps as in the conventional process [2]. The enzymatic action occurs in several stages including solid surface diffusion, enzyme adsorption and hydrolysis The mechanism of this biocatalytic depolymerization of raw starch has been well investigated for diluted conditions with starchy grains such as corn, triticale, wheat, etc. To scale-up the low-temperature hydrolysis process in a more economical and feasible way, two strategies have been developed: (i) to operate at very high gravity hydrolysis/fermentation (VHG) and (ii) to apply a dynamic control of process parameters [10]

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Results

Conclusion