The renewability, biocompatibility, and mechanical properties of cellulose nanocrystals (CNCs) have made them an attractive material for numerous composite, biomedical, and rheological applications. However, for CNCs to shift from a laboratory curiosity to commercial applications, researchers must transition from CNCs extracted on the bench scale to material produced on an industrial scale. There are a number of companies currently producing kilogram to ton per day quantities of sulfuric acid-hydrolyzed CNCs as well as other nanocelluloses, as described herein. With the recent intensification of industrially produced CNCs and the variety of cellulose sources, hydrolysis methods, and purification procedures, the characterization of these materials becomes critical. This has further been justified by the past two decades of research that demonstrate that the CNC stability and behavior are highly dependent on the surface chemistry, surface charge density, and particle size. This work outlines key test method...

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Benchmarking Cellulose Nanocrystals: From the Laboratory to Industrial Production

The objectives of this paper are to review the thermal degradation and stability of starch and starch-based materials, including both fundamental sciences such as detecting techniques, the effect of amylose/amylopectin content in starches and starches modifications, as well as the effect of different processing environments, such as an open or sealed system, and shearless or shear stress conditions. The decomposition temperature of starches was increased with increasing amylopectin content in an open system. In the open system, the initial water content did not affect the decomposition temperature because all water had evaporated from samples prior to reaching the decomposition temperature. Two decomposition temperatures were observed in the sealed system: the first at lower temperature represents long chain scission; and the second at higher temperature involves decomposition of glucose ring. In the sealed system, the first degradation was increased with increasing amylopectin content. There is no observable difference of the second degradation for the samples containing different amylose/amylopectin ratios. The higher the moisture content is, the lower the second decomposition temperature is detected in the sealed system. Significant shear degradation was observed in amylopectin component of starch, while high amylose starch proved less sensitive to shear stress. The achievements in this area have increased the knowledge of polymer science, in particular to understand the degradation of natural polymers.

Thermal degradation and stability of starch under different processing conditions

This paper reviews the recent development of starch-based materials, including both fundamental and application researches. In order to overcome the weakness of pure starch-based materials, such as lower mechanical properties found in natural polymers and moisture sensitivity, various blends and composites have been developed in the last two decades. In practical, incorporation of any additives is sensitive in developing fully biodegradable starch-based materials. Furthermore, safety issues will be considered as priority regarding any additives for food packaging applications. Based on these concerns, various natural filler and edible reinforce agents, such as natural fibers, starch or cellulous crystals, and laver, have been used in starch-based materials. So-called self-reinforced techniques, reinforcing starch matrix by modified starch particles, have also been used in developing starch-based composites. During developing starch-based foams the unique function of water, acts as both plasticizer and blow agent for starch-based foam, has been systematically studied. So far, various conventional processing techniques such as extrusion, injection, compression molding, casting and foaming, as well as some new techniques such as reactive extrusion, have been adapted for processing starch-based polymeric materials. Various starch-based products have been developed and commercialized.

Starch-based biodegradable materials: Challenges and opportunities

Research involving resistant starch (RS) is becoming more prominent. RS has the ability to modulate postprandial blood-glucose levels and can be fermented by the colonic microflora to produce short-chain fatty acids, which exert positive health benefits on the consumer such as increased colonic blood flow to ease colonic inflammation and a decreased risk of colon and/or other cancers. This paper reviews the effects of genetic manipulation on amylose levels in plants, enzymatic hydrolysis, physical treatments, chemical modifications, exposure to γ-rays, and the effects of lipid complexation on the RS content of starches from various botanical sources. All treatments reviewed increased the RS content; however, select treatments (namely genetic manipulation, enzymatic debranching, hydrothermal treatments, high hydrostatic pressure, most chemical modifications, γ-irradiation exposure, as well as lipid complexation) were more effective to varying degrees than were extrusion and mineral acid treatments. Various methods commonly used for measuring RS were compared. Additionally, the effects of food matrix components were also examined to gauge their effectiveness at inhibiting or enhancing RS formation, with lipids and gums known to be the most effective at enhancing (or apparently enhancing) RS. This review draws largely, but not exclusively, from research published post 2009.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12104

Methodologies for Increasing the Resistant Starch Content of Food Starches: A Review

Synthesis, characterization, bioactivity and potential application of phenolic acid grafted chitosan: A review.

Thermal oxidation degradation of high-amylose (80 %) cornstarch has been studied using thermogravimetry analyser coupled to Fourier transform infrared spectroscopy (TG-FTIR). The linear structure of amylose provides a modal material to understand how the starch microstructure affects on the decomposition mechanisms. Kinetics of the thermal oxidation has been studied using different methods. It is found that the thermal oxidation degradation is more complex than thermal degradation, thermal oxidation degradation kinetics of the starch can be interpreted in terms of multi-step degradation mechanism, the activation energies obtain from Flynn–Wall–Ozawa (F–W–O) method and modified Coats–Redfern method are in good agreement. TG-FTIR and FTIR results confirm that the thermal oxidation mechanism of starch is a process containing long chain scission and glowing combustion.

Thermal-oxidative degradation of high-amylose corn starch

High-amylose (80%) corn starch was modified by hydroxypropylation with different molar substitution (MS) The unique microstructure of high-amylose starch keeps its granules intact after hydroxypropylation However, the microstructures and thermal properties strongly depend on the MS of hydroxypropylation With increasing MS, the granule size was increased, which is partly due to disrupted granule structure, particularly in the amorphous region Unlike normal starch, the modified high-amylose corn starch showed a narrow gelatinization range measured by differential scanning calorimetry (DSC), which can be explained by destruction of amylose-lipid complex Internal microstructures and morphologies of hydroxypropylated starch were investigated using confocal laser scanning microscopy and to further explore the mechanism of chemical reaction and phase transitions

Morphologies and thermal properties of hydroxypropylated high-amylose corn starch.

The retrogradation process of the biphasic endotherms Gr and M1 r for waxy cornstarch was systematically investigated using differential scanning calorimetry (DSC). The high temperature endotherm M1r developed significantly within 2―5 h, while the retrograded endotherm Gr appeared after 5 h storage and increased with time. The single endotherm Gr was separated using an analytical software, and the enthalpy was found to be ∼36% of the total enthalpy of the retrograded starch. Compared to normal cornstarch (∼77% amylopectin content), the final retrogradation ratio of the waxy cornstarch was higher. Both the waxy and normal cornstarches investigated showed a similar pattern of retrogradation process, which developed quickly in the initial stage (up to 1 day) and then gradually came to a near-constant value in the second stage (from 1 to 20 days).

Zhen Tong

Papers

Thermal degradation and stability of starch under different processing conditions

Thermal-oxidative degradation of high-amylose corn starch

Morphologies and thermal properties of hydroxypropylated high-amylose corn starch.

Retrogradation of waxy cornstarch studied by DSC