Amylose content and pre-freezing regulate the structure and oil absorption of polyelectrolytes-based starch cryogel

Low density methacrylated pea, corn, and tapioca starch covalent cryogels with excellent elasticity and water/oil absorption capacity

Porous starch materials are promising in several applications as renewable natural biomaterials. This study reports an approach combining methacrylation of starch and chemical crosslinked cryogelation to fabricate highly elastic macroporous starch (ST-MA) cryogels with impressed water/oil absorption capacity and wet thermal stability among starch based porous materials. Five different types of starch, including pea, normal corn, high amylose corn, tapioca, and waxy maize starch with different amylose content, have been studied. The methacrylation degree is not related with amylose content. All cryogels exhibited excellent compressive elasticity enduring 90 % deformation without failure and good robustness in cyclic tests. The ST-MA cryogels from pea starch exhibited the highest Young's modulus and compressive strength among five types of starch. These covalent cryogels exhibit high wet-thermal stability and enzymatic hydrolysis stability, while still are biodegradable. The dry ST-MA sponges (2 wt%) showed outstanding liquid absorption capacity, absorbing ~40 folds (g/g) of water or ~ 36 folds (g/g) of oil respectively. All types of starch have similar liquid absorption performance. This study provides a universal approach to fabricate highly elastic covalent starch macroporous materials with impressed liquid absorption capacity and outstanding stability, especially wet-thermal stability, and may expand their applications.

Stabilization and release of thymol in pre-formed V-type starch: A comparative study with traditional method

Recently, pre-formed V-type starch has become popular as a versatile carrier in encapsulation systems of containing starch-guest inclusion complexes (ICs). However, the differences in stabilizing and dissociating guests between ICs prepared by either the traditional method or the pre-formed "empty" helix method have not yet been elucidated. Here, starch-thymol ICs were prepared using the traditional high temperature-water method and the pre-formed method, covering different complexation temperatures and solvents, to compare the loading capacity, crystalline structure, thermal stability, and release properties. The highest content of thymol in ICs prepared by the pre-formed and the traditional method was 74.2 and 65.3 mg/g, respectively. Different from ICs prepared by the traditional method (V7-type crystal), ICs prepared by the pre-formed method mostly exhibited a V6a structure with larger crystallinities and a better short-range ordered structure. ICs prepared at 90 °C were type II complexes and efficiently protected thymol from rapid heat loss. A slow release was observed in both cases: about 45 % and 75 % of thymol were released from ICs prepared by the pre-formed and traditional methods, respectively, after two weeks of storage at 25 °C.

Comparative study of the structure and mechanical properties of starch aerogels fabricated from air-classified and isolated pulse starches

Significant amounts of starch and protein are generated as co-products during fractionation of pulse seeds. While pulse proteins (PP) have garnered a lot of interest in numerous applications, little attention is shown to pulse starch (PS). The creation of novel materials such as bioplastics could revolutionize the use of pulse starches. In this study, we investigated the prospects of air-classified and isolated pea, lentil, and faba bean starches as a precursor for fabricating pulse starch bioaerogels (PSBs) via freeze-drying technique. The results evidenced ultra-low densities (<0.1 m2/g), mesopore sizes (2-50 μm), high porosities (∼99 %), low surface areas (SBET = ∼4-18 m2/g) for all the aerogels. The adsorption isotherm showed typical Type II and III profiles, while the thermogravimetric analysis showed more weight loss (74.39-78.12 %) in aerogels mostly developed from isolated starches. Microstructural studies showed a unique distribution of pores within the developed aerogels. FTIR and XPS studies confirmed the presence of an amide (I, II, III) at different absorption bands range (∼1600-1200 cm-1) and functional groups (carboxylic group and the amide group), respectively. All the PSBs became stiffer with a corresponding increase in load, and a reversible deformation in the linear region was identified at <5 % strain. Comparatively, saturated PSBs from air-classified starch at a relative humidity of 95 % showed a drastic reduction in their compressive moduli (CM), while PSBs from isolated starch experienced markedly high CM. Moisture saturation was achieved at 72 h for all the samples. This study provides crucial information that could spark a keen interest in the use of non-conventional starch for the creation of novel and sustainable biobased products with expanded applications.

Polymorphic nanostarch-mediated assembly of bioactives

Starch as an edible, biosafe, and functional biopolymer, has been tailored at nanoscale to deliver bioactive guests. Nanostarches fabricated in various morphologies including nanosphere, nanorod, nanoworm, nanovesicle, nanopolyhedron, nanoflake, nanonetwork etc., enable them to assemble different kinds of bioactives due to structural particularity and green modification. Previous studies have reviewed nanostarch for its preparation and application in food, however, no such work has been done for the potential of delivery system via polymorphic nanostarches. In this review, we focus on the merits of nanostarch empowered by multi-morphology for delivery system, and also conclude the assembly strategies and corresponding properties of nanostarch-based carrier. Additionally, the advantages, limitations, and future perspectives of polymorphic nanostarch are summarized to better understand the micro/nanostarch architectures and their regulation for the compatibility of bioactive molecules. According to the morphology of carrier, nanostarch effectively captures bioactives on the surface and/or inside core to form tight complexes, which maintains their stability in the human microenvironment. It improves the bioavailability of bioactive guests by different assembly approaches of carrier/guest surface combination, guest@carrier embedment, and nanostarch-mediated encapsulation. Targeted release of delivery systems is stimulated by the microenvironment conditions based on the complex structure of nanostarch loaded with bioactives.