Rice husk is a rich source of biogenic silica nanoparticles (SNPs) having excellent physico-chemical properties and numerous potential applications. Extraction yield of the biogenic SNPs may be influenced by many factors. In this study, morphology and the influence of solvent type (sodium hydroxide/NaOH, potassium hydroxide/KOH) and aging time (0, 6, 12, 18, 24h) on extraction yield and properties of selected biogenic SNPs from Indonesian rice husk were investigated. The biogenic SNPs were produced by a simple sol-gel method. The presence of biogenic SNP aggregates in the rice husk tissues was successfully identified by SEM-EDX micrographs. NaOH produced better SNPs extraction results than KOH. Aging time for 6h was the optimum condition for production of SNPs. The TEM image showed that SNPs from the best treatment were approximately spheroidal with particle sizes in the range of 20–50nm. The XRD patterns revealed the amorphous nature of the SNPs. Nitrogen adsorption–desorption analysis showed that the SNPs had BET surface area of 235,78m2/g, total pore volume of 0.58cc/g, and average pore radius of 4.91nm. The SNPs exhibited a type IV isotherm and H1 hysteresis loop indicating a characteristic of mesoporous materials. The results suggest that the sol-gel method developed could provide a simple and relatively fast extraction technique producing biogenic amorphous mesoporous SNPs that could extend their potential applications and increase the economic benefits of utilizing rice husk.

No abstract

No abstract

The quality charcteristics of rice could be changed during storage caused by respiration and enzyme activity. The respiration process remains during storage, producing carbon dioxides, vapour, and heat. This study aimed to examine the changes in physical and chemical properties of rice (cv. Mentikwangi) for six months of storage. Rice samples were packed using plastic polypropylene and stored at ambient temperatures of 27-30 °C and 54-62% of humidity. Rice sampling was done four times, i.e., months 0, 2, 4, and 6. Observations were made on starch crystallinity, particle morphology, reducing sugars, amylose, glucose, and maltose. The SEM image and XRD data showed that rice starch was less rigid and more amorphous after four months. In addition, eating quality data showed that the rice had high swelling and needed more water. Amylographic also performed that rice samples were getting harder. Sugar and amylose reduction levels increased by 1.84% and 2.5%, respectively. Unlike both, around 7.94% of starch was reduced. The γ-amylase had broken the amylopectin chain according to the glucose content degradation and occurred naturally during the six-month storage period.