Sandra Budžaki

The selection of suitable storage conditions and monitoring of changes in the wheat grains using suitable parameters are of great importance for the sustainability of technological quality and utilization of the entire stored quantity of wheat grains without waste generation until the next harvest. Wheat grains of three varieties, stored for 12 months at three different conditions of environmental temperature and relative humidity (% RH): (1) 40 ± 1.06 °C; 45 ± 3% RH; (2) 4 ± 1.05 °C; 45 ± 4% RH, (3) 15 ± 8.51 °C; and 67 ± 4% RH, were compared for germination percentage, protein and advanced glycation end products content, oxidoreductive and proteolytic enzyme activity, wet gluten content and falling number. A decrease in the activity of guaiacol peroxidase and polyphenol oxidase, as well as an increase in the content of advanced glycosylation end products and the falling number, was observed in wheat grains during storage conditions at 40 ± 1.06 °C; 45 ± 4% RH. On the other hand, storage of wheat grains at lower temperatures resulted in much lower changes in examined parameters, among which advanced glycation end-product content, peroxidase activity and falling number values were the greatest. Based on the obtained results, it can be assumed that changes in guaiacol peroxidase activity and falling number might be used as indicators of improper wheat grain storage.

The present study investigated the possibility of spent coffee ground (SCG) transformation to a cellulose-based enzyme immobilization carrier using a multistep extraction procedure. In the first step, SCGs were extracted with n-hexane by Soxhlet extraction in order to obtain SCG oil, while the remaining solid residue was subjected to continuous solvent flow sequential subcritical extraction with 96% and 50% ethanol and water. Afterwards, the obtained solid residue was subjected to alkaline liquefaction with 8% NaOH in order to remove lignin and produce cellulose-enriched SCGs as a potential enzyme immobilization carrier. Multistep extraction transformation of SCGs was monitored by chemical analysis of extracts and obtained solid residues. Soxhlet extraction of 100 g of SCGs yielded 10.58 g of SCG oil rich in linoleic and palmitic acid, while continuous solvent flow sequential subcritical extraction of 100 g of defatted SCGs yielded a total of 1.63 g of proteins, 5.58 g of sugars, 204 mg of caffeine, 76 mg of chlorogenic acid, and 11.97 mg of 5-(hydroxymethyl)furfural. Alkaline liquefaction of 100 g of sequentially extracted defatted SCGs by 8% NaOH yielded 7.45 g of proteins, 8.63 g of total polyphenols, 50.73 g of sugars, and 20.83 g of cellulose-enriched SCGs. Based on the characteristics of cellulose-enriched SCGs including a volume-weighted mean particle size of 277 μm, relative narrow particle size distribution with a span value of 1.484, water holding capacity of 7.55 mL/g, and a lack of carrier leakage, it could be safely concluded that produced cellulose-enriched SCGs fulfills criteria to be used as potential enzyme immobilization carrier. Overall, it seems that the proposed multistep extraction transformation of SCGs has great potential to be used for the production of several high-value added products.