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Nanocomposites of chitosan and nanoclays (MMT-Na ϩ and Cloisite 30B) were prepared by solvent casting. The structural properties, thermal behaviors, and mechanical properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy, differential scanning calorimetry, thermogravimetry analyses, and an Instron universal testing machine. XRD and TEM results indicated that an exfoliated structure was formed with addition of small amounts of MMT-Na ϩ to the chitosan matrix. Intercalation along with some exfoliation occurred with up to 5 wt % MMT-NaMicro-scale composite (tactoids) formed when Cloisite 30B was added to the chitosan matrix. Surface roughness increased with addition of a small amount of clay. Tensile strength of a chitosan film was enhanced and elongation-atbreak decreased with addition of clay into the chitosan matrix. Melt behavior and thermal stability did not change significantly with addition of clays.

Cereal Chem. 81(6):735-740Acetylation of high-amylose (70%) maize starch to high degree of substitution (DS) was studied by reacting starch with acetic anhydride using 50% aqueous NaOH as the catalyst. DS increased with increasing reaction times and increasing ratios of acetic anhydride to starch. Reaction efficiency (RE) increased with longer reaction times and decreased with increases in the ratios of acetic anhydride to starch for extended reaction times. Increasing the amount of NaOH increased both DS and RE. A series of starch acetates with DS values of 0.57-2.23 were prepared and their crystalline structures, chemical structures, thermal stability, and morphological properties were investigated. After acetylation, and as DS increased from 0.57 to 2.23, the crystalline structures of starch steadily disappeared. The carbonyl group's peak at 1,740 cm -1 appeared in the FTIR spectra. The intensity of this peak increased with a decrease in the peak intensity of the hydroxyl groups at 3,000-3,600 cm -1 , indicating that the hydroxyl groups on starch were replaced by the acetyl groups. Thermal stability of starch acetates increased. The smooth surface of the starch granules became rough with acetylation. Further acetylation led to the loss of the starch granules and the formation of beehive-and fibrouslike structures.

Grape pomace is a potential source of natural antioxidant and antimicrobial agents. Phenolic compounds, antioxidant, and antibacterial properties of pomace extracts from four Virginia‐grown grape varieties were investigated. White grape pomaces had higher (P < 0.05) solvent extraction yield than red varieties. Concentrations of total phenolic (TPC), total flavonoid (TFC), total anthocyanin (TAC), tannins, condensed tannins (CT), as well as antioxidant capacities (DPPH• and ABTS•+free radical scavenging) differed (P < 0.05) among four pomace extracts. ABTS•+ scavenging capacity was positively correlated with TPC, TFC, tannins, and CT (P < 0.05), whereas DPPH• capacity was positively correlated with TAC (P < 0.05). Nine flavonoid compounds were identified, of which catechin and epicatechin were the two most abundant. Antibacterial activity was observed against Listeria monocytogenes ATCC 7644 and Staphylococcus aureus ATCC 29213, but not against Escherichia coli O157:H7 ATCC 3510 and Salmonella typhimurium ATCC 14028. L. monocytogenes was more susceptible than S. aureus.

Stinging nettle (Urtica dioica L.) has a long history of usage and is currently receiving attention as a source of fiber and alternative medicine. In many cultures, nettle is also eaten as a leafy vegetable. In this study, we focused on nettle yield (edible portion) and processing effects on nutritive and dietary properties. Actively growing shoots were harvested from field plots and leaves separated from stems. Leaf portions (200 g) were washed and processed by blanching (1 min at 96–98°C) or cooking (7 min at 98-99°C) with or without salt (5 g·L−1). Samples were cooled immediately after cooking and kept in frozen storage before analysis. Proximate composition, mineral, amino acid, and vitamin contents were determined, and nutritive value was estimated based on 100 g serving portions in a 2000 calorie diet. Results show that processed nettle can supply 90%–100% of vitamin A (including vitamin A as β-carotene) and is a good source of dietary calcium, iron, and protein. We recommend fresh or processed nettle as a high-protein, low-calorie source of essential nutrients, minerals, and vitamins particularly in vegetarian, diabetic, or other specialized diets.