Control of Superoxide Dismutase Activity during Malting Using Plackett‐Burman and Box‐Behnken Experimental Design and Its Effect on Reducing Power of Wort

The Plackett‐Burman multifactorial design was employed to screen the important malting parameters for superoxide dismutase (SOD) in final malt of Ganpi‐3. The eight factors screened for SOD were steeping temperature, steeping time, peroxide hydrogen concentration in steeping water, germination temperature, germination time, withering temperature, drying temperature and kilning temperature. Variance analysis showed that steeping time, germination temperature and kilning temperature were significant for SOD activity. Box‐Behnken experimental design was further used to optimize the levels of the above three factors. By response surface methodology and canonical analysis, the optimal malting factors for higher SOD activity in final malt were: steeping time 42.2 h, germination temperature 16.9°C and kilning temperature 82.9°C. Under these conditions, the model predicted a SOD activity of 2234 U/g of dry weight malt. Verification of the optimization showed that a SOD activity of 2220 U/g was observed under optimal conditions. It showed that the experimental data could be reliably predicted by the polynomial model. Besides Ganpi‐3, three other barley varieties including Ganpi‐4, Ken‐2 and Hamelin were malted under optimal and common conditions under laboratory conditions. To some extent, SOD activities were higher in malts from the optimal malting process than those from the common malting process. Especially, SOD activities in Ganpi‐3 and Hamelin increased by 18.8% and 15.3%, respectively. Furthermore, twenty‐nine samples of malts, including eleven imported malts and eighteen domestic malts, were used. Relationships between SOD activity in malt and the reducing power of wort were examined. There was significant correlation between SOD activity and the reducing power of wort (R² = 0.8069).     

Microwave‐synthesized magnetic chitosan microparticles for the immobilization of yeast cells

An extremely simple procedure has been developed for the immobilization of Saccharomyces cerevisiae cells on magnetic chitosan microparticles. The magnetic carrier was prepared using an inexpensive, simple, rapid, one‐pot process, based on the microwave irradiation of chitosan and ferrous sulphate at high pH. Immobilized yeast cells have been used for sucrose hydrolysis, hydrogen peroxide decomposition and the adsorption of selected dyes. Copyright © 2014 John Wiley & Sons, Ltd.     

Microwave‐assisted extraction optimised with response surface methodology and antioxidant activity of polyphenols from hawthorn (Crataegus pinnatifida Bge.) fruit

Microwave‐assisted extraction (MAE) of polyphenols from hawthorn (Crataegus pinnatifida Bge.) fruit was investigated, and the best combination of extraction parameters was obtained using response surface methodology (RSM). The optimised procedure was achieved by soaking the sample powder with 83% ethanol for 90 min at solid–liquid ratio of 1–20, and then microwave irradiation for 13 min at power of 440 W. Under this condition, an extraction yield of 23.5% was obtained and the percentage of phenolic compounds in the extract reached 41.2%. The total content of polyphenols in hawthorn fruit was 96.9 ± 4.3 mg gallic acid equivalents per gram of dry weight measured by Folin‐Ciocalteu reagent method, and the main phenolic compounds were determined as procyanidin B₂, epicatechin, chlorogenic acid, procyanidin C₁ and rutin. Biological studies showed that the extract possessed a strong inhibitory effect against DPPH, hydroxyl radicals and lipid peroxidation, as well as strong reducing power.     

Enhanced thermal and antibacterial properties of cross‐linked waxy maize starch granules by chitosan via dry heat treatment

Cross‐linked starch was synthesised using chitosan as cross‐linking agent via a dry heating method. Thermal properties measured by DSC showed transition temperatures increased as compared with that of native starch (P < 0.001), which might indicate the starch and chitosan molecules interacted with each other. XRD demonstrated that the crystalline pattern of the starch remained the same, but there was slight change in the crystallinity degree after the cross‐links. The significant reduction of solubility, swelling power and transparency (P < 0.001) indicated that the cross‐links restricted the starch granules swelling and molecules leaching. Agar diffusion test showed that chitosan‐cross‐linked starch had excellent bacterial growth inhibition, and its antibacterial activity was stronger against Gram‐negative bacteria than against Gram‐positive bacteria. Its antibacterial activity was further confirmed using liquid broth method. Thus, the cross‐linked starch may be directly used in the food formula for protecting food as a natural antimicrobial ingredient.     

Modification of chitosan using hydrogen peroxide and ascorbic acid and its physicochemical properties including water solubility,oil entrapment and in vitro lipase activity

Chitosan was modified using H₂O₂ and ascorbic acid with different incubation temperatures (4–40 °C). The properties of modified chitosan, including its oil entrapment ability, water solubility and the lipase-resistant activities, using in vitro intestine model system were determined. Nuclear magnetic resonance analysis showed that ascorbic acid was bound to modified chitosan. All of the modified chitosan from 4 to 40 °C demonstrated improved water solubility (even in pH 7) compared to non-modified chitosan, which was only soluble at pH 4. Modified chitosan from 4 °C exhibited 27.40% of oil entrapment ability which was approximately four times higher than 6.87% of non-modified chitosan. Modified chitosan from 4 and 40 °C had increased resistance against lipase activity compared to other biopolymers, including beeswax, carnauba wax and non-modified chitosan. Modified chitosan could be used as a new food ingredient due to their high water solubility, oil-entrapping ability and resisting lipase activity.     

Effect of extrusion variables on antioxidant activity,total phenolic content and dietary fibre content of gluten‐free extrudate from germinated Chenopodium (Chenopodium album) flour

A Box‐Behnken design was used to study the effects of feed moisture content (18–20%), barrel temperature (115–135 °C) and screw speed (225–275 rpm) on the responses; antioxidant activity, total phenolics, dietary fibre, colour (L‐value), hardness, expansion ratio, water absorption index and overall acceptability for development of gluten‐free extrudate based on germinated Chenopodium album flour. Second‐order polynomial fitted model showed that temperature most significantly (P ≤ 0.05) affected the antioxidant activity (AoxA), total phenolics (TPC), expansion ratio, hardness and overall acceptability (OA). Antioxidant activity, total phenolic content and dietary fibre of extrudate varied from 11.56 to 15.93%, 56.77 to 81.28 mg/100 g and 18.65 to 22.06 g/100 g, whereas the lightness and hardness of extrudates ranged from 64.02 to 68.35 and 12.26 to 19.49 N, respectively. The results of this study validate the production of functional and acceptable snack product made from C.  album flour by extrusion cooking.     

Essential oil composition and antibacterial activity of the grapefruit (Citrus Paradisi. L) peel essential oils obtained by solvent‐free microwave extraction: comparison with hydrodistillation

The chemical composition of the essential oil (EO) obtained by solvent‐free microwave extraction (SFME) and hydrodistillation (HD) from the peel of grapefruit (Citrus Paradisi. L) was analysed by gas chromatography/mass spectrometry (GC/MS). Totally, twenty‐five components were identified in the EO. Limonene was observed as dominant (91.5–88.6%) for two extraction methods, SFME and HD, respectively. β‐Pinene (0.8–1.2%), linalool (1.1–0.7%), α‐terpinene (0.7–1.0%) and the other minor components were also detected. Disc diffusion method was applied to determine the antibacterial properties of the EO. The results showed that the EO of grapefruit peel had a wide spectrum of antimicrobial activities against Staphylococcus aureus, Enterococcus faecalis, Staphylococcus epidermidis, Escherichia coli, Salmonella typhimurium, Serratia marcescens and Proteus vulgaris, with their inhibition zones ranging from 11 to 53 mm.     

Target validation and ligand development for a pathogenic fungal profilin,using a knock‐down strain of pathogenic yeast Candida glabrata and structure‐based ligand design

The emergence of antifungal drug resistance is triggering vigorous searches for novel antifungal targets and lead compounds. In this study, we focused on fungal profilin, which is a small actin control protein sharing limited homology to human profilin. To validate its potentiality as a target, a profilin‐conditional mutant of the pathogenic yeast Candida glabrata was constructed, using a regulatable Tet promoter, and its growth was monitored in vitro. Repression of profilin expression led to severe growth defect, demonstrating the potential of this protein as a novel antifungal target. Next, novel peptides binding to the active interface of profilin were designed by computer simulation. ELISA analysis showed that these peptides did bind to the wild‐type profilin but bound less strongly to a profilin with amino acid substitutions at the active interface. Hence, we show here that profilin is a potential antifungal target and offer novel peptide ligands. Copyright © 2010 John Wiley & Sons, Ltd.