Summary Chitosan–pectin hydrogel beads that trap and release the maximal amount of combined garlic and holy basil essential oils to inhibit food microorganisms were developed based on the central composite design, with chitosan (0.2–0.7% w/v), pectin (3.5–5.5% w/v) and calcium chloride (CaCl2) (5.0–20.0% w/v) contents. The optimal bead consisted of 0.3–0.6% w/v chitosan, 3.9–5.1% w/v pectin and 8.0–17.0% w/v CaCl2, which had a high encapsulation efficiency (62.16–79.06%) and high cumulative release efficiency (31.55–37.81%) after storage at 5 °C for 15 days. Optimal hydrogel beads were packed into a cellulose bag to evaluate antimicrobial activity by the disc volatilisation method. The beads inhibited Bacillus cereus, Clostridium perfringens, Escherichia coli, Pseudomonas fluorescens, Listeria monocytogenes and Staphylococcus aureus but did not affect Lactobacillus plantarum and Salmonella Typhimurium. The oil‐containing beads could potentially be applied in food packaging to inhibit the mentioned microorganisms.
This research aimed to enhance the physicochemical and antioxidant properties of dried whole longan fruit using Maillard reaction or non-enzymatic glycosylation (glycation) in a moist-dry-heating system at 60 C with approximately 75% relative humidity for 5-50 days. During Maillard reaction, the browning index (BI) of the fruits increased significantly while lightless, redness and yellowness decreased. Interestingly, the rare sugars especially D-psicose and D-allose gradually increased by 2-3 folds when compared to the initial Maillard reaction. The development of D-mannose was additionally established through the glycation. The degree of glycation increased with the decrease of free amino acid, suggesting that conjugation of sugar with amino acids was involved. SDS-PAGE confirmed that the high molecular weight (HMW) of conjugated sugar-amino acid was the Maillard reaction product. The antioxidative properties including DPPH and ABTS radical scavenging activities, also ferric reducing antioxidant power (FRAP) were also increased as Maillard reaction progressed, which showed the activities in the range of 43.2-94.1 mg GAE/100 g dry basis, 0.23-3.09 g TE/100 g dry basis, and 0.35-5.95 g FeSO 4 /100 g dry basis, respectively. This study demonstrated a practical approach of Maillard reaction for the development of dried longan fruit with high antioxidative properties.
The ion interaction chromatographic technique has been widely used for the determination of inorganic anions. [1][2][3][4][5] This technique has high flexibility because the parameters can be readily varied to achieve suitable separation. Moreover, this powerful technique permits the separation of inorganic anions on commercially available reversed stationary columns and conventional HPLC instrumentation. 6 Culture media samples are complex because they contain inorganic salts, organic compounds, proteins and large particles (which make the solutions turbid). 7 Therefore, good sample preparation and optimization of the chromatographic conditions are needed for determining nitrite and nitrate ions.In this work, the determination of nitrite and nitrate ions in culture media (Staphyllococcus enrichment broth) including Staphyllococcus epidermis were studied. Most strains reduce nitrate ion to nitrite ion and/or ammonia as a result of nitratase and nitritase activities, respectively. 8 The goal was to find the optimum conditions for the simultaneous determination of nitrite and nitrate ions in the culture media by varying the ion interaction reagent concentration. Experimental InstrumentsThe chromatographic apparatus was a Hewlett Packard Series 1100 instrument, equipped with a quaternary pump, a diode array detector, a column thermostat and an autosampler. The chromatograms were recorded and analyzed with Microsoft Windows NT workstation version 4.0 and HP Chemstation for the LC 3D system. A Varian Microsorb MV column (3 µm, 4.6 × 50 mm) was used throughout. An Orion digital pH meter was used for pH measurements. ReagentsUltrapure water from a Millipore Milli-Q system was used to prepare all solutions. All reagents were of analytical grade. Octylamine and zinc sulfate were obtained from Aldrich, potassium hexacynoferrate was obtained from Alfa, and nitrite and nitrate ions in the form of sodium salts were obtained from Baker. Bacto m Staphyllococcus broth was prepared following a method of from the Difco manual. Chromatographic conditionsSolutions of octylammonium orthophosphate at pH 6.3 were used as the mobile phase. They were prepared by adjusting octylamine solutions (1 to 10 mM in concentrations) with orthophosphoric acid until pH 6.3 was obtained. Therefore, the concentration of the mobile phase is denoted by the concentration of the octylamine solution. No organic modifier was present. The chromatographic system was conditioned by passing the eluent through the column until a stable baseline signal was obtained. Usually, about 30 min were necessary. Then, 5 µl of the standard or sample were injected and detected at 210 nm. Sample preparationAfter 100 ml of a culture broth (Staphyllococcus enrichment broth) was prepared based on the method of Difco, Inc., the addition of the starting nitrate followed. The culture broth was sterilized in an autoclave for 15 min at a pressure of 15 pounds (121˚C). After cooling the broth to room temperature, the required amount of S. epidermis (5%v/v) was added into the sterili...
Shiitake mushrooms are prized for their unique flavor and bioactive properties. While there has been extensive research on drying methods, a comprehensive investigation of the effects of drying parameters in the dry-moist-heat system on shiitake quality is still needed. This study aimed to investigate the effects of dry-moist-heat aging on dried shiitake mushrooms comprehensively. Four aging temperatures, specifically 50, 60, 70, and 80 °C, were applied to the mushrooms, maintaining a constant humidity level of 75% RH and aging duration of 20 days. Color analysis revealed a progressive decrease in measured values as aging temperature increased, indicating noticeable changes in visual characteristics. Regarding amino acid composition, glutamic acid was found to be the predominant amino acid in shiitake mushrooms in the range of 90.29–467.42 mg/100 g. However, aging led to a reduction in overall amino acid content, with higher aging temperatures resulting in greater decline. Similarly, the equivalent umami content (EUC) also decreased (from 123.99 to 7.12 g MSG/100 g) with the increase in aging temperatures up to 80 °C, suggesting a decline in the overall umami taste sensation. Interestingly, despite the reduction in amino acid levels and umami content, the aging process positively impacted the phenolic compounds and the antioxidant activity of dried shiitake mushrooms. The antioxidative abilities of all aged mushroom extracts for DPPH, ABTS, and FRAP ranged from 65.01 to 81.39 µg TE/mL, 87.04 to 258.33 µg GAE/mL, and 184.50 to 287.68 µg FeSO4/mL, respectively. The utilization of aged temperature at 60 °C for 20 days with controlled relative humidity (~75%) should be a suitable aging condition of this edible mushroom with both antioxidant and umami qualities. Nevertheless, the control sample demonstrated higher levels of amino acid content and EUC compared to the aged samples. Conversely, the aged samples exhibited higher polyphenol content and greater antioxidant activity. Depending on specific requirements, these powders can be used in food formulation as flavor enhancers for control samples or as enriching agents for polyphenols and antioxidant activity in matured samples. Therefore, all of the powders obtained have potential applications in the field of nutrition.
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