Effect of UV-C irradiation on inactivation of Aspergillus flavus and Aspergillus parasiticus and quality parameters of roasted coffee bean (Coffea arabica L.)

ABSTRACT

This study investigated the antifungal effect of ultraviolet-C (UV-C) against Aspergillus flavus and Aspergillus parasiticus on roasted coffee beans. Also, any changes in the quality of the roasted coffee beans were measured after UV-C irradiation. As UV-C irradiation time increased (0–2 h), the number of surviving A. flavus and A. parasiticus spores significantly (P < .05) decreased. The reduction values of A. flavus in round part, crack part, and whole roasted coffee beans were 2.16, 0.71, and 1.58 log₁₀ CFU g^?1, respectively, and the reduction values of A. parasiticus in round part, crack part, and whole roasted coffee beans were 1.03, 0.37, and 0.72 log₁₀ CFU g^?1, respectively, after 2 h of UV-C irradiation. Field emission scanning electron microscopy showed that the morphology of A. flavus and A. parasiticus spores included expanded wrinkles that were deformed by UV-C irradiation. The Hunter colours were significantly reduced (P < .05). There was no significant change (P > .05) in moisture content, but the pH was significantly decreased (P < .05). Most of the sensory parameters did not change, but there was a significant difference (P < .05) in flavour. Based on this study, 2 h of UV-C irradiation was effective in reducing 90% of A. flavus, but it was not effective against A. parasiticus present on roasted coffee beans. Also, Hunter colour, pH, and sensory parameters (flavour) were changed by UV-C irradiation.     

Bioactive properties of enzymatic hydrolysates from abdominal skin gelatin of yellowfin tuna (Thunnus albacares)

Gelatin (90.6 ± 0.1%) was optimally prepared by response surface methodology from yellowfin tuna (Thunnus albacares, YT) abdominal skin. To investigate bioactive properties of enzymatic hydrolysates from the abdominal skin gelatin (ASG), ASG was hydrolysed with alcalase, protamex, neutrase and flavourzyme as affected by hydrolysis time. Antioxidant, nitrite scavenging and angiotensin‐I converting enzyme (ACE) inhibitory activities of the hydrolysates were determined. Antioxidant activities of the hydrolysates were found through linoleic acid peroxidation inhibitory effects. Alcalase‐derived hydrolysates (AHs) were more effective than others in metal ions chelating, superoxide anion scavenging and hydroxyl radical scavenging activities (P < 0.05). AHs showed significantly stronger nitrite scavenging activities (44.4–60.7%) than others (P < 0.05). Fraction A from AH showed strong ACE inhibitory activity (IC₅₀ of 0.75 mg mL^?1). These results suggest that YT ASG and its enzymatic hydrolysates could be functional food and/or pharmaceutical ingredients with potent antioxidant, anticarcinogenic and antihypertensive benefits.     

Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides

To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry.     

A resilient buffer allocation scheme in active queue management: a stochastic cooperative game theoretic approach

During the last decade, a plentiful number of active queue management schemes have been proposed, but their main objectives are simply allocating the buffer resource to all flows evenly, or protecting responsive flows from being degraded by unresponsive flows. However, the sending rates of the responsive flows can be determined diversely, and not all unresponsive flows have aggressively high sending rates. Furthermore, it is rational to reserve a portion of the buffer resource for certain privileged traffic. Grounded by these evidences, in this paper, we present a resilient active queue management algorithm, named Prior‐Core‐based Buffer Allocation considering diverse congestion control algorithms, fair‐unresponsive flows, and some privileged traffic. Our approach is based on stochastic cooperative game theory, where the payoffs yielded by cooperation are described by random variables, and the core is defined only over the distribution of these random payoffs; the core in this situation is called the prior‐core. As a result, it is shown that our buffer allocation, yielded by the prior‐core, achieves completely fair allocation for those flows whose requirement does not exceed the fair‐share regardless of the responsiveness, whereas aggressive flows are restricted according to availability of the buffer; all these are verified through ns‐2 simulation experiments. Copyright © 2014 John Wiley & Sons, Ltd.     

Flavonoids from Machilus japonica Stems and Their Inhibitory Effects on LDL Oxidation

Stems of Machilus japonica were extracted with 80% aqueous methanol (MeOH) and the concentrated extract was successively extracted with ethyl acetate (EtOAc), normal butanol (n-BuOH), and water. Six flavonoids were isolated from the EtOAc fraction: (+)-taxifolin, afzelin, (−)-epicatechin, 5,3''-di-O-methyl-(−)-epicatechin, 5,7,3''-tri-O-methyl-(−)-epicatechin, and 5,7-di-O-methyl-3'',4''-methylenedioxyflavan-3-ol. The chemical structures were identified using spectroscopic data including NMR, mass spectrometry and infrared spectroscopy. This is the first report of isolation of these six compounds from M. japonica. The compounds were evaluated for their diphenyl picryl hydrazinyl scavenging activity and inhibitory effects on low-density lipoprotein oxidation. Compounds 1 and 3–6 exhibited DPPH antioxidant activity equivalent with that of ascorbic acid, with half maximal inhibitory concentration (IC₅₀) values of 0.16, 0.21, 0.17, 0.15 and 0.07 mM, respectively. The activity of compound 1 was similar to the positive control butylated hydroxytoluene, which had an IC₅₀ value of 1.9 µM, while compounds 3 and 5 showed little activity. Compounds 1, 3, and 5 exhibited LDL antioxidant activity with IC₅₀ values of 2.8, 7.1, and 4.6 µM, respectively.     

An Integrative Loss Function Approach to Multi‐Response Optimization

Loss function approach is effective for multi‐response optimization. However, previous loss function approaches ignore the dispersion performance of squared error loss and model uncertainty. In this paper, a weighted loss function is proposed to simultaneously consider the location and dispersion performances of squared error loss to optimize correlated multiple responses with model uncertainty. We propose an approach to minimize the weighted loss function under the constraint that the confidence intervals of future predictions for the multiple responses should be contained in specification limits of the responses. An example is illustrated to verify the effectiveness of the proposed method. The results show that the proposed method can achieve reliable optimal operating condition under model uncertainty. Copyright © 2013 John Wiley & Sons, Ltd.     

New disposable microfluidic chip without evaporation effect for semen analysis in clinics and homes

The number of infertile couples considering using assisted reproductive technologies (ARTs) is growing. Several key indices, such as sperm concentration and motility, are considered when determining an appropriate technique among the existing ARTs. While microscopy is the only way to observe sperms, this method tends to overlook the actual swimming ability of sperms because sperms can be observed only within a very narrow field of view (FOV). In this paper, we propose a microfluidic chip capable of measuring the motility of sperms by inducing the actual swimming ability of sperms in microchannels. To determine whether sperms swim by themselves and reach the target point, 5–10 min is required in an incubator at 37 °C, which inevitably causes the evaporation of the fluid at the microfluidic chip inlet or outlet. A unique structure has been added to the microfluidic chip to prevent unwanted fluid flow due to evaporation, and counting and sorting capabilities of the fabricated device have been experimentally demonstrated. The microfluidic chip is shown to have a good agreement with commercial chips in total sperm counting. Another feature of sorting motile and progressive sperm to 95% on one chip is also verified. This feature differentiates our solution from the existing commercial chips and can help increase the success rate of ARTs. The developed MFC can provide a way to determine the actual swimming motility of sperms using a microscope in small clinics or a portable kit which is publicly available without the expensive sperm analysis equipment.