Plasma-activated water for disinfection and quality retention of sea bream fillets: Kinetic evaluation and process optimization

The efficacy of plasma-activated water (PAW) in the decontamination of sea bream fillets at various processing conditions including fish/immersion agent ratio (1/1–1/5) and immersion times (0–20 min), was evaluated. Deionized water (as control samples) and artificially produced water (artificial) with equal reactive species (H₂O₂, NO₂⁻, and NO₃⁻) concentrations to PAW were also used as immersion agents for comparison purposes. All the fillets were assessed in terms of their microbiological (total aerobic bacteria – TAB, yeasts/molds, hydrogen sulfide (H₂S)-producing microorganisms, lactic acid bacteria – LAB, Pseudomonas spp., Brochotrix thermosphacta, and Enterobacteriaceae) and physicochemical (color, texture, lipid oxidation) characteristics. PAW-treated samples exhibited the highest microbial reduction; the loads of TAB, Pseudomonas spp., yeasts/molds, Enterobacteriaceae, H₂S-producing bacteria and Brochotrix thermosphacta were reduced by approximately 1.58, 2.25, 3.95, 2.14, 1.96 and 1.48 logCFU/g, respectively compared to the fish initial natural microbiota (6.81, 6.25, 3.95, 5.14, 4.96 and 4.81 logCFU/g, respectively) at the most intense process conditions (fish/immersion agent ratio of 1/5 and immersion time of 20 min) (p < 0.05). Shelf-life study of all treated fillets was conducted to validate the efficiency of PAW. During 10-d storage at 4 °C, the PAW-processed sea bream fillets had lower microbial growth rates (i.e. for TAB growth, the rate was 0.440 d⁻¹ for PAW-treated compared to 0.640 d⁻¹ for untreated fillets) and retained their color and hardness, while total volatile basic nitrogen (TVB-N) remained at low levels (14.90 mg N/100 g) compared to the untreated ones (21.84 mg N/100 g). Their shelf-life was extended by approximately 60% and 30% for PAW- and artificially processed samples, respectively, (2.8- and 1.4-day shelf-life extension compared to control samples, respectively). These aforementioned data show that PAW can be efficiently used as a disinfectant agent to control microbial degradation, while retaining the quality of fish fillets.Industrial relevanceFish fillets are perishable food products, while none of the conventional or novel processing technologies or techniques may be applied for initial microbial population decrease. Storage and transportation at refrigeration temperatures below 1 °C (within Styrofoam insulated boxes full of ice flakes) is the target of the relevant companies for extending the shelf-life as much as possible.An alternative approach for reducing the initial microbial load and the microbial growth rate of fish fillets during storage and transportation is proposed, by immersing the fillets into Plasma activated water with antimicrobial properties. The microbial load is significantly reduced, resulting in a shelf-life extension by at least 60%. This allows for more distant transportation of the fillets and for less food waste since there is more time for consumption before spoilage.     

一种频率和功率可调的固态微波功率源

现有大功率无线能量传输系统多采用磁控管作为射频源，虽输出功率高，但带宽较窄且质量重，不利于系统集成，为此设计了一套功率和频率可调的固态微波功率源。该微波功率源采用具有宽带特性的放大器件和反馈调节方式，获得了较宽的带宽和输出功率动态范围。系统集成在28 cm×19 cm×10 cm的机箱中，具有体积小、可靠性高、散热性能良好和重量轻等优点，在无线能量传输/环境射频能量收集（模拟环境中射频能量产生设备，如基站、WIFI等）系统中具有很强的工程应用价值。在室温环境下，测试结果表明该固态微波功率源频率可调范围为0.7~2.8 GHz，频率调节步进为1 MHz，最大频率偏移量<0.3 MHz；功率可调范围为20.0~39.5 dBm，输出功率最大误差为±0.5 dB。此设计方法为高功率微波功率源研究与设计提供了一定指导。     

四川唐元韭黄和云南弥勒韭黄的品质比较分析

为明确四川和云南两地主栽韭黄的品质差异，分析测定并综合评价四川省成都市唐元韭黄和云南省弥勒市韭黄的营养品质（含水量、可溶性蛋白、可溶性糖、纤维素、抗坏血酸、总酚、总黄酮、蒜氨酸）、挥发性物质含量和外观品质（单株重、总长、茎叶比、最大叶宽、分蘖数）。结果表明，经商品化处理后的唐元韭黄和弥勒韭黄外观清洁整齐，长度均一（50 cm），均为标准化程度较高、商品性较好的产品，其中唐元韭黄单株更重，假茎长，叶片黄，质地脆嫩，富含抗坏血酸，挥发性物质总释放量大，以甲基烯丙基二硫醚为主要挥发性物质；弥勒韭黄叶片偏长，口感甘甜，富含酚类物质，以二甲基二硫醚为主要挥发性物质。综上所述，唐元韭黄与弥勒韭黄营养品质相当，外观和风味口感差异明显，特色各异。