Effects of non-thermal plasma treating wheat kernel on the physicochemical properties of wheat flour and the quality of fresh wet noodles

The effects of non-thermal plasma (NTP) on the physicochemical properties of wheat flour and the quality of fresh wet noodles ( FWN) were investigated. The results showed that NTP effectively decreased the total plate count (TPC), yeast and mould count (YMC) and Bacillus spp. in wheat flour. Wet gluten contents and the stability time reached the maximum when treated for 20 s. The viscosity of starch increased significantly after treatment due to the increased of damaged starch. The contents of secondary structure were altered to some extent, which was because that the ordered network structure of gluten protein broken. Furthermore, compared with the control, texture properties of FWN were enhanced significantly at 20 s, and the darkening rate of FWN was greatly inhibited due to the low polyphenol oxidase (PPO) activity. Consequently, the most suitable treatment was 500 W for 20 s, providing a basis for the application of NTP in flour products.     

馒头挥发物质的固相微萃取条件优化

以总峰面积和峰数为评价指标,研究了以聚二甲基硅氧烷(DVB/CAR/PDMS)为萃取头的固相微萃取(SPME)对馒头挥发物质萃取效果的影响.结果显示:当样品用量为2 g(15 mL样品瓶),萃取温度为60℃,吸附时间为60 m in,解析温度和时间分别为250℃和4 m in时,提取到的挥发物质数量较多,主要挥发物质的萃取效果较好.馒头的挥发物质主要有醇类64.88%、羰基化合物4.29%、苯类3.81%、酯类2.75%、酰基化合物18.11%、杂环类6.14%.     

壳聚糖-醋酸改性对小麦面筋蛋白溶解度的影响及蛋白质二级结构的分析研究

以自制的小麦面筋蛋白为原料,采用壳聚糖与醋酸共同作用改善小麦面筋蛋白的溶解性能.确定最佳工艺条件为:醋酸pH值为3、壳聚糖添加量为0.1%(占小麦面筋蛋白干基的质量,W/W)、加热温度为70℃、搅拌时间为50 min.在此奈件下,小麦面筋蛋白的溶解度由原来的0.35 g/L提高到了7.69 g/L.此外,红外光谱分析表明,在壳聚糖添加量为0.1%时,壳聚糖对面筋蛋白产生的仅仅是物理作用而不是化学接枝作用.     

Investigation on a spectral splitting photovoltaic/thermal hybrid system based on polypyrrole nanofluid: Preliminary test

The present work developed a spectral splitting hybrid photovoltaic/thermal (PV/T) system based on polypyrrole nanofluid. This hybrid PV/T system can overcome the limitation of temperature in traditional PV/T, and achieve a high-temperature thermal output. In this system, the polypyrrole nanofluid employed in the spectral splitting filter can absorb the solar radiation that can't be efficiently utilized by PV cell unit, and convert it into medium-temperature thermal energy. The principle and methodology of the experimental system design was discussed, and the effect of particle concentration on the performance of system was investigated as well. The present work not only verifies the application potential of polypyrrole nanofluid in spectral splitting PV/T system, but also obtains some important rules on the performance. The results indicate that the temperature of nanofluid and the PV efficiency of cell unit itself increases with the particle concentration, but the thermal efficiency decreases simultaneously. The maximum overall efficiency of this hybrid PV/T system with polypyrrole nanofluid filter was 25.2%, which was 13.3% higher than that without filter. More importantly, the medium-temperature thermal energy can be harvested in such a hybrid system. Furthermore, an optimal particle concentration can probably realize a higher overall efficiency.     

Inverse dynamic analysis type of MPPT control strategy in a thermoelectric-solar hybrid energy harvesting system

This study presents the development of a novel inverse dynamic analysis-maximum power point tracking (IDA-MPPT) scheme in a hybrid energy harvesting system between thermoelectric module (TEM) and solar array (SA). The proposed method initially changes the harvested voltage response from both sources to be the third-order exponential function. This input function selection is based on the capability of this function to stabilize the initial response system and maintain its final position despite a prolonged response time. The mV voltage value from TEM is easily boosted up to nearly 5 V using this method. With this hybridization, the total obtained voltage is doubled to become 9.7 V, which results in a total power of 0.722 W. Furthermore, the method also allows for a fast tracking system, which enables faster voltage boosting and supercapacitor charging. The supercapacitor only requires less than 5 min to complete charging and boost the voltage to almost 5 V. Thus, a satisfactory value is obtained as compared with that of the TEM system with a chosen MPPC board.     

Catalytic performance of a novel amphiphilic alkaline ionic liquid for biodiesel production: Influence of basicity and conductivity

Three novel alkaline guanidine ionic liquids as amphiphilic catalysts have been successfully synthesized for two-phase transesterification, which can efficiently improve the catalytic activity for the synthesis of biodiesel. They were characterized by a series of techniques including ¹H NMR, thermal stability, electronegativity (DFT calculation), basicity and conductivity. It was demonstrated that 1,1,3,3-trimethyl-2-octyl-guanidine hydroxide(IL3) exhibited better catalytic activity compared with other base guanidine ionic liquid catalysts, which was related to the better basicity and electronegativity of the ILs. The experimental results indicated that catalytic performance was relative to both enough alkaline center and conductivity of ionic liquid catalysts, but the former was a main factor in the catalytic system. The catalytic performance also revealed that optimum catalyst dosage was about 6 wt.%, the appropriate reaction temperature was about 55 °C, the optimum n(Methanol)/n(Soybean Oil) for the biodiesel synthesis was about 15:1 and the suitable reaction time was 4 h on the basis of biodiesel yield of 97%. In addition, the reaction mechanism of the amphiphilic catalyst was illuminated by the interaction between the methoxyl group and the carbonyl group of the triglyceride after activating for two-phase transesterification.     

Impact of cryoconcentration on casein micelle size distribution,micelles inter-distance,and flow behavior of skim milk during refrigerated storage

Cryoconcentration combined with a cascade effect was used to concentrate skim milk up to 25.12% total dry matter. Size, shape, and inter-micellar distance of casein micelles were characterized by ZetasizerNano-ZS, transmission electron microscopy, and ImageJ analyses. Flow properties of the cryoconcentrated skim milk were evaluated during 5 weeks of storage under refrigerated condition at 4 °C. Milk color was also evaluated according to the L*, a*, and b* system. The cryoconcentrated skim milk obtained after three cryoconcentration cycles was characterized by a monomodal distribution of its micelles with a tendency to smaller casein micelles. Approximately 60% of the total micellar volume was occupied by the casein micelles with a size of 100–200 nm, less than 18% of the volume with a size of 50–100 nm and only less than 1% was occupied by micelles with a size > 350 nm. This result shows that cryoconcentration changed the distribution of the mean size of the casein micelles to smaller units. No significant difference was observed on the inter-micellar distance. Cryoconcentration significantly improved the color of skim milk by increasing the L* value up to 67 which was similar to that of whole milk. Transition from a Newtonian to a non-Newtonian behavior was observed from the fourth week storage with a slight increase of casein micelle size.Industrial relevanceA concentration procedure of skim milk based on a complete block cryoconcentration technique was proposed. Application of this sub-zero technology permitted the concentration of skim milk total dry matter up to 25%. The casein micelle size was positively affected by moving the major part of the micelles toward the smaller size, whereas the inter-micellar distance was not affected. This new knowledge can be exploited in milk-based products to enhance the product stability. The cryoconcentrated skim milk color was positively affected since its L* value, which represents the milk whiteness, was significantly improved. The flow behavior of the cryoconcentrated milk was of Newtonian type up to 4 weeks of storage at 4 °C. The generated knowledge in this study can be easily used by the milk processing industry in order to make stable milk product with high dry matter content without adding milk powder, which negatively affects the product sensory properties (floury consistency).     

The effect of pectin concentration and degree of methyl-esterification on the in vitro bioaccessibility of β-carotene-enriched emulsions

Soluble fibers, like pectin, are known to influence the physicochemical processes during the digestion of dietary fat and may therefore affect the absorption of lipophilic micronutrients such as carotenoids. The objective of the current work was to investigate whether the pectin concentration and degree of methyl-esterification (DM) influence the bioaccessibility of carotenoids loaded in the oil phase of oil-in-water emulsions. The in vitro β-carotene bioaccessibility was determined for different oil-in-water emulsions in which 1 or 2% citrus pectin with a DM of 99%, 66% and 14% was present. Results show that pectin concentration and DM influence the initial emulsion properties. The most stable emulsions with the smallest oil droplets (D(v,0.9) of 15–16 μm) were obtained when medium or high methyl-esterified pectin was present in a 2% concentration while gel-like pectin structures (D(v,0.9) of 114 μm), entrapping oil droplets, were observed in the case where low methyl-esterified pectin was present in the aqueous emulsion phase. During in vitro stomach digestion, these gel-like structures, entrapping β-carotene loaded oil droplets, significantly enlarged (D(v,0.9) of 738 μm), whereas the emulsion structure could be preserved when the medium or high methyl-esterified pectin was present. Initial emulsion viscosity differences, due to pectin concentration and especially due to pectin DM, largely disappeared during in vitro digestion, but were still significant after the stomach digestion phase. The observed differences in emulsion structure before and during in vitro digestion only resulted in a significant difference between emulsions containing low methyl-esterified pectin (β-carotene bioaccessibility of 33–37%) and medium/high methyl-esterified pectin (β-carotene bioaccessibility of 56–62%).     

Analysis of chemical compounds and toxicological evaluation of Forsythia suspensa leaves tea

To determine the compositions of Forsythia suspensa leaves tea (FSLT) and its safety, the chemical compounds were analysed with some methods, and the toxicity was evaluated in Kunming mice and Wistar rats. The results showed that FSLT contained rich flavonoid, lignans, triperpene acids, amino acids, and mineral elements. In the acute toxicity study, none of the mice died, and no obvious poisoning symptoms were observed after 14 days in mice at the dose of 15 mg/g·body weight (bw) FSLT; in the sub-chronic toxicity, no abnormal or dead rat was found at the dose of 1, 3, and 10 mg/g·bw during 90 days feeding administration; there was no significant difference in bw and food consumption; no significant differences were found in each hematology and serum biochemistry parameter and organ/body weight ratio comparing with the control experimental group. The results revealed that the FSLT has low or no toxicity via oral administration. Therefore, FSLT is very suitable and safe to be used as a new resource food.