Achieving fabrication of highly transparent Y2O3 ceramics via air pre-sintering by deionization treatment of suspension

An easy albeit quite effective deionization suspension treatment was adopted to alleviate the detrimental effects related to the hydrolysis of Y₂O₃ in an aqueous medium. Fabrication of highly transparent Y₂O₃ ceramics with a fine grain size via air pre-sintering and post–hot isostatic pressing (HIP) treatment without using any sintering additive was achieved using the treated suspensions. The hydrolysis issue of Y₂O₃ powder in an aqueous medium was effectively alleviated by using deionization treatment, and a well-dispersed suspension with a low concentration of dissolved Y³⁺ species was obtained. The dispersed suspensions were consolidated by the centrifugal casting method, and the green bodies derived from the suspension of 35.0 vol% solid loading showed an improved homogeneity with a relative density of 52.1%. Fully dense Y₂O₃ transparent ceramic with high transparency was obtained by pre-sintering consolidated green compacts at a low temperature of 1400°C for 16 h in air followed by a post-HIP treatment at 1550°C for 2 h under 200 MPa pressure. The sample had a fine average grain size of 690 nm. The in-line transmittance of the sample reached 83.3% and 81.8% at 1100 nm and 800 nm, respectively, very close to the theoretical values of Y₂O₃.     

洋葱蛋白及多肽的制备及其体外抗氧化活性评价

对洋葱蛋白、4种不同水解度的粗洋葱多肽、4种分子量范围的纯化多肽组分的水解度、分子量、氨基酸组成、DPPH·清除能力进行了研究。结果表明,洋葱蛋白酶解后分子量大幅降低,必需氨基酸组分和支链氨基酸组分均有所提高,DPPH·清除能力大幅提高,且与水解度成正比;在4种水解度的粗洋葱多肽的纯化组分中,P-III(分子量为1~5kDa)的DPPH·清除能力均为最强,这归功于其合适的分子量分布。该研究为洋葱的高值化利用提供了理论依据。     

Hydrolytic degree and antioxidant activity of purified casein characterised by different haplotypes (αs1-, β- and k-casein) after enzymatic hydrolysis with pepsin and enzymatic extract from Pleurotus eryngii

The aim of this study was to estimate the hydrolytic degree and antioxidant activity of purified casein characterised by different haplotypes (α_s1-, β- and k-casein) after in vitro digestion with two different enzymatic systems: pepsin from porcine gastric mucosa (EP) and a crude enzymatic extract from the edible mushroom Pleurotus eryngii. The used enzymes showed a different mode of casein catalysis with a consequent production of peptides of different antioxidant activity. The CN haplotype significantly influenced peptides production; in fact, the amino acid substitutions caused by genetic polymorphisms at the α_s1-, β- and k-CN loci influenced the sites of enzymatic cleavage and therefore the produced peptides. The above is evidenced by the different antioxidant activity found in the hydrolysates depending on the used enzymatic system, the CN haplotype, and the CN haplotype × enzymatic treatment interaction. The findings of this study are a perspective for the production of specific foods that exert a biological effect in addition to the nutritional one.     

New batch and continuous systems for converting hydrogen from water hyacinth

Water hyacinth was the chosen alternative biomass for H₂ production in this study. A batch and a continuous pilot plant systems are proposed. A batch system of 500?ml capacity was developed first for finding an appropriate biomass ratio which was found to be 2.5%wt. Results from the batch system was used to construct a kinetic model of water hyacinth hydrolysis. The same biomass and water ratio was used in the continuous system. Besides water hyacinth, glucose and cellulose?+?lignin biomasses were tested. During processing, temperature, pressure, and electric consumption of the system were recorded. The quality and quantity of gas products were analyzed by gas chromatography (GC). The water hyacinth biomass attained the highest rate of H₂ production (providing energy of 11.43?kWh/mole of glucose). Comparing the batch and continuous pilot systems, the continuous system achieved 2.7 times more H₂ mole% than the batch system did.     

三液相酶催化体系水解橄榄油的研究

采用三液相酶催化体系水解橄榄油,考察构成三液相体系的物质对酶的影响;考察了硫酸铵的含量和PEG400的含量对酶的分配分数、回收率及催化效率的影响,研究了中下相与油的体积比对水解橄榄油的影响,并初步探究了三液相体系水解橄榄油的微观液滴结构。结果表明:在酶添加量142.5 U/g、硫酸铵含量15%、PEG400含量28%、中下相与油的体积比3∶1、转速200 r/min条件下,酶的分配系数达到28.28,酶的回收率达99.65%,水解24 h后,脂肪酸含量达98.17%,在对照(油水体系)中,相同条件下产生的脂肪酸含量仅为42.06%。显微镜下液滴观察结果表明,三液相体系中独特的液滴结构可能是该体系优于油水两相体系的原因。     

绿豆抗氧化肽的酶法制备及其抗氧化活性

为提高绿豆淀粉生产过程中产生的废弃物绿豆蛋白的资源利用率，研究了酶法制备绿豆抗氧化肽的最佳条件，并探究其抗氧化活性。通过选用不同蛋白酶及其复合酶，对绿豆蛋白进行水解，综合考虑反应时间、加酶量等因素，对酶解反应进行优化。通过体外抗氧化实验对水解制得的多肽溶液进行抗氧化能力检测，最终确立了最佳的反应条件，具体如下：选用中性蛋白酶进行酶解，底物质量分数3%，酶解时间3 h，加酶量质量分数2%，pH 7，温度50 ℃。按照该条件所制得的绿豆多肽溶液，质量浓度为5 mg/mL时，DPPH自由基清除率可达（91.58±2.44）%，同时还具有较强的还原能力。经凝胶层析柱分离纯化后得到5个分离组分，其中小分子肽段组分5的抗氧化能力最强，高于其他大分子肽段以及未分离多肽。     

芝麻粕蛋白酶法提取工艺优化及组分分析

为了综合利用芝麻粕资源，以芝麻粕为原料，利用硬脂酸、吐温80、十二烷基硫酸钠三种表面活性剂对其进行脱脂处理，再采用水剂法去除表面活性剂，最后利用中性蛋白酶、碱性蛋白酶和木瓜蛋白酶对芝麻粕蛋白进行水解，以芝麻粕蛋白溶出率为考察指标优选出最佳水解酶。在此基础上，通过单因素试验和正交试验对酶解工艺条件进行优化，并利用2,4-二硝基氟苯柱前衍生高效液相色谱法分析水解物成分。结果表明，吐温80脱脂效果最好，芝麻粕脱脂率达93.49%；碱性蛋白酶为最佳水解酶，其最佳酶解条件为料水比1∶10（g∶mL）、酶解温度50 ℃、加酶量0.04%、酶解时间3.0 h。在此最佳酶解条件下，芝麻粕蛋白溶出率为88.94%。水解物中含有20种氨基酸，其中8种人体必需氨基酸含量高于FAO/WHO的推荐值。     

Effects of ultrasound-assisted enzymatic hydrolysis and monosaccharides on structural,antioxidant and flavour characteristics of Maillard reaction products from sweet potato protein hydrolysates

Effects of ultrasound (US)-assisted enzymatic hydrolysis and different monosaccharides (arabinose; xylose, XY; galactose and glucose) on peptide structure, antioxidant activities and flavour characteristics of Maillard reaction products (MRP) from sweet potato protein hydrolysates were investigated. US markedly enhanced the MR progress, and USXY showed the lowest pH value of 5.04, the highest browning intensity and fluorescence intensity (P < 0.05). FTIR results revealed significant peptide structure changes in USXY, USAR and USGA compared to other samples. USXY exhibited the highest Oxygen radical absorbance capacity (ORAC) value of 109.15 µg TE/mL, followed by USGA and USAR (94.07 and 93.41 µg TE/mL), respectively (P < 0.05). USXY and USAR showed different aroma features as compared to other MRP (P < 0.05). In addition, US enhanced umami, sweetness and sourness attributes and reduced bitterness of all MRP. USXY exhibited the highest umami intensity score (7.4), followed by USGA (7.3) and USAR (7.2), respectively. Partial least square regression analysis showed that the stronger umami taste was strongly correlated to aldehydes, thiophenes, MW 1000–3000 and 500–1000 Da peptides. Thus, US-assisted enzymatic hydrolysis and MR with xylose (XY) could be a promising way to produce natural flavouring with improved antioxidant activity.     

Impact of defects on the decomposition of chemical warfare agent simulants in Zr-based metal organic frameworks

Metal organic frameworks (MOFs) containing zirconium secondary building units (SBUs) in UiO-67 and related MOFs, are highly active for neutralizing both the chemical warfare agents and simulants, such as dimethyl methylphosphonate (DMMP). However, two recent publications gave conflicting reports of DMMP reaction with UiO-67 under ultra high vacuum (UHV) conditions, with one reporting chemisorption and reaction (Wang et al., J Phys Chem C, 2017, 121, 11261–11272) and the other reporting only physisorption and reversible desorption (Ruffley et al., J Phys Chem C, 2019, 123, 19748–19758) from very similar temperature programmed desorption experiments. We show that the discrepancy between these experiments may be explained by different levels of missing linker defects in the UiO-67 samples. We present density functional theory calculations showing that SBU sites having two-adjacent missing linkers exhibit reaction barriers that are about 30 kJ/mol lower than SBU sites having a single missing linker. We also show that topology of the undercoordinated sites plays an important role in the reaction barrier under UHV conditions.     

The effect of hydrolysed tragacanth gum and inulin on the probiotic viability and quality characteristics of low‐fat yoghurt

This study investigates the effect of supplementation of tragacanth gum (GT, 0.05% w/v), low molecular weight gum tragacanth (LMWGT, 0.5% w/v) and inulin (0.5% w/v) on the viability of Bifidobacterium bifidum and the quality parameters of low‐fat yoghurt during a three‐week storage period. The count of probiotics was found to be 7.8 log cfu/g in inulin, and LMWGT enriched yoghurts at the end of the storage period. The minimum water holding capacity and the maximum syneresis values were also obtained in the low‐fat yoghurt enriched with GT throughout the storage time. The samples containing inulin and LMWGT revealed sensory attributes that were judged superior compared to those in GT.