永川豆豉发酵过程中总糖和氨基酸变化与滋味的形成

通过采集传统发酵过程中的永川豆豉样本,对其总糖、还原糖、糖化酶活性、总氨基酸、游离氨基酸构成进行测定。结果表明,在成品豆豉游离氨基酸中,鲜味氨基酸占总游离氨基酸的23.98%,鲜味风味突出。豆豉中甜味氨基酸和还原糖共同构成了其回甜的滋味特点。豆豉中短链脂肪酸和乳酸使其呈现一定的酸味,酚类物质和苦味氨基酸呈现一定的苦味。这些最终决定了永川毛霉型豆豉的特有的咸鲜回甘风味特点。     

1-甲基环丙烯对甘薯块根贮藏过程中品质相关指标的影响

以目前广泛栽培的4 个鲜食型甘薯品种为材料,研究了1-甲基环丙烯（1-methylcyclopropene,1-MCP）对贮藏过程中甘薯块根品质相关指标的影响。结果表明,1.00 μL/L的1-MCP对甘薯块根中可溶性糖、直链淀粉、支链淀粉以及胡萝卜素含量等甘薯品质相关指标有显著影响,并且这种影响因甘薯品种不同而存在明显差异。与对照处理相比,1-MCP处理的4 个甘薯品种可溶性糖含量达到高峰值的时间均有所提前,1-MCP显著提高了‘广87’和‘烟薯25’块根中可溶性糖含量峰值。1-MCP显著降低了0～7 d贮藏期间‘广87’、‘烟薯25’和‘龙薯9号’块根中直链淀粉含量,显著提高‘广87’和‘苏薯16’贮藏期间直链淀粉含量峰值,显著降低了‘苏薯16’和‘烟薯25’在贮藏28～120 d期间块根中直链淀粉含量。1-MCP还显著降低了‘苏薯16’和‘龙薯9号’在贮藏28～120 d期间的支链淀粉含量。1-MCP也显著改变了胡萝卜素含量的变化趋势,提前了‘广87’、‘苏薯16’和‘龙薯9号’在贮藏期间胡萝卜素含量达到最低值的时间。     

低糖紫薯果脯微波真空渗糖工艺优化

以紫薯为试材研究微波渗糖过程中微波功率、微波处理时间、真空度、液料比和明胶添加量对低糖紫薯果脯渗糖效果的影响。以果脯中还原糖含量为指标,采用响应面法对微波真空渗糖工艺进行优化。结果表明:经冷冻预处理紫薯,以液料比71(g/g)在混合糖液(糖液组成为质量分数20%麦芽糖与20%蔗糖,以355的质量比混合,明胶质量分数1%)中进行微波渗糖,微波功率560 W、渗糖时间7 min和真空度0.05 MPa。在该条件下制得的紫薯果脯中还原糖含量达3.60 mg/g,花色苷保留率达93%,品质较好。     

Technology Optimization of Lysozyme's Fresh Maintaining Effect on Apple

Lysozyme is a kind of alkaline globin, which functions well in the degradation of the cell wall of microbe. Currently, lysozyme is widely used in various fields, such as medicine, fruit, and vegetable industry, dairy industry, and so on. Therefore, the exploitation and utilization of lysozyme is of significant economic benefit. Taking apple as material, weight loss ratio and reducing sugar content as objectives, this paper studied the fresh‐keeping effect of lysozyme. Influential factors, lysozyme concentration, soaking time, modified temperature, and reaction time were discussed in detail. The results showed that reducing sugar content was 2.043% and the weight loss ratio was the minimum in the presence of soaking time of 2 min, modified temperature of 65 °C, reaction time of 4 d, and lysozyme concentration of 0.5 g/L.     

Local levels in La1-xSrxScO3-x/2 band-gap under interaction with components of O2, H2, H2O atmospheres

The paper studies the electronic structure of proton-conducting oxides based on the lanthanum scandate La_1-xSr_xScO_3-x/2 for advancing in understanding the mechanisms of hydrogen uptake from dry and humid atmospheres into the lattice of oxides with a perovskite structure. The process of protons incorporation from H₂O containing atmospheres is considered to describe by the reaction ${\text{H}}_2\text{O}+{\text{O}}_{\text{O}}^{\times }+{\text{V}}_{\text{O}}^{??}=2{\text{OH}}_{\text{O}}^{?}$. However, there is no established concept of a mechanism for proton uptake from a dry H₂ atmosphere. At such an uptake, a positively charged proton defect will be formed in the oxide lattice, and a negative charge must appear for compensation of the excess positive charge. Formally, the reaction of this process can be represented as $\frac{1}{2}{\text{H}}_2+{\text{O}}_{\text{O}}^{\times }={\text{OH}}_{\text{O}}^{?}+{\text{e}}^{\text{′}}$. In this case an uncompensated electron appears, and the question arises as to where it is localized. In order to answer this question, it is necessary to study the electronic structure of perovskites.With increasing in dopant concentration x the absorption band at 5.6 eV overlapping with the edge of fundamental absorption increases. Most probably it can be related with oxygen vacancies. When protons are incorporated from the H₂ atmosphere into the La_1-xSr_xScO_3-x/2 lattice, the absorption intensity in this band decreases, which can be due to the transition of the defects causing this band to another charge state. In addition, specific defects that absorb in the red and IR region at hν < 2.2 eV are formed. They are found to be located deep enough in the bang-gap and not to be an electronic traps. It is also shown that in La_1-xSr_xScO_3-x/2 there are electron traps located at a depth of 2–4.5 eV in the band-gap relative to the bottom of the conduction band. On the basis of the obtained data, it can be assumed that these defects are somehow associated with oxygen vacancies, but their charge state is not obvious. It is important that these traps participate in the capture of uncompensated electrons during the proton uptake from the H₂ atmosphere.     

高效液相色谱法测定台农6 号菠萝果实中的糖分

采用高效液相色谱法测定台农6 号菠萝果实中糖分含量的方法。以90% 乙醇作为提取液,色谱柱为CHO-820(钙型)糖柱(300mm × 7.8mm),柱温90℃,流动相为超纯水,流速0.5ml/min,进样体积10μl,用示差折光检测器检测菠萝果实中的糖分。本方法的相对标准偏差为0.59%～0.85%,相关系数在0.9998 以上,加标回收率为98.84%～100.6%。台农6 号菠萝果肉含糖量与成熟季节有关,夏季果(7 月成熟)和秋季果(9 月成熟)含蔗糖最高,其次为葡萄糖和果糖,冬季果葡萄糖含量最高、蔗糖含量最低。     

减少低温锌系磷化工艺中沉渣量的几点举措

为解决钢板磷化过程中沉渣量大的问题,由磷化沉渣形成的原因入手,将试验中得出的数据绘制成图形和表格,从磷化液技术配方和磷化工艺指标两方面分析了影响沉渣量的诸因素,找出规律,提出了解决措施和合理的工艺指标,使钢铁在表面处理过程中磷化膜合格的前提下沉渣量减少了近1/2,达到了改进磷化液配方和工艺的目的.     

Phenolic content and antioxidant capacity of Philippine sweet potato (Ipomoea batatas) varieties

The study established baseline data on the total phenolic content and antioxidant activities of five sweet potato (Ipomoea batatas) varieties grown in the Philippines including Dakol, Emelda, Haponita, PSBSP and Violet. Phenolic content ranged from 192.7 to 1159.0 mg gallic acid equivalent (GAE) /100 g dry sample. Antioxidant activities were highest for Dakol, with an EC₅₀ value of 0.7 ± 0.2 mg/mL for DPPH radical scavenging activity, 2.5 ± 0.5 mg/mL for reducing power, and 2.4 ± 0.3 mg/mL for iron-chelating ability, on a dry basis. However, Haponita had the best inhibitory action on linoleic acid oxidation at 99.4 ± 0.9%. Methanolic sweet potato extracts had higher radical scavenging activity, reducing power and oxidation inhibition than α-tocopherol and higher iron-chelating capacity than ethylenediamine tetraacetic acid (EDTA). Significant (∗P < 0.05) negative correlation was observed between total phenolic content and the EC₅₀ for DPPH radical scavenging activity (R = −0.826), reducing power (R = −0.876) and iron-chelating capacity (R = -0.800).     

Synthesis and antioxidant activity of selected 4-methylcoumarins

A series of selected 4-methylcoumarins (4-methyl-2H-1-benzopyran-2-ones) were synthesised and tested for radical-scavenging ability using the stable 1,1-diphenyl-2-picrylhydrazyl radical, and for reducing power ability with a test based on the reduction of ferric to ferrous cation. All studied compounds showed activity comparable to Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), an already known antioxidant, which is used as standard in most of the testing methods. Observations from the study were made with regard to structural features that regulated the behaviour of the compounds. The antioxidant activity of some 4-methylcoumarin representatives is presented here for the first time and extends our knowledge of the range of valuable biological activities and possible roles in therapy and for food preservation associated with this group of compounds.