Effect of malondialdehyde oxidation on structure and physicochemical properties of amandin

Oil, accounting for 45% of almonds, is easily oxidised and can further induce the protein oxidation to reduce their quality. Structure and physicochemical properties of amandin, the main water-soluble protein in almonds, inducing oxidation by malondialdehyde (MDA) were investigated. The results showed that the content of carbonyl group increased from 5.23 to 33.25 nmol mg⁻¹ of protein with the increase in MDA concentration (P < 0.05). However, the sulphydryl content, surface hydrophobicity, particle size and the absolute value of ζ-potential first increased and then decreased. Fourier-transformed infrared spectroscopy (FT-IR) confirmed that the structure of amandin changed from order to disorder. Fluorescence spectroscopic analysis revealed that mild oxidation (0–0.1 mmol L⁻¹ MDA) exposed hydrophobic groups of the protein. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) suggested that protein oxidation promoted crosslinking between protein molecules. Furthermore, protein oxidation markedly declined the total amino acid content of amandin (P < 0.05). In conclusion, MDA oxidation changed the structure and amino acid content of amandin, and caused the protein aggregate and crosslink through hydrophobic interaction and electrostatic interaction.     

Postharvest quality and shelf life of radish microgreens as impacted by storage temperature,packaging film,and chlorine wash treatment

Microgreens are new and emerging products, which are young seedlings of vegetables and herbs. A recent study showed that microgreens contain higher nutrients compared to their mature counterparts. However, they typically have a short shelf life (1–2 days) at ambient temperature. The objective of this study was to optimize postharvest handling conditions to reduce the quality loss and extend the shelf life of daikon radish (Raphanus sativus L. var. longipinnatus) microgreens. Storage temperature, packaging film, and wash treatment were investigated. Changes in headspace composition, quality index, chlorophyll concentration, tissue electrolyte leakage, and aerobic mesophilic bacteria (AMB) and yeast & mold (Y&M) counts were monitored periodically during storage. Results indicated that (1) storage temperature significantly (P < 0.05) affected package atmosphere, product quality and shelf life. One degree Celsius was the optimal temperature for storage of radish microgreens with no chilling injury observed; (2) film oxygen transmission rate (OTR) significantly (P < 0.05) affected O₂ and CO₂ composition, but OTR did not significantly affect quality attributes during 28 days of storage at 1 °C; (3) Chlorine wash treatment (100 mg/L) significantly reduced initial microbial populations by 0.5 log cfu g⁻¹, including AMB and Y& M. However, microbial populations rebounded after day 7.     

浅析塑料薄膜凹版印刷用油墨

<正>随着人们对商品包装要求的不断提高,塑料薄膜及塑料复合薄膜软包装材料以其优良的展示功能、保护功能以及轻便易储运等优点在商品包装上得到了广泛的应用。为了制得合格的塑料薄膜包装产品,     

Monitoring of the prokaryotic diversity in pit mud from a Luzhou‐flavour liquor distillery and evaluation of two predominant archaea using qPCR assays

Pit mud plays a crucial role in the production of the Luzhou‐flavour liquor. Its quality directly determines liquor quality and yield. The aged pit mud produced good quality liquor but aging pit mud did not. The aim of this work was to investigate the prokaryotic diversity of the aged and aging pit mud from a Luzhou‐flavour liquor distillery using molecular methods. Two bacteria‐specific and two archaea‐specific 16S rRNA gene clone libraries were constructed and analysed using amplified ribosomal DNA restriction analysis. A total of 273 clones were studied, which resulted in 28 operational taxonomic units. Bacteroidetes and Firmicutes predominated in both the aged and aging pit mud, but Synergistetes and Actinobacteria were only detected in the aged pit mud. The family Methanosaeta dominated in the aged pit mud, while the Methanosarcina predominated in the aging pit mud. These results were confirmed using two genus‐specific quantitative real time PCR assays. This research distinguished microbial community structure in the aged and aging pit mud for the first time, and has laid an initial foundation for identifying good quality pit mud and for maintaining the quality of pit mud. Copyright © 2014 The Institute of Brewing & Distilling     

香辛料饮料研制及其对人体经络电压的作用

香辛料可以改善食品品质、色泽、风味和滋味,同时有多种保健功能,可用于散寒、除湿、疏通经络等。本研究目的为以性味甘、温的甘草、桂皮和生姜为原材料,研制一款可口且能作用于经络的天然香辛料饮料。饮料配方通过6~8人组成的感官小组进行感官评价来确定。对经络的作用通过观察受试者经络电压的变化来确定。结果表明,当甘草0 mg/mL、桂皮1.5 mg/mL、生姜0.5 mg/mL时,该香辛料组合饮料感官评价效果最佳。经络电压测量表明,7种香辛料组合(甘草、桂皮、生姜、甘草-桂皮、甘草-生姜、生姜-桂皮、甘草-生姜-桂皮)中生姜-桂皮组对人体经络电压作用最为突出,能够大幅度提高肝经、脾经和肾经的经络电压,显示对肝经、脾经和肾经具有特殊的作用。     

热处理对牛骨酶解液美拉德反应产物呈味物质及挥发性成分的影响

探讨不同热处理条件(温度110,115,120,125,130 ℃和时间25,40,55,70,85 min)对牛骨酶解液美拉德反应产物(EBBH-MRP)呈味特性及挥发性风味成分的影响。结果表明:热处理温度低于130 ℃时,总游离氨基酸含量降低,这与鲜味氨基酸和苦味氨基酸变化趋势一致。风味核苷酸含量随温度上升呈增加趋势。在不同温度下,共检测到63种挥发性风味物质,包括醛类、酮类、醇类、酸类和杂环类化合物。当热处理时间超过40 min时,总游离氨基酸含量不断增加,风味核苷酸含量也缓慢增加。随着热处理时间的延长,挥发性风味物质种类减少,共检测到54种。醛类、酮类含量随时间的延长而明显增加,至70 min,其含量保持相对稳定。结论:适当的热处理条件可以提升EBBH-MRP的呈味及风味特性。     

利用蛋壳生产柠檬酸钙的初步研究

为充分利用蛋壳中的CaCO3,采用中和法制备柠檬酸钙,使其中的无机钙转化为有机钙,进行了煅烧条件、原料配比、反应物浓度、温度、时间等因素对产物收率和纯度的影响实验研究。结果表明：最适宜工艺条件分别为：蛋壳在900℃煅烧分解1-2h,CaO收率为95％以上。中和反应条件：石灰乳浓度5％,柠檬酸浓度50％,反应温度60℃,反应时间1h,产品收率高、质量好、安全无毒。     

饲料植酸酶制剂储存稳定性的研究

酶制剂的储存稳定性问题是酶应用过程中最常遇到的实际问题。该研究的周期长,样品保存困难,研究手段缺乏。文中系统探讨了糖类和金属盐类物质对植酸酶制剂热稳定性的保护作用,添加金属盐离子对植酸酶制剂的热稳定效果明显优于各种糖类物质的保护效果,其中以添加金属盐MgSO4的热稳定效果最佳,糖类物质中淀粉最适合作为固体酶制剂的载体。同时创新性地引入了药物制剂稳定性的恒温加速试验研究方法,用于酶制剂储存稳定性的研究。比较了糖类和金属盐添加剂对植酸酶制剂储存稳定性的影响,为酶制剂储存稳定性的研究提供了新的研究方法。     

石花菜醇提物提取工艺及抗氧化、抗菌活性研究

在单因素实验基础上,通过响应面法优化石花菜醇提物的提取工艺。将石花菜醇提物经石油醚、乙酸乙酯和正丁醇依次萃取,研究不同萃取相的抗氧化和抑菌活性。结果表明,石花菜醇提物的最佳提取工艺为:60%乙醇溶液、料液比1∶35、提取时间64 min、超声功率350 W、提取温度55 ℃。在此条件下,石花菜醇提物得率为0.0165 g/g,DPPH自由基清除率为58.29%(质量浓度2 mg/mL)。不同萃取相抗氧化和抗菌活性均具有浓度依赖性,其中乙酸乙酯相活性最强,清除DPPH自由基、ABTS+自由基和羟基自由基的IC50值分别为672.4,14.1,599.7 μg/mL。对金黄色葡萄球菌和副溶血性弧菌的最小抑菌浓度(MIC)分别为156.3,156.3 μg/mL,最小杀菌浓度(MBC)分别为625,312.5 μg/mL。