Effect of lactose content on dielectric properties of whole milk and skim milk

Dielectric properties (dielectric constant ε′ and dielectric loss factor ε′′) of whole milk and skim milk with the lactose content of 4.56–6.44% and 4.57–6.47%, respectively, were measured over the frequency range of 20–4500 MHz at 25 °C using a vector network analyzer. The results showed that ε′ decreased with increasing frequency, and ε′′ changed with V shape and its minimum was noted at about 2000 MHz. Whole milk had lower dielectric properties than skim milk at almost same lactose content and a given frequency. ε′ had weak positive linear relationship with lactose content for whole milk, but had negative linear relationship for skim milk. No matter for which milk, ε′′ had very good negative linear relationship with lactose content below 1000 MHz and had good positive linear relationship above 2300 MHz. The study provides information on developing rapid lactose detector for milk in future.     

金属盐离子对纤维素离子凝胶性能的影响研究

本研究利用竹纤维素构建导电凝胶的网络骨架,通过添加离子液体形成复合竹纤维素离子凝胶(CCIGel),并引入金属盐离子强化纤维素离子凝胶的性能。结果表明,ZnCl₂、CaCl2和FeCl3可激发纤维素-离子液体凝胶的成形,且CCIGel-Zn和CCIGel-Ca的机械性能均优于CCIGel-None;添加AlCl3的体系无法形成凝胶。其中质量分数15%的ZnCl₂制备的CCIGel-Zn性能最为优异,其拉伸强度、韧性和离子电导率分别高达1.344 MPa、29.85 MJ/m3和47.1 mS/cm,透光率为86.9%。     

采收时间对核桃青皮成分和功能活性的影响

目的探究采收期对新鲜核桃青皮的化学成分、抗氧化和抗菌特性的影响。方法以不同采收成熟度(1P:2017.8.20、2P:2017.8.26、3P:2017.9.1)的"香铃"核桃为实验材料,手工脱除新鲜的核桃青皮,通过测定不同采收成熟度所得青皮中的胡桃醌、总酚、黄酮、水解单宁的含量,抗氧化和抗菌活性,以探讨采收期对新鲜核桃青皮的影响。结果随着采收成熟度的增加,核桃青皮中的抗氧化活性呈现上升趋势;总酚和水解单宁的含量先上升后趋于平稳。其中,第二成熟度(2P)采收的核桃青皮中,胡桃醌和黄酮的含量最高,分别为0.58 mg/g FW、2.67 mg/g FW。所有成熟度所得核桃青皮水提物,对革兰氏阳性菌有不同程度的抑制。第三成熟度(3P)所得核桃青皮水提物对枯草芽孢杆菌的抑菌圈直径达到了1.35 cm。结论第二、三成熟度采收的核桃青皮,含有丰富的活性成分,且具有良好的抗氧化和抗菌活性。     

绿茶多酚对马铃薯淀粉壳聚糖复合膜影响研究

为开发新型抗氧化活性包装材料,以马铃薯淀粉壳聚糖复合膜为基材,研究添加绿茶多酚对复合膜抗氧化能力、物理性能和化学结构影响。结果表明:添加绿茶多酚显著（p<0.05）提高了复合膜DPPH自由基清除能力,添加2%绿茶多酚的复合膜在3 min内自由基清除率达到94.48%,绿茶多酚添加也显著（p<0.05）地增强了复合膜的阻湿性。但添加绿茶多酚增加了复合膜红色和黄色、水溶性,降低了膜的柔韧性,红外光谱显示添加绿茶多酚影响了-O-H键的弯曲和伸缩振动,干扰了复合膜体间的氢键相互作用。研究结果表明添加0.5%绿茶多酚既能提高复合膜的抗氧化能力,又可使复合膜拥有较好的柔韧性。      

Effect of different brewing methods on antioxidant properties of steaming green tea

The extracts were prepared from cold or hot brewed steaming green tea at different concentrations (2, 6, and 10%), its antioxidant properties studied and potential antioxidant components determined. The yields of hot water extracts (17.49–28.27%) were significantly higher than those of cold water extracts (11.72–14.70%). EC₅₀ values in antioxidant activity determined by the conjugated diene method and reducing power were 2.19–3.10 and 0.22–0.28 mg/ml, respectively. EC₅₀ values in scavenging ability on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals were 29.45–43.80 and 2.88–3.22 mg/ml, respectively. EC₅₀ values in chelating ability on ferrous ions were 6.45–13.51 mg/ml. Contents of total phenols were 221.71–330.22 mg/g whereas those of total catechins in cold and hot water extracts were 135.05–193.14 and 161.57–195.05 mg/g, respectively. Based on the results obtained, hot water extracts were more effective in antioxidant activity and reducing power. However, cold water extracts were more effective in scavenging ability on DPPH and hydroxyl radicals, and chelating ability on ferrous ions. Summarily, the cold brewing method would be a new alternative way to make a tea.     

Effect of alkali treatment on mechanical properties of the green composites reinforced with milkweed fibers

Polymeric composites disadvantages in terms of high price and non-recoverability make them unsuitable for some applications. Otherwise, natural fibers would be degraded easily and their prices are much lower as compared with most of the commonly used synthetic fibers, especially in composite manufacturing. Hollow Milkweed fiber with non-crimped nature is a known natural fiber which could have high potential to be used as composites reinforcements due to its low-density property. Increasing demand for natural fiber-reinforced composites as well as unique characteristics of Milkweed fibers reveal the need to study the mechanical properties of such fiber-reinforced composites. In this study, milkweed fibers were initially fed to laboratory carding machine in order to be formed as a nonwoven layer which was then applied to a low-velocity needle-punching operation. Surface modifications were carried out on the needle-punched nonwovens using 5% NaOH at 50–60 °C and three different treating time levels (30, 60 and 90 min). The produced nonwovens were then treated in a mixture of boiling water and detergent for 1 h. For making composite parts, the modified nonwovens were impregnated in Ploy vinyl acetate (PVAc) resin using the hand-layup method. The alkali treatment effects regarding the process time period on mechanical properties of the natural-reinforced composites were investigated. The findings suggested significant affectability of the composites mechanical properties by varying the time of alkali treatment, NaOH concentration as well as the type of surface modification process which are all mainly resulted in improving the interaction between fibers and matrix phase.     

冷冻水产品复合相介电特性与射频解冻研究

本实验对冷冻水产品的复合相介电常数模型、实部和虚部进行了分析研究,在分析研究冷冻鲅鱼的解冻时间、射频穿透深度的基础上,通过实验验证了射频解冻的质量优于微波解冻和一般常用的解冻方法。     

后区牵伸对等线密度棉段彩纱性能的影响

段彩纱是一种在纱线纵向色彩呈分段变化的花式纱线,现有的生产工艺不可避免产生竹节纱的效果,导致不能大规模地推广。本文首次采用改进细纱机的牵伸机构,制备线密度恒定,而组份、色彩是分段变化的棉段彩纱。并探讨分段时间、某一分段时间内两组份的质量比例对成纱性能的影响。结果表明通过合理控制后区牵伸工艺,可以生产线密度恒定且性能良好的段彩纱。并提供了牵伸机构的改进方案,为实际生产提供参考。     

Effect of green plantain flour addition to gluten‐free bread on functional bread properties and resistant starch content

Green plantain flour (GPF) was used as a functional ingredient to produce gluten‐free (GF) bread based on a flour blend of rice flour and GF wheat starch (50:50) to improve their functional properties and to increase their resistant starch (RS) content. In pretrials, an addition of up to 30% GPF provided acceptable bread quality with maximum RS content. Based on these trials, two 2³ factorial screening experimental designs were applied, where water content, baking temperature and baking time of GF bread containing 30% GPF addition were optimised. The best baking conditions to achieve satisfying GF bread quality – higher loaf volume, softer crumb firmness and regular porosity structure at the highest RS content could be defined to a maximum addition of water at 160%, baking temperature of 180 °C and baking time of 90 min. The incorporation of GPF showed good potential to improve the quality of GF bread.     

超微绿茶粉生鲜面的研制及特性研究

以小麦粉,超微绿茶粉为原料制作生鲜面,通过对面团的粉质特性、面条色泽、蒸煮特性及质构特性的测定评价,确定了超微绿茶粉的最适添加量为2%。并对绿茶粉添加量为2%的绿茶生鲜面的功能特性及抑菌效果进行了研究,结果表明,绿茶生鲜面的总酚含量、还原能力均明显高于未添加绿茶粉的生鲜面,抗氧化性大大增强,且具有较好的抑菌效果,可在一定程度上延长生鲜面的货架期。     

Effects of vacuum degree on the water status,physicochemical properties and microstructure of fast frozen dumpling wrappers

Vacuum mixing is a new method of dough making, and little literature is available regarding its effects on the product quality of frozen food. This research studied the effects of different degrees of vacuum (0.00, −0.02, −0.04, −0.06, −0.08 MPa) on the water state, thermal properties, cooking characteristics and microstructure of fast frozen dumpling wrappers during different storage times (0, 14 and 30 days). Vacuum mixing significantly decreased the spin–spin relaxation times (T₂) and freezing water content, thus indicating that it decreased the mobility of moisture and enhanced the binding of dough components with water molecules. Furthermore, the increases in the cooking loss rate and hardness of fast frozen dumpling wrappers during storage were inhibited by vacuum mixing, especially after storage for 30 days, possibly because vacuum mixing formed a more continuous and compacted dough structure, thereby generating a smaller ice crystal structure. These results should provide a theoretical basis for the application of vacuum mixing to fast frozen dumplings.     

不同贮存方式对核桃青皮色素的性质及生物活性影响

研究了两种保存方式下（晒干、冷藏）的核桃青皮棕褐色色素的理化性质及抗氧化活性。考察了p H、温度、不同金属离子、氧化还原剂、不同的食品添加剂等因素对核桃青皮色素的稳定性的影响,并对两种保存方式下提取的核桃青皮色素的抗氧化性进行了研究。研究表明,两种保存方式下提取的核桃青皮色素对温度、Na⁺、K⁺、食盐、山梨酸钾、安赛蜜及还原剂稳定;p H、氧化剂及Fe³⁺、Mg²⁺、Cu²⁺、Ca²⁺、Al³⁺对两种色素的影响均较明显;蔗糖对色素有增色效果,柠檬酸、抗坏血酸对色素有减色效果。两种色素均具有还原力和清除·OH的能力,晒干核桃青皮色素的还原力和对·OH的清除能力高于冷藏的。核桃青皮色素有较好的稳定性,抗氧化活性与色素溶液的浓度存在一定的量效关系。      

柠檬烯乳化液对青椒采后生理和贮藏品质的影响

用柠檬烯乳化液浸泡青椒3min,研究柠檬烯对青椒采后生理和贮藏品质的影响。结果表明,供试浓度的柠檬烯乳化液浸泡处理对青椒的腐烂有明显的抑制作用,贮藏期内柠檬烯乳化液处理组腐烂率较对照组低30%(p<0.01);对青椒的细胞膜系统有保护作用,贮藏第6、12d,对照组细胞膜受损程度分别是柠檬烯乳化液处理组的2.103倍和1.329倍(p<0.01);可以减缓青椒中维生素C、叶绿素、可滴定酸的消耗和分解,贮藏期内柠檬烯乳化液处理组含量均极显著地高于对照组(p<0.01);柠檬烯乳化液处理对青椒中的可溶性蛋白质、可溶性固形物也有一定的保留作用,但含量与对照组相比未达到极显著(p>0.01)。柠檬烯乳化液可以有效延缓青椒的采后生理变化,保持青椒的品质,提高其耐贮藏性。      

不同烹饪与冷却方法对冷配送中式快餐中3种绿色蔬菜品质的影响

目的探究烹饪及冷却方法对冷配送中式快餐中绿色蔬菜的品质影响。方法以西兰花、青椒及青刀豆为研究对象,分别对其进行热烫、微波、急炒烹饪,再分别进行自然冷却、冷风冷却及冷水冷却,检测其失重率、亚硝酸盐含量、叶绿素含量及可滴定酸含量等指标的变化。结果热烫的西兰花重量不减反增,青刀豆及青椒急炒时失重率最高。3种蔬菜热烫后使用不同的方法冷却,其亚硝酸盐含量均上升。所有处理都使3种蔬菜中的叶绿素含量显著降低。冷却方式不会影响3种蔬菜中的可滴定酸含量,而烹饪方式却有影响。结论烹饪及冷却方式对中式快餐中的绿色蔬菜品质有一定的影响,且与蔬菜品种有关。     

不同干燥方式对核桃青皮活性物质含量和生物活性的影响

目的研究不同干燥方法对核桃青皮提取物的生物活性物质含量、抗氧化活性和抑菌活性的影响。方法分别采用Folin-Ciocalteu法、硝酸铝显色法和分先先度法测定核桃青皮提取物的多酚含量、黄酮含量和单宁含量;采用自由基清除法和三价铁离子还原法测定抗氧化活性;采用抑菌圈法、最低抑菌浓度值法(minimum inhibitory concentration,MIC)和最低杀菌浓度值法(minimum bactericidal concentration,MBC)测定抑菌活性。结果真空冷冻干燥后的提取物的生物活性成分保留量最大,1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除能力和铁还原能力(ferric reducing antioxidant power,FRAP)均最强,对革兰氏阳性菌的抑制作用强于革兰氏阴性菌;自然干燥后的提取物清除2,2-联氮-二(3-乙基-苯幵噻唑-6-磺酸)二铵盐(2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate),ABTS)自由基的能力最强;红外干燥后的提取物对革兰氏阴性菌的抑制作用强于革兰氏阳性菌。结论不同干燥方式对核桃青皮提取物的生物活性物质的含量和活性均有不同的影响     

丁香和青花椒精油在酱卤鸭肉保鲜中的应用

以酱卤鸭肉为研究对象,将丁香精油和青花椒油应用于热封包装的酱卤鸭肉保鲜,研究酱卤鸭肉在4℃冷藏过程中的感官品质、理化品质和微生物品质的变化。结果表明:采用丁香精油(0.05 g/kg)和青花椒油(0.1 g/kg)对酱卤鸭肉进行二次拌料,在不影响产品风味和质地的情况下,与空白组相比,在贮藏过程中,添加组的挥发性盐基氮(TVBN值)明显低于空白组,前期的2~6 d,添加组对脂肪氧化有一定的抑制效果,酱卤鸭肉保质期由10 d延长至12 d。丁香精油与青花椒油对酱卤鸭肉的保鲜具有抗氧化和抑菌作用。      

酸奶发酵对绿茶粉功效成分和抗氧化性的影响

为促进茶叶消费,生产营养全面、风味独特的新型酸奶,研制了绿茶粉酸奶。通过测定绿茶粉酸奶的功效成分及其抗氧化性,以研究酸奶发酵过程对绿茶粉的影响。数据表明,主要的儿茶素含量剩余93.64%;茶多酚79.71%;叶绿素a减少46.83%,叶绿素b减少87.02%,叶绿素总量下降63.94%;而抗氧化性提高了9.37%。根据以上的测定结果,将绿茶粉添加到酸奶中发酵可以引入其功效成分和抗氧化性,因此产品的开发有效可行。     

Effect of some operating variables on the microstructure and physical properties of a novel Kefir formulation

In this work, the rheological and textural properties, water-holding capacity (WHC), syneresis, and microstructure of a novel formulation of Kefir were studied by varying the incubation time and temperature, as well as the ratio of peanut-milk and skimmed-milk. Generally, all the experimental responses resulted to be significantly affected (p < 0.05) by all dependent variables examined. Kefir WHC was not significantly influenced (p > 0.05) by the fermentation temperature.     

采后剪柄和伤口密封对青辣椒冷藏品质变化的影响

为研究青辣椒采后剪柄和伤口密封情况对其冷藏品质的影响,对其进行不剪柄、留2cm柄和不留柄以及柄处伤口密封和不密封处理,青辣椒处理后放于8℃,相对湿度95%左右的环境下冷藏,观察和测定其腐烂指数、质量损失、VC含量和MDA含量的变化情况。结果表明,剪柄后若不处理伤口,会增加辣椒的腐烂指数,柄越短腐烂指数越高;辣椒柄越长质量损失越大;无柄辣椒的VC含量最高,对照组次之,2cm柄辣椒的VC含量最低。密封伤口降低了青辣椒的腐烂指数,且无柄密封组和2cm密封组的效果较显著;剪柄后再密封,辣椒的质量损失无差异;伤口密封抑制了果实中VC含量的下降,贮藏后期效果更明显。从18d开始,2cm柄密封组和无柄密封组MDA含量显著低于对照组。