gamma-Radiation influences browning, antioxidant activity, and malondialdehyde level of apple juice

Apple juice was gamma-irradiated at 5 degrees C at doses ranging from 0 to 8.9 kGy and then stored at 5 degrees C for 15 days. Ionizing radiation reduced the browning of apple juice and increased antioxidant activity measured by the ferric-reducing antioxidant power (FRAP) assay. The magnitude of changes increased with radiation dose. The level of malondialdehyde (MDA) measured using the thiobarbituric acid reactive substrates assay increased at radiation doses above 2.67 kGy. The browning of irradiated juices increased during storage at 5 degrees C, but the irradiated juices were still lighter than controls at the end of storage. Differences in FRAP values disappeared during early periods of storage while higher MDA levels were observed in irradiated samples during most of the storage period. Elimination of suspended matter from apple juice did not alter irradiation-induced changes in browning, FRAP, or MDA formation. As compared to irradiation conducted at 5 and 20 degrees C, treatment at -15 degrees C was less effective in reducing browning and in increasing MDA formation but elevated FRAP values. The exclusion of oxygen from juices did not affect the reduction in browning due to irradiation but promoted the increase in FRAP values and decreased the irradiation-induced MDA formation.     

射频加热杀灭浓缩苹果汁中鲁氏接合酵母的工艺优化

为研究射频对苹果汁中鲁氏接合酵母杀灭作用,该文以鲁氏接合酵母为试验菌株,通过单因素试验分析了射频加热时间、极板间距、果汁体积、果汁可溶性固形物对杀菌效果及果汁升温速度的影响。在固定果汁可溶性固形物为70%的条件下,通过响应面试验,建立了鲁氏接合酵母菌落总数降低对数值的二次多项数学模型,确定了在极板间距为110 mm、果汁体积40 m L、果汁可溶性固形物70%的条件下射频加热处理70 s,可以使果汁中鲁氏接合酵母菌落总数下降6个对数值以上。研究比较了相同样品经射频和传统水浴杀菌达到相同杀菌效果时,处理前后果汁理化指标及风味变化程度,结果表明,射频(70 s)比水浴(330 s)能更快达到杀菌目的,同时对果汁品质以及风味的影响(P0.01)小于水浴处理。研究结果为射频杀菌方面的深入研究及实际应用提供了参考。     

Processing effects on the composition of sea buckthorn juice from Hippophae rhamnoides L. Cv. Indian Summer.

Sea buckthorn juice is one product that can be derived from the sea buckthorn berry, a new alternative crop for the Canadian western provinces. Fresh pressed juice separates into three phases when allowed to stand overnight in the refrigerator: an upper cream phase, juice in the middle portion, and a sediment at the bottom. Enzymatic hydrolysis with commercial, broad spectrum carbohydrate hydrolyzing enzyme preparations reduced the juice viscosity, assisted juice separation, and provided an opalescent juice. Soluble solids averaged 10.2 degrees Brix, pH averaged 3.13, ascorbic acid averaged 174.2 mg/100 mL, and titratable acidity averaged 1.97% as malic acid all determined on centrifuged (10 000 rpm, 15 min) juice. Soluble sugars included glucose, fructose, and an unidentified component that was not sucrose or other common soluble monomeric or dimeric sugar. Quinic acid was quantitatively most important, while malic was next, and oxalic, citric, and tartaric acids were minor components. Washing berries by dipping reduced soluble solids (degrees Brix) in juice suggesting uptake of wash water.     

石榴汁粉替代发酵基质中蔗糖提升酸奶品质

石榴汁中含有丰富的多酚类物质,是抗氧化剂的良好来源。酸奶是抗氧化剂等生理活性物质的优质载体。为了加快石榴加工产业的发展、丰富酸奶的种类、提升酸奶的品质,该文使用1%、3%、5%石榴汁粉(pomegranate juice powder,PJP)分别等量代替凝固型酸奶发酵基质中的蔗糖,研究了PJP对发酵过程中酸奶基质的pH值、滴定酸度、表观黏度和乳酸菌活力的影响,并分析了对照组与PJP替代组酸奶的拉曼光谱、质构、流变学特性、总酚含量及抗氧化活性的差异。结果表明,PJP的替代没有显著改变发酵终了时基质的pH值、可滴定酸度、表观黏度和拉曼光谱,但缩短了发酵时间,促进了乳酸菌的生长,提高了酸奶的硬度、稠度、黏聚性、黏度指数和总酚含量、FRAP及DPPH·清除率。PJP完全替代蔗糖时,发酵时间从300缩短至280 min,总多酚含量、FRAP和DPPH·清除率分别是对照组的1.84,2.26和1.76倍。酸奶品质的提升可能与PJP中多酚有关,PJP有望替代蔗糖制备更健康的凝固型酸奶。     

Simultaneous transgenic suppression of LePG and LeExp1 influences rheological properties of juice and concentrates from a processing tomato variety

Processing tomato lines suppressed in the accumulation of ripening-related polygalacturonase or expansin were generated by introduction of transgenes to silence expression of the LePG and LeExp1 genes, respectively. The rheological properties of juice and juice reconstituted from paste produced from lines suppressed in one of these genes, or in both, were compared with azygous controls. When assayed by measuring Bostwick consistency, paste produced from either suppressed LePG or suppressed LeExp1 lines and diluted to 5 degrees Brix was approximately 18% more viscous than that produced from controls. Simultaneous suppression of LePG and LeExp1 produced a small additional increase in viscosity of 4%. Rheometric flow analysis at 5 or 10 degrees Brix also showed substantial increases in the consistency index due to suppression of either LePG or LeExp1 alone, and a small additional increase when both genes were suppressed in the same transgenic line. Measurements by laser diffraction and [1H]NMR showed that suppression of LePG or LeExp1 accumulation altered the size distribution of insoluble particles and modified their surface properties. The data are consistent with suppression of LePG increasing serum viscosity, and suppression of either LePG or LeExp1 altering the properties of the insoluble particles and improving some aspect of particle-particle or particle-serum interaction, or both. However, relative to that caused by suppression of either gene alone, the additional increase in viscosity caused by simultaneous suppression of LePG and LeExp1 together was slight.     

Cut-off shoots method for estimation of partial resistance in apple cultivars to fruit tree canker caused by Neonectria ditissima

Fruit tree canker, caused by the fungus Neonectria ditissima, is an economically devastating disease in apple orchards, especially in north-western Europe. Complete resistance has not yet been reported in apple, but variation in levels of partial resistance has been described and could be valuable in plant breeding programmes. A screening method based on spore inoculation of manually inflicted leaf scars on cut shoots was evaluated for reliability and repeatability in discrimination of 11 apple cultivars during two years – 2012 and 2013 – in two different facilities – biotron and standard greenhouse – and different time periods (February–May). The resulting cankers were counted (infection percentage), first appearance noted (incubation period) and lesion size measured at regular intervals during a period of 25–29 days for comparison of resistance levels. Results of two-way analysis of variance and correlation analyses showed that the area under the disease progress curve yielded the most robust data. This parameter was then applied for screening 30 apple cultivars using the same cut-shoot method. ‘Elise’ showed very high susceptibility, while the ornamental ‘Prairifire’ showed the highest level of partial resistance. Results suggested that cut shoots can be used to assess levels of resistance among cultivars, but great care must be taken to provide stable experimental conditions.     

~(60)Co γ射线辐照对红玉苹果斑点病发病率的影响

自1978至1985年对红玉苹果进行了~(80)Coγ射线辐照试验,辐照剂量为24、49、73、97和146krad,剂量率为44rad/min。每处理重复4—7次,果实辐照后置自然通风库贮藏。七年共处理红玉苹果5吨多。试验结果表明:用~(60)Coγ射线辐照红玉苹果,能十分明显地降低其斑点病的发病率,对照果发病率为55%左右,辐照果为5%左右;比较适宜的辐照剂量为49-73krad;适宜剂量辐照对果实风味和化学成份没有不良影响。     

Effects of hydrocolloid thickeners on the perception of savory flavors

The perceived intensities of savory flavors in hydrocolloid-thickened solutions were investigated using sensory paired comparison tests between two distinct thickener concentrations (high and low viscosities). The perceived saltiness of 3.5 g/L NaCl was found to be significantly reduced (P < 0.01) at the higher thickener concentration of both hydroxypropylmethyl cellulose (HPMC) and lambda-carrageenan, relative to the lower concentration. Mushroom flavor (8 ppm of 1-octen-3-ol with 3 g/L NaCl) was perceived as significantly more intense (P < 0.05) in 1.7 g/L lambda-carrageenan as compared with the same concentration of flavoring in 10.2 g/L lambda-carrageenan. Garlic flavor (2.5 ppm of diallyl disulfide with 2 g/L NaCl) was perceived to be significantly more intense in 2 g/L HPMC (P < 0.01) than in 10 g/L HPMC. However, when the NaCl concentration in the more viscous sample was increased to 3 g/L, the garlic flavor intensities of the two systems were not significantly different, suggesting a perceptual interaction (enhancement) between salt taste and garlic flavor. In vivo aroma release measurements from the same samples, using API-MS, showed that hydrocolloid concentration did not significantly alter the amount of mushroom or garlic aromas released when solutions were consumed. It was concluded that changes in perceived saltiness were driving the reduction in savory flavor perception even though the aroma stimulus was unchanged (a taste-aroma interaction). These findings parallel previous results in sweet hydrocolloid-thickened solutions.     

Parallel synthesis: a new approach for developing analytical internal standards. Application to the analysis of patulin by gas chromatography-mass spectrometry

The polymer-assisted reaction of 4-(hydroxymethyl)furan-2(5H)-one (4HM2F) with 21 carboxylic acids using polystyrene-carbodiimide (PS-carbodiimide) yielded an ester library. Four of the esters, (5-oxo-2,5-dihydrofuran-3-yl)methyl acetate (IS-1), (5-oxo-2,5-dihydrofuran-3-yl)methyl butyrate (IS-2), (5-oxo-2,5-dihydrofuran-3-yl)methyl 2-methylpropanoate (IS-3), and (5-oxo-2,5-dihydrofuran-3-yl)methyl chloroacetate (IS-4), were tested as internal standards for the quantification of patulin in apple juice by gas chromatography-mass spectrometry in the selected ion monitoring mode (GC-MS-SIM). The developed method combines an AOAC official extractive step and a GC-MS-SIM analysis. Using a chromatographic column containing trifluoropropylmethylpolysiloxane as the stationary phase and IS-1 as the internal standard, it was possible to perform an accurate and precise quantification of underivatizated patulin in apple juice at concentrations down to 6 microg/L. A detection limit of 1 microg/L was established.     

挤奶机真空度对牛奶体细胞数和牛乳头末端壁厚的影响

为了研究挤奶机系统真空度不同时的挤奶效果,解决目前挤奶机使用中系统真空度缺乏科学设定依据的问题,该文以12头高产泌乳牛(单产(7.4±0.4)t)为试验对象,以体细胞数(somatic cell count,SCC)、乳头末端壁厚变化率以及挤奶量等作为挤奶效果评价指标参数,在系统真空度分别为44、46以及48 kPa时,研究了系统真空度对泌乳牛挤奶过程不同阶段的内套真空度和挤奶杯口真空度的影响,量化了系统真空度对挤奶效果评价指标的影响程度。研究表明,当系统真空度从44 kPa增加至48kPa时,挤奶量、挤奶时间以及平均奶流量均无显著差异,但体细胞数的对数(P0.05)和乳头末端壁厚变化率(P0.05)均显著增加。研究认为试验挤奶机用44 kPa的系统真空度比用46或48 kPa时的效果更好。该文为中国挤奶机使用中系统真空度的优化设置提供技术支持。     

基于PWM技术的大型变量喷灌机整机水力性能研究及优化

基于脉冲宽度调制（Pulse Width Modulation, PWM）技术的变量喷灌机虽然能实现更精细的地块水分管理,但因实现变量的电磁阀的持续开闭动作,喷灌机主输水管道内流量呈现持续的阶跃变化,进而导致变量喷灌过程中存在压力脉动和机械激振现象。该研究基于Matlab/Simulink,对基于PWM技术的大型变量喷灌机在变量喷灌过程中的压力脉动进行了研究分析及改善优化。针对已研制的基于PWM技术的大型变量喷灌机实体系统,首先构建了其关键器件和整机的水力模型,并验证了模型的正确性。然后基于所建模型,对变量喷灌机的压力脉动进行了分析,得到了变量喷灌过程中的压力脉动规律,进而提出了PWM脉冲相位错开的缓减方法,并介绍了该方法的3种具体实施方式,即\     

渭北旱塬红富士苹果不同时期叶片营养诊断

为推动渭北旱塬苹果合理施肥,通过测定红富士苹果不同时期叶片养分含量,并运用Beaufils、Jones和Elwali&Gascho提出的3种DRIS指数计算法对红富士苹果营养状况进行诊断。结果表明,从6月到8月红富士苹果叶片各养分元素含量变化存在差异,高产果树(单株产量>25 kg)叶片N含量呈先降低后升高趋势,P含量逐渐降低;低产果树(单株产量≤25 kg)叶片N含量一直降低,P含量变化则与高产叶片N相同。其他元素在两种果树中的变化趋势一致,K和Zn含量降低,Ca和Mg含量升高,Cu、Fe和Mn呈先升高后降低趋势。不同时期根据DRIS标准程序确定的重要诊断参数不同;与Elwali&Gascho提出的DRIS诊断指数计算法相比,采用Beaufils和Jones的方法得出的各元素诊断指数不但与其含量相关性高,且需肥顺序差异不大,Beau-fils方法得出高产果树6月到8月最缺乏的元素为K、Fe、Ca+Mg,Jones方法为K、Ca、Ca+Mg,低产果树均为K、Fe、N。综上,本研究建议针对不同时期进行红富士苹果叶片营养状况评价。     

苹果采摘机器人夜间图像边缘保持的Retinex增强算法

为了提高采摘机器人的适用性和工作效率,保证成熟苹果果实的及时采摘,需要机器人具有夜间连续识别、采摘作业的能力。针对夜间苹果图像的特点,该文提出一种基于引导滤波的具有边缘保持特性的Retinex图像增强算法。利用颜色特征分量采用具有边缘保持功能的引导滤波来估计出照度分量;进而利用单尺度Retinex算法对图像进行对数变换获得仅包含物体本身特性的反射分量图像;分别对照度分量和反射分量图像增强后,再合成为新的夜间苹果的增强图像。文中选取30幅荧光灯辅助照明下采集到的夜间苹果图像进行试验的结果显示,该文增强算法处理后的30幅图像的平均灰度值,分别比原始图像、直方图均衡算法、同态滤波算法和双边滤波Retinex算法处理后的图像平均提高230.34%、251.16%、14.56%、7.75%,标准差平均提高36.90%、-23.95%、53.37%、28.00%,信息熵平均提高65.88%、99.68%、66.85%、17.53%,平均梯度提高161.70%、64.71%、139.89%、17.70%。且该文算法较双边滤波Retinex方法的运行时间平均减少74.56%。表明该文算法在夜间图像增强效果和运行时间效率上有明显的提高,为后续夜间图像的分割和目标识别提供了保障。     

中国北方主产地苹果始花期与气候要素的关系

选取福山、万荣、洛川、旬邑和阿克苏分别代表中国渤海湾、黄土高原和新疆苹果产区,利用1999-2018年各地富士苹果始花期物候观测数据,分析苹果始花期变化趋势,并利用偏最小二乘回归法,分析日尺度平均气温、平均地温、降水量、相对湿度和日照时数对苹果始花期的影响,明确影响苹果始花期的关键气候因子及其影响时段和强度,在此基础上,利用逐步回归法建立各主产地苹果始花期预测模型。结果表明,近20a来,中国北方主产地苹果始花期平均出现在4月7-20日,但变化趋势不显著。影响各地始花期的关键气候因子中,平均气温和平均地温为主导因子,其中关键影响时段内平均气温和平均地温每上升1℃,5个主产地苹果始花期将显著提前2.31～4.10d和2.34～4.96d;降水量每增加1mm,万荣、旬邑和阿克苏苹果始花期将显著推迟0.12～0.57d;平均相对湿度每增加1个百分点,旬邑和阿克苏苹果始花期推迟0.33d和0.51d;日照时数每增加1h,福山和万荣苹果始花期分别提前0.12d和0.07d。在明确影响各主产地苹果始花期关键气候因子的基础上,建立中国北方苹果主产地始花期预测模型,经回代检验,实测值与预测值相差小于5d...     

喷硒时期与浓度对红富士苹果果实品质及各部位全硒和有机态硒含量的影响

本试验通过叶面喷施外源硒肥、原子荧光法测定样品硒含量,研究不同硒喷施浓度对果树各部位无机硒含量、硒有机化程度及果实品质的影响,筛选红富士苹果的最佳施硒方案。结果表明, 1）在花期和幼果期叶面施硒效果较为稳定,叶片和果实中硒的有机化程度高。在接近果实着色期或采收期叶面施硒,虽然果实中总硒量较高,但硒的有机化程度较低。2）相同喷施浓度下,树体各器官硒含量顺序依次为叶＞枝＞果＞根,果树地上部分配的硒占较大比例。3）叶面喷施硒可增加果实中可溶性固形物、可溶性糖和Vc 含量,从而改善了果实风味,但降低了果实硬度,影响其贮藏运输品质。4）红富士苹果以在5、6、7月中旬喷施 3 次100 mg/L 亚硒酸钠效果最佳,此时叶片中总硒含量为2728.30 g/kg, FW,有机化程度达85.71%。各项果实品质指标佳,平均单果重达256.8 g。果实总硒含量为10.10 g/kg, FW,有机化程度为87.72%。     

抽水蓄能机组甩负荷试验时尾水锥管压力

抽水蓄能机组水力调节过渡过程计算控制核心要求之一是尾水锥管压力不超过设计值。设计值是根据水力过渡过程理论的一维数值模拟\     

不同品种稻米品质形成对盐胁迫的响应

为明确盐浓度对稻米品质形成的影响及其机制,以江苏省大面积种植水稻品种南粳9108和盐稻12号为试验材料,种植于土培池中,全生育期以盐水灌溉代替淡水灌溉,盐浓度设置0.10%、0.15%、0.20%、0.25%、0.30%、0.35%,并以淡水(盐浓度0%)灌溉为对照(CK),研究不同盐浓度对稻米品质形成的影响。结果表明,与CK相比,在低盐浓度(0.10%～0.15%)下,直链淀粉含量显著降低,稻米的糙米率、精米率和整精米率增加,稻米淀粉黏滞特性(RVA谱)的峰值黏度、热浆黏度和最终黏度增加,米饭的外观、黏度、平衡度和食味值在0.10%盐浓度下高于CK,南粳9108和盐稻12号的胶稠度在0.10%盐浓度下分别较CK高4.5和3.5 mm;在中、高盐浓度(0.20%～0.35%)下,稻米的加工品质、蒸煮食味品质和稻米淀粉黏滞特性明显降低。稻米的垩白粒率和垩白度随着盐浓度的增加而减小。综上可知,在低盐浓度(0.10%～0.15%)下,稻米的品质总体有一定的改善;高盐浓度(0.35%)下,稻米品质明显变劣。本研究通过分析不同盐浓度下水稻的品质状况,为滩涂水稻高产与品质调优栽培提供了参考。     

番茄果实蠕变特性表征的Burger's修正模型

针对经典Burger’s模型在蠕变特性表达中的不足,进行了绿熟期、变色期、红熟前期和红熟中期番茄果实的蠕变试验,并在Burger’s模型和常用指数型与幂函数型修正模型分析的基础上构造提出了4元件6参数修正模型.该模型对不同成熟期蠕变段试验数据拟合的平均决定系数与和方差分别达0.9975~0.9994和0.04047~0.07633,蠕变变形率和弹性度的拟合平均相对误差分别为2.54%~3.04%和2.89%~7.12%,蠕变量预测的平均相对误差为0.29%~0.46%,蠕变速率也与实际更加吻合,其曲线拟合精度、关键指标表达精度和蠕变预测精度大大优于Burger’s模型和常用修正模型.研究表明该模型实现了蠕变行为的更准确表征与预测,从而为果实收获、储运、分选的减损提供了更好的模型依据.     

Role of hydrocolloids in the creaming of oil in water emulsions

The influence of guar gum and xanthan gum on the creaming of 10% oil in water emulsions has been investigated. The presence of very low concentrations of the polysaccharides (typically < approximately 0.075%) was found to induce depletion flocculation of the emulsion droplets and increased the rate of creaming. However, at higher polysaccharide concentrations (typically > approximately 0.1%) the creaming rate was reduced due to the increased viscosity of the aqueous phase. For most systems a delay period was noted before creaming started, which was found to be dependent on the zero shear viscosity of the continuous phase and independent of polysaccharide type. The delay period increased significantly at zero shear viscosities approaching 1 Pa s. A mathematical model has been used to fit the creaming rate profiles and a simple exponential relationship obtained between delay time and polysaccharide concentration.     

超声辅助萌芽联合超高压处理对花生-黑豆芽复合汁品质的影响

为有效提高豆种的萌芽特性、明确其生长过程中营养成分变化规律,并对萌芽产品进行绿色深加工以最大限度保留豆芽营养成分,该论文采用超声波处理提高豆类发芽率和发芽指数,筛选营养丰富的萌芽阶段开发花生-黑豆芽复合汁,并研究超高压和常规热杀菌对花生-黑豆芽复合汁品质的影响。结果表明：300 W和10 min的超声处理可显著提高黑豆和花生的发芽率和发芽指数（P<0.05）。超声处理组的黑豆在第6萌芽阶段（芽长6 cm）时γ-氨基丁酸（gamma-aminobutyric acid,GABA）含量最高,达175.13mg/100g,超声处理组的花生在第5萌芽阶段（芽长2cm）时白藜芦醇含量较高,为0.92 mg/g。以上述阶段原料制备富含白藜芦醇和GABA的花生-黑豆芽复合汁,进一步研究发现,相比于传统热杀菌,超高压杀菌（450MPa和15min）可显著提高花生-黑豆芽复合汁的稳定性和总酚含量（P<0.05）,减少颜色劣变,贮藏过程中能更好地保持GABA和白藜芦醇。研究结果将为高品质豆芽深加工产品探索提供理论依据和技术支撑。