两种不同晾房中无核白葡萄太阳能干燥特性

研究分析比较两种不同的晾房(塑料膜温室型晾房与纱网晾房)中无核白葡萄的晾干特性.在新疆哈密某农场用木材建立了两个相同大小、不同覆盖材料的晾房,并用自动记录仪测定了晾房中的空气相对湿度、气流速度以及内外空气温度,同时测定了葡萄的干燥速率和葡萄干的绿品率.结果表明:塑料膜温室型晾房具有较好的集热效果,具有较快的干燥速度,能够获得较高的葡萄干绿品率.虽然塑料膜温室型晾房各部位干燥速度并不均匀,但比传统晾房干燥周期缩短了17%～67%.上述实验结果对于葡萄干燥晾房进一步优化设计,缩短葡萄干燥周期,提高葡萄干燥质量具有参考价值.     

不同晾房晾制吐鲁番无核白葡萄的干燥特性及品质比较

针对吐鲁番地区的土坯晾房、砖结构晾房和棚架晾房3种不同材料建造的晾房,比较西南、东南、南北、东西4个走向下的无核白葡萄干燥时间、绿品率、糖度、维生素C含量、感官指标及色泽(包括L*、a*、b*平均值及R、G、B值)。结果表明:在砖结构晾房和土坯晾房中,西南走向中的无核白葡萄干燥时间均为24d,绿品率分别为32%,24%,糖度分别为721.3,719.6 mg/g、维生素C含量分别为7.84,7.65mg/100g,效果显著优于东南、南北、东西走向。而棚架晾房除干燥时间较短外,其他各方面品质均显著低于砖结构晾房和土坯晾房。结合L*、a*、b*平均值及R、G、B值综合分析可知,长轴迎风建造的西南走向的砖结构晾房在干燥速率及葡萄干品质方面都优于其他几组晾房,为最佳干燥晾房。     

挂串密度对晾房干燥吐鲁番无核白葡萄干品质的影响

为了探讨无核白葡萄晾房干燥挂串密度对无核白葡萄干品质指标的影响。以产自新疆吐鲁番的无核白葡萄作为研究对象,分别以1:0.5、1:0.75、1:1的密度进行晾房干燥挂串,对无核白葡萄干成品的外观、果粒均匀度、破损果粒率、干燥时间、总糖、V_C等6项指标进行分析,探究挂串密度对晾房干燥吐鲁番无核白葡萄干品质的影响。结果表明:1:0.5密度挂串的葡萄干外观、果粒均匀度达到一级要求的概率分别为83%、85%,破损果粒率为11.5%,干燥时间为26 d,总糖平均含量为701.9 mg/g,V_C平均含量为7.05 mg/100 g;1:0.75密度挂串的葡萄干外观、果粒均匀度达到一级要求的概率分别为85%、86%,破损果粒率为12.0%,干燥时间为26 d,总糖平均含量为702.4 mg/g,V_C平均含量为7.34 mg/100 g;1:1密度挂串的葡萄干外观、果粒均匀度达到一级要求的概率分别为80%、85%,破损果粒率为17.3%,干燥时间为28 d,总糖平均含量为691.5 mg/g,V_C平均含量为7.21 mg/100 g。其中1:0.5及1:0.75密度挂串的干燥速率显著高于1:1密度(p<0.05);1:0.75密度挂串的葡萄干平均糖度含量及平均V_C含量显著高于1:0.5密度及1:1密度(p<0.05)。根据无核白葡萄干成品的6项指标的综合考虑,确定1:0.75的葡萄晾房挂串密度为最佳晾房干燥挂串密度。     

预处理对无核白葡萄热风干燥特性的影响

为研究预处理对无核白葡萄热风干燥特性的影响,用5 g/100 mL碳酸钾和0.6 g/100 mL橄榄油混合液浸泡无核白葡萄,进行不同干燥温度条件下的热风干燥实验。然后对4 种常见的农产品薄层干燥模型进行非线性拟合,并比较评价决定系数（R2）、卡方（χ2）值和标准误差（RMSE）。结果表明：Parabolic模型更加适合描述无核白葡萄热风干燥水分比与干燥时间之间的关系。在干燥温度分别为50、60、70 ℃时,预处理组的干燥时间比对照组的干燥时间分别缩短33.3%、19.2%、15.4%。预处理组的无核白葡萄的有效水分扩散系数分别提高47.4%、32.0%、32.4%;预处理组的平均活化能比对照组降低16.1%。预处理组葡萄干制品的复水率大于对照组。干燥前预处理可以缩短干燥时间、提高物料有效水分扩散系数、降低干燥活化能和保持干制品良好品质。     

‘无核白’葡萄热风干燥特性及色泽研究

为探究干燥温度、装载密度和风速对‘无核白’葡萄干燥特性及色泽的影响,通过调查制干过程中葡萄重量变化,葡萄干含水量、色差,以及总酚、叶绿素、总糖、总酸含量等品质指标,计算出干率、绿品率、成干时间,分析不同处理对加工效率和葡萄干品质的影响。结果表明,干燥时间与物料温度和风速呈正相关,与装载量呈负相关,葡萄干总糖含量与果实的干燥工艺无相关性。当干燥温度为40℃时,‘无核白’葡萄会发生明显的褐变;而装载量超过15.62 kg·m^-3和风速超过2 m·s^-1时,褐变现象逐渐加重。综上,温度为35℃、风速1.0 m·s^-1、装载量7.81 kg·m^-3时,‘无核白’葡萄干燥时间为148 h,叶绿素、总酚含量分别为0.55、0.15 mg·g^-1,与原材料色差为6.99,绿品率达到64%。葡萄干整体表现颗粒饱满,色泽良好。     

葡萄促干剂对无核白葡萄干燥的研究

为了提高新疆吐鲁番地区无核白葡萄干的品质,加快干燥速率和减少干制过程中的褐变率,以新疆吐鲁番地区的无核白葡萄为试验材料,研制不同促干剂(A1、A2、A3、A4、A5)自行研制的促干剂添加了螯合剂、增加了油酸乙酯和氢氧化钠的用量,既能加快干燥速率又能护绿。本实验采用在烘箱中干燥的方式,温度设置为40℃,风速为1m/s。根据干制过程中葡萄水分含量的损失、干燥速率以及干制结束后葡萄干多酚氧化酶的活性差异确定最优促干剂配方。通过数据测定及分析发现A4处理第1天的水分含量损失比CK组提高6%,整个干燥过程的干燥速率提高40%,干燥时间缩短了4d,多酚氧化酶活性降低了0.426 U,各组数据均优于其他配方。即得到最优处理为A4(碳酸钾84%,氢氧化钠2%,油酸乙酯5%,三聚磷酸钠3%,十二烷基苯磺酸钠4%,酒精1%,螯合剂1%)。     

热风干燥温度对无核白葡萄干品质的影响

为了研究不同热风温度对葡萄品质的影响,以新疆吐鲁番无核白葡萄为材料,经促干剂处理后,分别在30,35,40,45℃条件下进行热风干燥。结果表明:在干燥无核白葡萄过程中,葡萄中的抗坏血酸、可滴定酸、总酚含量下降,而褐变度上升。综合比较可知,40℃热风干燥制得的葡萄干品质较好。     

不同促干剂处理对无核白葡萄干褐变的影响

为了探究不同促干剂配方对葡萄干褐变的影响,从自行配制的促干剂配方中筛选出干燥速率最快、保绿效果最好的2个配方(R1、R2)与市场上购买的促干剂成品(T)进行比较,考察无核白葡萄在晾房中自然风干干燥过程中的含水量的变化、色泽、褐变度、多酚氧化酶活性。结果表明:无核白葡萄在干燥的第3天开始出现明显的褐变,之后随着干燥时间的延长褐变程度不断加深,表现为红值(a*)上升,亮度值(L*)、黄绿值(b*)下降,干制后的无核白葡萄干的褐变度与a*极显著(P0.01)正相关性,与PPO活性呈极显著负相关性。而干燥速率较快的R2处理组的无核白葡萄干的褐变度明显低于其他处理组。这些结果表明:快速干燥能够有效降低葡萄干的褐变率,对无核白葡萄干的保绿有一定的功效。     

不同添加剂渗透预处理对热泵干燥罗非鱼片品质的影响

为了获得不同渗透预处理试剂对罗非鱼热泵干燥综合品质的影响,以罗非鱼为实验材料,以干燥时间,Ca~(2+)-AT、Pase活性、复水率、白度、硬度及其综合评分作为指标,进行了罗非鱼经不同浓度的海藻糖、聚葡萄糖、茶多酚、甘露醇和谷氨酸钠浸渍预处理后的热泵干燥实验,获得不同浓度试剂预处理的热泵干燥曲线和品质变化规律。结果表明:5种添加剂的浸渍均能减少干燥时间,提升干燥品质。实验中最短的干燥时间比对照组减少了31%。品质综合评分较优的浓度分别为50 g/L海藻糖、20 g/L聚葡萄糖、6 g/L茶多酚、2 g/L甘露醇和2 g/L谷氨酸钠,且各自对应的综合评分与对照组相比分别提高了60.35%、60.25%、32.23%、41.63%和42.00%。     

甘蓝的新型组合干燥工艺

为了克服单一干燥造成的品质缺陷,提出了一种新型的组合干燥方式,以改善产品的外观品质和复水特性。以甘蓝为研究对象,主要探讨了组合干燥过程中热风温度、干燥转换点的物料含水率、微波强度、渗透处理对干燥特性的影响;并以成品色泽、复水比、Vc保留率为指标,对不同干燥方式获得的产品性能进行了比较。研究获得的组合干燥工艺参数为:70℃热风干燥至物料含水率60%,2.5 W/g微波强度下干燥至40%含水率,25℃下以2.8 g/mL料液比向半干产品中加入28%葡萄糖和15%NaCl混合渗透液处理15 min,最后70℃二次热风干燥至成品。产品的水分活度为0.466,含水量为16.34%,复水比为8.71,Vc保留率为31.05%。结果显示,组合干燥方式干燥速率快,能耗低,产品含有高水分含量、低水分活度,产品品质与真空冷冻干燥的产品相近,是一种工业化生产果蔬干制品的新方法。     

Raisin processing: physicochemical,nutritional and microbiological quality characteristics as affected by drying process

Processing and conservation of grapes by suitable techniques has been a major challenging issue for a long time. Optimization of drying and pretreatment operations of this fruit have been extensively studied. However, in order to achieve the production of high-quality raisins and reach consumers’ acceptance, special attention for quality attributes should be taken into account. Quality characteristics of grapes such as color, texture, vitamins, phytochemicals, aroma profile and microbial stability are of paramount importance since they could vary throughout the dehydration procedure and would directly determine quality perception and consumer choice. This paper presents a comprehensive review of the physicochemical, nutritional and microbiological characteristics of dried grapes as affected by the drying process. In addition, it investigates the changes of different grapes quality attributes (mainly nutritional and aromatic proprieties) during processing, which enables professionals and scientists to better choose and optimize grape processing to deliver the highest raisin quality to consumers.     

Impact of gliding arc plasma pretreatment on drying efficiency and physicochemical properties of grape

The effect of cold plasma pretreatment with different durations 10, 20, 30, 40, 50, and 60 s on the mass transfer rate and quality of grape fruit during hot-air drying at 60 °C and 1.5 m/s were studied. It was found that cold plasma pretreatment significantly increased effective moisture diffusivity, reducing the drying time and energy consumption by up to 26.27% and 26.30%, respectively. Longer exposure resulted in smaller shrinkage and higher rehydration ratio. Furthermore, plasma pretreatment resulted in improved quality of dried grapes, in particular higher total phenolic content, antioxidant activity, and vitamin C retention by up to 3.06–30.53%, 7.31–62.29%, and 17.87–168.73%, as compared to the untreated ones. Among all pretreatments, 50 s exposure was preferred due to the minimal energy consumption and the least effect on the samples color.     

无核白葡萄热风干燥过程中总酚与抗氧化活性的变化

为了评价褐变的发生对葡萄营养与功能活性的影响,跟踪考察无核白葡萄在30℃热风干燥过程中的色度、总酚含量及DPPH自由基清除能力、ABTS+·清除能力和还原能力等抗氧化活性的变化。结果表明：无核白葡萄在干燥的第8天开始出现明显的褐变,之后随着干燥时间的延长褐变程度不断加深,表现为红值(a*)上升,亮度值(L*)、黄值(b*)和色彩饱和度(c*)下降;干燥过程中,葡萄果实中总酚含量和抗氧化活性均呈总体下降趋势,但在第8天时有突然增大,之后又迅速下降;第8天时总酚含量的突然增大与葡萄开始褐变和红值(a*)峰值的出现时间相吻合;整个干燥过程中的总酚含量与3种抗氧化活性评价结果之间呈极显著正相关。这些现象说明,无核白葡萄中总酚是赋予其抗氧化活性的主要物质,褐变程度的加深会导致葡萄中总酚含量和抗氧化活性的下降。     

Grape Drying: A Review

The drying of grapes is a more complex process compared to the dehydration of other agricultural materials due to the necessity both of a pretreatment operation prior to drying and further processing operations after drying. To date, most researchers have concentrated on pretreatment and drying where the primary effects of pretreatment on drying have been evaluated. It seems appropriate that a review should now be presented to critically examine all the corresponding published data in the literature and to compare the conditions used in these studies in order to highlight the grape drying process by considering the important aspects of both the pretreatment and post-drying operations. The result of this study will be useful in identifying the future research directions needed for grape drying and also to facilitate the development of an analytical framework for the design of novel drying equipment.     

Grape Drying: A Review

The drying of grapes is a more complex process compared to the dehydration of other agricultural materials due to the necessity both of a pretreatment operation prior to drying and further processing operations after drying. To date, most researchers have concentrated on pretreatment and drying where the primary effects of pretreatment on drying have been evaluated. It seems appropriate that a review should now be presented to critically examine all the corresponding published data in the literature and to compare the conditions used in these studies in order to highlight the grape drying process by considering the important aspects of both the pretreatment and post-drying operations. The result of this study will be useful in identifying the future research directions needed for grape drying and also to facilitate the development of an analytical framework for the design of novel drying equipment.     

亚硝酸盐在广式腊肠干燥过程中的变化

对广式腊肠热风干燥的研究表明：水分含量,发色反应和pH值是影响整个干燥过程中亚硝酸盐含量的主要因素。三者在干燥进程中交替占据主导地位,在干燥后期,亚硝酸盐含量和三个影响因素均与干燥时间呈一定的线性关系。实验发现,pH值（X）与亚硝酸盐的（未）分解率的对数（Y）之间存在良好的线性关系：Y＝6ln10-2.63X.