Nondestructive Determination of Moisture Content in Dry Fruits by Impedance and Phase Angle Measurements

An electronic method to estimate the moisture content (MC) of dry fruits by measuring the impedance (Z) and phase angle (θ) of a cylindrical parallel-plate capacitor with dry fruit sample between the plates, using a CI meter (Chari’s Impedance meter) at 1 and 9 MHz is described. Capacitance C was derived from Z and θ, and using the C, θ, and Z values of a set of dried cherries, whose MC values were later determined by the vacuum hot air-oven method, a calibration equation was developed. Using this equation, and their measured C, θ, and Z values, the MC of a group of cherries, not used in the calibration, was predicted. The predicted values were compared with their air-oven values. Similar predictions were done using the same method on dried blueberries. The method worked well with a good R2 value, and showed a low standard error of prediction (SEP) in the measured MC range between 5% and 30% for cherries, and 9% and 22% for blueberries.

Experimental Study and Modeling of a Convective Dryer for Fruits and Vegetables

The present work deals with the study of the thermal performances of a convective dryer for fruits and vegetables. This dryer, operating with energy generated from the combustion of biomass in a boiler connected to a water/air heat exchanger could be a solution to the problematic of energy related to drying. An experimental and theoretical study is carried out on the temperature profile inside the dryer. For this purpose, 10.3 kg of tomatoes were dried on the experimental setup. The operation lasted about 16 hours and reduced the moisture content from 93.8% to 12% in wet basis. The overall thermal efficiency of the convective dryer during the trial is 10.76%. For the theoretical study, the dryer components (boiler, water/air exchanger and drying chamber) are first modeled individually;the different sub-programs are then coupled to form the convective dryer program. The method of global heat balances combined with the one called “ε-NUT” is used. The set of equations is discretized using the implicit method of finite differences, then solved with the Gauss algorithm in Fortran 90. The theoretical results obtained are in good agreement with those measured.

Effects on Sucrose Metabolism,Dry Matter Distribution and Fruit Quality of Tomato Under Water Deficit

Four irrigation treatments were designed with 2,4,6 and 8 d intervals to irrigate, respectively. Watering was stopped when the reading of the moisture tension sensor reached zero. The results indicated that glucose and fructose content of tomato's fruit were increased but sucrose content was decreased with fruit growth and development. In different stages, carbohydrate content of tomato fruit in the treatment 3 was the highest, in the treatment 2 was higher, and in the other treatments was the lowest. SS(sucrose synthase)activity was decreased but SPS(sucrose phosphate synthase)activity was increased with development of tomato. SS and SPS activity were increased but acid invertase and neutral invertase activity of ripe stage were decreased under deficit irrigation. Glucose and fructose content were increased in leaves of tomato under water deficit. Soluble sugars, organic acid and the ratio of sugar/acid in tomato fruits were increased and dry matter accumulation of plant was enhanced under water deficit. But the growth of fruits upside the plant and its dry matter accumulation were badly affected under water stress.

Design of Fruits Solar Energy Dryer under Climatic Condition in Jordan

In this paper, a new design of a natural convection solar dryer used to dry fruits is presented;taking into account the local climatic conditions prevailed in Jordan during summer season. The dryer will have a capacity of 100 kg of sliced apples and the simulation is based on mass and heat balances. It is deemed that such new design will be able to reduce the original moisture content, of the final product, to 10% within two days. The special tailored program could be used to calculate drying parameters for similar products under different climatic conditions. The next step will be focused on constructing the solar dryer in order to conduct actual experiments in the field.

真空冷冻预干燥对压差膨化干燥果蔬脆片质地特性的影响

为探索预干燥处理对不同果蔬脆片结构及质地特性的影响,该研究采用真空冷冻干燥作为预干燥,并选取了3个水分转换点(60%、45%、30%),对预干燥过程中6种典型果蔬(苹果,梨,桃,山药,马铃薯,青萝卜)水分状态、细胞结构、收缩率、孔隙度、应力-松弛特性与质地特性进行测定与分析。结果表明,随着预干燥的进行,水分含量逐渐降低,自由水逐渐散失,以不易流动水为主,收缩率逐渐减小,孔隙度逐渐增大,硬度、咀嚼性、弹性模量逐渐增加;水分转换点为60%时不同果蔬脆片具有较高的硬脆度,其中马铃薯与山药脆片硬度较高,桃与梨的脆片脆度较高;水分转换点为30%时,6种果蔬的孔隙度最高,且青萝卜的孔隙度显著高于其他果蔬(P <0.05);在干燥后期,果蔬样品骨架基本形成,且收缩率较低,致使内部孔隙度变大;由相关性分析可知真空冷冻预干燥过程中水分转换点、孔隙度与果蔬脆片质地特性极显著相关(P <0.05),研究结果可为预干燥对果蔬脆片质地影响提供参考。

预处理对热风-压差膨化干燥香菇脆片品质的影响

为提高香菇产品的质量,以香菇片为原料,采用了冻融预处理、海藻酸钠涂膜预处理、蔗糖溶液渗透预处理和纤维素酶解预处理四种不同的预处理方法,并结合热风-压差膨化联合干燥技术对香菇片进行干燥.研究了不同预处理方式对香菇水分分布的影响,对不同预处理香菇片在热风预干燥过程中的热风干燥特性曲线进行干燥动力学模型拟合,并对所得压差膨化香菇脆片的色泽、质构、复水性、感官评分和微观结构进行分析.结果表明,与未预处理的香菇片相比,预处理显著影响了香菇片的水分状态.Modified Page模型能更准确地描述不同预处理方式处理后香菇片的热风预干燥过程,从而预测预干燥过程中水分含量的变化.冻融和酶解预处理均显著提高了热风干燥过程中的水分扩散系数,有效的提高了热风干燥速率,缩短了预干燥时间,但最终压差膨化产品的色差较大,感官评分较低,膨化效果不明显.渗透预处理在色泽和口感方面表现出优势,但在热风干燥过程中,其水分扩散系数显著降低,导致预干燥时间延长,且压差膨化后的产品硬度相对最高.涂膜预处理的香菇脆片在热风干燥过程中与未处理的样品具有相同的热风干燥时间,并且其压差膨化后的产品膨化效果明显,具有相对较好的色泽和感官评分.其微观结构呈现规则、均匀的空腔结构,质构和复水性相较于未经预处理的香菇明显提升.综合比较,相对于其他预处理方法,涂膜预处理显著提高了香菇脆片的品质和感官评价,是生产压差膨化香菇脆片的较优方法,为香菇产品生产提供了有益的借鉴和参考.

不同干燥方式对灵芝子实体干燥品质的影响

采用热风干燥、热泵干燥、微波热泵耦合干燥、热泵梯度升温干燥、热泵梯度降温干燥等干燥方式,探究不同干燥方式对灵芝子实体感官、营养及理化品质的影响。结果表明,微波12 min+60℃热泵干燥脱水效率最高,较单一热风干燥至少缩短180 min;微波4 min+60℃热泵干燥色泽保持相对较好;微波12 min+60℃热泵干燥粗多糖含量最高,较60℃热风干燥提高了63.26%;热泵梯度降温干燥对DPPH自由基的清除能力最强;60℃热泵干燥水溶性指数最高。从提高生产效率和营养成分保留率角度考虑,优先选择微波12 min+60℃热泵干燥方式;从产品良好色泽角度考虑,优先选择微波4 min+60℃热泵干燥方式;从产品良好功能活性角度考虑,优先选择热泵梯度降温干燥、60℃热泵干燥方式,为灵芝子实体干燥方式的选择提供理论依据。

干燥方式对桑叶枸杞固体饮料品质的影响及其口感优化

为研究不同干燥方式对桑叶枸杞固体饮料品质的影响,以桑叶、枸杞为基本原料,通过微波干燥、鼓风干燥和真空冷冻干燥3种方式分别制备桑叶枸杞固体饮料,并检测干燥后粉体的质构、色泽及营养品质变化。从物理性质来看,真空冷冻干燥的粉体在稳定性、可压性与均一性上表现较好,鼓风干燥的粉体在堆积性和流动性上相对更好。真空冷冻干燥粉体的总糖含量最高,亮度值最大,湿润下沉时间短。结合吸湿特性与微观结构判断,真空冷冻干燥制备的粉体品质优于其他2种干燥方式。为了改善饮料风味,采用响应面试验进行口感优化,结果表明,当木糖醇添加量为27.30%(质量分数,下同)、甜菊糖苷添加量为3.67%、苹果酸添加量为0.11%时,口感最好。

计算流体力学在果蔬干燥领域的研究进展

干燥是延长果蔬保质期的主要方法之一。随着计算机技术的发展,计算流体力学在果蔬干燥领域中得到广泛的应用。该技术可以对果蔬干燥过程中的流体流动、传热传质等动力学现象进行模拟和预测,并输出可视化结果。与传统实验相比,计算流体力学技术拥有节能、低成本、模拟速度快、灵活度高等优点。本文详细介绍了计算流体力学在果蔬干燥领域的工作原理,并对其在不同果蔬干燥方式中的研究进展进行综述,报道了耦合收缩的数值模型研究进度,并对计算流体力学在果蔬干燥领域的发展方向进行展望,以期为研究者提供新的见解和参考。

微波参数对果蔬物料温度特性的影响

为提高微波加热效率和加热均匀性,应用有限元分析软件COMSOL Multiphysics建立微波干燥的电磁波-热传导双向耦合模型,模拟微波干燥果蔬样品的过程。探索微波参数对微波加热效率的影响,并采用脉冲微波方式,优化微波加热均匀性。结果表明,从X轴和Y轴方向同时入射0.5 kW微波时,物料温升最大,且比单微波温升最快时的加热效率高了9.3%;脉冲微波可将物料温度均匀性提高53.7%。探索微波干燥的均匀性规律,可为改善微波干燥均匀加热提供参考。

现代水果干制工艺技术研究进展

干制水果营养丰富、色味俱佳,深受大众喜爱。随着水果产量的逐年增加,如何对大量应季水果在保鲜期内进行干制加工,在保证果干品质的前提下进一步降低能耗、节约成本,是水果干燥行业的一大难题。从不同干制加工工艺技术出发,探讨了传统的单一干燥方式、联合干燥方式、辅助干制技术工艺的优缺点及对果干品质、营养成分、生物学活性的影响,较为全面地对当今水果干制技术的研究进展进行了总结概述,为促进水果干制加工产业的发展提供参考借鉴。

真空冷冻联合干燥技术在果蔬加工中的应用现状

果蔬的干燥加工可以有效降低其水分含量,延长货架期,减少损耗,在一定程度上保留营养物质。目前,在果蔬干燥领域,为了最大限度地保留营养,应用较多的是真空冷冻干燥技术。本文综述真空冷冻联合干燥技术在果蔬加工中的应用现状,为真空冷冻联合干燥技术在果蔬加工中的应用提供参考。

宁夏枸杞果实性状和预处理对果实制干的影响

【目的】探究不同品种(系)宁夏枸杞果实性状和预处理对果实制干的影响,为枸杞制干工艺提供有价值的理论依据。【方法】以制干差异较大的不同品种(系)宁夏枸杞为试验材料,采用称重法、石蜡切片和扫描电镜等方法,对果实加工性状、果皮及角质层结构、果皮蜡质微形态和不同预处理枸杞果实制干时间进行探究,明确不同品种(系)宁夏枸杞果实性状和预处理对果实制干的影响。【结果】1)不同品种(系)枸杞果实纵径、百粒质量、单果体积存在显著差异,‘16-23-7-8’横径、纵径、百粒质量、单果体积均最高,‘宁杞1号’最低。2)随着果实发育,果皮和角质层厚度逐渐增加且存在显著差异。‘宁杞5号’果皮厚度最大,达768.273μm;‘宁杞1号’果皮厚度最小,为445.100μm。‘14-402’角质层最厚,达9.420μm;‘16-23-7-8’最低,为7.528μm。3)成熟期枸杞果实表皮被束状蜡质层覆盖,蜡质晶体呈无规则片状,片状蜡质层较厚,排列较紧密。4)不同品种(系)枸杞果实制干时间存在显著差异,由易到难依次为‘宁杞1号’、‘Z44’、‘16-23-7-8’、‘14-402’、‘宁杞5号’。与对照相比,碱处理后,平均制干时间缩短4.10 h;氯仿处理后,平均制干时间缩短16.94 h。【结论】枸杞果皮结构通过影响水分运输进而影响枸杞果实制干过程;预处理可破坏枸杞表皮蜡质层缩短制干时间。本研究5个枸杞品种(系)中,‘宁杞5号’不易制干,‘宁杞1号’最易制干,在枸杞制干时,应用的预处理方式必须考虑品种间存在的组织和形态解剖学特征的差异。

火龙果粉冷冻-真空微波干燥工艺优化及贮藏品质

为优化火龙果粉的冷冻干燥结合真空微波干燥工艺并研究其贮藏品质,以火龙果为原料,以复水比和维生素C保留率加权转化的综合评分为指标,通过单因素和响应面试验优化火龙果粉的工艺条件并分析其贮藏品质。结果表明,优化后的工艺条件为采用冷冻干燥将火龙果干燥到水分含量35%后,再采用真空度40 Pa、微波功率1 500 W的真空微波干燥继续将其干燥至水分含量3.5%。该条件下,产品实际综合评分为85.17,与理论预测值基本吻合。联合干燥技术的产品在25℃、相对湿度65%的条件下贮藏30 d时,火龙果粉中的VC保留率为(83.36±0.65)%,感官评分65.6,VC的保留率和感官评分均较高,具有较好的贮藏品质。

鲜油茶果快速制油工艺研究

为提高油茶果的制油效率,对传统油茶果制油工艺进行改进,采用先整果压破果壳再鼓风加热进行干燥达到蒲、壳与仁分离,得到的油茶籽仁经破碎烘干后进行压榨制油,经冷冻过滤得到成品油。对油茶籽仁烘干工艺条件和压榨工艺条件进行优化,以常温过滤为对照,对成品油的品质进行测定并考察了其在45℃储存18个月的稳定性。结果表明:油茶果干燥采用先压破果壳再鼓风加热可节约爆蒲(果壳炸开)时间0.5 h;油茶籽仁最佳烘干条件为烘干温度140℃,油茶籽仁颗粒直径6~8 mm,采用鼓风干燥;油茶籽仁含水率和油茶籽壳添加量对出油率有明显的影响,在添加30%油茶籽壳条件下,当含水率为3%时,出油率最高;油茶籽原油采用冷冻过滤得到的成品油的酸值(KOH)、过氧化值和苯并芘含量分别为0.6 mg/g、0.2 g/100 g和3μg/kg,符合食品安全国家标准要求,且储存稳定性优于常温过滤。该工艺节约了油茶果制油时间,提高了出油率和成品油的储存稳定性,可实现油茶籽油的快速制备。

Multi-mycotoxin exposure and risk assessments for Chinese consumption of nuts and dried fruits

In this study, 15 mycotoxins were detected in 233 nut and dried fruit samples from China. The 15 mycotoxins included aflatoxins （AFs： AFB1, AFB2, AFG1 and AFG2）, trichothecene toxins （TCs： T-2, ZEA, ENA, ENA1, ENB, ENB1 and BEA）, Alternaria toxins （ATs： TEN, AOH and AME） and ochratoxin A （OTA）. The mycotoxins were detected in 47.6% of the samples and all 15 of the mycotoxins were found. Two samples were positive for AFB1 and exceeded the maximum tolerable levels allowed in China. The contamination levels of the mycotoxins found in nuts, dried jujubes, raisins, dried figs and dried Iongans were in the ranges of 0.1-462.7, 0.2-247.3, 0.8-10.1,0.2-384.1 and 0.1-89.2 μg kg^-1, respectively. Dried figs （80.0%） had the highest incidence of mycotoxins, followed by dried Iongans （60.0%）, dried jujubes （57.1%）, nuts （43.6%） and raisins （26.7%）. The estimated daily intake （EDI） values of each individual mycotoxin and all of the mycotoxins collectively were calculated by both the deterministic approach （DA） and the probability approach （PA）. For risk characterization, dietary exposure to TCs, ATs and OTA through consumption of nuts and dried fruits according to both approaches, showed no health risk to Chinese adults by exposure to either individual mycotoxins or in combination. To the best of our knowledge, this is the first work in which risk assessment of multimycotoxins is performed, specifically including the emerging ENNs and BEA, in nuts and dried fruits of China.

Optimization of Spray Drying Processing Technology of Mulberry Powder

With concentrated juice of mulberry as raw material, the influence of type and dosage of dry aid, the inlet air temperature, inlet flow rate, and rotating speed on spray drying was studied. The spray drying processing conditions of mulberry powder were optimized by the L9(34) orthogonal test on the basis of single factor experiment. The results showed that optimum technical parameters to produce mulberry powder were: β-cyclodextrin as dry aids with dosage of 30%, inlet air temperature of180 ℃, rotating speed of 18 000 r/min and inlet flow rate of 30 m L/min. The mulberry powder under this optimum process conditions had a loose structure and bright color, fruity flavor was rich, the anthocyanin content for 54.67 mg/g, moisture content for5.6% and sensory scores for 83.

Energy Analysis of Pid Controlled Heat Pump Dryer

In this experimental study, a heat pump dryer was designed and manufactured, in which drying air temperature was controlled PID. Manufactured heat pump dryer was tested in drying kiwi, avocado and banana from among tropical fruits and energy and exergy analyses were made. Drying air temperature changed between 40 oC - 40.2 oC while drying the tropical fruits. Before the drying process in heat pump dryer, initial moisture contents were determined as 4.31 g water / g dry matter for kiwi, 1.51 g water / g dry matter for avocado and 4.71 g water / g dry matter for banana. Then tropical fruits were dried separately in heat pump dryer. Drying air temperature was kept unchanged with the error of +0.2 oC. Drying air velocity changed between 0.3 and 0.4 m/s in a period of 310 min. COPws of the heat pump dryer was calculated as 2.49 for kiwi, 2.47 for banana and 2.41 for avocado during the experiments. EUR changed between 13 % and 28 % for kiwi, 18% and 33% for avocado and 13% and 42% for banana in heat pump dryer.

油橄榄雌性繁殖成功的花粉和资源限制

雄全同株植物油橄榄(Olea europaea L.)鲜果肉为优质食用油原料,但存在结果率低下的问题.研究对油橄榄的开花特性进行观察,运用人工授粉、补施肥料、不同比例剪叶处理以及不同比例疏花处理研究了油橄榄花粉和资源限制对雌性繁殖成功的影响,并进一步探讨了该植物的“花多果少”的繁殖机制.结果表明:油橄榄单花序花期3~4 d,表现为完全花先熟,雄花后熟,有支持异交降低自交的倾向.油橄榄单株花期4~5 d,群体盛花期6~9 d,呈“集中开花模式”,花朵具芳香,能吸引多种昆虫前来访花,易造成自花授粉.异交人工授粉、风媒授粉与自然授粉3个处理间的结果率及单果重量没有显著差异,表明花粉来源与数量对油橄榄雌性繁殖成功没有影响.油橄榄雌性繁殖成功存在资源限制:补充施肥显著提高了植株的单生殖枝花序数、单花序完全花数、结果率与单果干重.随着剪除叶片比例增加,结果率显著下降,单果干重也显著降低,其中剪除叶片1/4的结果率与单果干重有所下降,但与对照差异不显著,而剪除叶片2/4、剪除叶片3/4及剪除全部叶片的结果率与单果干重均显著低于对照.随着疏花比例增加,初始花的结果率呈下降趋势,保留花的结果率则先降后升;单果干重则疏花1/4处理时增加,随着疏花比例继续增加,单果干重与对照差异不大.整体看来,油橄榄结果率极低,不同因子对其低水平坐果率可能产生相互作用.雄性功能假说和资源限制假说似乎是油橄榄“花多果少”繁殖策略的合理解释.

A Novel Method of Fruit Raw Material Reprocessing

We introduced a method of deep resources-economy reprocessing of fruit raw material. Based on the raw material fractionation at decreased temperatures the method results in the production of bioactive food stuffs, which are dry juice and refuse and natural water. The method includes the production of directly extracted juice and pulp refuse, juice evaporation in vacuum with the production of concentrate and natural water, and air drying the concentrate and the refuse. The method is realized for garden strawberry and cucurbit pulp. The mass concentration of solid in the fractions of cucurbit pulp is defined and the specific weight of the fractions are defined. It is shown that the solid of the cucurbit pulp is uniformly allocated between the fractions and amounts 34% for the dry juice, 31% for the dry refuse, and 35% for the natural water. Food and biological values of the cucurbit pulp fractions are determined. It is determined that the cucurbit includes silicium, nickel, and chromium. Silicium is contained only in dry fractions;nickel is present everywhere;chromium is discovered only in the natural water. Food and biological values of the cucurbit pulp are defined and their allocation between the fractions is determined. Separate components concentrations of the solid considerably differ between the fractions. Thus, two thirds of pulp protein is concentrated in the dry juice and a third is concentrated in the refuse. The natural water contains up to 90% of fat and sugar, from a half to two thirds of B-group vitamins, and the bulk of the mineral substances (K, Na, Ca, Mg, S, Co, Cu, Ni, Cr, and Zn), which concentration composes from 73% for potassium up to 100% for chromium.