真空、脉冲真空、超声波对芒果渗透脱水的影响

为研究真空、脉冲真空和超声波对芒果渗透脱水动力学的影响,将大小为26mm×26mm×5mm的块状样品浸于65°Brix果葡糖浆溶液中,渗透脱水处理180min。结果表明,菲克扩散模型能很好地描述渗透脱水过程中芒果失水率和固增率的变化规律;真空、脉冲真空和超声波均促进了水分和固形物的扩散,其中超声波作用使水分扩散系数具有最大值,而真空处理导致了固形物扩散系数最高。     

不同渗透方式对芒果脱水效率和品质的影响

为了比较在夏季（30 ℃）和冬季（20 ℃）生产环境下不同渗透方式在芒果脱水效率和品质上的差异,本文以失水率、固增率、水分有效扩散系数、可溶性固形物扩散系数、V_C和总酚保留率以及三态水转化为考察指标,探究固态渗透（SSD）和液态渗透（LOD）对糖渍芒果脱水效率和品质的影响。结果表明,固态渗透的脱水效率以及营养物质保留率高于液态渗透;在糖渍48 h后,在环境温度20 ℃下SSD40（蔗糖:芒果(w/w)=4:10）的失水率和固增率最大为49%和5.11%,SSD20（蔗糖:芒果(w/w)=2:10）的V_C和总酚保留率最高为47.43%和43.66%;在环境温度30 ℃下,SSD40的失水率和固增率最大为57.41%和6.36%,SSD20的V_C、总酚保留率最高为43.79%和42.43%。渗透过程改变了芒果样品中水的结合状态,自由度高的水分向自由度低的方向迁移。本文研究结果将为果干类产品固态渗透预处理技术的应用提供理论参考。     

常压、真空和脉冲真空渗透脱水加工芒果脯

在24℃下,以60%蔗糖水溶液作为渗透溶液,在常压、真空和脉冲真空(压力为510 mmHg)条件下对芒果进行渗透脱水,然后置于热风干燥箱中70℃干燥制成芒果脯,测定芒果脯的硬度、颜色、含水量、复水率.通过感官评定及统计分析得出,真空和脉冲真空渗透脱水制成的芒果脯品质明显优于常压渗透脱水制成的芒果脯.     

不同渗透脱水处理对芒果品质的影响

研究了不同条件下渗透脱水加工对芒果品质以及质量传递的影响,渗透脱水条件是采用不同质量分数(30%,40%和50%)、不同种类的糖溶液(蔗糖,葡萄糖和麦芽糖)、温度30℃,时间2 h。结果表明,随着渗透液质量分数增大,芒果的失水率逐渐变大。在硬度、色泽、维生素C含量等其他生理指标与质量传递方面,经综合考虑得到经45%麦芽糖渗透处理后,芒果品质较好,失水率较高,为最优条件。     

超声波辅助渗透脱水预处理对山药干燥特性及品质的影响

为提高山药干燥的效率与品质，将超声波辅助渗透脱水预处理技术应用于铁棍山药热泵干燥前处理中，文章探究了不同处理条件对山药干燥特性及品质的影响。结果表明，与单纯渗透处理相比，处理时间为60 min时，超声波辅助渗透脱水预处理山药的失水率(17.6%～22.2%)及增固率(1.45%～2.19%)较高，干燥时间(231.6～243.3 min)较短，并且其干制品色差值(5.6～13.4)及硬度(558.3～566.2 g)较低，复水比(2.22～2.31 g/g)较高，并且具有较强的抗氧化能力。此外Weibull distribution模型能够较好地模拟超声波联合渗透处理山药的热泵干燥过程。在超声波辅助渗透处理组中，山梨醇处理组山药干制后丁香酸及槲皮素含量较高(分别为35.7μg/g DW及28.3μg/g DW)，其提取物DPPH及OH^-自由基清除能力较强，分别为58.5%及65.5%。超声波辅助渗透脱水处理是一种良好的干燥预处理方式，有利于提高山药干燥效率及品质，并且山梨醇能够作为蔗糖的替代品应用于山药的超声波辅助渗透脱水中以提高山药干燥品质。     

不同渗透加工方式对冷贮藏芒果粒的硬度影响

本研究以早熟台农芒果品种果粒加工为研究对象,运用质构仪检测超高压渗透加工对商业酶制剂前处理液浸渍冷储藏芒果粒的硬度,分析果胶甲酯酶、钙含量组成处理液和超高压相结合对芒果粒品质属性硬度的影响,且进行相关性分析;在不同压力渗透加工操作单元过程中探讨经预处理的低温储藏果粒硬度变化。主要研究结果如下:添加果胶酯酶有助于提升果粒的质构,有效降低了机械加工果粒硬度的损失。芒果粒经过果胶甲酯酶PME和0.5%(m/m)CaCl2·2H2O组成预处理液及0.09 MPa,15 min真空协助渗透,结合450MPa,15 min超高压压力渗透,经TPA检测真空协助超高压渗透加工预处理组的果粒硬度比水渗透组的变化显著增加,冷藏果粒硬度从水渗透组的358.5g上升至预处理组的1111.7g,预处理组果粒硬度比水渗透组提高83.7%,且前处理技术果粒硬度比鲜果组提高18%,得到果粒的质构特性最好,有助于产品品质的提升。     

物理场辅助渗透脱水技术及其在果蔬干燥中的应用

渗透脱水是一种促进果蔬干燥、保持果蔬感官和功能特性、延长果蔬货架期的非热加工技术。渗透脱水技术的主要缺点是传质效率低,物理场辅助渗透脱水技术可有效地提升渗透脱水效率。物理场辅助渗透脱水技术包括:超声波辅助技术、真空辅助技术、高静水压和高压脉冲电场辅助技术,是近年来果蔬干燥研究的热点。通过研究归纳国内外相关文献,分别从果蔬渗透脱水的机理及其传质效率影响因素、物理场辅助渗透脱水技术及动力学模型、物理场辅助渗透脱水在果蔬干燥的应用3个方面综述了物理场辅助渗透脱水技术近年来的研究进展,总结应用中存在的问题,提出未来发展方向。     

超声辅助糖液渗透处理对真空冷冻干燥桃脆片干制品品质及吸湿性的影响

为探究超声辅助糖液渗透处理对真空冷冻干燥桃脆片干制品品质及吸湿性的影响,本实验比较了白桃经4 种糖液（蔗糖、麦芽糖、葡萄糖、低聚异麦芽糖）超声辅助渗透处理后桃片的水分损失率、固形物增加率以及真空冷冻干燥后桃脆片的微观结构、质构特性（硬度、脆度）、吸湿性及玻璃化转变温度。结果表明：与对照组相比,经超声辅助糖液渗透处理的桃片水分损失率、固形物增加率提升,孔隙更加致密且细胞组织发生破裂和结构坍塌,硬度显著提高（P＜0.05）;且超声辅助糖液渗透处理可以降低桃脆片的吸湿性,在相对湿度从0梯度增加到90%的过程中,各处理组样品最终达到吸湿平衡时的质量变化率范围为55.16%～59.63%,对照组为61.43%;与对照组玻璃化转变温度（52.37 ℃）相比,超声辅助麦芽糖渗透脱水处理使桃脆片体系的玻璃化转变温度升高到64.27 ℃。综上,超声辅助糖液渗透处理对桃脆片品质产生影响的同时,也对降低桃脆片吸湿性和改变桃脆片体系玻璃化转变温度具有重要影响,本研究可为改善和提升白桃干制品品质提供技术参考。     

真空、脉冲真空和常压下蓝莓渗透脱水的研究

研究了真空渗透脱水、脉冲真空渗透脱水和常压渗透脱水下蓝莓水分含量和水分活度的变化规律，结果表明：真空渗透脱水时，蓝莓的水分含量和水分活度降低得最快。真空渗透脱水、脉冲真空渗透脱水、常压下渗透脱水蓝莓的有效水分扩散率分别为1.6777×10^-9、1.3629×10^-9、0.5679×10^-9m^2/s。真空渗透脱水、脉冲真空渗透脱水、常压下渗透脱水的有效固性物扩散率分别为9.1705×10^-10、6.3919×10^-10、5.1007×10^-10m^2/s。     

不同浸糖方式对杏脯品质和香气的影响

以新鲜明星杏为原料,探讨超声辅助、微波辅助、真空、煮制浸糖4 种不同浸糖方式对其色泽、质构、复水率、总糖含量、香气和感官评价的影响。对比不同浸糖工艺对于杏果脯品质的影响,结果表明：超声辅助浸糖的杏脯色泽与其他组具有显著性差异（P＜0.05）,L*值为43.86,b*值为30.09,超声辅助浸糖的杏脯硬度、黏性和咀嚼性与煮制组具有显著性差异（P＜0.05）,采用超声辅助浸糖工艺的杏果脯复水率比煮制浸糖处理所得成品低24.97%,超声辅助浸糖总糖含量最高,为40.58%,香气测定结合感官评价超声辅助浸糖制备的杏果脯滋味最佳。     

Effects of Ultrasound on Mass Transfer Kinetics,Structure, Carotenoid and Vitamin C Content of Osmodehydrated Sweet Potato (Ipomea Batatas)

The effects of ultrasound pretreatments on mass transfer kinetics, microstructure, carotenoid and vitamin C contents of sweet potato were investigated. Sweet potato samples were treated in distilled water with ultrasound (DWU), osmotic dehydration without ultrasound (OD) and ultrasound-assisted osmotic dehydration (UOD). Samples were subjected to ultrasound probe of 2 cm diameter, frequency of 28 kHz at 300 W maximum power at different pretreatment times of 20, 30, 45 and 60 min. The Azuara model used in this study fitted the experimental data well with high coefficient of correlation ranging from 0.92 to 0.98, low values of chi-square (<0.6), root mean square error (<0.9) and percent mean relative deviation (<10%). The results showed that UOD significantly (p < 0.05) had the highest mass transfer coefficient and equilibrium value for water loss and solid gain, compared to DWU and OD. DWU had no significant effect on the structure of sweet potato samples, while UOD had the highest effect on the structure. The samples treated in OD had the highest carotenoid retention compared to DWU and UOD at all pretreatment times. However, ultrasound enhanced the retention of vitamin C (>70%) in sweet potato samples treated in DWU and UOD.     

超声辅助渗透处理对冷冻干燥双孢蘑菇冻干效率和品质的影响

为了在生产高品质冷冻干燥产品的同时进一步降低干燥过程中的能耗与成本,选取双孢蘑菇为研究对象,以冷冻和冷冻干燥过程中双孢蘑菇的共晶点、共熔点、冻干温度及冻干产品的质构、微观结构、色泽和营养品质为考察指标,研究普通渗透和超声辅助渗透处理对冷冻干燥双孢蘑菇冻干效率和品质的影响。结果表明,与新鲜样品相比,经超声辅助渗透处理45 min后,样品冷冻时间和冷冻干燥时间分别缩短了21.24%和28.62%,并且其冻干产品的可滴定酸、总蛋白质以及多酚等营养物质的保留率高于普通渗透120 min处理组。此外,与普通渗透120 min处理组相比,超声辅助渗透45 min处理组冻干样品复水比、硬度更高,其微观结构更加接近于未经渗透处理的冻干样品。     

Influence of ultrasound pretreatments on diffusion coefficients,texture and colour of osmodehydrated sweet potato (Ipomea batatas)

The moisture and solute diffusivities, texture and colour of sweet potato pretreated in distilled water with ultrasound (UD), osmotic dehydration without ultrasound (OD) and osmotic dehydration with ultrasound (UOD) were investigated to determine the effects of ultrasound on osmodehydrated sweet potato. The moisture and solute diffusivities of all the pretreatments ranged from 2.89 to 4.95 × 10^?10 and 1.17 to 1.67 × 10^?10 m² s^?1, respectively. The moisture diffusivity of samples treated in UOD was significantly (P < 0.05) higher than that of OD and UD by 30.82% and 41.62%, respectively. Compared to the fresh sample, the firmness of samples treated in OD and UOD was reduced by 83.53% and 92.47%, respectively. UD increased the brightness (L*) and reduced the redness (a*) of sweet potato, while UOD enhanced the yellowness (b*) and chroma (C*) of sweet potato. The sweet potato samples treated in UOD had the highest total colour difference (ΔE).     

Effects of ultrasound pretreatments on the kinetics of moisture loss and oil uptake during deep fat frying of sweet potato (Ipomea batatas)

The possibility of ultrasound assisted pretreatments of sweet potato to lower the moisture content and oil uptake during deep fat frying and its effects on the mass transfer rate was investigated. Sweet potato samples prior to frying were immersed in distilled water with ultrasound (UD), osmotic dehydration without ultrasound (OD) and ultrasound assisted osmotic dehydration (UOD). Ultrasound probe having frequency of 28 kHz at 300 W maximum power and time of 30 min was used for the pretreatment. The control (without pretreatment) and the pretreated samples were fried using sunflower oil at temperature of 130, 150 and 170 °C for 2, 4, 6, 8 and 10 min. The first order kinetic model was used for the mass transfer rate for moisture loss and oil uptake. The lowest moisture content was found in fried samples pretreated in UOD and OD while the lowest oil uptake was obtained in fried samples pretreated in UD having 65.11 and 71.47% oil reduction at temperature of 150 and 170 °C, respectively, compared to the untreated sample. The k values of all pretreated samples were higher than that of the untreated at 150 and 170 °C. The highest activation energy for moisture loss was found in untreated samples while the lowest activation energy for oil uptake was found in samples pretreated in UOD. The results from this work proved that ultrasound is a good pretreatment that can be used to obtain a low moisture content and oil uptake during deep fat frying of sweet potato.Industrial relevanceUltrasound is a novel technology that is widely used in the food industries because of its numerous advantages over conventional methods. Its application in the frying of foods could also help in the reduction of oil uptake, thus making safe the consumption of fried foods. The information about frying kinetics could also help in the design and optimization of the process in the food industry.     

Modelling of mass transfer during osmotic dehydration of apple tissue pre-treated by pulsed electric field

The osmotic dehydration mechanism of apple sample pre-treated by pulsed electric field (PEF) was investigated over a range of 44.5-65 ° Brix sucrose concentrations. Apple disks treated by PEF field of 0.90 kV/cm during a constant time were immersed in sucrose solution at ambient temperature with 3:1 syrup to apple ratio (w/w). Increase of the initial solute concentration and the PEF treatment resulted in acceleration of the osmotic dehydration (OD). The PEF-treated samples had a higher water loss (WL) and higher solid gain (SG) than the untreated samples. The osmotic dehydration kinetics was studied on the basis of two approaches: Fick's unsteady state diffusion equation and a two-exponential kinetic model. The coefficients of effective diffusion of water and solute were calculated. Their values were higher for samples pre-treated electrically. The effect of PEF was more pronounced for the WL comparatively to the SG. The two-exponential kinetic model permits evaluating of both convective and diffusion stages of OD. The PEF pre-treatment accelerates the kinetics of water and solute transfer during convective and diffusion stages of OD.     

Mass transfer kinetics and regressional‐desirability optimisation during osmotic dehydration of pumpkin,kiwi and pear

Mass transfer kinetics and optimisation of osmotic dehydration (OD) of fruits and vegetables with diverse structures were studied. Different concentrations of sucrose (20–60 °Brix) and process times (0–24 h) were used. Magee’s model was appropriate for predicting water loss (WL), while Azuara’s model fitted well solids gain (SG) data and represented more accurately the evolution of the complete process close to equilibrium. Polynomial equations for each kinetic variable [WL, SG and weight reduction (WR) – for pumpkin, kiwi and pear] using multiple linear regression were fitted for a selected range of experimental data (30–240 min, 20–60 °Brix). A complete solution algorithm for desirability function was coded in Matlab^® 7.2 (Mathworks, Natick, MA, USA) with the aim to optimise osmotic dehydration process in terms of WL, SG and WR; optimal conditions were found for each fruit. Besides, an optimal common zone was identified for OD corresponding to process time from 114 to 240 min and sucrose concentration from 54 to 60 °Brix.     

Evaluation of process conditions on osmotic dehydration and quality indexes of pumpkin (Cucurbita moschata) and further polymeric film selection for packaging and refrigerated storage

We studied the influence of composition and concentration of solutions and product size on mass transfer kinetics during Anco pumpkin osmotic dehydration (OD). Once optimal conditions were determined, samples packed in commercial polymeric films were microbiologically analysed during refrigerated storage. The optimal OD time was 3 h, when the efficiency index WL/SG (water loss/solid gain) was stabilised. At this time, 1.0 and 1.5 cm cubes presented the highest index value (about 11) in binary solution (sucrose 55°Bx). WL was higher in 1.0 cm cubes for each dehydrating ternary salt solution tested, and no significant differences in firmness were observed with Calcium Lactate addition. Thus, optimal condition for OD in ternary solutions was 180 min and 55°Bx – 2% NaCl. Microbiological determinations were done for dehydrated (55°Bx without/with 2% NaCl) and untreated samples, packaged in different polymeric films. The combination with lowest mesophilic and psychrophilic counts at day 10 was: samples dehydrated with ternary solution of sucrose-salt packed in Polypropylene film.     

Optimisation of the pulsed vacuum osmotic dehydration of cladodes of fodder palm

Fodder palm, a great source of nutrients for human and animals, grows even in arid climates. Pulsed vacuum osmotic dehydration is an efficient process for obtaining semidehydrated food. It was used to slice cladodes of fodder palm. The independent variables used were temperature (30–50 °C), pulsed vacuum pressure (50–150 mbar) and NaCl concentration (5–15 g per 100 g solution). The response variables were water activity (a_w), moisture content (X), colour parameters, water loss (WL), solid gain (SG) and weight reduction (WR). The pulsed vacuum osmotic dehydration process was optimised for minimum values of a_w, X and SG, and maximum values of chroma. The experimental data obtained with the optimum condition (100 mbar; 10 gNaCl per 100 g solution, 44 °C) were near the estimated ones. For example, WL, a_w and ?E, and their error were 8.15 g per 100 g, 11%; 0.985, 0.3% and 6.15, 15.2%, respectively.     

Osmotic dehydration of the Indian fig (Opuntia ficus indica) with binary and ternary solutions

The objective of this work was to study osmotic dehydration (OD) of the Indian fig with two binary solutions (sucrose/water and glucose/water) and a ternary solution (sucrose/NaCl/water) according to a 2³ factorial design with independent variables: temperature (30–50 °C), immersion time (90–240 min) and concentration (40–60 °Brix). The dependent variables were water loss (WL), solid gain (SG) and dehydration efficiency index. The temperature had greater influence on the WL in the three hypertonic solutions studied; the concentration had greater influence on the SG in the three hypertonic solutions investigated and the best conditions for the OD of the Indian fig were in glucose solution at 40 °Brix, 40 °C and 165 min.