渗透液特性对渗透脱水黄桃质构品质的影响

为明确渗透液特性对渗透脱水黄桃片质构品质的影响，本实验以‘金童8号’黄桃为原料，追踪分析渗透脱水过程中渗透液特性和黄桃质构品质的变化行为。黄桃片经超声或真空处理后，分别浸渍于糖度为30 °Brix的蔗糖、低聚异麦芽糖、果糖和葡萄糖溶液中（25 ℃），并于0.5、1、2、3、4 h和5 h时进行取样分析。测定渗透脱水过程中渗透液特性，如可溶性固形物（total solid soluble，TSS）含量、渗透压、pH值和浊度以及黄桃果肉质构参数的变化。结果表明，不同溶质的初始渗透液呈现出相同的TSS含量，但浊度、渗透压和pH值明显不同。渗透初期，渗透液渗透压和TSS含量均呈现明显降低的趋势，且超声和真空预处理会明显加速这一降低趋势，随着渗透脱水的进行，渗透后期TSS含量降低缓慢；渗透液pH值在渗透0.5 h后下降至与新鲜黄桃（4.30±0.32）接近的水平，后期未呈现出显著变化；渗透液浊度随着渗透过程中传质的发生，呈现先快速上升后缓慢上升的趋势。追踪分析渗透脱水过程中黄桃片质构品质变化发现，黄桃质构品质明显改变，其中硬度和咀嚼性显著降低（P＜0.05）。利用相关性分析发现，黄桃质构与渗透液渗透压、TSS含量和pH值总体呈显著正相关，与渗透液浊度呈显著负相关。综上，可以从渗透液特性调控入手，辅以合适的预处理，以改善渗透脱水黄桃片的质构品质。     

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。     

渗透条件对罗非鱼肉渗透-真空微波干燥的影响

为获得罗非鱼片渗透-真空微波干燥前最佳的渗透条件,研究渗透液组成、渗透时间、渗透温度和切片大小对鱼片渗透-真空微波干燥后的含水率、水分活度及品质(收缩率、复水率、色差)的影响。结果表明:鱼片在糖浓度较高的渗透液中,渗透脱水效果较好,但品质不理想;在2 h内鱼片含水率随渗透时间的延长而减少,2 h后渗透效果不明显;渗透温度升高脱水效率增加,但温度过高会破坏组织结构,不利于渗透的进行;切片越大,干燥后含水率越高但品质较差。结论:罗非鱼片渗透-真空微波干燥渗透最佳条件是渗透液组成为20%食盐+10%白砂糖,渗透时间2 h,渗透温度30℃,切片大小为500 mm2。     

樱桃番茄渗透预处理热风干燥特性研究

为了提高干制品的营养保留率和品质,进行了渗透预处理联合热风干燥的工艺路线的实验研究。以樱桃番茄为例,分别对不同浓度(50%,70%)蔗糖溶液常压渗透以及真空渗透处理后热风干燥的干燥时间、干燥速率、样品体积比、Vc保留率、硬度、颜色等参数分别进行测定和比较。结果表明:渗透预处理可以除去新鲜樱桃番茄中的大部分自由水,从而减少其热风干燥时间,使产品在高温中的暴露时间减少,从而缩短整体干制时间、提高干制效率及营养品质。经渗透预处理的樱桃番茄干制产品的体积比和Vc保留率要比直接热风干燥的产品增加,而硬度大大下降;其中经浓度为50蔗糖溶液真空渗透预处理后干燥产品的体积比、Vc保留率以及硬度是直接70℃热风干燥的1.72、2.26和0.12倍;而且产品的色泽更加接近新鲜原料,使产品的口感和感官品质更好。研究表明,渗透预处理联合热风干燥是1种很有发展前景的制干工艺。     

芒果片真空预处理联合超声辅助渗透脱水的传质动力学及品质分析

为解决芒果果脯生产过程中传质效率低、加工时间长的问题,该文研究了脉冲真空预处理联合超声辅助渗透脱水对芒果传质动力学、质量特性和微观结构的影响。结果表明：脉冲真空预处理联合超声辅助渗透脱水组的芒果失水率（54.43%）最高,较常规渗透脱水、脉冲真空预处理渗透脱水、超声辅助渗透脱水组分别高45.85%、14.06%、29.38%,增固率（12.81%）较常规渗透脱水、超声辅助渗透脱水、脉冲真空预处理渗透脱水组分别高90.03%、53.43%、32.06%。用Azuara模型拟合渗透脱水过程中失水率和增固率的变化,高回归系数（R2>0.97）和低RMSE表明Azuara模型可以较好拟合芒果渗透脱水过程,预测脉冲真空预处理联合超声辅助渗透脱水组的平衡脱水率、增固率最高,分别为65.06%和23.35%。测定色泽和质构,发现超声辅助渗透脱水组、脉冲真空预处理联合超声辅助渗透脱水组芒果硬度值显著低于常规渗透脱水组和脉冲真空预处理渗透脱水组（p<0.05）,而芒果色泽得到了较好保护。通过扫描电镜的观察,发现超声处理使芒果细胞壁塌陷与变形、细胞横截面积变小、微孔增多。此外,真空对芒果硬度和微观结构的影响均较小。综上,脉冲真空预处理联合超声辅助渗透脱水通过改变芒果细胞结构、增加传质微通道,提高了渗透脱水的效率,缩短加工时间,可以较好保护芒果色泽,但会导致硬度的下降。     

渗透处理结合热风干燥对桃脯干燥特性的影响

为提升桃脯产品的品质,采用渗透处理结合热风干燥,探究其对桃脯干燥特性的影响.结果表明:相比于直接干燥,渗透处理可在干燥前除去原料中的大部分自由水,有效缩短桃脯的干燥时间,提高了干燥效率.此外,经渗透处理的桃脯理化品质优于直接干燥,其色泽接近新鲜样品,硬度较低,维生素C含量、总酚含量及抗氧化能力均维持在较高水平,且能较好地保持桃脯的表面微观结构,尤其对于真空渗透处理组这种效果更为明显.相关性分析表明,硬度与维生素C含量和L*值呈极显著负相关;维生素C含量与L*值呈极显著正相关,与铁离子还原能力(ferric reducing antioxidant power,FRAP)和DPPH·清除能力呈显著正相关;总酚含量与FRAP和DPPH·清除能力呈极显著正相关;FRAP与DPPH·清除能力呈极显著正相关.通过聚类分析可将3组样品分为两类,直接干燥组和常压渗透组聚为一类,真空渗透组单独为一类;理化品质可分为3类,硬度单独为一类,L*值与维生素C含量聚为一类,总酚含量、FRAP和DPPH·清除能力聚为一类.因此,真空渗透处理结合热风干燥在有效缩短桃脯干燥时间的同时,能提升其产品品质,可作为桃脯加工的适宜方式.     

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.     

预处理方式对真空冷冻干燥苹果片品质的影响

比较分析热烫、护色液、超声波3种预处理方式对真空冷冻干燥苹果片品质的影响。结果显示:热烫预处理组冻干样品细胞壁孔室形态破坏较为明显,呈软塌、皱缩现象,VC含量最低,复水比(4.97g/g)最高,复水后可溶性固形物含量最高(P0.05);护色液预处理组冻干样品细胞壁网络骨架紧固,孔室形态饱满、完整,硬度(7.17N)最高,综合色差指标ΔE最高,冻干苹果片颜色更加亮白(P0.05);超声波预处理组冻干样品网络结构中细胞壁薄而疏松多孔,结构松散,冻干耗时(10h)最短,VC含量最高,复水后可溶性固形物含量最低(P0.05)。     

多维度表征渗透脱水组合干燥桃脆片的质构特性

为解析糖液渗透脱水组合干燥桃脆片质构品质的差异性,以桃为试材,采用两种渗透糖液(蔗糖和低聚异麦芽糖)对桃片进行渗透脱水预处理,之后分别组合热风干燥、真空冷冻干燥和压差闪蒸干燥制备桃脆片。多角度追踪分析不同渗透脱水组合干燥桃脆片宏观质地和微观结构方面的差异性。试验结果表明:渗透脱水预处理中糖分子渗入原料组织均能诱导原料细胞出现一定程度的坍塌和破损,同时糖分子的渗入增强了组织固化,使产品硬度增加了9.03%~158.98%。基于各干燥技术的特点分析,渗透脱水预处理使真空冷冻干燥脆片体积减小,而显著促进热风干燥和压差闪蒸干燥桃脆片皱缩度降低至0.724~0.798和0.436~0.570,同时增加脆片表面积,降低吸光性,改善产品色泽。相关性分子表明,硬度与固形物增加量(SG)呈现正相关,表明渗透脱水能够显著影响干制桃脆片的质构特性。此外,本研究所选用的质构评价指标之间均呈现一定的相关性。采用多角度进行渗透脱水组合干燥桃脆片的质构品质分析,为揭示桃脆片质构形成机制提供理论依据。     

不同护色预处理对牛蒡片真空冷冻干燥特性的影响

研究护色预处理方式对牛蒡片真空冷冻干燥特性的影响,采用复合护色液、热烫、超声波-热烫3种护色处理方式,并进行真空冷冻干燥对比实验和分析。结果表明:超声波-热烫组冻干耗时12.20 h,分别比护色液、热烫组缩短冻干时间15.86%、6.87%(P0.05);超声波-热烫组冻干牛蒡片复水比最高,为5.52 g/g,分别高出护色液、热烫组复水比18.71%、12.42%(P0.05);护色液组冻干牛蒡片体积皱缩比最大,为0.93,稍高于热烫、超声波-热烫组体积皱缩比(P0.05);护色液组冻干牛蒡片硬度最高,为54.32 N,分别高于热烫、超声波-热烫组硬度90.53%、120.73%(P0.05);护色液组冻干牛蒡片色泽变化ΔE最小,其次为超声波-热烫组,热烫组ΔE最大;护色液组冻干牛蒡片复水后ΔE显著高于热烫、超声波-热烫组(P0.05);扫描电子显微镜观察分析表明,热烫、超声波-热烫组细胞轮廓形态产生皱缩、卷曲现象比护色液组更明显;低场核磁共振分析表明,超声波-热烫组、热烫组冻干片横向弛豫时间T2图谱相对于护色液组呈现不同程度右移趋势,冻干牛蒡片残留水分自由度增加、束缚作用变小。     

Effects of processing on kiwi fruit dynamic rheological behaviour and tissue structure

The effects of blanching and osmotic dehydration on the small deformation rheological properties and structure of kiwi fruit were determined. Kiwi fruit tissue behaved as an elastic solid with storage moduli (G′) dominating the viscoelastic response (G′′/G′∼0.2). Both storage (G′) and loss (G′′)moduli were frequency independent and a clear linear viscoelastic range was evident. In general, G′ and G′′ decreased upon blanching and osmotic dehydration due to tissue damage. Structural changes caused by blanching included swelling of the cell walls and increases in the extent of cell–cell separation in the middle lamella. For atmospheric osmotic dehydration, high levels of solutes were observed within the cells which lead to a reduction of freezable water. For unripe tissue, G′ and G′′ increased with vacuum dehydration and it seemed that both cell wall integrity and cellular turgor were preserved to a greater extent than in ripe processed tissue. When calcium was added to the osmoticum during osmotic dehydration under vacuum, no differences in dynamic rheological behaviour or tissue structure were detected.     

Influence of Blanching-osmotic Dehydration Treatments on Volatile Fraction of Strawberries

ABSTRACT: The effects of steam (S) and microwave (MW) blanching and osmotic treatments, applied either singularly or combined, on the volatile fraction of strawberry have been evaluated. Osmotic dehydration was carried out at atmospheric conditions (OD) and by applying a vacuum pulse at the beginning of the process (PVOD). Volatiles were obtained by a simultaneous distillation-extraction procedure and identified/quantified by gas chromatography-mass spectrometry. Esters and 2,5-dimethyl-4-hydroxy-3(2H)-furanone were the major compounds. Differences in volatile concentration promoted by blanching and/or osmotic processes were evaluated. Osmotic treatments promote formation of esters and furanones, differently for either OD or PVOD treatments, but this effect was greatly inhibited when osmosis was preceded by blanching. The kind of blanching (MW or S) also affected the sample final volatile profile.     

Acceleration of mass transfer rates in osmotic dehydration of elephant foot yam (Amorphophallus paeoniifolius) applying pulsed-microwave-vacuum

The elephant foot yam slices were processed with combined pulsed-microwave-vacuum osmotic drying. Osmotic dehydration at ambient (28 °C and 45% RH) was carried out using different levels of sucrose concentration (30, 40, 50 and 60% w/w), salt concentration (5, 7.5, 10 and 12.5% w/w) and dehydration time (10, 20, 30, 50, 70, 90 and 120 min). During the osmotic dehydration, pulsed microwave vacuum (15 kPa pressure, 1 W/g power density and 1.853 pulsating ratio) was maintained for 2 min over the sample and solution to enhance the mass transfer. For this purpose, the osmotic dehydration experiments were conducted in the microwave-vacuum cavity. Azuara model predicted the moisture loss and solid gain by elephant foot yam slices during osmosis. It was observed that both the moisture loss and the solid gain increased with increasing concentration of the osmotic solution. The optimum conditions found in the process were 40% w/w sucrose concentration, 6% w/w salt concentration and 70 min osmotic dehydration time, resulting in to 42.80% moisture loss (initial weight) and 14.65% solid gain (initial weight). Further, samples were dried using microwave vacuum dryer up to moisture content of 5–6% d.b. by varying microwave power density (2, 4, 6 and 8 W/g) and pulsating ratio (1.312, 1.625, 1.983 and 2.250). Page model was fitted to the data to study the microwave vacuum drying kinetics. The microwave vacuum drying at 1.625 pulsating ratio with microwave power density 4 W/g yielded a product with the highest overall acceptability score. Guggenheim, Anderson and deBoer (GAB) model was used in the study of the sorption behavior of dehydrated elephant foot yam and shelf life prediction.Industrial relevanceThe production of elephant foot yam in India and South East Asia is comparatively higher than other vegetables. Although, it is nutritious product and good source of energy, food industries are not interested to process elephant foot yam using a time consuming traditional osmotic dehydration process followed by hot air drying. Therefore, present research work was undertaken from industry suggestion to develop accelerated osmotic dehydration process for elephant foot yam using novel pulsed-microwave-vacuum combination followed by finish drying by microwave-vacuum. This research has been carried out to decrease industrial processing time, energy consumption and improving quality of the product. Industry will start adopting this new hybrid process of drying elephant foot yam on large scale.     

不同组合渗透与冷冻前处理对蓝莓干燥品质的影响

为研究渗透、冷冻前处理对食品干燥品质的影响,同时为改善产品品质提供理论支撑和技术指导,以蓝莓为研究对象,在对样品进行相同干燥处理(热风,30 h,60℃)前,进行不同组合模式的渗透(海藻糖、氯化钙、蔗糖)和冷冻-解冻(液氮-80℃,室温)前处理,以干果的脱水速率、含水量、色泽、质构、总糖、抗氧化活性物质等作为评价指标进...     

微波烫漂对速冻怀山药品质的影响

采用不同的微波烫漂水平处理怀山药,通过测定过氧化物酶活性、多酚氧化酶活性、失重率、可溶性固形物含量和游离氨基酸总量5项指标,研究微波烫漂对速冻怀山药品质的影响。同时对护色剂处理、热水烫漂、微波烫漂3种不同处理条件下怀山药解冻后的硬度、质地以及感官特性进行比较。结果表明：微波烫漂怀山药短时间内即可达到灭酶效果,而且营养成分损失少,解冻后品质较好。最佳的微波功率及相应的处理时间为407.6W和60s。     

Viscoelastic Behavior of Melon Tissue as Influenced by Blanching and Osmotic Dehydration

ABSTRACT: Viscoelastic properties of melon tissue exposed to steam blanching and osmotic dehydration (atmospheric or under vacuum) in glucose aqueous solutions were analyzed in a dynamic rheometer using oscillatory shear and creep tests. The storage modulus (G') greatly exceeded the viscous modulus (G') for raw and treated melon tissues, but the elastic component was partially lost because of processing. Blanching caused less than a 1 -fold decrease in G', whereas osmotic dehydration resulted in approximately a 3-fold decrease in G'relative to the untreated melon. Both moduli showed a weak dependence on frequency, with greater slope of the G'frequency lines for treated samples. A mechanical model, consisting of a spring in series with 2 Voigt elements and a dashpot element, properly predicted the creep compliance response for all melon samples. In general, overall compliance significantly increased by the treatments. The instantaneous elastic compliance and the viscoelastic compliances were the most sensitive viscoelastic parameters for distinguishing the differences in cell wall structure among osmotically dehydrated sample at atmospheric pressure and the tissues exposed to the other osmotic treatments. In contrast, G'modulus did not show an ability to evidence these structural differences because there were no significant differences in the G'values of osmotically dehydrated tissues at atmospheric pressure or in vacuum, with or without calcium addition.     

Effect of Selected Pretreatments on Impregnation of Curcuminoids and Their Influence on Physico-chemical Properties of Raw Banana Slices

The effect of pretreatments, namely, blanching, ultrasound, vacuum and their combinations on curcuminoid impregnation in raw banana slices, was studied in conjunction with treatments in pure water as well as in 10 % NaCl solution. The treatments such as ultrasound, vacuum and combination of vacuum and blanching with ultrasound resulted in higher curcuminoid infusion compared to control for both pure water and 10 % NaCl osmotic treatments. The blanching treatment resulted in lower infusion of curcuminoids as compared to that of control due to the gelatinisation of starch present in banana. Further, the increase in surrounding solution concentration from pure water to 10 % NaCl resulted in enhanced curcuminoid infusion (e.g. from 85 to 95 mg/100 g for combined vacuum and sonication treatment). However, the direction of the mass transfer of water as well as solid was reversed. The samples subjected to combined vacuum and sonication treatment resulted in lowest compressive force, highest infusion of curcuminoids and highest total colour difference compared to other treatments. Besides, the dehydration of such product also resulted in the highest retention of curcuminoids compared to the individual treatments. The present study concluded that osmotic treatment can be a feasible technology for the infusion of functional ingredients into foods without altering its matrix. The extent of infusion can be significantly enhanced by the application of combined treatment such as vacuum and ultrasound.