超声波强化紫薯渗透脱水工艺

分别以蔗糖质量分数、渗透温度、渗透时间和超声波功率为单因素,研究其对紫薯超声波渗透脱水的脱水率和固形物增加率的影响。以各因素为自变量,以脱水率和固形物增加率为因变量,对紫薯渗透脱水进行响应面工艺研究,得出最优工艺参数。结果表明：影响脱水率和固形物增加率的主次顺序均为渗透时间＞渗透温度＞糖液质量分数＞超声波功率;响应面优化最优工艺参数为糖液质量分数56.29%、渗透液温度65℃、渗透时间2.46h、超声波功率142.33W。结合实际操作,响应面优化的最优工艺调整为糖液质量分数56%、渗透液温度65℃、渗透时间2.5h、超声波功率140W,经验证,此条件下脱水率为40.79%,固形物增加率为8.33%。     

Design of Continuous Flow Osmotic Dehydration and its Performance on Mass Transfer Exchange During Osmotic Dehydration of Broccoli Stalk Slices

A continuous flow solution unit was designed and built with a sole purpose of achieving better hydrodynamic control during the osmotic dehydration pre-treatment process. The initial study was set up to calibrate the flow meter at different sucrose solutions at different concentrations and temperatures to obtain a flow velocity range between 1.5 to 3.5 mm/s. In this study, broccoli stalk slices were used to investigate the effect of the flow velocity on mass transfer kinetics and compared with static condition. Further, the optimization of this equipment system was performed to achieve higher water loss with minimal solute gain as pre-drying condition. Comparative studies between static and dynamic conditions show that flow velocity helps in faster rate of water removal with lower solute gain during the osmotic dehydration process of broccoli stalk slices. The optimum condition was found to be at a temperature of 30 °C with concentration of 54 °Brix for 120 min of immersion time at flow velocity of 3.5 mm/s.     

樱桃番茄真空渗透预脱水工艺优化

以苏龙一号樱桃番茄作为试材,通过比较烫漂划线、针刺、划线、超声波预处理方法,确定了烫漂划线作为真空渗透预脱水的预处理方法。在该基础上,运用单因素试验研究了真空度、糖液浓度、渗透温度、渗透时间对樱桃番茄渗透预脱水效果的影响,进而确定真空度为0.080MPa,并应用响应曲面法优化其它参数,得出樱桃番茄真空渗透预脱水的最佳工艺条件为:糖度50°Brix、温度53.37℃、时间4.88h,该条件下樱桃番茄失水率与固形物增加率比值最大,为7.24。     

Application of High Hydrostatic Pressure as a Pretreatment for Osmotic Dehydration of Banana Slices (Musa cavendishii) Finish-Dried by Dehumidified Air Drying

The process variables high hydrostatic pressure (HHP; 100–500 MPa), sucrose concentration (30–70 °Brix), immersion time (5–9 h) and immersion temperature (30–70 °C) were optimised to yield maximum water loss (WL), minimum solid gain (SG), minimum water activity (a _w) and minimum browning index (BI) during osmotic dehydration (OD) of banana slices (Musa cavendishii) pretreated by HHP using response surface methodology. The pressure-treated samples showed significantly higher WL and SG during OD (p?<?0.05), which was attributed to the rupture of cell wall with applied pressure, making the cells more permeable, also evident from the scanning electron micrographs of the banana tissue. The optimised operating conditions were: HHP of 200 MPa for a dwell time of 5 min at room temperature (26 °C), sucrose concentration of 60 °Brix, immersion time of 5 h and immersion temperature of 40 °C. A study of the concentration profiles during OD revealed no appreciable increase in SG and WL after 4 h; hence, immersion time was reduced to 4 h. The optimised product developed was dried to a moisture content of 15 % (wet basis) in a dehumidified air dryer at an air temperature of 40, 55 and 70 °C with a fixed air velocity of 3.8 m/s and relative humidity maintained at 20 %. The final dried product was analyzed for total soluble solids content, BI and a _w. A drying temperature of 55 °C was found to give superior quality OD banana slices in terms of reduced bulk, improved flavour, decreased a _w (<0.60), and reduced dehydration time and energy using HHP as a pretreatment.     

超声及超声渗透预处理对红外辐射干燥特性研究

为探究超声及超声渗透预处理对桃片水分迁移及红外辐射干燥特性的影响,经超声及超声渗透30、60 min预处理后,进行红外辐射80℃干燥处理,采用低场核磁共振技术测定预处理后桃片横向弛豫时间T2图谱,分析水分状态及分布变化,得到干燥特性曲线,并分析水分状态及分布对干燥特性的影响。结果表明,超声降低桃片固形物含量,超声渗透明显增加固形物含量并降低水分含量;不同预处理均改变桃片内部水分状态和分布。超声后,桃片不易流动水和自由水弛豫时间增加,水分自由度增加,从而提高干燥速率,增加水分有效扩散系数;超声渗透后,桃片结合水、不易流动水及自由水弛豫时间均减小,且自由水含量明显降低,而不易流动水及结合水含量相对升高,从而降低干燥速率,减小水分有效扩散系数。该研究为超声及超声渗透预处理对红外辐射干燥水分扩散研究提供参考。     

雪莲果超声波辅助渗透脱水工艺参数的优化

以渗透脱水温度、时间、蔗糖质量分数、超声波功率和处理时间为因素,以失水率(water loss,WL)和固形物增加率(sugar gain,SG)为指标,通过单因素试验,研究雪莲果的渗透脱水工艺参数。以渗透脱水温度、时间、蔗糖质量分数、超声波处理时间为因素,以WL、SG和二者比值(WL/SG)为指标,通过二次回归正交旋转组合试验设计建立雪莲果超声波辅助渗透脱水过程中各响应值(WL、SG和WL/SG)与各因素之间的回归方程,并得到超声波辅助渗透脱水的最优工艺参数。结果表明,超声波辅助处理可显著提高雪莲果渗透脱水效果;影响WL的因素主次顺序是温度＞时间＞蔗糖质量分数＞超声波处理时间;影响SG的因素主次顺序依次是渗透脱水时间＞超声波处理时间＞温度＞蔗糖质量分数;影响SG/WL的因素主次顺序是渗透脱水时间＞蔗糖质量分数＞超声波处理时间＞温度。雪莲果超声波辅助渗透脱水的最佳工艺参数为渗透脱水温度41℃、时间1.7h、蔗糖质量分数60.18%、超声波处理时间35min。在此组合参数条件下,SG/WL平均值为0.059。     

Mass Transfer Modeling During Osmotic Dehydration of Hexahedral Pineapple Slices in Limited Volume Solutions

The study of mass transfer during osmotic dehydration process in limited volume solutions was carried out to evaluate the diffusion coefficients of sucrose and water in the osmotic treatment of hexahedral pineapple slices. The experimental osmotic dehydration kinetics for pineapple slices of two different sizes were conducted at 25 °C using a 1:1 solution to fruit weight ratio. The analytical solution of a 3D mass transfer model considering a limited volume of osmotic solution (i.e., an osmotic media of variable solute concentration) was used for describing the mass transfer in osmotic dehydration of pineapple slices. This model was fitted to the experimental kinetics by means of nonlinear regression to obtain the diffusion coefficients. Additionally, the diffusion coefficients were evaluated considering an infinite volume of osmotic solution (i.e., an osmotic media of constant solute concentration). Results showed that the proposed model may be fitted accurately to the experimental osmotic dehydration kinetics and allows the estimation of diffusion coefficients when solute concentration in the osmotic media varies along the process.     

渗透脱水循环处理对糖液及桃片理化特性的影响

以白桃片为实验材料,追踪分析了单阶段(糖液浓度不变)和多阶段(糖液浓度逐渐增加)渗透脱水循环处理后糖液特性和桃片理化特性的变化。糖液循环利用5次,期间不做任何调整。结果表明:随着糖液循环利用次数的增加,单阶段渗透脱水处理过程中糖液黏度降低、稀化现象严重,导致渗透压力差减小,使桃片水分损失率和固形物增加率逐渐降低,同时桃片中可溶性物质的溶出致使糖液电导率、浊度、色差值显著增加;多阶段渗透脱水循环处理基于多浓度糖液组合利用,有效降低了循环利用过程中糖液稀化现象的发生,保持了较好的渗透压力差,进而有利于桃片更多固形物的获得和更多水分的散失,且糖液的电导率、浊度等特性得到了较好的保持,但是多阶段渗透脱水循环处理会使桃片与空气接触更多,不利于产品色泽的保持,且长时间的高渗透压导致桃片中可滴定酸含量显著改变。从糖液循环利用中桃片渗透脱水效率和糖液特性保留角度出发,多阶段渗透处理可在桃片渗透方式的选择上提供一种新颖的思路,具有良好的应用前景。     

响应面法优化渗透脱水板栗工艺

研究了渗透脱水板栗的最佳工艺,以浓度(45%～65%)、温度(20℃～60℃)、液固比(6.25∶1～25∶1)、时间(60 min～540 min)为自变量,失水率和固形物得率为响应值,通过可旋转中心组合试验设计,得到最大失水率和最小固形物得率的条件为:糖质量浓度52.58%、温度40℃、液固比13.72∶1、渗透时间474.17 min。在此条件下失水率23.94%、固形物得率5.41%。     

桃片超声渗透-红外辐射干燥特性及能耗研究

超声波的空化效应可提高渗透过程中传质效率。为研究桃片超声渗透-红外辐射干燥特性及干燥能耗,进行了超声渗透后红外60、70、80℃干燥试验,得到干燥特性曲线,建立干燥动力学模型;同时,对干燥过程的能耗进行了分析。结果表明:超声可增加桃片渗透脱水速率和固形物渗入率,超声渗透时间选择30 min(T_1)及60 min(T_2)为宜;Verma et al.模型较好拟合了桃片超声渗透-红外辐射干燥规律,未经渗透、T_1及T_2渗透处理桃片在60、70、80℃干燥条件下水分有效扩散系数分别为8.8789×10~(-9)~1.3011×10~(-8)、7.1213×10~(-9)~1.0393×10~(-8)、6.6771×10~(-9)~8.7785×10~(-9) m~2·s~(-1~;随着温度升高,干燥所需能耗降低;经超声渗透脱水后,干燥所需能耗增加。不同条件下,干燥能耗均在干基水分含量0.3左右急剧增加,可作为水分转换点,利用其它干燥方式,如变温压差膨化干燥,达到节约能耗、提高产品品质的目的。试验结果为桃片红外辐射干燥工艺参数优化及开发新型果蔬脆片提供参考。     

超声辅助低温固态渗透脱水制备茉莉花风味糖浆工艺优化及品质分析

随着中国风味食品和功能饮料市场的不断发展,具有特定营养和健康功效的风味糖浆被用来满足人们对风味饮料的需求。然而目前我国风味糖浆主要采用热浓缩技术进行生产,易导致热敏性芳香物质损失。鉴于此,该研究以茉莉花和黄冰糖为原料,采用超声辅助低温固态渗透脱水方法（Ultrasonic-Assisted Solid Osmotic Dehydration,USOD）制备茉莉花风味糖浆,通过单因素试验确定最佳工艺条件为：黄冰糖用量为茉莉花质量的120%（m/m）、颗粒度为6~20目、渗透时间为168 h及超声时间120 min。在此条件下风味糖浆得率为41.40%;总酚含量、总黄酮含量和DPPH自由基清除能力分别为175.18 mg GAE/kg dw、187.92 mg RE/kg dw和 313.55 mg Trolox/kg dw;茉莉花中绝大部分风味化合物都能被有效地提取出来,尤其是醇类化合物,芳樟醇37.94%~46.06%,其次是苯甲醇20.80%~23.90%,说明SOD工艺条件对风味物质提取影响显著。因此,该研究能有效提高风味糖浆得率且保留了茉莉花本身的风味成分和营养物质,为风味糖浆的开发利用奠定了一定的理论基础。     

Pulsed Vacuum Osmotic Dehydration of Beetroot,Carrot and Eggplant Slices: Effect of Vacuum Pressure on the Quality Parameters

Pulsed vacuum osmotic dehydration (PVOD) is a widely used technique for reducing moisture content and water activity in biological products. This study aimed to analyze the effect of vacuum application (VA) on PVOD of beetroot, carrot, and eggplant slices, with respect to chemical (moisture, water activity, specific pigments, polyphenols, and sodium content), optical (color), mechanical (shrinkage, maximum stress, and elasticity), and structural (microstructure) properties. PVOD was conducted at three different vacuum pressures (0, 40, and 80 kPa, for 10 min), during a total process time of 300 min. Osmotic processing was performed at 35 °C by using a ternary osmotic solution [40% sucrose +?10% sodium chloride (w/w)]. Eggplant and carrot samples were more sensitive to VA, compared to beetroot. This was related to their porous and less compact structure. In general, VA reduced the moisture content and water activity and preserved the carotenoid content. VA caused loss of betalain and phenolic acid, favored sodium uptake, and induced significant changes in the optical, mechanical, and structural properties, compared to the osmotic processing conducted at atmospheric pressure.     

Magnetic Resonance Imaging of Strawberry (Fragaria vesca) Slices During Osmotic Dehydration and Air Drying

The aim of this study was to develop experience in acquiring water mobility and moisture data that could be used to develop improved models for predicting water loss during osmotic dehydration and/or air-drying. One-dimensional magnetic resonance imaging protocols were used to follow temporal and spatial changes in water mobility via T₂ profiles, water content via M₀ profiles, and structural shrinkage of strawberry slices during osmotic dehydration with 600 g/kg aqueous sucrose over 2 h. Those measurements were also made for 1 h during air-drying of normal and osmotically dried slices at 20, 30, 45 and 60 °C. Air-drying above 20 °C resulted in changes in the strawberry matrix, which suggests the need for a model that incorporates the interaction between the strawberry tissue and the water that diffuses during drying. Modelling of the air-drying of osmotically pretreated slices would be complicated by the variable amounts of sucrose solution remaining after osmotic dehydration.     

Enrichment of Banana with <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> Using Double Emulsion and Osmotic Dehydration

The aim of this study was to use the process of osmotic dehydration to enrich banana slices with Lactobacillus rhamnosus encapsulated in a double emulsion. The effect of a pulsed vacuum and the concentration of the osmotic solution on the impregnation of the microorganism and on mass transfer during osmotic dehydration of the fruit were assessed. The kinetics of the water loss (WL), solid gain (SG) and water activity (a_w) were obtained using an aqueous solution with 40, 50 and 60% sucrose with emulsion and a vacuum pulse of 50 mbar for 10 and 20 min at the beginning of the osmotic process. The high concentrations of sucrose in the osmotic solution, combined with the application of a pulsed vacuum, produced an increase in the rates of WL and SG of the osmodehydrated banana, as well as a reduction of its a_w. L. rhamnosus survived at levels above 10⁷ CFU/g in the hypertonic solution and in the osmodehydrated bananas. Scanning electron microscopy (SEM) showed that the encapsulated probiotic adheres to the banana’s surface, which demonstrates that double emulsions can be used to impregnate probiotics in vegetal tissues.