Enhanced Mass Transfer During Osmotic Dehydration of High Pressure Treated Pineapple

High pressure pretreatment (100–700 MPa) was applied to enhance mass transfer rates during osmotic dehydration of pineapples and accelerate the process. Experimentally determined diffusivity values, based on a Fickian model, increased fourfold for water and twofold for sugar. Diffusivity values were correlated with pretreatment pressure by an equation of the form D=A exp(–B/P), which suggests that diffusivity would level after an initial increase in pressure. The increase was attributed to breaking-up of cells walls which facilitated the transport of water. Evidence for the extent of cell wall break-up with applied pressure was based on differential interference contrast microscopic examination of tissue. Preliminary experiments on rehydration characteristics showed high pressure pretreated samples did not absorb as much water as controls.     

Rehydration Kinetics of High-Pressure Pretreated and Osmotically Dehydrated Pineapple

Rehydration kinetics of high‐pressure pretreated (100, 300, and 500 MPa for 10 min) and osmotically dehydrated pineapple (Ananas comsus) cubes (2 × 2 × 1 cm) were studied at different temperatures (5, 25, and 35°C), and compared with ordinary osmotically dehydrated samples. The effective diffusion coefficients for water and solute were determined, assuming the rehydration process to be governed by Fickian diffusion. Diffusion coefficients for water absorption into the tissue as well as for solute diffusion out of the tissue were found to be lower in the samples subjected to high‐pressure treatment. Further, the diffusion coefficients decreased with increase in treatment pressure. A possible explanation for the observed decrease in diffusion coefficients can be attributed to the permeabilization of cell membranes, the release of cellular components, and structural changes of the cell materials. The diffusion coefficients were correlated with rehydration temperature (T) and treatment pressure (P) by an Eq. of the form D = A exp[–(B.P + C/T)], where A, B, and C are constants.     

超声渗透脱水-热风干燥梨的研究

超声波的空化效应及机械效应可有效增强脱水过程中物料内外的质量传递速率,因此超声波技术可用于果蔬渗透脱水的强化,而超声渗透脱水又常作为其他干燥方式的预处理以提高脱水速率。本研究以砀山梨梨片为实验材料,进行超声波渗透脱水预处理联合热风干燥研究。结果表明：提高超声功率及渗透液糖度可显著增加失重率;与直接热风干燥相比,单一的渗透脱水预处理延长总脱水时间约30～60 min;而超声渗透脱水预处理可缩短热风干燥的干燥时间40～120 min,并提高有效水分扩散系数11%～56%。因此,在热风干燥前进行超声渗透脱水预处理,可有效缩短总工艺时间,提高干燥效率。     

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%。     

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.     

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。     

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.     

预处理方式对干制莲藕品质特性的影响

[目的]探究莲藕热泵干燥后适宜的预处理方式。[方法]将护色(CP)、渗透脱水(OD)、超声护色(USCP)、超声渗透脱水(USOD)、护色+超声渗透脱水(CP+USOD)及超声渗透脱水同步护色(USOD-CP)预处理应用于莲藕热泵干燥前,探究其对干制莲藕外观色泽、微观结构、营养成分和抗氧化活性的影响。[结果]在CP和OD过程中施加超声可以扩大莲藕的微观孔道;USCP预处理的莲藕多酚和烟酸含量最高,分别为15.64,21.08 mg/100 g,且色差值最低,为5.02;USOD-CP组莲藕的黄酮和总游离氨基酸含量最高,分别为207.05,149.04 mg/100 g;USCP和USOD-CP预处理的莲藕清除羟自由基能力较强,清除率分别为45.96%,45.94%;多酚与羟自由基清除率的正相关性最强。[结论]在莲藕热泵干燥前进行USCP和USOD-CP预处理可以进一步提升莲藕的干燥品质。     

蘑菇渗透脱水规律的研究

对蘑菇片在糖溶液中的脱水规律进行初步的试验研究。通过多因素正交试验，得出影响蘑菇渗透脱水因素的主次顺序及因素间交互作用的关系；通过应用均匀试验，建立了蘑菇渗透脱水的回归数学模型，其理论值与实测值具有很好的一致性；利用回归模型，建立了不同条件下的渗透脱水规律预测表。     

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。     

Original article: Effect of sucrose and glycerol mixtures in the osmotic solution on characteristics of osmotically dehydrated mandarin cv. (Sai‐Namphaung)

This study investigated the effects of a series of osmotic solutions consisting of sucrose and glycerol on the quality of osmotically dehydrated mandarin, namely mandarin cv. (Sai‐Namphaung). Mandarin samples were peeled and osmotically dehydrated at 55 °C with agitation at 3.5776 × 10^?1g in five osmotic solutions containing various mixtures of 60% sucrose and 60% glycerol (9:1, 8:2, 7:3, 6:4 and 5:5 w/w, respectively). The osmotically dehydrated mandarin was further dried using hot‐air drying at 70 °C for 360 min. Increasing the glycerol ratio in the mixtures significantly (P ≤ 0.05) increased water loss and solid gain during osmotic dehydration, and significantly (P ≤ 0.05) affected kinetic rate constants during drying. An increase in the glycerol ratio in the mixtures caused a significant decrease in the quality factors of hardness, moisture content, water activity and reducing sugar. However, the increase resulted in an increase in the darkness of the dried mandarin, compared with increasing the sucrose ratio in the mixtures (P ≤ 0.05). The increase had an insignificant (P > 0.05) effect on vitamin C content.