首页 | 官方网站   微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
As a new type of blanching technology, vacuum-steam pulsed blanching (VSPB) has higher blanching efficiency and quality, but the mechanism of this technology on texture softening and drying enhancement is still unclear. In this study, the mechanism was revealed from texture, pectin, nanostructure, cell ultrastructure, calcium, and water state. Results revealed that VSPB treatment reduced the hardness and chewiness, increased water-soluble pectin, decreased sodium‑carbonate-soluble and chelate-soluble pectin concentration, and resulted in depolymerization and degradation of pectin nanostructure. However, transmission electron microscopy showed that blanching damaged the cell wall structure and the integrity of the middle layer. Scanning electron microscope - Energy dispersive X-ray spectroscopy measurement observations indicated that lipid droplets containing calcium ions were formed under the action of VSPB. In addition, low field nuclear magnetic resonance showed that the redistribution of moisture in carrot was facilitated by VSPB. The findings reveal the mechanism of texture softening and drying rate enhancement driven by blanching.Industrial relevanceThermal blanching is an essential thermal treatment for many fruits and vegetables processing. Hot water blanching and steam blanching are the two most frequently employed blanching methods due to simple to establish and easy to operate. However, hot water and steam blanching holds several disadvantages, e.g., hot water blanching requires a huge amount of water and generates an excessive amount of wastewater, particularly loss of water-soluble nutrients during blanching due to leaching and diffusion, while for steam blanching, the existence of air and water vapor among the piled materials leads to low blanching efficiency and un-uniform heating. VSPB is an innovative steam blanching method. In the VBSP process, the air and water vapor are expelled by the vacuum pump to facilitate steam deep penetration in the materials, particularly the piled materials, so as to improve blanching efficiency and uniformity. Previous study indicated VSPB could soften texture and reduce the drying time of carrot, but the mechanism was not clear. The current work reveal that VSPB softens texture and enhances drying rate of carrot via micro-, ultra-structure modification, pectin polysaccharides degradation and changes of water state. The findings have important implications for understanding and controlling the blanching triggered texture formation and drying enhancement.  相似文献   

2.
The purpose of this study was to evaluate the effects of different pretreatment methods including blanching (30, 60 and 90 s), ultrasound (10, 30 and 60 min), pectinase treatment (15, 30 and 60 min), and osmotic dehydration treatment (0.5, 1.0 and 4.5 h) on the drying characteristics, three-dimensional (3D) deformation, color, total polyphenol content (TPC), antioxidant activity and microstructure of apple slices during drying. The shrinkage and height standard deviation (HSD) were calculated to evaluate the 3D deformation such as surface curl and flatness of the apple slices. The results showed that blanching, pectinase and osmotic dehydration treatment could increase the shrinkage and reduce the surface curl of the samples. Blanching, ultrasound and osmotic dehydration pretreatment could inhibit the color changes of dried apple slices, while pectinase treatment could aggravate the color deterioration of the samples. The apple slices pretreated with blanching for 60 s contained the highest TPC of 4.86 mg/g, and the samples also had the highest antioxidant activity. In addition, microstructure of the pretreated samples was significantly different from those of untreated samples. Therefore, pretreatment technology before drying is of great significance to improve the appearance and quality of products.  相似文献   

3.
热风脱水红辣椒前处理护色技术   总被引:1,自引:0,他引:1  
红辣椒在热风干燥脱水过程中极易变色,本文通过干燥前处理技术来稳定其色素,从而找出有效而安全的护色工艺。试验通过测定红辣椒干燥后的色差值以及贮藏一定时期总色差值和感官指标的变化,选出可行的护色方法。试验结果表明,最佳护色方案为热烫温度90℃、热烫时间2 min或3 min、护色剂VC浓度0.40%。  相似文献   

4.
Peeling is an essential operation for tomato processing. A new peeling method, high-humidity hot air impingement blanching (HHAIB) heating technology, was developed as an alternative to the conventional lye and hot-water peeling to eliminate the use of chemicals and the discharge of wastewater. The current work explored the feasibility of HHAIB for tomato peeling. The effects of heating temperature (100–120 °C), relative humidity (20%–40%) and heating time (0–180 s) on the peeling performance were investigated. The optimum treatment was found to be 110 °C heating temperature in combination with 40% of relative humidity and 75 s treatment time, which resulted in lower peeling loss, firmness loss and color deterioration compared with other HHAIB conditions that achieved 100% peelability. The comparative study of optimized HHAIB peeling with conventional lye and hot-water peeling showed that HHAIB peeled tomato obtained lower peeling loss and firmness loss, and higher preservation of phytochemicals, antioxidant capacity and color. In addition, compared with fresh tomatoes, HHAIB processing increased the antioxidant activity, lycopene, and total phenolic content in peeled tomatoes by 16.01%, 10.46%, 12.80%, respectively. The laser scanning confocal microscopy image of fresh tomato skin surface and the scanning electron microscope images of peels and flesh showed that HHAIB caused cracking of the epidermis and melting of the cuticular membrane while reduced the serious damage of flesh.Industrial practicePeeling is a necessary step in tomato processing, which impacts subsequent processing efficiency and product quality. At present, the most common used peeling methods in the industry are hot water or/and alkali peeling, but it induces the loss of water-soluble nutrients, chemical residues and waste liquid treatment. Therefore, the industry urgently needs an alternative peeling technology. The current work shows that HHAIB is a very promising peeling technology as it not only has an excellent peeling performance, but also enhances the preservation of phytochemicals, antioxidant capacity and quality attributes compared to conventional lye and hot-water peeling.  相似文献   

5.
A new drying technology, far-infrared radiation heating assisted pulsed vacuum drying (FIR-PVD) was applied to process blueberries. Influences of drying temperature, vacuum pressure duration (VPD), and ambient pressure duration (APD) on drying characteristics and quality attributes of blueberries were investigated under FIR-PVD. Results showed that drying temperature, APD, and VPD had significant influence on drying time and quality attributes of dried blueberries expect for color and cohesiveness. Compared to hot air dried blueberries, FIR-PVD seriously damaged the cellular walls of blueberries during drying at 65 °C. The highest total phenolics (TP) and total monomeric anthocyanins (TMA) contents of dried blueberries were obtained at 65 °C with pulsed ratio of 15 min: 4 min and 15 min: 2 min, respectively. The FIR-PVD products obtained lower color difference, better mechanical properties and rehydration performance and maintained higher antioxidant capacity by shortening drying time, reducing exposure to oxygen, and modifying the microstructure compared to hot air drying.Industrial relevanceBlueberry is a popular function fruit around the world. With high moisture content and tender tissue, fresh blueberry is very susceptible to microbial infection even under low temperature storage conditions. Drying is a good alternative to extend the shelf life and increase the availability of fresh blueberries. However, the existence of waxy hydrophobic layer covered the surface of blueberries inhibits moisture diffusion during drying. Chemical dipping and thermal blanching pretreatments were usually used to reduce the influence of skin hydrophobicity and promote moisture diffusion. Nevertheless, the chemical additive residue leads to food safety risk and it's a big challenge to deal with the corrosive waste chemical solutions, while thermal blanching resulted a high loss of bioactive compounds. FIR-PVD is a recent developed emerging drying technology to process berries with waxy layer beyond pretreatments. Results indicated that FIR-PVD is a very promising technology for processing blueberries with the improvement of drying efficiency and quality attributes.  相似文献   

6.
The enzymes activity, texture, pectin, microstructure and colour change in bamboo shoots (Dendrocalamus latiflorus) were examined to evaluate the effect of blanching and drying treatments on quality of bamboo shoot slices (BSS). Peroxidase (POD), phenylalanine ammonia‐lyase and polyphenol oxidase in BSS will become completely inactive at 95 °C for 6‐, 9‐ and 12‐min blanching treatments, respectively. The hardness and protopectin (PP) content decreased after the blanching treatment. Meanwhile, the content of water‐soluble pectin increased initially and then decreased gradually during the blanching. After the blanching treatment, the L* and a* of BSS decreased, while b* increased, Δ> 2. The hardness of rehydrated BSS decreased by 43.57% after freeze drying (FD), which, however, decreased more after hot air drying (HAD). The pectin of rehydrated BSS was also determined to explain the hardness change in BSS. The BSS acquired similar microstructure of fresh samples after FD, while microstructure of BSS was severely damaged after HAD. The colour of BSS changes significantly after drying treatment. However, FD can maintain better colour of BSS than HAD. The results may provide a reference for industrial production of BSS.  相似文献   

7.
In this study, polyphenol oxidase (PPO) and vitamin C were used as the indicators of enzymes and nutrients to evaluate the apple quality during high humidity air impingement blanching (HHAIB) process. The PPO can be completely inactivated within 7 min at 90–120 °C and can retain relatively more vitamin C in the case of PPO fully inactivation. PPO inactivation followed zero‐order kinetics model at 90 and 100 °C, and followed first‐order fraction model at 110 and 120 °C. Activation energy (Ea) of PPO inactivation was between 11.61 and 13.66 kJ mol?1 by Arrhenius equation. Vitamin C degradation under all processing temperatures was well described by first‐order model and its Ea value was 26.69 kJ mol?1. Therefore, the HHAIB process was proved to be an effective pretreatment for Fuji apple quarters to inactivate PPO fast and meanwhile to maintain produce quality.  相似文献   

8.
The effects of temperature and pretreatment on drying kinetics and thermal degradation of phytonutrients present in pomegranate arils were investigated. The arils were divided into two groups, and half of the samples were pretreated by dipping into 80 °C hot water for 2 min. The drying process was conducted in the vacuum drier at the temperatures of 55, 65 and 75 °C. The fastest drying was completed at 75 °C after pretreatment of the samples. The highest anthocyanin–phenolic compound contents and antioxidant capacity were detected in the arils dried at 55 °C. Seven thin‐layer drying models were used to predict drying curves, and Arrhenius and Eyring–Polanyi models were employed to predict phytonutrient degradation kinetics. Activation energy for drying was 24.26 kJ mol?1 for pretreated samples and 31.54 kJ mol?1 for untreated samples. Effective moisture diffusivities were ranged from 1.43 × 10?9 to 6.03 × 10?9 m2 s?1.  相似文献   

9.
ABSTRACT The effect of various pre‐drying treatments on the subsequent quality of sun‐dried tomatoes was evaluated by determining moisture, color, rehydration ratio, mold, yeast, sulfur dioxide, and/or salt content. The 4 pre‐drying treatments under investigation were (1) steam blanching or (2) boiling brine blanching, followed by gas sulfuring and (3) dipping in either salt (0%, 10%, 15%, 20%) or (4) sodium metabisulfite (0%, 4%, 6%, 8%) for 0, 2.5, 5.0, and 7.5 min. Neither blanching pretreatment improved the quality of the dried product. Salt dipping resulted in significant differences in rehydration ratio, yeast, and salt. The most effective salt pretreatment conditions were a 10% or 15% salt dip for 5 min. Sodium metabisulfite dipping caused significant differences in rehydration ratio, yeast, color, and sulfur dioxide. Dipping tomatoes in 6% or 8% sodium metabisulfite for 5 min before drying established the best color. The 9 pretreatments studied were also evaluated for storage stability at 25 °C and 30% to 34% relative humidity for 3 mo.  相似文献   

10.
为研究预处理方式对丰水梨压差闪蒸干燥的影响,以丰水梨为原料,探讨热烫预处理、深冻预处理、柠檬酸浸渍预处理和果葡糖浆浸渍预处理对丰水梨干燥产品色泽、硬度、脆度、复水性、感官、可溶性固形物含量、可滴定酸含量、总糖含量、总酚含量、总黄酮含量、抗坏血酸含量和微观结构等的影响。结果表明:适当的热烫预处理有利于干燥产品感官品质的提高;深冻预处理虽有助于产品总酚和抗坏血酸的保留,但其硬度较小,膨化效果不明显;柠檬酸浸渍预处理的硬度较大,可滴定酸含量最高,口感偏酸,感官评价喜好度为中等;果葡糖浆浸渍预处理有助于增加干燥产品可溶性固形物和总糖含量,但其硬度较大,脆度较小,失去商品性质。综合比较,热烫处理是丰水梨压差闪蒸干燥较适宜的预处理方式。  相似文献   

11.
The combined effects of pretreatment and drying methods on the resistance of Salmonella attached to vegetable surfaces as well as some physical properties, in terms of color and shrinkage, were investigated. Cabbage was used as a test vegetable and Salmonella Anatum was used as a test microorganism. Cabbage leaves were pretreated either by soaking in 0.5% (v/v) acetic acid for 5 min, blanching in hot water for 4 min or blanching with saturated steam for 2 min prior to either hot air drying, vacuum drying (10 kPa) or low-pressure superheated steam drying (10 kPa) at 60 °C. Based on an initial Salmonella contamination level of approximately 6.4 log CFU/g, soaking in acetic acid, hot-water and steam blanching resulted in 1.6, 3.8 and 3.6 log CFU/g reduction in the number of Salmonella, respectively. Drying without pretreatment could not completely eliminate Salmonella attached on the cabbage surfaces, while no Salmonella was detected on the pretreated samples at the end of the drying process. Volumetric shrinkage was not affected by the pretreatment and drying methods. Dried blanched samples exhibited greener and darker color than the dried acetic acid pretreated and untreated samples.  相似文献   

12.
The effect of pressure treatments of 100 and 200 MPa (10 and 20 min) and of thermal blanching at 70 °C, 80 °C and 98 °C (1 and 2.5 min), on sweet green and red bell peppers was compared. Pressure treated peppers showed a lower reduction on soluble protein and ascorbic acid contents. Red peppers presented even an increased content of ascorbic acid (15–20%), compared to the untreated peppers. Peroxidase and pectin methylesterase (whose activity was only quantifiable in green peppers) showed a higher stability to pressure treatments, particularly the latter enzyme, while polyphenol oxidase was inactivated to the same final level by the thermal blanching and pressure treatments. Pressure treatments resulted in comparable (in green pepper) to higher (in red pepper) microbial loads compared to blanching. Pressure treated green and red peppers presented similar to better firmness before and after tunnel freezing at −30 °C, compared to thermally blanched peppers, particularly those blanched at 98 °C. The results indicated that pressure treatments of 100 and 200 MPa can be used to produce frozen peppers with similar to better nutritional (soluble protein and ascorbic acid) and texture (firmness) characteristics, comparable activity of polyphenol oxidase and higher activity of pectin methylesterase, while pressure treated peppers show a higher level of peroxidase activity. It would be interesting to use higher pressures in future studies, as an attempt to cause a higher reduction on microbial load and on enzymatic activity.  相似文献   

13.
Cold filamentary microplasma (CFM) pretreatment assisted by thermionic emission (TE) is a promising, cold drying technology for agricultural products. Such novel pretreatment method based on local electroporation process in the air gap. Brief theory and treatment mechanism are explained. A fractional factorial design 33 was used to determine the effect of CFM treatment assisted by TE parameters such as pulse frequency (F = 40, 80 and 120 Hz), pretreatment duration (D = 60, 120 and 180 s) and temperature of thermionic source (T = 700, 850 and 1000 °C) on drying time and drying rate of potato samples. Maximal CFM pretreatment effect was observed at frequency of 80 Hz, treatment duration of 120 s and temperature of thermionic source of 1000 °C, and the corresponding drying rate and drying time were 35·10−5 (kg/kg s−1) and 130 min. The use of CFM treatment had minor effects on the main quality characteristics (total sugar and starch content) of potato samples. Fourier-transformed infrared spectroscopy confirmed the absence of any modifications of functional group composition of potato samples after CFM pretreatment. Results indicate that cold pulsed filamentary microplasma can enhance the drying rate and decrease drying time without changes in quality characteristics.Practical applicationsCold filamentary microplasma pretreatment assisted by thermionic emission can improve the efficiency of potato drying. Furthermore, it has potential application for reducing energy consumption in drying. CFM pretreatment could be potentially applied for agricultural products drying.  相似文献   

14.
Pretreatments of either water blanching or NaCl immersion and airborne ultrasound-assisted air drying were combined to dehydrate apple slices. The drying time was found to be reduced by 1.6–69.0% compared with air drying without any pretreatment and sonication. Meanwhile, it was found that sequential water blanching coupled with air drying with sonication gave the shortest drying time. A modified diffusional model incorporating temperature-dependent moisture diffusivity (Deff) could simulate the apple drying process well. Water blanching pretreatment and airborne sonication were found to lower the activation energy required for the enhancement of moisture diffusive ability, and intensify water exchange on apple surface to speed up the drying process. Both water blanching and NaCl immersion significantly increased the amounts of procyanidin B2 in dehydrated apple slices. However, airborne sonication promoted the loss of procyanidin B2 in apple slices with pretreatments during air drying. In addition, sonication had no obvious influences on apple PPO activity and individual organic acids throughout drying. Overall, the sequential NaCl immersion pretreatment (or water blanching pretreatment) and drying with airborne sonication are effective to improve the quality of dried apple slices.  相似文献   

15.
To investigate the structure-function relationship of pectin during (pre)processing, broccoli samples (Brassica oleracea L. cultivar italica) were subjected to one of the following pretreatments: (i) low-temperature blanching (LTB), (ii) LTB in combination with Ca2+ infusion, (iii) high-pressure pretreatment (HP), (iv) HP in combination with Ca2+ infusion, or (v) no pretreatment (control sample), whether or not in combination with a thermal treatment of 15 min at 90 °C. The macroscopic attributes of broccoli were linked to the chemical structure of broccoli pectin. By enhancing the cross-linking of pectic polymers, both LTB and HP reduced the texture loss that occurred during thermal processing of broccoli. During these pretreatments, homogalacturonan was de-esterified by pectin methylesterase, which led to changes in pectin solubility. When LTB or HP was combined with Ca2+ infusion, changes in the structure of pectin occurred, however not always reflected at the macroscopic level. The degree of esterification of pectin in Ca2+-soaked broccoli samples was lower compared to non-Ca2+-soaked samples and, in addition, a higher amount of ionically cross-linked pectin was retrieved.  相似文献   

16.
采用5%柠檬酸溶液、20%糖溶液、20%NaCl和柠檬酸混合溶液浸渍、烫漂4种处理方式处理玫瑰花瓣,以未预处理的花瓣作为对照,进行热风干燥对比试验和分析,对花瓣品质特性(色泽、总黄酮含量、总酚含量)以及微观结构等进行比较,并结合模糊数学综合评判法进行感官评定。结果表明:预处理方式对玫瑰花瓣的干燥速率有显著影响,且在含水率较高时尤其明显;微观结构有一定的差异性。其中,5%柠檬酸溶液组耗时最长,ΔE最小;20%糖溶液组复水比最低;混合溶液组色泽变化ΔE最大,总酚含量最高;烫漂组耗时最短,总黄酮含量和复水比最高。经烫漂预处理后的花瓣干燥后得到的感官评分值最高,对应的干燥时间、ΔE、复水比、总黄酮含量及总酚含量分别为120min、18.17±0.54、3.01、0.27mg/g、1.43mg/g。因此,采用烫漂预作为预处理方式可以提高食用玫瑰花瓣干制品的品质。  相似文献   

17.
Investigations were carried out to see the impact of blanching time, pretreatment and storage and packaging on the physico‐chemical properties of solar dehydrated cauliflower. The processing treatments selected for the study were blanching time of 3, 5, 7 and 9 min, potassium metabisulphite (KMS) pretreatment having 0.5%, 1.0% and 1.5% concentration level and storage in high‐density polyethylene, laminated aluminium foil and polypropylene. The cauliflowers were further processed and dehydrated in solar dryer before packing it into different packaging materials. Packed dehydrated cauliflower was stored for 6 months at room temperature. The stored cauliflower samples were tested periodically for their moisture content, rehydration ratio, rehydration coefficient, ascorbic acid and browning. Ranking of blanching time, chemical concentration level and packaging materials were statistically analysed by using SAS package. The samples with 9 min blanching time, followed by dipping in 1.0% KMS solution, and packed in laminated aluminium foil showed better results in comparison with other treatments.  相似文献   

18.
The effect of low‐temperature blanching and drying processes on the ultrastructural and physical properties of Anaheim chilli pepper was studied and optimum conditions to provide a final product with maximum firmness were determined. Lots of Anaheim pepper were blanched in water for 4 min at 48, 55, 65, 75 and 82 °C and maintained for hold times of 35, 45, 60, 75 and 85 min, blanched again for 4 min at 96 °C and dehydrated at 53, 60, 70, 80 and 87 °C. After treatment the samples were rehydrated in water at 30 °C. Rehydration ratio, texture and structural changes were evaluated. Optimisation used a second‐order rotatable central composite design. Texture and rehydration ratio were affected by blanching temperature and the interaction of blanching temperature with hold time (p ≤ 0.05); drying temperature did not show a significant effect. The best results, ie those which gave greatest firmness, were obtained by blanching at 64 °C for 4 min, holding for 55 min after blanching, followed by a second blanching at 96 °C for 4 min and then drying at 70 °C. Evaluation of the rehydrated dried pepper by microscopy showed that low‐temperature blanching close to the optimum conditions provided a protective effect in maintaining cell wall integrity. The results of processing increased firmness in the rehydrated product by a factor of 1.97. Copyright © 2003 Society of Chemical Industry  相似文献   

19.
This study evaluated the use of Infrared (IR) and microwave (MW) dry blanching technology as an alternative to the conventional hot water (HW) blanching of Irish potato slices. Product quality, cell integrity, and Peroxidase (POD) inactivation kinetics were investigated. Also, the POD inactivation kinetics curve was fitted with both mathematical models and artificial neural networks (ANNs). The result showed that MW blanching technique had the shortest POD inactivation time (5 and 7 mins), when compared with HW blanching (7 and 9 mins) and IR blanching (18 and 21 mins). IR blanched samples had the lowest colour change, slowest moisture loss, and lower microbial activity when compared with HW and MW blanching, although the level of vitamin C retention was similar with MW blanched samples. Furthermore, MW blanching had lower electrolyte leakage and microstructure damage, and better texture, when compared with HW and IR blanching. ANNs (R2 = 1.000, RMSE = 1.1597e-14, and SSE = 2.8994e-15) outperformed Weibull distribution (R2 = 0.9914, RMSE = 0.0348, and SSE = 0.0073) in fitting the POD inactivation curve. In conclusion, IR and MW technology were efficient in dry blanching of Irish potato, and ANNs allows for smart industrial control and monitoring of dry blanching equipments, since it can combine multiple process variables.  相似文献   

20.
Simultaneous application of osmotic dehydration and high pressure as a pretreatment to drying process on red abalone (Haliotis rufescens) slices was studied. During drying process the process time was reduced by increasing temperature from 40 to 60 °C along with the application of different pretreatments: high pressure (350 and 550 MPa), pressure time (5 and 10 min), and osmotic solution (10 and 15% NaCl). Effective moisture diffusivity was determined and varied from 4.35 to 9.95 × 10 9 m2/s, for both control and pretreated samples (R2  0.97). The Weibull, Logarithmic and Midilli–Kucuk models were applied to drying experimental data, where Midilli–Kucuk model was found to be the best fitting model. Furthermore, all drying curves were normalized and then modelled by the same three above models showing a R2  0.96. As to energy consumption and efficiency values for drying processes were found to be in the range of 777–1815 kJ/kg and 8.22–19.20%, respectively. Thus, knowledge on moisture transfer kinetics, energy consumption and data normalization, is needed to manage and control efficiently drying process under different pretreatment conditions.Industrial relevanceThis article deals with the mass transfer modelling and energy consumption during simultaneous high hydrostatic pressure treatment and osmotic dehydration as a pretreatment to drying process of abalone slices. Water and salt transfer during this combined process was satisfactorily simulated with the Midilli–Kucuk model. Results indicated that application of this combined innovative technology improved abalone slices dehydration rates compared to atmospheric pressure operation resulting in a dried abalone with intermediate moisture content ready to be used as input material of further processes. Furthermore, the different energetic features were determined in order to realize the importance of the changes that can influence to alter process time.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号