Influence of Pre-drying treatments on Quality and Safety of Sun-dried Tomatoes. Part II. Effects of Storage on Nutritional and Sensory Quality of Sun-dried Tomatoes Pretreated with Sulfur, Sodium Metbisulfite, or Salt

ABSTRACT Pre‐drying treatments have been found to improve the quality of stored sun‐dried tomatoes. Based on previous investigation (Part I), 5 specific pretreatments were chosen for effects on nutritional value, sensory quality, and safety before and after 3 mo of storage (25 °C and 30% to 34% relative humidity). These pretreatments included (1) direct gas sulfuring with 2.3 kg (5 lb) SO₂; (2) with 3.6 kg (8 lb) SO₂; (3) dipping in 10% salt for 5 min; (4) 8% sodium metabisulfite for 5 min; and (5) 8% sodium metabisulfite and 10% salt for 5 min. The use of SO₂ improved color, rehydration ratio, and minimized the loss of ascorbic acid and lycopene. Sodium metabisulfite dipped tomatoes had better rehydration ratio and color than gas sulfured sun‐dried tomatoes. Untrained consumers ranked gas sulfured tomatoes higher than sun‐dried tomatoes produced by dipping in either sodium metabisulfite alone or sodium metabisulfite plus salt.     

EFFECT of LOW TEMPERATURE BLANCHING, CYSTEINE-HCi, N-ACETYL-L-CYSTEINE, Na METABISULPHITE and DRYING TEMPERATURES ON the FIRMNESS and NUTRIENT CONTENT of DRIED CARROTS

Low temperature long time (LTLT) blanching (70C for 20 min) together with calcium treatment can be used to significantly improve the texture of rehydrated dried carrots when compared to high temperature short time (HTST) blanching (100C for 3 min). LTLT blanching allows pectin methyl esterase to deesterify pectin which can then react with calcium to form salt bridges. 0.3% L-cysteine-HCl was found to be most effective in preventing ascorbic acid loss and obtaining a product with the highest rehydration ability, compared to pretreatments with 0.3% N-acetyl-L-cysteine and 0.1% sodium metabisulphite. On the other hand 0.1% sodium metabisulphite was most effective in preserving the carotenoids content of dried carrots. Ascorbic acid and rehydration ability were more adversely affected by long drying time than high drying temperature, while carotenoids were more sensitive to high drying temperature than drying time. Hence, 60C drying temperature was good for ascorbic acid and rehydration ability, while 40C drying temperature was good for carotenoid and color of dried carrots.     

EFFECTS OF BLANCHING, CHEMICAL TREATMENTS AND FREEZING METHODS ON QUALITY OF FREEZE-DRIED MUSHROOMS

SUMMARY –Mushrooms, Agaricus bisporus, were cut into slices about 5 mm thick. The polyphenoloxidase activity in the sliced mushrooms was inhibited by: (a) dipping in sodium metabisulfite solution containing 200 ppm SO₂; (b) dipping in 2% NaCl solution; and (c) blanching in boiling water for 2 min followed by evaporative cooling. The products were frozen with Freon-12 at –22°F for 60 sec. The frozen mushrooms were dried to 3% moisture in a Stokes freeze drier and sealed under vacuum in No. 2–1/2 cans. The freeze-dried product made by the Freon-dipping process was better in quality and firmer in texture than that made by the slow-freezing process. Blanching the fresh mushrooms in boiling water for 2 min prior to freezing results in a lighter color in the freeze-dried products after rehydration. However, the product was less attractive in flavor and texture. The blanching process caused considerable loss of water-soluble solids and ascorbic acid. The effects of processing variables on the chemical, physical and organoleptic quality of the rehydrated products are presented.     

热蒸汽烫漂联合热风微波耦合干燥香菇的工艺优化

本文基于热风干燥探究了不同热蒸汽烫漂预处理时间(0、60、120、180、240 s)对香菇干燥特性及色泽的影响。单因素实验确定最优的预处理时间后,基于热风微波耦合干燥研究间歇比(2、3、4、5、6)对香菇干燥特性、能耗及干品品质(色泽、收缩模式、香菇多糖)的影响,并获得热风微波耦合干燥香菇的最优工艺。结果表明:热蒸汽烫漂处理后可缩短约0%~30%的干燥时间,烫漂180 s时效果最佳;热风微波耦合干燥间歇比越小,干燥时间越短,能耗越小,随着间歇比的增加,香菇多糖含量先减小后增大;在干燥过程中,香菇片厚度比与水分比呈二次函数关系,间歇比为2~6时,热风微波耦合干燥的拟合度为0.83~0.97,模型拟合良好;在微波间歇比为2(1 min:1 min,t_on:t_off)时,产品色差较小,香菇多糖含量最高,能耗最低。结果表明180 s热蒸汽烫漂联合热风微波耦合干燥,在间歇比为2时,能够实现对香菇的快速干燥,并保证较好的干品品质。     

不同预处理方式对花椰菜干制品品质影响研究

为筛选适宜花椰菜干制的预处理方法,本研究通过采用沸水烫漂、蒸汽烫漂、微波加热和超声波辅助烫漂4种不同预处理方式处理新鲜花椰菜,考察干燥后其干制品收缩率、复水比、色泽、V_C、总黄酮、总酚及总硫代葡萄糖苷含量等感官和营养指标的变化情况。结果表明:不同预处理方式处理后花椰菜干燥时间均有缩短,其中沸水烫漂、蒸汽烫漂和微波加热较未处理缩短了18.18%,而超声波辅助烫漂处理后缩短了27.27%。微波加热和超声波辅助烫漂处理后花椰菜干制品的色泽变化较小,超声波辅助烫漂收缩率最小,为67.41%,微波加热复水能力较强,为3.77。不同预处理方式对花椰菜干制品营养成分影响不同,与未处理样品相比,不同烫漂方式处理后还原糖损失率为8.85%~23.96%、总糖损失率为3.74%~39.35%。微波加热花椰菜干制品可溶性蛋白和总硫代葡萄糖苷保留率分别为81.80%和31.93%,超声波辅助烫漂后花椰菜干制品V_C、总黄酮和总酚保留率分别为40.18%、83.70%和38.40%。综合比较表明:超声波辅助烫漂后花椰菜干制品感官及营养品质最佳。     

高密度CO2预处理对樱桃番茄干燥的影响

将樱桃番茄经过和未经过高密度CO2(DPCD)预处理,然后进行热风干燥,以比较干燥速率和干燥后产品品质的变化,探索新型干燥工艺。结果发现,经过1、2和3MPaDPCD处理组与对照组相比,干燥速率提高,干燥时间缩短,产品收缩率降低,复水率提高,褐变度没有显著变化;但经高压处理的干燥产品VC和颜色比对照组差。综合各指标分析,除了VC和颜色,DPCD预处理后的干燥指标优于对照组。     

预处理方式对热风干燥玫瑰花瓣品质特性的影响

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。     

预处理对压差闪蒸干燥丰水梨脆片品质及微观结构的影响

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。     

MICROWAVE and SPOUTED BED DRYING of FROZEN BLUEBERRIES: the EFFECT of DRYINGAND PRETREATMENT METHODS ON PHYSICAL PROPERTIES and RETENTION of FLAVOR VOLATILES

Frozen blueberries (Vaccinium corymbosum L cv. 'Elliott') were dried in a microwave and spouted bed combined dryer (MWSB) at 70C air temperature and 3.7 W/g microwave power (wet material). the effect of pretreatment using a 2.5% Ethyl Oleate & 0.2 NaOH dipping solution followed by sucrose osmotic treatment was investigated. the drying kinetics of MWSB drying was compared with spouted bed (SB) drying with dipping treatment, and with tray drying. the rehydration ratio, the color, and the bulk density of MWSB dried blueberries were compared with those of freeze, tray, and SB drying. the drying time needed to reduce blueberry moisture content from 82.5% to 15% (wet basis) using MWSB drying was 1/19 and 1/24 (with and without pretreatment) of the time for tray drying. the MWSB drying resulted in a low bulk density and more reddish and less blue color compared with other methods. MWSB dried frozen blueberries exhibited a higher rehydration ratio in short soaking times. Analysis of flavor volatiles by GC/MS identified ten heat-generated compounds. Microwave heating generated three unique flavor compounds (2-Butanone, 2-methyl butanal, and 3-methyl butanal). Freeze-dried frozen blueberries lost several flavor compounds including the typical blueberry aroma, the 1, 8-Cineole.     

不同预处理方式对热风干燥黄花菜褐变及干燥特性的影响

本实验探究不同护色液（0.1 g/100 mL柠檬酸、0.2 g/100 mL柠檬酸、0.2 g/100 mL碳酸氢钠、1.0 g/100 mL氯化钠溶液,浸泡45 min）对烫漂（蒸汽和热水,处理2 min）处理后黄花菜成品褐变抑制及干燥特性的影响,对其干制品外观色泽、营养成分和微观结构进行表征,同时采用傅里叶变换红外光谱法比较不同预处理对其结构的影响,并通过主成分分析获取具有较高商品价值的黄花菜干燥预处理条件。结果表明,抑制褐变效果方面：蒸汽烫漂>热水烫漂;0.2 g/100 mL柠檬酸溶液>0.1 g/100 mL柠檬酸溶液>1.0 g/100 mL氯化钠溶液>0.2 g/100 mL碳酸氢钠溶液。干燥处理效果方面：采用0.2 g/100 mL柠檬酸溶液进行护色处理的黄花菜干燥速率最快且复水效果较好;综合考量,以蒸汽烫漂（2 min）+0.2 g/100 mL柠檬酸溶液浸泡（45 min）条件进行预处理后,黄花菜干制品的外观色泽、黄酮与多酚含量及微观结构等品质较佳。经主成分分析可知,多酚含量、5-羟甲基糠醛含量与色差、褐变度高度相关,咀嚼性与硬度相关性最高...     

干燥方式及碱液处理对鲜枸杞干燥特性和品质的影响

为了缩短鲜枸杞干燥时间,降低能耗,提高枸杞干制品品质,采用清水和不同质量分数（2%、4%和6%） 的Na2CO3溶液对枸杞进行前处理后,分别进行热风和热泵干燥,测定并分析了所获得枸杞干果的干燥速率、色 泽、复水率以及主要营养成分（多糖、总类胡萝卜素、黄酮）含量。结果表明：Na2CO3前处理能使枸杞表皮蜡质 层变薄、断裂,形成水分通道,进而缩短枸杞干燥时间,较为适宜的Na2CO3质量分数为2%。在干燥效率方面,热 泵和热风干燥没有显著性差异,但是在干燥产品品质上,热泵干燥要明显优于热风干燥。相对于恒温恒湿干燥, 分阶段变温干燥在保证干燥产品品质的同时,加快干燥速率,缩短干燥时间。因此枸杞干燥的最适工艺参数为 2% Na2CO3前处理,干燥温度40 ℃（2 h）-45 ℃（4 h）-50 ℃（6 h）-55 ℃（10 h）,干燥相对湿度40%的热泵干 燥。此工艺条件下枸杞干燥时间为22 h,干燥枸杞色差值为15.09,复水率为2.35 g/g,多糖含量为10.29 g/100 g,黄 酮含量为0.43 g/100 g,总类胡萝卜素含量为1 503.13 μg/g。     

3 种预处理方式对双孢菇干制品品质的影响

研究漂烫、超声漂烫、常温超声3 种预处理方式在远红外干燥条件下对双孢菇干制品硬度、脆度、色泽、VC含量和微观结构的影响。结果表明：常温超声预处理的双孢菇干燥时间缩短,与未处理产品相比,其硬度值明显下降、脆度值显著提高。同时常温超声预处理显著提高了双孢菇干制品复水比、降低了收缩率。超声漂烫和漂烫两种预处理方式因存在高温作用,使双孢菇细胞结构遭到严重破坏,导致双孢菇干制品色泽变化明显、复水比降低、收缩率提高且VC含量降低。因此采用常温超声作为预处理方式可以提高双孢菇干制品的品质。     

Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

The objectives of this work were to evaluate infrared (IR) dry blanching in comparison with conventional water blanching prior to hot air drying of mango to inactivate polyphenol oxidase (PPO) and ascorbic acid oxidase (AAO) enzymes, and to study its effect on color change and retention of vitamin C and β‐carotene. Mango cylinders were blanched under similar temperature–time conditions either by IR heating or by immersion in a water bath during 2 min at 90 °C (high‐temperature‐short‐time—HTST) or for 10 min at 65 °C (low‐temperature‐long‐time—LTLT). After blanching mango was hot air dried at 70 °C. PPO was completely inactivated during the blanching treatments, but AAO had a moderate remaining activity after LTLT treatment (～30%) and a low remaining activity after HTST treatment (9% to 15%). A higher retention of vitamin C was observed in mango subjected to IR dry blanching, 88.3 ± 1.0% (HTST) and 69.2 ± 2.9% (LTLT), compared with water blanching, 61.4 ± 5.3% (HTST) and 50.7 ± 9.6% (LTLT). All‐trans‐β‐carotene retention was significantly higher in water blanched dried mango, 93.2 ± 5.2% (LTLT) and 91.4 ± 5.1% (HTST), compared with IR dry blanched, 73.6 ± 3.6% (LTLT) and 76.9 ± 2.9% (HTST). Increased levels of 13‐cis‐β‐carotene isomer were detected only in IR dry blanched mango, and the corresponding dried mango also had a slightly darker color. IR blanching of mango prior to drying can improve the retention of vitamin C, but not the retention of carotenoids, which showed to be more dependent on the temperature than the blanching process. A reduction of drying time was observed in LTLT IR‐blanching mango.     

热泵式长豇豆干燥工艺优化

为保证热泵干燥后长豇豆产品的复水性和色泽等品质参数良好,同时降低豇豆干燥过程中的能量消耗,提高豇豆干燥生产的效率,采用Box-Behnken试验设计,分析干燥温度、漂烫时间和铺料密度3 个因素对豇豆产品的复水率、色差、单位耗能量和耗时4 个参数的影响,建立多元回归模型,并对干燥工艺参数进行优化,得到热泵式长豇豆干燥工艺的最佳条件为漂烫时间3 min、铺料密度2 kg/m2、干燥温度50 ℃。在该工艺条件下,实际测得长豇豆复水率1.15,色差值22.39,单位耗能量14.31（kW·h）/kg,耗时7 h,与预测值误差极小,为豇豆在实际热泵式干燥设备生产加工中的应用提供一定的理论依据。     

Pulsed electric field treatment of carrots before drying and rehydration

BACKGROUND: In this study the effects of pulsed electric field (PEF) pretreatment were evaluated during drying and rehydration of carrots. Carrots pretreated with an electric field intensity of 1 kV cm^?1 (capacitance 0.5 µF, 20 pulses) or 1.5 kV cm^?1 (capacitance 1 µF, 20 pulses) as well as blanched (100 °C, 3 min) carrots were used for the study. Following pretreatment, samples were oven dried at 70 °C and then rehydrated in distilled water (1:30 w/v) at room temperature (24 ± 1 °C). RESULTS: PEF pretreatment increased the drying rate of carrots. However, the rehydration rate of PEF‐pretreated carrots was lower than that of blanched carrots. There were no colour differences between PEF‐pretreated and blanched carrots before drying and after rehydration. In terms of texture, PEF‐pretreated carrots were firmer than blanched carrots. PEF pretreatment reduced the activity of peroxidase by 30–50%, while blanching completely inactivated the enzyme (>95%). CONCLUSIONS: Overall, the results suggest that PEF could be an effective pretreatment during drying and rehydration of carrots. Copyright © 2009 Society of Chemical Industry     

High-Pressure and Freezing Pretreatment Effects on Drying, Rehydration, Texture and Color of Green Beans, Carrots and Potatoes

High-pressure pretreated and frozen green beans, carrot dice or potato cubes were fluidized bed dried and compared to untreated, pressure-treated or water-blanched dried samples. Drying rates varied with pre-treatments. Freezing resulted in highest drying rates. Pressure-treated and water-blanched samples retained highly acceptable colors. Freezing or hot-water blanching or high-pressure pretreatment, followed by freezing, gave good rehydration. High-pressure treatment resulted in incomplete rehydration but combined with freezing, water uptake was between 2.1 and 4.8 mL/g. Retention of cell wall structures of frozen samples during drying was presumed responsible for more efficient mass transfer. Texture measurements revealed significant effects of pretreatments. Pressure-treated samples had texture nearest that of the raw material. No major differences in color were observed.     

Impact of processing treatments and packaging material on some properties of stored dehydrated cauliflower

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.     

Rehydration properties of dried onion

Abstract

The effect of pretreatment preceding convective drying and the mode of drying on reconstitution properties of dried onion was investigated. Soaking in water, dipping in starch solution and osmotic dewatering were used as pre‐drying treatments. Convective drying at 60, 70, and 80°C, infrared drying and convective drying assisted with microwaves were applied to remove water from raw onion. Rehydration was done in water at room temperature and in boiling water. In general amount of absorbed water and increase in mass during rehydration, both were higher for pretreated material than those observed with dried raw onion. The mode of drying seemed to affect the course of rehydration of dried onion, and to improve its reconstitution properties. However, this was observed at room temperature rehydration only. Pre‐drying treatment followed by convection drying affected much stronger reconstitution properties of dried onion than the mode of drying.     

盐渍对鲍鱼微波真空干燥过程和品质的影响

盐渍是鲍鱼微波真空干燥过程前处理的关键因素. 以不同浓度盐溶液-0, 5%, 7 5%, 10%, 15%和饱和盐溶液-盐渍鲍鱼,在微波功率2 000 W、真空度-80 kPa条件下进行微波真空干燥. 以其微波真空干燥特性、干燥后色泽、复水性及复水后质构特性为指标,考察盐渍对鲍鱼干燥过程和品质的影响. 结果表明：蒸馏水浸泡和盐浓度大于15%的盐溶液盐渍都不利于鲍鱼微波真空干燥的进行和干制后的品质. 当食盐浓度为7 5%~10%时,鲍鱼的微波真空干燥速率明显加快,复水率和复水比均较好,复水后呈现较佳咀嚼性,且色泽为均匀的淡黄色. 综合考虑,经过7 5%盐溶液浸渍24 h后,沸水煮2 min的鲍鱼进行微波真空干燥效果较佳.