Influence of modified blanching treatments on inactivation of Salmonella during drying and storage of carrot slices

Documented outbreaks of human illness associated with consumption of minimally processed produce have increased in recent years. This study evaluated the influence of modified treatments on inactivation of Salmonella during preparation, home-type dehydration (60 degrees C, 6h) and storage of carrot slices. Inoculated (five strains, 7.8 log cfu/g) slices were subjected to the following treatments: (i) untreated control, (ii) steam blanching (88 degrees C, 10 min), (iii) water blanching (88 degrees C, 4 min), (iv) blanching in a 0.105% citric acid solution (88 degrees C, 4 min), or (v) blanching in a 0.21% citric acid solution (88 degrees C, 4 min), dried for 6h at 60 degrees C (140 degrees F), and stored for up to 30 d. Bacterial populations were reduced by 3.8-4.1, 4.6-5.1 and 4.2-4.6 log cfu/g immediately following steam, water or citric acid blanching, respectively. After 6h of dehydration, total reductions were 1.6-1.7 (control), 4.0-5.0 (steam blanched), 4.1-4.6 (water blanched) and 4.9-5.4 (blanched in citric acid solution) log cfu/g. Populations continued to decrease throughout storage, but were still detectable by direct plating at 30 d on all samples except for those blanched in 0.21% citric acid. Results suggest that blanching carrot slices, particularly blanching in 0.21% citric acid, before drying should enhance inactivation of Salmonella during home-type dehydration and storage.     

Effect of blanching and drying treatments on quality of bamboo shoot slices

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, ΔE > 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.     

不同热烫处理对马铃薯片中还原糖浓度的影响研究

以还原糖含量为评价指标,还原糖的含量通过DNS法测得,旨在研究不同热烫处理在降低马铃薯片中还原糖含量方面的作用,从而抑制切片型薯片油炸过程中致癌物质丙烯酰胺的生成。在单因素实验的基础上进行正交实验,考察热烫温度和时间两个因素在降低还原糖含量方面的作用。结果表明,热烫处理的最佳工艺条件为：热烫温度75℃、热烫时间135s。     

The effect of blanching on the mechanical and rehydration properties of dried potato slices

 Short-time blanched (2 min, 90  °C), long-time blanched (30 min, 90  °C) and non-blanched potato slices were dried in a convective air drier and their mechanical and rehydration properties were compared. Blanching increased the flexibility and strength of dried potato slices, although the effects of short and long blanching were not significantly different. Unblanched potato slices did not have larger rehydration ratios than blanched ones. After rehydration for 30 min, samples from all treatments had higher strength and flexibility than cooked potatoes. Received: 2 November 1998 / Revised version: 15 February 1999     

Starch gelatinization temperatures within potato during blanching

The progression of gelatinization within potato cylinders blanched at 65,75 and 85°C for 2, 4 and 6 min was followed by iodine staining of sections. The distance to the gelatinization front was measured on photographs of both blanched and stained potatoes. A time-temperature simulation was performed with a finite difference computer program using thermal conductivity, specific heat, phase transition, density, heat-transfer coefficient, and initial temperatures as input data. Measured distances were used to determine the simulated temperature at the gelatinization front. The computer-simulated temperatures used to determine the gelatinization temperature within blanched potato were in good agreement with published values.     

烫漂方式对苹果脆片褐变和多酚及其抗氧化活性的影响

为阐明烫漂方式对热风干燥苹果片品质特性的影响,采用热水、蒸汽和微波对苹果片进行烫漂处理,测定苹果片在烫漂和干燥过程中的色泽、多酚及其抗氧化活性的变化情况。结果表明,热水烫漂苹果片的干燥时间最短,为270 min;不同烫漂方式对苹果片褐变有显著影响(P<0.05),其中热水烫漂的苹果片色泽变化最小,微波烫漂的苹果片色泽最差;与鲜样相比,烫漂方式对苹果片还原糖含量影响较小;干燥过程中微波烫漂的苹果片中产生的5-羟甲基糠醛含量最高,蒸汽烫漂次之,热水烫漂最低;苹果片经热水烫漂和干燥后维生素C损失率分别为34%和52%,而蒸汽烫漂和微波烫漂的苹果片中维生素C损失率较小;热水烫漂的苹果脆片总酚含量最高,达到11.82 mg GAE/g DW;苹果片经烫漂处理后游离多酚和结合多酚单体无显著性变化(P>0.05),但干燥后,所有样品中结合多酚单体含量均显著提高(P<0.05)而游离多酚单体的含量无显著性变化(P>0.05),表明3种烫漂方式都有利于多酚单体的保留;多酚抗氧化能力实验表明烫漂和干燥后苹果片中结合多酚抗氧化活性有显著性变化(P<0.05),其中热水烫漂的苹果...     

Inactivation of Salmonella during drying and storage of Roma tomatoes exposed to predrying treatments including peeling, blanching, and dipping in organic acid solutions

The objective of this study was to evaluate the influence of predrying treatments, i.e., peeling, blanching prior to inoculation, and dipping in organic acid solutions, on inactivation of Salmonella during drying (60 degrees C for 14 h) and aerobic storage (25 degrees C for 28 days) of inoculated (five-strain composite, 7.1 to 7.4 log CFU/g) Roma tomato halves. Four predrying treatments groups were established. One group received no treatment (C). In the other three groups, unpeeled-unblanched, unpeeled-blanched (steam blanched at 88 degrees C for 3 min), peeled-unblanched, and peeled-blanched tomato halves were immersed for 10 min in water (W), ascorbic acid solution (AA; 3.40%, pH 2.48), or citric acid solution (CA; 0.21%, pH 2.51). Appropriate dilutions of homogenized tomato samples were spread plated on tryptic soy agar with 0.1% pyruvate and XLT4 agar for bacterial enumeration during drying and storage. Ten minutes of immersion in W, AA, or CA reduced bacterial populations by 0.7 to 1.6 log CFU/g. After 14 h of dehydration, total log reductions in the populations of bacteria were 3.2 to 4.5 (C), 3.7 to 4.9 (W), > 5.6 to > 6.1 (AA), and 4.5 to 5.5 (CA) log CFU/g, depending on type of agar used and condition of tomato samples. During drying and storage, the order of pathogen inactivation for predrying dipping treatments was AA > CA > W > C, with AA and CA rendering bacterial populations below detectable levels ( < 1.3 log CFU/g) prior to storage and between 7 and 14 days of storage, respectively. The results also indicated that peeling and blanching of tomatoes prior to inoculation may not necessarily affect destruction of Salmonella during the drying process. Use of predrying acid dipping treatments of tomatoes, especially in AA, may improve destruction of Salmonella during the dehydration process.     

Modelling the effect of different sterilisation treatments on antioxidant activity and colour of carrot slices during storage

The effect of F₀ treatment time (min) and storage on the antioxidant activity and Hunter colour parameters (L*, a*, b*) of carrot slices was investigated. Carrot slices were sterilised for 0 (control), 3, 15 and 50 min and subsequently stored for 0, 3 and 6 months. Significant differences were observed in colour values of carrot slices with no significant difference beyond F₀ treatment of 3 min. Regression modelling was used to investigate the main effects of treatment time and storage. Treatment time and storage period was found to be significant. Predicted models were found to be significant (p < 0.05) with low standard error and high coefficients of determination (R²). This study proposes the predicted models for quality parameters of sterilised carrot slices.     

果蔬微波真空干燥（MVD）技术研究进展

为了提高甘薯干燥效率和改善产品品质,本文采用微波真空干燥（MVD）技术,研究了超声处理（US）、渗透脱水（OD）、超声辅助渗透（USOD）、真空辅助渗透（VAOD）和超声/真空辅助渗透（VUOD）对甘薯切片干燥动力学、微观结构、孔隙特征及理化性质的影响。采用Weibull分布函数和Dincer模型对干燥曲线进行拟合,并结合尺度参数（α）、形状参数（β）、滞后因子（G）、干燥系数（S）、毕渥数（Bi）探讨了MVD甘薯切片干燥过程的热、质传递机制。结果表明：相比其他处理,USOD和VUOD可显著提高甘薯切片的水分流失率（WL）和固形物增加率（SG）（P<0.05）。Weibull分布函数和Dincer模型对MVD甘薯切片的干燥曲线具有较好的拟合效果。模型参数（α, β, G, S）结果表明,经USOD处理的MVD甘薯切片干燥效率最高,加速阶段历时最短;毕渥数（Bi）处于0.243~3.617之间,表明MVD干燥过程甘薯切片温度变化由内部传导热阻和表面对流热阻共同控制。基于Weibull和Dincer模型计算获得的水分扩散系数D_cal和D_eff分别为7.986×10⁻⁸~1.249×10⁻⁷和1.508×10⁻⁸~8.272×10⁻⁸ m²/s,且均是USOD样品最大,OD最小。USOD和VUOD甘薯切片呈现蜂窝状、多孔结构,其中VUOD样品孔隙率最大（为33.30%）,而USOD样品平均孔径最小（仅为164.50 nm）、迂曲度最大（为41.97）。相比其它预处理,USOD和VUOD处理显著提升了MVD甘薯切片的复水性能（P<0.05）,降低了体收缩率,较好地保持了原有色泽,缩小了色差。研究结果可为甘薯切片的微波真空干燥条件筛选和品质调控提供参考。     

热烫前处理对鲜食玉米贮藏过程中保鲜品质的影响

由于鲜食玉米在贮藏期间品质会不断下降,本文利用热烫对鲜食玉米进行前处理,研究其对贮藏期间品质的影响。对鲜食玉米先进行热烫,然后用复合生物保鲜剂进行保鲜,分析含水量、质量损失率、TPA指标、气味与感官品质等,研究贮藏期间鲜食玉米的品质变化。结果表明,热烫前处理的鲜食玉米在贮藏期间,水分含量显著(p<0.05)高于对照,热烫处理可有效抑制鲜食玉米水分散失。热烫处理的鲜食玉米在贮藏0~10 d时,质量损失率略低于对照,30 d时高于对照2.2%,但差异不显著(p>0.05)。热烫处理鲜食玉米的弹性、粘性及回复性与对照差异不显著;而内聚性显著高于对照(p<0.05),硬度、胶粘性和咀嚼性均极显著高于对照(p<0.01)。热烫处理的鲜食玉米气味变化较小。热烫处理对鲜食玉米的保鲜效果较好,能较好保持色、香、味等感官品质。     

Influence of cold storage and blanching on the carotenoid content of Kintoki carrots

A high consumption of lycopene is associated with a decreased risk of cardiovascular diseases and cancer. A lycopene containing carrot variety, Kintoki, with about 9 mg lycopene on a wet weight basis could, besides tomatoes, probably serve as an additional source of lycopene in the diet. High availability and stability of lycopene is achieved in carrot products after blanching at high temperatures (T=90 °C) and oxygen-free conditions.     

Influence of fruit treatments on perishability during cold storage of sweet chestnuts

With a view to enhancing the quality of local chestnut in southern Switzerland, the impact of three treatments [‘soaking’, ‘cold bath’ (hydrotherapy) and ‘warm bath’ (thermo‐hydrotherapy)] on the qualitative, chemical and sensory characteristics of the nuts during 90 days of cold storage was evaluated. Weight and water content decreased significantly with increasing duration of storage. Starch content decreased following a negative logistic trend. Sucrose, however, increased steeply according to a monomolecular trend and was significantly higher between 0 and 60 days of storage in the soaked chestnuts than in the cold‐bath treated nuts. The mean proportion of mouldy fruit remained constant at 27% for the warm‐bath treated nuts and increased from 16 to 30% for the cold‐bath treated fruit and from 28 to 63% for the soaked nuts during the 90 days of cold storage. The most frequently isolated moulds were Ciboria batschiana, Penicillium spp. and Mucor hiemalis. Warm and cold baths were successful in eliminating the larvae of Cydia splendana but the cold bath was inadequate to control Curculio elephas. Cold bath significantly reduced the sensory qualities (sweetness, aroma, texture) of the nuts, but made them easier to peel, as did the warm bath. Copyright © 2006 Society of Chemical Industry     

Influence of process variables on the drying of potato slices

Investigation of the effects of varying air velocity, slice thickness, and pre-treatment with sodium chloride solutions and surface active agents on drying potato slices indicated that the drying occurred entirely in the falling rate period and was controlled by the mechanism of liquid diffusion. The rate of drying, and therefore the diffusion coefficients, increased with the addition of sodium chloride and surface active agents. Diffusion coefficients were also influenced by air velocity and slice thickness, suggesting that the rate of drying of potato slices is controlled by a combination of internal and external resistances.     

Inactivation of Salmonella during drying and storage of apple slices treated with acidic or sodium metabisulfite solutions

This study was undertaken to determine whether pretreating inoculated Gala apple slices with metabisulfite or acidic solutions enhanced the inactivation of Salmonella during dehydration and storage. Apple slices inoculated with a five-strain mixture of Salmonella (7.6 log CFU/g) were pretreated, dried for 6 h at 60 degrees C, and stored aerobically at 25 degrees C for 28 days. Predrying treatments included (i) no treatment, (ii) 10 min of immersion in sterile water, (iii) 10 min of immersion in a 4.18% sodium metabisulfite solution, (iv) 10 min of immersion in a 3.40% ascorbic acid solution, and (v) 10 min of immersion in a 0.21% citric acid solution. Samples were plated on tryptic soy agar with 0.1% pyruvate (TSAP), brilliant green sulfa (BGS) agar, and xylose lysine tergitol 4 (XLT4) agar for the enumeration of bacteria. Populations were not significantly (P > 0.05) reduced by immersion in water but were reduced by 0.7 to 1.1 log CFU/g by immersion in acidic solutions. Immersion in the sodium metabisulfite solution reduced populations by 0.4, 1.3, and 5.4 log CFU/g on TSAP, BGS agar, and XLT4 agar, respectively. After 6 h of dehydration at 60 degrees C, populations on untreated and water-treated slices were reduced by 2.7 to 2.8, 2.7 to 2.9, and 4.0 to 4.2 log CFU/g as determined with TSAP, BGS agar, and XLT4 agar, respectively. In contrast, populations on slices treated with sodium metabisulfite, ascorbic acid, and citric acid were reduced after 6 h of dehydration by 4.3, 5.2, and 3.8 log CFU/g, respectively, as determined with TSAP; by 4.7, 5.5, and 3.9 log CFU/g, respectively, as determined with BGS agar; and by 5.5, 5.7, and 5.6 log CFU/g, respectively, as determined with XLT4 agar. Bacteria were still detectable by direct plating after 28 days except on slices treated with ascorbic acid. Immersion in metabisulfite or acidic solutions prior to dehydration should enhance the inactivation of Salmonella during the dehydration and storage of Gala apple slices.     

Influence of sodium replacement and vacuum pulse on the osmotic dehydration of eggplant slices

Partial replacement of sodium chloride by potassium and calcium chlorides has been proposed as a strategy for reducing the sodium content of osmodehydrated eggplant. The influence of sodium substitutes and vacuum application (VA) on mass transfer parameters and chemical, mechanical and optical properties were investigated. Kinetics of water loss, solid gain and water activity were performed and fitted by the model of Barbosa Junior et al. This model was satisfactorily adjusted, mainly for the osmotic dehydration at atmosphere pressure. VA and the calcium increased the ascorbic acid retention in 29.33 and 85.06%, respectively. VA increased water loss up to 53% and ions incorporation, especially that of potassium (648%). The VA caused a higher total color difference, maximum stress and elasticity as compared to the osmotic dehydration at atmospheric pressure.Industrial relevanceThe present paper evaluates the osmotic process with atmospheric and reduced pressures and the production of osmodehydrated eggplant slices with reduced sodium content by the partial replacement of sodium chloride by potassium chloride and calcium chloride. Vacuum can accelerate the osmotic process and enhance the diffusion of water and solutes within the products. The coupling of sodium substitution with reduced pressure could offer an interesting array of different processes and healthier products. This project is a feasibility study of the partial replacement of NaCl by KCl and CaCl₂ and the application of vacuum with regard to effects on mass transfer parameters and the chemical, optical and mechanical properties of osmodehydrated eggplant slices.     

不同保鲜处理对鲜切苹果保鲜效果的影响

为研究不同保鲜剂及热处理对鲜切苹果品质的影响,将鲜切寒富苹果(Malus domestica)分别进行1.5%柠檬酸溶液、1.5%异抗坏血酸钠溶液、0.08%溶菌酶溶液和50℃的水浴中浸泡2 min处理,沥干后用0.08mm厚度CPP包装袋包装,抽真空(0.098 MPa)后密封,置于4℃冷库中贮藏,每3d测定与保鲜相关的生理生化指标。结果表明:不同保鲜剂及热处理均可适度延缓苹果切块感官品质、营养物质含量的下降、抑制微生物的繁殖,其中1.5%异抗坏血酸钠溶液浸泡处理的保鲜效果最好,能在4℃、15d贮藏期内较好地维持鲜切苹果的品质。     

Changes in texture,microstructure and nutritional quality of carrot slices during blanching and freezing

Thermal processing of vegetables has pronounced effects on the cell structure, often lowering the final textural properties of the product. In order to investigate the effect of thermal processing on carrot, slices were subjected to different blanching and freezing treatments before frozen storage. Microwave-, steam- or water-blanched material was frozen and then stored at −24 °C. Steam-blanched carrots were subjected to blast freezing or cryogenic freezing at different temperatures before frozen storage. The influence of these process conditions on the texture (maximum load and slope), microstructure, dry matter, sugars, carotene and drip loss was investigated. Microwave blanching differed from the other blanching methods by resulting in a heterogenic cell structure. The content of dry matter, carotene and sucrose was higher following microwave blanching. Blast freezing resulted in low maximum load which seemed to be caused by major tissue damage. Concerning cryogenic freezing, lowering the temperature from −30 °C to −70 °C resulted in better preservation of the native microstructure together with an increase in maximum load, which was most pronounced after one month of storage. No significant effect was observed when lowering the temperature from −30 °C to −70 °C for any of the other measured parameters. © 1999 Society of Chemical Industry     

The effect of blanching on quality attributes of dehydrated carrots during long-term storage

 The effect of blanching on the retention of β-carotene and ascorbic acid, and non-enzymatic browning (NEB) during storage of dehydrated carrot slices was studied. Blanched carrots contained higher β-carotene but lower ascorbic acid than their unblanched counterpart just after drying, whereas NEB was unaffected by blanching. During storage of dehydrated carrots a decrease in β-carotene and ascorbic acid content with an increase in NEB values was observed. Blanching was helpful in limiting the loss of quality parameters irrespective of storage and packaging conditions. Received: 22 May 2000 / Revised version: 11 October 2000