三种不同预处理的冻干苹果片品质比较

为了解决冻干苹果片加工过程中的护色问题,设计了对照组(CK)、热烫组(BT)、护色液浸泡组(CP)、热烫-护色液浸泡复合护色组(BCP)四组,再采用真空冷冻干燥技术将苹果片制成即食脆片,对每组产品的含水率、维生素C含量、滴定酸度、复水比、质构、色差、感官评价、微观结构等品质进行比较分析。结果表明,四组冻干苹果片的含水率在5.13%～5.47%,维生素C含量在9.56～17.06 mg/100 g,滴定酸度在2.22～2.37 g/100 g,复水比在5.15～3.49,硬度在9715.67 g～9384.67 g,脆度在1762.50 g～1989.00g,亮度在77.73～84.04,感官评分在5.82～8.02,其中CK组的维生素C含量显著高于其他三组(p0.05);BCP组的复水比显著高于CK组(p0.05);BCP组的护色效果最佳,产品亮度值L*84.04,综合评分8.02。微观结构的结果表明,经预处理与真空冷冻干燥复合处理后细胞呈现杂乱排离,结构松散破碎。总体来说,四组冻干苹果片虽然在营养成分和感官评价上具有差异,但均保留了苹果的风味,BCP组具有更好的冻干片品质。本研究为冻干苹果片的工业化生产提供理论和技术指导。     

Impact of pulsed electric fields on physical properties of freeze-dried apple tissue

The aim of this study was to analyze the impact of pulsed electric field (PEF) pre-treatment of apple tissue on kinetics of freeze-drying preceded by vacuum freezing and physical properties of such processed material. PEF intensified freeze-drying kinetics and thus reduced processing time by 57% in comparison to untreated apples slices. Furthermore, the effective water diffusion coefficient increased by 44% as a result of PEF application. Water activity changes during storage of freeze-dried apple tissue were more evident in the case of untreated material albeit initial water activity was higher in the case of electroporated samples. As proved by thermal properties measurements these differences were linked to higher crystallinity of the PEF treated samples (35.5%) in comparison to the untreated material (11.0%). The freeze-dried fruits subjected to PEF pretreatment absorbed more water than the untreated samples while no changes were observed for hygroscopicity and loss of the soluble solids during rehydration.Industrial relevanceObtained results confirm that application of pulsed electric field before freeze-drying makes possible to obtain high quality freeze-dried product preceded by vacuum freezing performed inside freeze-dryer which could reduce freeze-drying time. Since the rehydration capacity of PEF treated material, expressed as ability to absorb water, is better than untreated samples the application of this method could be beneficial when designing instant products. Performed research indicates also that PEF treated freeze-dried apples exhibit better stability expressed by water activity which in turn is related to crystallinity. What more, higher crystallinity of PEF pre-treated freeze-dried samples not only complements the explanation of different physical properties in comparison with intact freeze-dried material but also suggest that sensorial properties may vary.     

Effects of Ripeness Stages on the Storage Atmosphere, Color, and Textural Properties of Minimally Processed Apple Slices

ABSTRACT: Fruit maturity is a determinative factor in maintaining the original color and, to a greater extent, the texture of minimally processed fresh-cut apple slices. Mature-green apples (because of their lower respiration and ethanol formation) were the most suitable to process for extending post-cutting-quality shelf life. Sliced apples processed at an earlier stage of ripeness, but dipped in a solution of ascorbic acid (C₆H₈O₆) and calcium chloride (CaCl₂) and stored under 100% N₂, preserved their original color with minor changes. However, these processing and packaging treatments could not effectively prevent the apple slices from softening, and apple flesh underwent a progressive loss of firmness from 8.0 to 4.8 N.     

The impact of pulsed electric fields on quality parameters of freeze-dried red beets and pineapples

The effect of pulsed electric fields (PEF) on the cell disintegration index (Zp), the freeze-drying process and the final product quality of red beet and pineapple tissue was studied. Red beets and pineapples were PEF-treated at an electric field strength of 1.07 kV/cm and specific energy inputs of 1 kJ/kg and 4 kJ/kg (PEF₁ and PEF₂, respectively). Freeze-drying was performed at a pressure of 1 mbar and heating plate temperature of 50 °C for red beet and 40 °C for pineapple. The quality of freeze-dried tissue was evaluated by the analysis of residual moisture content, macrostructure, texture, colour and rehydration properties. For freeze-dried red beets, the betalain content from extracts was studied. It could be stated that PEF pre-treatment had no significant influence on drying time reduction, however significantly improved the final quality of freeze-dried product. Moreover, the effect of PEF was strongly depending on type of plant material used.     

Drying of carrot slices using infrared radiation

Carrot slices were dried from initial moisture content of 8.52 kg water kg⁻¹ dry matter to 0.11 kg water kg⁻¹ dry matter by infrared dryer. Experiments were conducted using three levels of infrared power (300, 400 and 500 W) and at air velocities (1.0, 1.5 and 2.0 m s⁻¹). The effects of process variables on the drying kinetics of carrot, drying time, specific energy consumption and quality parameters of dried carrot (shrinkage, rehydration ratio and colour) were investigated. The drying time at infrared power of 300, 400 and 500 W was 252 and 277 min, 205 and 236 min, and 145 and 155 min at air velocities of 1.0 and 2.0 m s⁻¹, respectively. The drying rate increased with increasing infrared power. The specific energy consumption values varied between 12.22 and 14.58 MJ kg⁻¹-evaporated water for all the drying conditions. Shrinkage, rehydration ratio and colour parameters were found to be affected by process variables.     

Optimization of ingredients and process conditions for the preparation of tandoori roti using response surface methodology

A model capable of predicting the product quality of tandoori roti has been developed using response surface methodology (RSM) and used to determine the optimum processing conditions. The overall sensory score, which is an indicator of blister size, colour, appearance, handfeel, texture, mouthfeel, taste and aroma, was used to assess the product quality in the preparation of tandoori roti. The optimum conditions which were attained for maximum sensory score (31.6) were: water level – 720mL kg⁻¹ flour (the corresponding farinograph consistency – 800 BU at lever position 1:1), salt level – 11g kg⁻¹ flour, mixing time – 3.7 min in a Hobart mixer at 58 r.p.m., baking time – 37 s, and baking temperature – 425°C.     

不同前处理和冻结方式对苹果片真空冷冻干燥效率及干制品品质的影响

冻干前处理和冷却固化环节是果蔬冻干的关键工序,为进一步缩短干燥时间并提高干制品品质,该研究选用苹果片作为试验对象,采用超声波技术、真空冻结技术、超声波-真空冻结技术,将苹果片分为常规组、超声-常规组、真空冻结组、超声-真空冻结组,比较不同前处理方式对苹果片冻干效率及干制品品质的影响。结果表明,超声-常规组苹果片冻干效率最高,由16.00 h缩短至11.83 h;干制品复水比最大,较常规组增加了62.16%;色泽指标b*值由28.24降至19.46,颜色更加洁白;维生素C保留率最高,可达83.90%;硬度最小且松脆可口,感官评价最好。真空冻结组苹果片冻干时间由16.00 h缩短至14.17 h;干制品复水比较常规组增加了17.99%;色泽指标b*值由28.24降至22.98,颜色较为洁白;酥脆性良好且有较好的咀嚼感,感官评价良好。研究结果为苹果片在冻干前处理环节参数优化及新型果蔬脆片的开发提供参考。     

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.     

不同分切形状对贵州小黄姜真空冷冻干燥效率及品质的影响

目的 比较不同分切形状对贵州小黄姜真空冷冻干燥效率及品质的影响。方法 以贵州小黄姜为原料,研究真空冷冻干燥过程中姜片、姜丝、姜粒3种不同分切形状干燥效率及小黄姜品质的影响,采用称量法测定复水率;色差仪测定色泽变化;质构仪检测硬度、弹性等参数;营养成分分别采用Folin-Ciocalteu比色法、硝酸铝显色法和分光光度法测定小黄姜提取物中的多酚、黄酮、多糖和姜辣素含量。结果 切片厚度为3～4 mm的冻干姜片的干燥效率最高、复水率(577.08%)最佳、色差值(5.76)最低、硬度(494.98 g)最小、弹性(0.71 mm)和回复性(0.25 mm)最好、咀嚼性(145.26 g)最高、营养成分保留率最高,多酚、黄酮、姜辣素、多糖保留率分别为99.35%、70.52%、88.41%、96.27%,且风味浓郁、感官评分最高。结论 不同分切形状对小黄姜真空冷冻干燥效率及产品品质具有显著影响,片状的冻干效率更高,营养成分损失较少,可获得品质较好的冻干小黄姜。     

Quality changes in fresh-cut Fuji apple as affected by ripeness stage, antibrowning agents, and storage atmosphere

ABSTRACT:  The effect of ripening state, modified atmosphere, and the use of antibrowning agents was investigated in an attempt to determine optimum ripeness and processing conditions for extending the shelf-life of fresh-cut Fuji apple. Apples were classified in 3 groups: mature-green, partially ripe, and ripe; after peeling and slicing, fruits were treated with 1% (w/v) N -acetylcysteine, or 1% (w/v) ascorbic acid (control), and then packed into polypropylene trays with air or a gas mixture (2.5% O₂+ 7% CO₂+ 90.5% N₂) and sealed. Trays containing the apple slices were stored in darkness at 4 °C ± 1 °C and analyzed periodically during 43 d. Changes in atmosphere composition, color, and firmness were examined. Partially ripe apples, based on their lower ethanol production and maintenance of their original color and firmness, were the most suitable to prepare the fresh-cut commodities. A postcutting dip in 1% (w/v) N -acetylcysteine was the most effective treatment to prevent cut surface browning and preserve the initial appearance of Fuji apple slices during more than 1 mo at 4 °C. Low O₂ and elevated CO₂ (2.5% O₂+ 7% CO₂) atmosphere extended the shelf life of apple slices because of a significant inhibition of ethylene production.     

Partial characterization of the in situ activity of pectinesterase in Bramley apple

The characteristics of pectinesterase (PE) have been examined in waste material (peel, cores and offcuts) obtained from Bramley seedling apples barn stored for 2, 4 and 12 weeks. A crude enzyme extract was prepared by suspending the dried and milled apple waste in 0.1 m NaCl at pH 8.5. The activity of PE under standard assay conditions of 0.5% apple pectin, 0.1 m NaCl, pH 8.5 and 30°C was low, between 4 and 8 units g⁻¹ dry matter, but activities up to 60 units g⁻¹ dry matter were obtained at higher temperatures. The optimum temperature was 60°C with the enzyme stable up to 40°C with 5 min heating. The mean activation energy for PE in the three samples was calculated at 39.2 kJ mol⁻¹ K⁻¹. The optimum pH was high at 10.0 probably due to the PE assay measuring the extraction/solubilization and stability of the enzyme in addition to its activity. Optimum activity was obtained in 0.15 m NaCl with optimum stability at 0.5 m.     

Canning of vegetable soybean: procedures and quality evaluations

Some aspects of the preservation process of vegetable soybean are discussed in this paper. Factors, like the effects of blanching duration, and brine composition, were discussed in relation with the quality attributes of the product including enzyme activity, texture and colour. It was observed that the concentration of CaCl₂ influenced the texture and luminosity (L), while the pH affected luminosity (L) and green colour (– a / b ) of the processed product. Furthermore, blanching for 90 s before heat-processing was effective to inactivate 99% of the initial lipoxygenase activity. It was found that a brine containing 150 g L⁻¹ NaCl and 2.9 g L⁻¹ CaCl₂, at pH 6.5 that was thermally treated for 9 min generated a lethality of 4 min that is enough to produce a 12-log reduction required for low acid foods and at the same time retaining desirable colour and texture.     

ANTIOXIDANT ACTIVITY AND QUALITY OF SOY ENRICHED APPLE BAR

Antioxidant activity of a soy enriched apple bar (SEAB) prepared from the pulp of culled apples and soy protein isolate (3%) was determined using a ferric reducing antioxidant power (FRAP) assay. The antioxidant activity was 8500 μM g⁻¹ FRAP and phenol content was 175 mg 100 g⁻¹. The soy enriched apple bar had 20 fold protein and 1.6 fold higher antioxidant activity than the plain apple bar. No significant change in antioxidant activity and total phenols was recorded during storage at ambient (22–31C) or low (4±1C) temperatures. The pectin, protein and ascorbic acid contents decreased while nonenzymatic browning and total sugars increased significantly with increase in storage periods. The product was organoleptically acceptable and microbiologically safe after 180 days of storage. A shelf stable soy enriched apple bar with high antioxidant activity, phenol content and sensorial quality can be an ideal source of dietary antioxidants.     

Effects of meat piece size and phosphate on maximum slicing rate, cooking loss and sensory quality of a re-formed pigmeat shoulder product

Summary Two pre-tumbling treatment variables (meat piece size; raw product phosphate content) were evaluated for their effects on maximum slicing rate (MSR), cooking loss and sensory quality of a commercially produced, cooked re-formed pigmeat shoulder product. At 0.457% phosphate, incremental reductions in meat piece size which increased specific surface from 0.60 to 0.93 cm² cm⁻³ enabled MSR to increase from 300 to 400 slices min⁻¹, reduced cooking losses from 0.875 to 0.60% and gave a more tender product. At 0.60 cm² cm⁻³ specific surface, increasing phosphate incrementally from 0.457 to 0.532% produced similar positive effects on MSR and cooking loss but at phosphate above 0.482% sensory quality declined. Combination of optimal specific surface (0.93 cm² cm⁻³) and phosphate (0.482%) permitted a MSR of 420 slices min⁻¹, reduced cooking loss to 0.50% and gave an acceptable product. These process modifications can thus be advocated for improved production rate, yield and sensory quality.     

Explosion puffing of bananas

Banana slices were satisfactorily dehydrated by incorporating explosion puffing into the drying process. Water contents in the range 27–38%, steam temperatures of 152–160°C, internal pressures of 0.8–1.0 Kg cm^-2 and residence times of approximately 1 min were typical explosion puffing conditions. Initial and final drying were performed with hot air at a temperature of 70°C, velocity 3.6 m s^-1, and relative humidity 35%. The increase in porosity obtained by puffing clearly reduced the total drying time compared with conventional air dried (CAD) samples. A simple diffusional model was applied to calculate the effective diffusivities of water vapour during drying of samples with and without puffing treatment. Analytical tests for colour differences, bulk density, porosity, rehydration parameters, and scanning electron microscopy in both puffed and CAD banana samples were also performed.     

Microwave and convective dehydration of ethanol treated and frozen apple – physical properties and drying kinetics

The objective of this study was to examine how the drying kinetics and physical properties of apples are affected by pre-treatment with 95% ethanol or freezing at –18 °C before microwave-assisted air dehydration at 50, 60 and 70 °C. Microwave heating was used to obtain these temperatures in the centre of the apple cubes. After dehydration the shrinkage and rehydration capacity were measured. The texture of dehydrated and rehydrated samples was analysed with a puncture test in a texture analyser. Samples were also analysed with confocal laser scanning microscopy to determine the correlation between physical and microstructural properties. Diffusivity in the different dehydration processes was calculated. Ethanol-treated apples showed both high rehydration and high effective rehydration capacity compared with the other samples. Freezing before dehydration increased the diffusivity and reduced the firmness of rehydrated apples compared with no pre-treatment.     

不同干燥方法对乌贼品质及微观结构的影响

为了解不同干燥方法对乌贼干后品质及微观结构的影响,采用自然晾晒干燥、热风干燥和真空冷冻干燥3种方法对乌贼进行处理,研究其对乌贼感官特征、色泽、收缩率、风味、甲醛含量和微观结构的影响,以及在后续复水过程中复水率和复水完成后质构参数的变化。结果表明,干制后乌贼的收缩率变化为:自然晾晒干燥热风干燥真空冷冻干燥,且差异显著(P0.05)。真空冷冻干燥的乌贼在色泽、复水率方面优于其他两组,在第9小时的纯水复水率可达524.25%,为自然晾晒干燥组的2.5倍,而在质地和风味方面的品质一般,其微观肌肉纤维形变较小,纤维间孔径较大;热风干燥后的样品在感官、质地以及风味方面具有显著优势,呈味氨基酸含量总和达1 519.20 mg/100 g,显著高于其他干燥组(P0.05),但样品中的甲醛含量较高,为260.83 mg/kg,是新鲜样品的4.7倍,且肌肉纤维形变大,排列致密;自然晾晒干燥的乌贼肌肉纤维形变较小,排列较致密,其甲醛含量较低,仅为22.06 mg/kg,感官品质和色泽还有待进一步提高。     

MODELING THE SENSORY QUALITIES OF PROCESSED APPLES AFTER CONTROLLED ATMOSPHERE STORAGE AND FROZEN STORAGE1

Durational effects of controlled atmosphere storage (CA) and frozen storage on apple quality were studied for commercially processed pies made from Northern Spy, Idared and Nova Spy apples. Sensory tests on apple pie quality indicated that the duration of apples in CA significantly affected the quality of the processed apple. Extending the CA duration of the apples to 45 weeks resulted in a pie filling with reduced apple flavor, tartness and astringency, and with increased sweetness and off‐flavor. To minimize flavor/taste changes throughout the processing season, close attention must be given to the product's sugar/acid formulation: by week 27 for Idared apples and by week 33 for Northern Spy and Novaspy apples. The texture and appearance of processed Novaspy and Idared fruits were affected earlier in CA than Northern Spy apples. The frozen product was relatively stable for all three varieties, especially for apples processed early in the storage season (15–27 weeks). A strategy that utilizes short‐ to medium‐term CA with longer‐term frozen storage would optimize quality across the season.     

INFLUENCE OF PLATE TEMPERATURE AND MODE OF REHYDRATION ON TEXTURAL PARAMETERS OF PRECOOKED FREEZE-DRIED BEEF

The effects of various plate temperatures and rehydration procedures in texture of precooked freeze-dried beef, were evaluated. Frozen precooked commercial beef was freeze-dried at 20, 40, 60 and 80C during 24 h. The rehydration procedure involved two main variables: distilled water at room-temperature and at 80C, for 30 min. The texture profile analysis was performed with a TA-XT2 Texture Analyzer (SMS) for freeze-dried rehydrated samples and compared to frozen precooked beef. The results showed that with a same drying period, the 60C plate temperature and rehydrated in distilled water at room-temperature resulted in a better product texture, in regards to texture parameters hardness and chewiness.     

Quality Measurement of Intact and Fresh-cut Slices of Fuji, Granny Smith, Pink Lady, and GoldRush Apples

ABSTRACT: Development of fresh-cut apple products requires consideration of cultivars that store well as both intact and fresh-cut fruit. We compared the instrumental and sensory quality of 2 apple cultivars, Granny Smith and Fuji, that are used for fresh cutting with 2 new cultivars, Pink Lady and GoldRush, which were considered to have quality characteristics suitable for fresh cutting. Firmness, titratable acidity (TA), soluble solids content (SSC), and aromatic volatile concentration were measured in intact fruit of the 4 cultivars during 12 mo storage in air at 0 °C and during 3 wk storage at 5 °C as fresh-cut slices. After 1 wk storage as fresh-cut slices, sensory evaluations for acceptability of flesh and peel appearance, flavor, texture, and overall eating quality were performed. During storage, GoldRush apples maintained > 80 N firmness, approximately 17% SSC, > 0.5% TA, and had high aromatic volatile production, that is, maintained quality better than the other cultivars. The quality and shelf stability of GoldRush slices were also as good as or better than slices from the other cultivars, whereas Granny Smith slices generally rated lower than the other cultivars. The acceptability of flavor, texture, and overall eating quality of GoldRush slices was as good as that for Pink Lady and Fuji. The quality of GoldRush apples can be maintained throughout the year in refrigerated air storage and still remain suitable for fresh-cut processing. The results indicate that GoldRush and Pink Lady are 2 promising new, high-quality apple cultivars for fresh cutting. Keywords: fresh-cut fruit, Malus × domestica , postharvest quality, respiration rate, shelf life