Effect of Osmotic Dehydration and Vacuum-Frying Parameters to Produce High-Quality Mango Chips

ABSTRACT:  Mango ( Mangifera indica  L.) is a fruit rich in flavor and nutritional values, which is an excellent candidate for producing chips. The objective of this study was to develop high-quality mango chips using vacuum frying. Mango (" Tommy Atkins ") slices were pretreated with different maltodextrin concentrations (40, 50, and 65, w/v), osmotic dehydration times (45, 60, and 70 min), and solution temperatures (22 and 40 °C). Pretreated slices were vacuum fried at 120, 130, and 138 °C and product quality attributes (oil content, texture, color, carotenoid content) determined. The effect of frying temperatures at optimum osmotic dehydration times (65 [w/v] at 40 °C) was assessed. All samples were acceptable (scores > 5) to consumer panelists. The best mango chips were those pretreated with 65 (w/v) concentration for 60 min and vacuum fried at 120 °C. Mango chips under atmospheric frying had less carotenoid retention (32%) than those under vacuum frying (up to 65%). These results may help further optimize vacuum-frying processing of high-quality fruit-based snacks.     

EFFECT OF HIGH-PRESSURE PROCESSING ON TEXTURE AND DRYING BEHAVIOR OF PINEAPPLE

The effect of high-pressure processing on texture and drying behavior of pineapple slices was investigated. Pineapple slices were high pressure processed at 50, 100, 300, 500 and 700 MPa at 25C for 10 min. The control, hot water-blanched and high-pressure processed samples were then dehydrated at 70C. Application of high pressure reduced the sample hardness, springiness and chewiness while it had no significant effect on cohesiveness of pineapple. Elevated pressure treatment (≥500 MPa) reduced drying time more effectively than for the other pretreated samples. Experimental dehydration data were empirically fitted using six thin-layer drying models. Among the models tested, logarithmic model best described the drying behavior of pineapple slices. The effective moisture diffusivity was found to increase with an increase in the level of pressure up to 500 MPa, and the samples processed at 500 and 700 MPa had higher diffusivity values than blanched samples.

PRACTICAL APPLICATIONS

This work shows that high-pressure blanching of pineapple can be an alternative for hot water blanching, before dehydration. The results may find application in development of quality snack food from pineapple fruits.     

Predicting safety and quality parameters for UHT-processed milks

A spreadsheet was developed to evaluate safety and quality parameters for milks subjected to different heating and cooling profiles and holding time conditions in a continuous heat exchanger. Safety parameters evaluated were lethality ( Fo ) and microbial inactivation ( B *) values; quality parameters were chemical change ( C *), thiamin loss, lactulose formation, Maillard browning and hydroxymethylfurfural (HMF) formation. The spreadsheet was used to predict these parameters for a pilot plant, heating milks at 120–150°C for 4, 27 and 58 s, using its heating and cooling profiles. Milks were processed in the same plant at these conditions and a selection of the milks were analysed to establish the validity of the spreadsheet. All samples with a C * value < 3 gave a positive Aschaffenburg turbidity. The activation energy that gave the best agreement between the predicted and experimental results for lactulose was found to be 122 kJ/mol. One set of optimized conditions for this product was 135°C for 10 s, giving B * = 1.24 and C * = 0.55. This milk was compared with two others and its sensory characteristics were similar to that with a C * of 1.5 but different to that with a C * value of 6. Browning was only found to be noticeable in the most severely heat-treated sample immediately after processing, but would become apparent on storage at 30°C and above. The spreadsheet is useful for comparing the characteristics of products from plants with different heating profiles or as a means for optimizing UHT plant performance where the heating and cooling rates are fixed.     

Effect of temperature and fruit-moisture content on discolouration of dried, sulphured Bon Chretien pears during storage

Summary Discolouration of Bon Chretien pears which had been treated with sulphur dioxide and which had moisture contents of either 16, 18 or 20%, was monitored during storage at 4, 7, 10 and 20 °C. Colour was quantified in terms of CIE L*, a*, b*, hue and chroma. L* was used to predict quality retention. Discolouration was categorized as a decrease in all colour parameters, except a* which increased with storage. Measurement of L* showed that only fruit at 16% moisture content and stored at T ≤ 10 °C retained their original colour. The rate of change in overall colour was observed in the following order at 20 °C, 20% > 18 > 16% moisture content. Fruit with 18 and 20% moisture content could be stored at 10 °C for at least 140 weeks without changing their quality grading. Storage at 20 °C shortened this period to 60 and 27 weeks for fruit at 18 and 20% moisture content, respectively.     

Change of Hygienic Quality and Freshness in Tuna Treated with Electrolyzed Water and Carbon Monoxide Gas during Refrigerated and Frozen Storage

ABSTRACT:  Among different fish slices used for sashimi preparation, tuna is the most popular and preferable fish type for Taiwanese people. To improve the hygienic quality of fish slices, electrolyzed (EO) water containing 10, 50, and 100 mg/L chlorine, was used in combination with CO gas treatment. Effect of different treatment on aerobic plate count (APC), volatile basic nitrogen (VBN), K value, and Hunter L*, a*, b* values of yellow-fin tuna steak during storage (4 °C and −20 °C) were evaluated. It was found that APC, VBN, and K values increased with storage time for all treatment. Except for K value, APC and VBN of tuna steak treated with the combination of more than 50 mg/L chlorine EO water and CO gas had the lowest value after 8 d of refrigerated storage. Hunter a* value of tuna steak treated with only CO gas was the highest, followed by those treated with EO water and CO gas. These results demonstrated that EO water containing 50 mg/L chlorine combined with CO gas treatment in tuna fish steak would be an effective method for enhancing the hygienic quality and freshness for tuna meat and extending refrigerated storage time. Tuna treated with EO water containing 100 mg/L chlorine and CO gas combination had the lowest APC immediately after treatment and reduced further to below detection limit after 1 mo frozen storage at −20 °C.     

Osmotic Dehydration of Tomato in Sucrose Solutions: Fick's Law Classical Modeling

ABSTRACT:  Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 °Brix and at 35, 45, and 55 °C. Other experiments were done in a 70 °Brix sucrose solution at 35 °C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and °Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh _s = 1.3 Re ^0.5 Sc _s^0.15 and Sh _w = 0.11 Re ^0.5 Sc _w^0.5, respectively. The effective diffusion coefficients of water (4.97 10⁻¹¹– 2.10 10⁻¹⁰ m²/s) and sucrose (3.18 10⁻¹¹– 1.69 10⁻¹⁰ m²/s) depended only on temperature through an Arrhenius-type relationship.     

Physiology of pre-cut mango. I. ACC and ACC oxidase activity of slices subjected to osmotic dehydration

Physiologically mature mangoes were ripened for 6 days at 24°C and 98% relative humidity. Slices from these fruits were osmotically dehydrated by immersion in sucrose 65°Brix at 30°C and 211 mbar vacuum during 30 min. Slices not subjected to osmotic dehydration (NOD) and slices with osmotic dehydration (OD) were stored at 24, 13 or 5°C. The respiration rate of both slice types was affected by the storage temperature. 1-Aminocyclopropane-1-carboxylic acid (ACC) synthesis indicated activity of ACC synthase in both slices as well as in the whole fruit. ACC oxidase activity was greater in OD slices as compared to NOD and that was associated to better membrane stability. OD favored compaction of external layer in slices. No ethylene was detected in slices; however, the tissues did not lose their ability to synthesize ethylene. Results suggest that OD under vacuum may be beneficial as a pre-treatment of mango slices for longer shelf life under refrigeration.     

超声预处理对真空冷冻干燥猕猴桃片品质的改善作用

目的 以“海沃德”猕猴桃为原料,采用超声预处理改善真空冷冻干燥猕猴桃片的品质。方法 分别采用不同功率（60 W,120 W,180 W,240 W,300 W）和时间（1 min,5 min,10 min,15 min,20 min）的超声波预处理猕猴桃,经真空冷冻干燥制成真空冷冻干燥猕猴桃片,分析真空冷冻干燥果片的水分含量、可溶性糖、可滴定酸、维生素C含量、水分活度、色度等指标,探讨超声预处理对真空冷冻干燥果片品质的影响规律。结果 超声功率为60 W~180 W时,真空冷冻干燥猕猴桃片的含水量提高2.51%~13.70%;超声时间为1 min~10 min时,含水量提高9.23%~11.75%。与空白相比,所有超声组的可溶性糖含量、可滴定酸含量、糖酸比均略有提高,但维生素C含量平均下降9.66%。超声预处理显著降低真空冷冻干燥猕猴桃片的水分活度,60 W~300 W超声组的水分活度下降4.29% ~20.86%;1 min~20 min超声组的真空冷冻干燥猕猴桃片水分活度下降4.91%~15.34%。所有超声组的a*值均下降,显著低于空白,其中300 W超声波使a*值下降25.08%,超声冻干果片颜色更绿。结论 猕猴桃在真空冷冻干燥加工之前,使用功率120 W ~240 W和时间1 min ~5 min超声波进行预处理,有助于改善真空冷冻干燥猕猴桃片的整体品质。     

Effect of different pre-treatments and dehydration methods on quality characteristics and storage stability of tomato powder

Dehydration process was carried out for tomato slices of var. Avinash after giving different pre-treatments such as calcium chloride (CaCl₂), potassium metabisulphite (KMS), calcium chloride and potassium metabisulphite (CaCl₂+KMS), and sodium chloride (NaCl). Untreated samples served as control. Solar drier and continuous conveyor (tunnel) drier were used for dehydration. Quality characteristics of tomato slices viz. moisture content, sugar, titratable acidity, lycopene content, dehydration ratio, rehydration ratio and non-enzymatic browning (NEB) as affected by dehydration process were studied. Storage study was also carried out for a period of 6 months for tomato powder packed into different types of packaging materials viz. metalized polyester (MP) film and low density polyethylene. Changes in lycopene content and NEB were estimated during storage at room temperature. Pre-treatment of 5 mm thickness of tomato slices with CaCl₂ in combination with KMS and drying using a tunnel drier with subsequent storage of product in MP bags was selected as the best process.     

Quality Changes in Fresh-cut Pear Slices as Affected by Cultivar, Ripeness Stage, Fruit Size, and Storage Regime

Fresh-cut fruit slices prepared from partially ripened Bartlett pears had longer shelf life than those from Bosc, Anjou, and Red Anjou pears. Pear fruit ripeness, based on flesh firmness of 44 to 58 N, is optimal for fresh-cut pear slice processing. Pear slices derived from smaller size fruit (122 to 135 g) have greater cut surface discoloration and deteriorate more rapidly than slices derived from larger fruit (152 g). Recently harvested Bartlett pear fruit and whole pears held at –1 °C in a controlled atmosphere of 2%O₂+ 98%N₂ had a longer post-cutting shelf life than those held in air at –1 °C for the same duration. Cut surface browning, flesh softening, and surface dehydration of the slice cut surface were all contributors to loss of product quality.     

Structural properties of dehydrated products during rehydration

The following structural properties of dehydrated apple, banana, carrot and potato were examined during rehydration: true density, apparent density, porosity and specific volume. Samples were dehydrated using five different drying methods: conventional, vacuum, freeze, microwave and osmotic; after which they were rehydrated in an air dryer at 50 °C and 80% air humidity. Structural properties were examined during rehydration to various moisture contents, ranging from 0.01 to 3.5 kg kg^–1 (dry basis). The dehydrated products did not recover their structural properties after rehydration as a result of structural damage that occurred during drying and the hysteresis phenomenon which took place during rehydration. Porosity of the rehydrated products was higher during rehydration than during dehydration. A generalized structural model was used to describe the structural properties, and of the four parameters that were incorporated, only the shrinkage coefficient, which represents volume expansion, changed on rehydration.     

Flavour Changes in Asian White Radish (Raphanus sativus) Produced by Different Methods of Drying and Salting

Asian white radish pieces were dried to < 10% moisture using a hot air drier, a heat pump drier and a freeze drier, and whole roots were partially dried by salting under pressure with sodium chloride. The level of the primary flavor compound, 4-methylthio-3-trans-butenyl isothiocyanate (MTBITC), decreased in all treatments. Freeze-dried white radish showed the lowest loss of about 15% MTBITC. Radish dried with hot air and heat pump driers showed increasing MTBITC loss with increasing drier temperature with a lower loss in the heat pump drier at equivalent temperatures with the rate of drying also faster with the heat pump drier. Osmotic dehydration with salt caused a substantial loss of MTBITC with the loss increasing with increasing salt concentration. Use of 5% salt resulted in the lowest loss of MTBITC while achieving an acceptable rate of water loss.     

Osmotic dehydration of guava: influence of replacing sodium metabisulphite with honey on quality

Guava slices were subjected to pre-treatment by soaking in a solution containing 0.25% (w/v) sodium metabisulphite, 0.5% (w/v) ascorbic acid, 1% (w/v) citric acid, 1% (w/v) calcium chloride and either 0%, 1% or 3% (v/v) honey. A higher concentration of metabisulphite [0.5% (w/v)], but no honey, was also prepared as a reference. After osmotic dehydration, the guava slices were dried at 60 °C. During 24 weeks of storage, the measured texture values of products indicated that an addition of honey significantly delayed the increase in hardness and cutting work in guava slices compared to other treatments ( P  ≤   0.05). Pre-treatment with 0.5% (w/v) metabisulphite without honey or 0.25% (w/v) metabisulphite with 1% (v/v) honey maintained colour during storage better than with 0 or 3% (v/v) honey. The result showed good agreement with colour score evaluation. Overall results suggested that 1% (v/v) honey was the best pre-treatment condition.     

Influence of osmodehydrofreezing with different sugars on the quality of frozen rambutan

The objective of this research was to study the effect of osmotic pretreatment with different sugars on the quality of frozen rambutan. Rambutan pieces were osmotically dehydrated in 50% sucrose, trehalose and maltitol solutions. The amount of water loss and solid gain during osmotic dehydration were determined. The increase of water loss and solid gain were not significantly different among the syrups ( P  > 0.05). For osmodehydrofreezing, the fruit pieces were immersed for 1 h before freezing at −40 °C with an untreated sample used for comparison. The physical and chemical properties of samples stored at −18 °C for 3, 60 and 120 days were studied. Pretreatment with sucrose received the highest scores in terms of taste, texture and acceptability. The glass transition temperature values of treated samples, especially those treated with trehalose, increased significantly compared to the untreated sample, but they were all much lower than the storage temperature of −18 °C. All of the experimental samples were in a rubbery state, and therefore the glass transition concept could not be used to predict quality.     

Microbial growth and colour of minimally processed shiitake mushroom stored at different temperatures

The effect of storage temperature on the microbiological and sensory characteristics of minimally processed shiitake was investigated. Shiitake mushrooms were washed, sanitised, packed in polystyrene trays, overwrapped with plastic film and stored at 7, 10 or 15 °C. Microbial counts, polyphenoloxidase activity, external lightness ( L* ) and acceptance tests were conducted. Mesophilic, aerobic psychrotrophic bacteria, yeasts and moulds predominated during storage. Pseudomonas was detected after 10 days' storage showing an increase of, approximately, 7 log cycles at 15 °C. Mushroom rejection occurred when the microbial population was lower than 10⁶ CFU g⁻¹, suggesting that, other factors, such as browning, affect mushroom spoilage more than microbial activity. Mushrooms treated with citric or ascorbic acids maintained high L * value during 10 days. The shelf life of minimally processed shiitake mushrooms was 10 days at 7 °C, but less than 5 days at 10 °C, and approximately 3 days at 15 °C.     

Effect of sonication on orange juice quality parameters during storage

Freshly squeezed orange juice was sonicated at various amplitude levels (40%, 70%, 100%), treatment times (2, 6 and 10 min) at a constant frequency of 20 kHz. Samples were stored for periods of up to 30 days at 10 °C. The combined effect of amplitude level, treatment time and storage period on pH, ^oBrix, titratable acidity, colour values ( L* , a* , b* ), non-enzymatic browning (NEB), cloud value and ascorbic acid content were investigated. Second order polynomial models were employed to investigate the effect of independent variables. No significant differences ( P <  0.05) in ^oBrix and titratable acidity were observed. Significant changes were observed in juice pH and colour values. During storage NEB increased while both cloud value and ascorbic acid content decreased. Predictive models developed for colour values, cloud value, NEB and ascorbic acid content were highly significant and were closely correlated to experimental data. Degradation mechanisms are proposed for the key quality parameters.     

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.     

Microbiological quality of ice creams commercialized in some cities in the state of Rio de Janeiro, Brazil

The microbiological quality of 60 ice cream samples of three commercial brands (A, B and C) of various flavours, commercialized in some towns in the State of Rio de Janeiro, Brazil, was evaluated. Total bacteria count (TCB), coliforms at 35°C (CT), coliforms at 44°C (CF) and presence of Staphylococcus aureus were performed on all samples. TCB ranged from 2.0 × 10 ² to 6.9 × 10 ⁵ cfu/mL, CT from < 3–≥ 2400 MPN/mL, CF from < 3–1100 MPN/mL and S. aureus from < 10–1.4 × 10 ⁶ cfu/mL. The level of bacterial contamination found in this study reflects the unhygienic conditions prevalent in manufacturing and storage of ice creams. Actions are thus necessary by the Brazilian regulatory agencies to require the ice cream processing plants to adopt quality guarantee systems, such as good manufacturing practices and hazard analysis and critical control points system.     

Process–quality optimization of the vacuum freeze-drying of apple slices by the response surface method

Summary Working pressure (P) and heating plate temperature (T) were considered to be the most important factors affecting the kinetics of the freeze-drying operation for apple slices as well as the criteria of final product quality (appearance/shape, colour, texture, rehydration ratio). Freeze-drying experiments involving a thick layer of slices under different processing conditions were designed according to a central composite rotatable system with two factors (P, T). Results were analysed by response surface methodology (RSM). By superimposing all quality criteria contour plots, the optimum levels of processing conditions yielding the best quality freeze-dried apple slices were determined to be an operating pressure of 50 Pa, and a heating plate temperature of 55 °C. For a product loading of 17 kg m⁻², the freeze-drying time ranged from 48 to 50 h. The experimental values of the freeze-drying time, appearance and colour of freeze-dried apple slices obtained with these optimal conditions were very similar to those predicted by the corresponding second order polynomial model. The rehydration ratio of freeze-dried apples was about 0.55 g g⁻¹ of water removed and the texture loss of rehydrated apples was estimated to be more than 85%.