Effect of drying methods on the physical properties and microstructures of mango (Philippine ‘Carabao’ var.) powder

Mango powders were obtained at water content below 0.05 kg water/kg dry solids using Refractance Window® (RW) drying, freeze drying (FD), drum drying (DD), and spray drying (SD). The spray-dried powder was produced with the aid of maltodextrin (DE = 10). The chosen drying methods provided wide variations in residence time, from seconds (in SD) to over 30 h (in FD), and in product temperatures, from 20 °C (in FD) to 105 °C (in DD). The colors of RW-dried mango powder and reconstituted mango puree were comparable to the freeze-dried products, but were significantly different from drum-dried (darker), and spray-dried (lighter) counterparts. The bulk densities of drum and RW-dried mango powders were higher than freeze-dried and spray-dried powders. There were no significant differences (P ? 0.05) between RW and freeze-dried powders in terms of solubility and hygroscopicity. The glass transition temperature of RW-, freeze-, drum- and spray-dried mango powders were not significantly different (P ? 0.05). The dried powders exhibited amorphous structures as evidenced by the X-ray diffractograms. The microstructure of RW-dried mango powder was smooth and flaky with uniform thickness. Particles of freeze-dried mango powder were more porous compared to the other three products. Drum-dried material exhibited irregular morphology with sharp edges, while spray-dried mango powder had a spherical shape. The study concludes that RW drying can produce mango powder with quality comparable to that obtained via freeze drying, and better than the drum and spray-dried mango powders.     

Studies on the effects of microwave drying and cabinet tray drying on the chemical composition of volatile oils of garlic powders

Garlic cloves in the form of bits were dried in a cabinet tray dryer and a microwave dryer, and pulverized to obtain free flowing powder. The volatile oil was obtained by hydro-steam distillation method. Fresh cloves and the powders resulting from the two drying methods were used for obtaining the volatile oil, which was analyzed by GC-MS. The studies were mainly restricted to comparing the effect of drying methods on the volatile oil composition of the powders. Although the drying time was reduced considerably from 8 h in a cabinet dryer to 0.25 h in a microwave dryer, essential oil yield and color values were lower, and flavor quality varied considerably. The relative concentrations of major peaks such as diallyl disulfide, diallyl tetrasulfide increased in both the drying methods, and it was more so in microwave-dried samples. However, the concentrations of the other two major peaks, diallyl trisulfide and allyl methyl trisulfide, decreased in both drying methods, and they were lower in microwave-dried samples. Hunter values of L and b were lower for samples obtained by microwave drying as compared to those of cabinet-dried samples.     

带式连续真空干燥加工香蕉粉的工艺研究

利用国产设备(GZD-S型)带式连续真空干燥设备为平台,以香蕉为原料,研究在连续式真空干燥的条件下,加热板温度、真空度、进样量、输送带前进速度等因素对物料干燥的影响,优化了关键工艺,为生产香蕉粉及连续真空干燥生产其他产品提供了基本参数。     

Quality Retention in Strawberry and Carrot Purees Dried with Refractance WindowTM System

ABSTRACT: The quality retention characteristics of strawberry and carrot purees dried using the Refractance Window^TM (RW) drying method were evaluated against freeze drying, drum drying, and spray drying methods. Ascorbic acid retention of the strawberry purees (94.0%) after RW drying was comparable to 93.6% in freeze-drying. The carotene losses for RW drying were 8.7% (total carotene), 7.4% (α-carotene), and 9.9% (β-carotene), which were comparable to losses of 4.0% (total carotene), 2.4% (α-carotene), and 5.4% (β-carotene) for freeze-dried carrot purees. The color of the RW-dried carrot purees was comparable to fresh puree. For RW-dried strawberry purees, the color retention was comparable to freeze-dried products. RW drying altered the overall perception of aroma in strawberries.     

Process optimisation and physicochemical characterisation of potato powder

Samples of two potato cultivars (Agria and Merit), cultivated either conventionally or organically, were analysed to evaluate their suitability to transformation into powder. Agria cultivar potatoes from the conventional farming were selected as the most suitable for drying process both for their high-dry matter and good nutritional value. Blanching resulted in the most effective treatment to prevent potato browning. The potato powder was obtained by means of a drum dryer using different process parameters (temperature, time and product thickness) to minimise thermal damage on the final product. The effects of these different processes were evaluated by analysing some quality indicators, as final moisture, nutrients (carbohydrates, proteins and amino acids) and colour of the powder, and rheological properties of the rehydrated puree. The results of such analyses showed that the lower the process temperature, the better the powder quality.     

滚筒干燥数学模拟的研究进展

滚筒干燥机因其操作简便、适应性广、热效率高、干燥时间短而被广泛应用于食品工业中.以经验为基础的滚筒干燥工艺不能满足生产需要.建立滚筒干燥过程的数学模型有助于优化工艺参数、提高产品质量、改进滚筒干燥机设计.本文对滚筒干燥原理及其传热传质机理进行了概述,重点介绍了滚筒干燥过程数学模拟的研究进展,并通过对文献的分析总结,对数...     

滚筒干燥技术与应用

<正> 滚筒干燥技术是一项历史悠久的连续式间接干燥技术。与直接干燥技术相比较,滚筒干燥技术不会对车间造成粉尘污染。 技术原理 滚筒干燥技术的基本操作原理是将料浆均匀地分布于以蒸汽加热的滚筒表面,形成一层薄膜,料浆随即迅速被蒸发掉,然后利用以液压控制的刮刀将薄     

Wärme- und Stoffaustausch-Probleme bei der Herstellung von Lebensmitteln auf Walzentrocknern

Problems of Heat and Mass Exchange at the Manufacturing of Foodstuffs on Drum Dryers The drum dryer as contact dryer will be presented by means of several drying characteristics. Bases on these experiences there will be demonstrated possibilities of influencing the heat and mass exchange on the drum dryer in respect to a conserving drying by variation of the operation conditions, as drum speed, feeding temperature and air flow. Especially the exhaust of vapours by means of particular devices, as casing of the drying zone, has an important influence on the evaporation capacity respectively on the heat transmission coefficient. In addition to an improved quality of the final product with the improved process it can be demonstrated a better efficiency by saving of investment by a better exploitation of the available drying surface. Additional vapours exhaustion devices have stood the test on drum dryers with high speed and can be recommended there particularly.     

Moisture sorption characteristics and glass transition temperature of apple puree powder

The aim of this study was to characterise the influence of different foam‐mat‐drying methods on the moisture sorption characteristics and glass transition temperatures of apple puree powder. Apple puree was foamed with the addition of 2.5% egg albumin and 0.5% methylcellulose. Convective air‐drying and microwave‐drying techniques were used. Also foamed puree with and without maltodextrin (6% or 15% w/w) was freeze‐dried. Moisture equilibrium data of powders were determined by using a static desiccator method in a water activity range of 0.0–0.903. Modulated differential scanning calorimetry (MDSC) was used to obtain the glass transition temperature. No effect of drying method on sorption properties and glass transition temperatures of apple puree powders was observed. The addition of maltodextrin to the apple puree caused an increase in T_g by 10–30 °C depending on the amount of incorporated additive. Addition of maltodextrin significantly reduced the hygroscopicity of apple puree powders.     

Drum Drying of Tropical Sweetpotatoes

A process for the manufacture of instant drum dried flakes from the tropical sweetpotato ( Ipomoea batatas ) grown in South Florida and the Caribbean area was evaluated. The effects of sodium acid pyrophosphate, citric acid and sodium metabisulfite added to the puree before drum drying for control of nonenzymatic (after-cooking) darkening of the flakes were determined. Sodium acid pyrophosphate and citric acid prevented discoloration of the reconstituted flakes. Alpha-amylase treatment resulted in improved puree drying characteristics and in increased bulk density and water soluble solids of the dry flakes.     

Influence of different drying methods on carotenoids and capsaicinoids of paprika (Cv., Jalapeno)

Influence of Refractance Window™ Drying (RWD), a novel contact drying method, on carotenoids, capsaicinoids, Retinol Activity Equivalent (RAE) and Scoville Heat Unit (SHU) of paprika (Cv., Jalapeno) was investigated in comparison with freeze drying (FD), oven drying (OD), and natural convective drying (NCD) methods. Eight carotenoids (capsanthin, capsorubin, capsolutein, β-carotene, β-cryptoxanthin, mutatoxanthin, violaxanthin and zeaxanthin) and five capsaicinoid analogues (capsaicin, dihydrocapsaicin, homodihydrocapsaicin, isodihydrocapsaicin, nordihydrocapsaicin) were identified in paprika. All these components were significantly (P < 0.05) decreased by the RWD, FD and OD methods. However, due to ongoing synthesis, the NCD method resulted in higher carotenoids, except violaxanthin and mutatoxanthin, and capsaicinoids content than those of the others, even puree. Mutatoxanthin, naturally occurring pigment in red pepper, could only be detected in FD paprika. The highest RAE and SHU values, which were derived from the data of carotenoids and capsaicinoids, respectively, were also determined in NCD paprika.     

ENERGY UTILIZATION AND MICROBIAL REDUCTION IN A NEW FILM DRYING SYSTEM

Experiments were conducted with pureed pumpkin to evaluate energy efficiency and microbial reduction effect of a new thin-film Refractance Window^TM (RW) drying method. The RW drying system was designed based on a novel concept that uses hot water circulating beneath and in contact with a transparent plastic conveyor belt on which a thin film of puree is dried. In the energy study, water temperature, water circulation velocity, puree temperature, and puree moisture content were determined. In both pilot and commercial scale RW dryers with circulating water at 95C, drying of pumpkin puree from 80% to 5% moisture content (wb) was achieved in less than 5 min. The Refractance Window^TM dryer demonstrated 52% to 70% energy efficiency. The pilot scale unit was used to evaluate the effect of RW drying on microbial reduction. At a circulating water temperature of 95C, RW drying of inoculated pumpkin purees resulted in at least 4.6, 6.1, 6.0, and 5.5 log reductions of total aerobic plate counts (APC), coliforms, Escherichia coli, and Listeria innocua, respectively.     

滚筒干燥技术及其在变性淀粉生产中的应用

对滚筒干燥机进行分类,简述其干燥原理。最后重点介绍滚筒干燥机在预糊化淀粉、羧甲基淀粉、接枝淀粉等几种变性淀粉生产中的应用。     

Processing of pigmented‐flesh potatoes (Solanum tuberosum L.) on the retention of bioactive compounds

Retention of bioactive compounds in white‐ (WFP), yellow‐ (YFP), red‐ (RFP) and purple (PFP)‐fleshed potatoes after drum‐drying (DD) and Refractance Window? drying (RW) was compared with freeze‐drying (FD). Processing, generally, did not influence total phenolics. Total carotenoid was high in YFP, but decreased with DD. Both DD and RW decreased lutein concentration in YFP. The RFP and PFP had the highest total anthocyanin, and their concentrations were decreased by DD. RW decreased total anthocyanin in PFP only. Total antioxidant activity in WFP was higher with DD but lower with RW. In contrast, DD and RW drying had no significant effect on total antioxidants in YFP, RFP and PFP. Therefore, drying generally decreased antioxidants, with FD and RW retaining the highest concentration of bioactive compounds.     

A PROCESS FOR PRODUCING DEHYDRATED PUMPKIN FLAKES

Single strength pumpkin puree is difficult to drum dry due to its low solids content. It was found in this investigation that the rate of dehydration and quality of the finished product were improved by the addition of corn syrup solids and starch to the puree in amounts sufficient to raise the total solids to around 16%. The quality of pies made from flakes containing added starch and corn syrup solids was also improved over those made from unmodified single strength pumpkin puree. Best results were obtained with pumpkin flakes containing approximately 46% pumpkin solids, 38% corn syrup solids and 16% starch. Based on the average overall acceptable drying conditions and product quality, a ratio of 1 part starch to 2.5–3.0 parts corn syrup solids appeared to be in the optimum range.     

Effects of spray drying on antioxidant capacity and anthocyanidin content of blueberry by-products

The effect of spray drying on degradation of nutraceutical components in cull blueberry extract was investigated. Samples collected before and after spray drying were tested for antioxidant capacity using oxygen radical absorbance capacity (ORAC(FL) ) and total phenolics; and for individual anthocyanidins. In Study 1, four different levels of maltodextrin (blueberry solids to maltodextrin ratios of 5: 95, 10: 90, 30: 70, and 50: 50) were spray dried a pilot-scale spray dryer. There was significantly higher retention of nutraceutical components with increased levels of maltodextrin indicating a protective effect of maltodextrin on the nutraceutical components during spray drying. In Study 2, the air inlet temperature of the spray dryer was kept constant for all runs at 150 °C, with 2 different outlet temperatures of 80 and 90 °C. The degradation of nutraceutical components was not significantly different at the 2 selected outlet temperatures. ORAC(FL) reduction for blueberry samples after spray drying was 66.3% to 69.6%. After spray drying, total phenolics reduction for blueberry was 8.2% to 17.5%. Individual anthocyanidin reduction for blueberry was 50% to 70%. The experimental spray dried powders compared favorably to commercial blueberry powders. Results of the study show that use of blueberry by-products is feasible to make a value-added powder. PRACTICAL APPLICATION: Results can be used by producers to estimate final nutraceutical content of spray-dried blueberry by-products.     

Nutritional and rheological characterization of spray dried sweetpotato powder

Spray drying feasibility of sweetpotato puree is enhanced using alpha-amylase treatment to reduce puree viscosity and maltodextrin (MD) addition to facilitate drying. To better determine potential applications of powders produced with various levels of amylase and MD, nutrient composition and rheological properties of the hydrated spray dried sweetpotato powders were examined and compared with sweetpotato puree. Proximate composition, beta-carotene, vitamin C, and mineral analyses were performed. Steady shear rheology of reconstituted powder solutions was also evaluated at different temperatures and shear rates. Spray drying significantly reduced the β-carotene and ascorbic acid contents. Additionally, the all-trans form of beta-carotene was further transformed to the cis-isomers during dehydration. The viscosity of the reconstituted solutions was much lower than that of the puree at the same solid concentration. Rheologically, the reconstituted sweetpotato slurries behaved similarly to pregelatinized starch solutions. Thus, spray dried sweetpotato powders have a potential to enhance food systems as a thickener despite the need for increased nutrient retention.     

A new technique for spray drying orange juice concentrate

A new technique for spray drying concentrated orange juice using dehumidified air as drying medium and maltodextrin as drying agent was developed. A pilot-scale spray dryer was employed for the spray drying process. The modification made to the original design consisted in connecting the dryer inlet air intake to an absorption air dryer. 21 DE, 12 DE, and 6 DE maltodextrins were used as drying agents. Concentrated orange juice was spray dried at inlet air temperatures of 110, 120, 130, and 140 °C and (concentrated orange juice solids)/(maltodextrin solids) ratios of 4, 2, 1, and 0.25. Data for the residue remaining on the walls were gathered and the powders were analyzed for moisture content, bulk density, rehydration, hygroscopicity, and degree of caking. The combination of maltodextrin addition and use of dehumidified air was proved to be an effective way of reducing residue formation.Industrial relevanceOrange juice powder has many benefits and economic potentials over its liquid counterparts and provides a stable, natural, easily dosable ingredient, which generally finds usage in many foods and pharmaceutical products such as flavoring and coloring agents. However, the dehydration of orange juice is not a simple task. Thus, the objective of this study was to develop a new technique for spray drying orange juice using dehumidified air as drying medium and maltodextrin as drying agent.     

Finding critical variables for food heating

It is important to identify intrinsic critical variables affecting the heating of products in processes aiming to achieve microbiological safety. The Taguchi method has enabled the identification of critical variables for heating of a complex canned product (spaghetti in a sauce) in an agitated process in a water immersion retort. Within the ranges tested one of eleven variables exerted a large effect upon product heating. The most important variable was the concentration of tomato puree in the sauce, which affected the process F ₀ by15–18 min between the two concentrations tested.     

OPTIMIZATION OF GUAVA JUICE AND POWDER PRODUCTION

Enzyme treatment of guava puree was optimized for yield and clarity by first determining the most effective concentration, then varying both incubation time and temperature. Application of Pectinex Ultra SP-L® was optimal using 700 ppm enzyme for 1.5 h at 50C. Clarified guava juice was clearer (89.6%) when prepared using ultrafiltration (MW cut-off 40–60 kDa) rather than plate and frame filtration (82.8%); however, the latter was higher in both soluble solids and ascorbic acid. Clarified guava juice powders were made using freeze-drying, spray drying and tunnel drying. The freeze-dried product had superior quality; however, the spray-dried product was stable and may be more economical. Sensory panelists ranked the cloudy juice prepared from aseptic guava puree highest, and there were no significant differences between the juices from pasteurized, clear nectar, freeze-dried puree powder or juice powder.