Drying Techniques (drying + techniques)

Distribution by Scientific Domains


Selected Abstracts


A two-stage convective air and vacuum freeze-drying technique for bamboo shoots

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2005
Yanyang Xu
Summary To obtain dehydrated bamboo shoot slices of high quality, a two-stage hybrid method of drying was tested to see if it could be cost-effective. While freeze-drying provides the best quality bamboo shoot it is a very expensive process. In this study, the drying techniques (a) hot airflow drying followed by vacuum freeze drying and (b) the reverse of the process (a) were examined. The quality of bamboo shoots dried by process (b) was found to be approximately equal to that of freeze-dried bamboo shoots but at a significantly lower cost. This paper reports results comparing the two processes in terms of energy consumption and the physico-chemical properties of the dried bamboo. [source]


PHYCOCYANIN CONTENT OF SPIRULINA PLATENSIS DRIED IN SPOUTED BED AND THIN LAYER

JOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2008
E.G. OLIVEIRA
ABSTRACT The aim of this work was to study the drying of Spirulina platensis, evaluating the final product characteristics about its phycocyanin content and its protein solubility in water. Two drying techniques were used: the spouted bed and the thin layer. For drying in a spouted bed, the cone-cylindrical geometry was chosen, namely type conventional spouted bed (CSB) and jet-spouted bed, with a paste concentration of 5%. The thin-layer drying was performed at temperatures of 50 and 60C, with a load of material of 4 kg/m2 in the tray. The spouted bed dryer type CSB demonstrated good functionality, not presenting a collapse during the experiments. The solubility in aqueous mean was similar in all the drying techniques used, being the values found around 37%. The largest phycocyanin values were found in the thin-layer temperature of 50C and in the spouted bed type CSB; however, the thin layer was excluded so as not to reach the commercial moisture content. PRACTICAL APPLICATIONS Phycocyanin is the major phycobiliprotein in Spirulina. Phycocyanin has significant antioxidant, anti-inflammatory, hepatoprotective and radical scavenging properties. It is used as colorant in food and cosmetics. It was also shown to have therapeutic value (immunomodulating activity and anticancer activity). The drying operation is commonly used to prolong the shelf life of microbial biomasses. Preservation of cyanobacteria is a difficult process, since the cells are small and, moreover, the cultures are usually diluted. Drying of liquids and pastes in spouted beds with inert bodies has been presented as an alternative to spray drying in an attempt to obtain high-quality powdered products at a low cost. [source]


CONCENTRATION BOUNDARY CONDITIONS IN THE THEORETICAL ANALYSIS OF CONVECTIVE DRYING PROCESS

JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2007
AHMET KAYA
ABSTRACT In the theoretical analysis of convective drying process, two boundary conditions are common for concentration: constant concentration and convection. In this study, these two boundary conditions were comparatively examined by comparing theoretical results obtained with regard to experimental ones. Pumpkin (Cucurbita pepo) was considered as the product to be dried while air was the drying medium. The drying characteristics of pumpkin were determined for various values of drying air parameters, including temperature, velocity and relative humidity. Sorption isotherms of the dried pumpkin were also determined for different temperatures and water activities. The values of the effective moisture diffusivity, Deff, and the convective mass transfer coefficient, hm, were predicted, and these values were found to agree fairly well with those available in the existing literature. PRACTICAL APPLICATIONS Convective drying as well as other drying techniques are used in order to preserve and store agricultural products for longer periods by removing some of their moisture content. Drying is a complicated process involving simultaneous heat and mass transfer under transient conditions. Understanding the heat and mass transfer in the product will help to improve drying process parameters and hence the quality. [source]


Effect of Maturity Stages and Drying Methods on the Retention of Selected Nutrients and Phytochemicals in Bitter Melon (Momordica charantia) Leaf

JOURNAL OF FOOD SCIENCE, Issue 6 2009
Min Zhang
ABSTRACT:, The purpose of this study was to investigate the nutrient and phytochemical composition of bitter melon leaves under varying maturity levels and drying techniques. Fresh, oven-dried, and freeze-dried leaves were evaluated over 3 maturity stages. In fresh leaves at various stages, crude fat, crude protein, and soluble dietary fiber contents ranged from 4.2% to 13.6%, 6.4% to 23.1%, and 0.04% to 3.50% on dry-weight basis, respectively. The contents of K, Ca, Mg, Fe, and Zn ranged from 1850.8 to 2811.8, 837.4 to 4978.2, 317.3 to 512.4, 8.4 to 16.7, and 4.1 to 5.9 mg/100 g dry-weight basis, respectively. Vitamin C, ,-carotene, and lutein contents ranged from 397.4 to 1275.1, 154.2 to 422.8, and 737.6 to 1304.6 ,g/g dry-weight basis. The major flavonoids and phenolic acids were rutin, gentistic acid, and,o -coumaric acid, which ranged from 7.57 to 12.75, 2.53 to 10.11, and 4.24 to 9.75 mg/g dry-weight basis, respectively. In oven-dried samples, 40.2% to 52.3% of vitamin C, 35.4% to 55.4% of ,-carotene, 25.6% to 71.6% of lutein, 26.4% to 84.0% of rutin, trace to 11.4% of gentistic acid, and 7.4% to 46.6% of,o -coumaric acid were retained, while the retainment ratios of these components in freeze-dried samples were 84.7% to 99.0%, 76.4% to 99.3%, 90.4% to 96.1%, 39.8% to 99.3%, 24.1% to 68.4%, and 75.8% to 87.0%, respectively. The data showed that freeze-drying better preserves the nutrient and phytochemical quality of bitter melon leaves in comparison to oven-drying. Bitter melon leaf is a rich source of selected nutrients and phytochemicals. [source]


Terahertz spectroscopy to identify the polymorphs in freeze-dried mannitol

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2010
Reshmi Chakkittakandy
Abstract We show how terahertz time-domain spectroscopy (THz-TDS) in the range from 0.1 to 7.5,THz can be used to identify the polymorphs of Mannitol, a frequently used excipient in the freeze drying industry. The results are subsequently used to study the effect that different freeze drying techniques have on the formation of these polymorphs. We find that, depending on the freeze-drying technique, the Mannitol either crystallizes in the , form, or in a mixture of both the , form and the , form. The results are in agreement with conventional X-ray diffraction measurements used to identify the polymorphs. 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:932,940, 2010 [source]