Naphaporn Chiewchan

Effect of Processing on Antioxidants and Their Activity in Dietary Fiber Powder from Cabbage Outer Leaves

It is well known that Brassica vegetables (e.g., cabbage) contain significant amounts of bioactive compounds with high antioxidant activities. Outer leaves of white cabbage (Brassica oleracea L. var. capitata), a typical by-product from a cabbage processing plant, have the potential of being transformed into dietary fiber powder with high levels of antioxidants. However, losses of health-beneficial bioactive compounds in cabbage leaves may occur during processing and should first be identified. This work was aimed at studying the effects of various processing steps, that is, sample preparation, which included sample slicing and blanching using either hot water or steam, as well as hot air drying, on the evolutions of various phytochemicals in cabbage outer leaves. The dominant antioxidants, that is, phenolics (measured in terms of the total phenolic content, TPC), vitamin C, β-carotene, α-tocopherol, and their total antioxidant activity (TAA), were assessed both during sample preparation and drying. The results showed that slicing prior to blanching led to higher losses of antioxidants during either hot water or steam blanching. Water blanching led to lower retention of water-soluble antioxidants; namely, TPC and vitamin C. No significant changes in the contents of β-carotene and α-tocopherol were observed after blanching. The results further illustrated that all antioxidants degraded significantly during drying. This resulted in approximately 50% retention in β-carotene and less than 40% retention in TPC, vitamin C, and α-tocopherol. The final powdery products exhibited a TAA, as assessed by 2,2-diphenyl-2-picryl-hydrazyl (DPPH) and β-carotene bleaching assays, of approximately 70%.

Electrodialysis Desalination of Fish Sauce: Electrodialysis Performance and Product Quality

Fish sauce has a unique, pleasant flavor, but contains high levels of sodium chloride, which is nowadays not desirable for health-conscious consumers. Although many researchers have attempted to solve this problem by substituting sodium with potassium in fish sauce, potassium-based products are still unsuitable for patients with kidney disease. Thus, electrodialysis (ED) desalination of fish sauce was carried out. The rate of salt removal, evolution of total soluble solids, and electrical conductivity of the electrodialysis-treated fish sauce were investigated. Moreover, the system performance in terms of yield, energy consumption, and current efficiency were examined. Density, viscosity, ion concentrations (that is, Na(+), K(+)), total nitrogen, amino nitrogen, and color were investigated at various values of input voltage (6, 7, and 8 V) and remaining salt concentration (22%, 18%, 14%, 10%, 6%, and 2%[w/w]). The results indicated that an increase in the input voltage led to an increase in the rates of salt removal, electrical conductivity, and total soluble solids. The energy consumption increased whereas current efficiency and yield decreased significantly with an increase in input voltage and the salt removal level. Physicochemical properties of the treated fish sauce, in terms of the total soluble solids, density, viscosity, ion concentrations (that is, Na(+), K(+)), total nitrogen, and color were significantly affected by the input voltage and the salt-removal level.

Thermal resistance of Salmonella enterica serovar Anatum on cabbage surfaces during drying: effects of drying methods and conditions.

The effects of selected drying methods, i.e., hot air drying, vacuum drying and low-pressure superheated steam drying (LPSSD), on the heat resistance of Salmonella attached on vegetable surface, which are data that have never been reported elsewhere, were investigated at drying temperatures of 50-70 °C; vacuum drying and LPSSD were carried out at an absolute pressure of 10 kPa. The selected Salmonella serovar, i.e., S. Anatum, was used as a test organism. Cabbage was used as a vegetable model to represent uneven natural surface. The results showed that drying methods had a significant effect on the drying kinetics as well as the destruction rate of Salmonella. Higher drying temperatures resulted in higher destruction rates of S. Anatum. Hot air drying was noted to be the slowest drying process, while vacuum drying and LPSSD could be used to shorten the drying time. By considering the reduction in the number of Salmonella at the end of drying, LPSSD is recommended as it has proved to yield the highest degree of S. Anatum inactivation.

Application of Drying Technology to Control Aflatoxins in Foods and Feeds: A Review

Aflatoxins are secondary metabolites produced by certain species of Aspergillus, i.e., A. flavus, A. parasiticus, and the rare A. nomius, during their growth under favorable conditions of temperature and humidity. Aflatoxins are highly toxic compounds, which can cause acute and chronic toxicity in humans and animals. The incidence of aflatoxins in foods and feeds is relatively high in tropical and subtropical regions, where the warm and humid weather provides optimal condition for the growth of molds. As aflatoxins are very heat stable and cannot be easily eliminated by domestic cooking, rapid drying of agricultural products to reduce their moisture content is important, as this can avoid the favorable conditions for the growth of fungi. This article reviews general information on aflatoxins, products prone to be contaminated with aflatoxins, and the use of different drying techniques to control mold growth and aflatoxins production, as well as to reduce the contamination level of aflatoxins in food products.

Effects of Pretreatment and Drying on Composition and Bitterness of High-Dietary-Fiber Powder from Lime Residues

Lime residues after juice extraction were used as a starting raw material to produce high-dietary-fiber powder. The effects of pretreatment—i.e., blanching and ethanol soaking (55–95% v/v)—and hot air drying at 60–100°C on the proximate composition and limonin, a substance responsible for bitterness in citrus fruits, were evaluated. Hydration properties—i.e., water retention capacity and swelling capacity—and visual color were also determined. It was found that using selected pretreatments in combination with the drying process caused significant effects on dietary fiber contents and visual color. The higher reduction in limonin contents was observed for the samples having subjected to higher ethanol concentration and higher drying temperature. Blanching and ethanolic pretreatment also improved the water retention and swelling properties of the final product.

Effects of drying temperature and surface characteristics of vegetable on the survival of salmonella.

The heat resistance of Salmonella Anatum inoculated on the surface of a model vegetable as affected by hot-air drying temperature (50 to 70 degrees C) and surface characteristics was determined in this study. Cabbage was selected as a model vegetable to demonstrate the effect of topographical feature of vegetable surface on the Salmonella attachment ability. An image analysis technique was developed to monitor the change of cabbage surface during drying and the specific surface characteristics were described in terms of the roughness factor (R). It was found that the water activity of the vegetable decreased while R-value increased with longer drying time and higher drying temperature. However, the changes of both parameters during drying did not show a significant effect on the susceptibility of Salmonella attached on the cabbage surface. Drying temperature was found to be a major factor influencing the heat resistance of Salmonella during drying.

Natural colorants: Pigment stability and extraction yield enhancement via utilization of appropriate pretreatment and extraction methods

ABSTRACT Natural colorants from plant-based materials have gained increasing popularity due to health consciousness of consumers. Among the many steps involved in the production of natural colorants, pigment extraction is one of the most important. Soxhlet extraction, maceration, and hydrodistillation are conventional methods that have been widely used in industry and laboratory for such a purpose. Recently, various non-conventional methods, such as supercritical fluid extraction, pressurized liquid extraction, microwave-assisted extraction, ultrasound-assisted extraction, pulsed-electric field extraction, and enzyme-assisted extraction have emerged as alternatives to conventional methods due to the advantages of the former in terms of smaller solvent consumption, shorter extraction time, and more environment-friendliness. Prior to the extraction step, pretreatment of plant materials to enhance the stability of natural pigments is another important step that must be carefully taken care of. In this paper, a comprehensive review of appropriate pretreatment and extraction methods for chlorophylls, carotenoids, betalains, and anthocyanins, which are major classes of plant pigments, is provided by using pigment stability and extraction yield as assessment criteria.

Desalination of Fish Sauce by Electrodialysis: Effect on Selected Aroma Compounds and Amino Acid Compositions

UNLABELLED Fish sauce is an ingredient that exhibits unique flavor and is widely used by people in Southeast Asia. Fish sauce, however, contains a significant amount of salt (sodium chloride). Recently, electrodialysis (ED) has been successfully applied to reduce salt in fish sauce; however, no information is available on the effect of ED on changes in compounds providing aroma and taste of ED-treated fish sauce. The selected aroma compounds, amino acids, and sensory quality of the ED-treated fish sauce with various salt concentrations were then analyzed. The amounts of trimethylamine, 2,6-dimethylpyrazine, phenols, and all carboxylic acids except for hexanoic acid significantly decreased, whereas benzaldehyde increased significantly when the salt removal level was higher. The amounts of all amino acids decreased with the increased salt removal level. Significant difference in flavor and saltiness intensity among ED-treated fish sauce with various salt concentrations, as assessed by a discriminative test, were observed. PRACTICAL APPLICATION Information obtained in this work can serve as a guideline for optimization of a process to produce low-sodium fish sauce by ED. It also forms a basis for further in-depth sensory analysis of low-sodium fish sauce.

Effects of Acetic Acid Pretreatment and Hot Air Drying on Resistance of Salmonella on Cabbage Slices

The heat resistance of Salmonella anatum inoculated onto the surface of cabbage slices as affected by acetic acid pretreatment (0.5–1.5% v/v) and hot air drying at 50–60°C was investigated. Approximately 1.5 log10 of Salmonella numbers was reduced after soaking the vegetables in acetic acid solution. The inhibitory effect of acetic acid on the bacteria was more pronounced during drying. The heat resistance of Salmonella on the cabbage surface treated with acetic acid decreased considerably compared with untreated cabbage. Moreover, the vegetable treated with higher acetic acid concentration resulted in a higher degree of acid injury and hence increased the susceptibility to heat during drying. The results revealed that acetic acid pretreatment may be used as an additional processing step to increase the safety margin of dried vegetable products.

Composition Profiles and Functional Properties of Dietary Fiber Powder from Lime Residues: Effects of Pretreatment and Drying Methods

Lime residues after juice extraction have proven to be a potential raw material for producing dietary fiber (DF) powder due to their good functional properties. Compositions and antioxidant activity of DF powder from lime residues as affected by selected pretreatment (hot-water blanching and ethanolic soaking) and drying methods, viz. hot air drying, vacuum drying, and low-pressure superheated steam drying (LPSSD) at 60–80°C, were investigated. Fresh lime residues contained significant amounts of vitamin C, phenolic compounds, and flavonoids. Hesperidin was a major flavonoid and only one polymethoxyflavone (i.e., tangeretin) was detected in small amounts. A decrease in the amount of interested bioactive compounds and their antioxidant activity was noted at almost all steps of processing. Higher retention of bioactive compounds was noted when the residues were subject either to vacuum drying or LPSSD; the total antioxidant activities were 61–62% and 81–82% when being assessed by the β-carotene bleaching and DPPH assays, respectively. Vacuum drying at 80°C was the most suitable condition for preparing DF powder from lime residues due to its short required drying time and its ability to retain bioactive compounds. The in vitro analyses imply that DF powder prepared by vacuum drying at 80°C has the potential to reduce blood glucose and cholesterol levels by exhibiting high glucose retardation index (GRI) and bile acid retardation index (BRI).