Influences of pretreatment and drying methods on composition,micro/molecular structures and some health‐related functional characteristics of dietary fibre powder from orange pulp residues

Influences of pretreatment methods (washing, blanching, soaking in ethanol), drying methods (hot air‐drying, infrared‐drying, microwave‐drying) and drying temperature on selected characteristics of dietary fibre powder from orange pulp residues were investigated. Pretreatments improved the hydration properties, oil‐holding capacity and glucose dialysis retardation index, but led to losses of fibres, decreased α‐amylase inhibitory activity and aflatoxin B₁ adsorption capacity. Hydration properties, oil‐holding capacity and glucose uptake depended on the structure and porosity of the fibre, while the ability to inhibit α‐amylase and AFB₁ adsorption depended more on the content and molecular fingerprinting of the fibre. Drying condition did not significantly affect functional properties of the fibre, except for the ability to uptake glucose, inhibit α‐amylase and adsorb AFB₁ (P ≤ 0.05). Hot air‐drying at 60 °C resulted in fibre with the highest ability to decrease the rate of glucose and AFB₁ adsorption.     

Effects of pretreatment and drying methods on molecular structure,functional properties and thermal stability of fibre powder exhibiting colour from Centella asiatica L.

Effects of pretreatment and drying methods and particle size on characteristics of fibre powder from Centella asiatica L. leaves were investigated. Thermal stability of oil‐based colour solutions was also assessed. Steaming and combined steaming and alkaline soaking resulted in the powder with more greenness and higher chlorophylls contents, while combined steaming and acid soaking yielded dark yellow powder with lower chlorophylls contents. Chemical soaking led to the powder with decreased water holding capacity and solubility. Vacuum‐drying reduced chlorophylls degradation, hence retention of the greenness of the powder. Increased particle size resulted in decreased lightness of the powder, but in increased lightness of the solutions; water and oil holding capacities of the powder increased with the particle size. Fourier transform infrared (FTIR) spectra and X‐ray diffraction (XRD) patterns of the powder corresponded to its colour and functional property changes. Colour of the solutions changed only slightly upon heating at 80 and 180 °C for 1 h.     

Comparative evaluation of microwave‐assisted extraction and preheated solvent extraction of bioactive compounds from a plant material: a case study with cabbages

Preheated solvent extraction (PSE) was evaluated via the analysis of the extraction kinetics, microstructure of extracted samples and energy consumption as alternative to microwave‐assisted extraction (MAE). Cabbage outer leaves and ethanol were used as test material and extraction solvent, respectively. MAE was first optimised in terms of glucosinolates and phenolics yields; total antioxidant activity of the extracts was also assessed. MAE at a specific absorbed power of 0.37 W g^?1 for 9 min was selected as optimum condition to extract glucosinolates and phenolics, while PSE was optimised at 6 min of the extraction. The highest normalised total glucosinolates and phenolic contents as well as antioxidant activities of the extracts obtained via MAE were not significantly different from those obtained via PSE. Confocal laser scanning microscopy revealed no significant differences in cabbage cell damages rendered by MAE and PSE. PSE nevertheless exhibited slightly higher specific energy consumption than MAE.     

Effects of Drying Temperature and Particle Size on Hydration Properties of Dietary Fiber Powder from Lime and Cabbage By-Products

The use of by-products from fruit and vegetable processing plants as sources of dietary fiber and bioactive agents is currently of interest, both from the waste management and from the production of value-added products points of view. This work aimed at studying the use of lime residues and outer leaves of white cabbage to produce dietary fiber powder, which included the study of the product pretreatment and preparation, drying, and grinding dried residues into powder. Dietary fiber content during each processing step was determined to calculate the loss of functionality of the products through the process. Hydration properties, i.e., water holding capacity (WHC) and swelling capacity (SWC), of the two residues were also determined after hot air drying at 60–80°C. The effect of particle size of dietary fiber powder, which was obtained by grinding dried residues, in the range of 63–450 μm, on the hydration properties was also evaluated and discussed.     

Desalination of fish sauce by electrodialysis: effect on selected aroma compounds and amino acid compositions

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.     

Quality changes of shrimp during boiling in salt solution

ABSTRACT:  Boiling shrimp in salt solution is an important step during the production of dried shrimp. In this study the effects of various boiling parameters, namely, concentration of salt solution (2, 3, and 4% w/v), mass ratio of shrimp to salt solution (1:2 and 1:3), boiling time (1, 3, 5, and 7 min), and shrimp size (small and large), on the various quality attributes of shrimp were investigated. The quality of boiled shrimp was evaluated in terms of its salt content, moisture content, which is in turn related to the other qualities, namely, protein content, colors, shrinkage, and texture (hardness and toughness), as well as microbiological quality. It was found that higher concentration of salt solution and longer boiling time and lower mass ratio of shrimp to salt solution led to higher salt content of shrimp but to lower levels of moisture and proteins, leading to higher values of hardness, toughness, shrinkage, and color changes of shrimp. However, the mass ratio of shrimp to salt solution alone did not significantly affect any qualities of boiled shrimp ( P > 0.05). It was found that the minimum boiling time of 3 min was enough to reduce the number of microorganisms to a safe level and inactivate enzymes causing melanosis in boiled shrimp.     

Structural modification by different pretreatment methods to enhance microwave-assisted extraction of β-carotene from carrots

Since the structure of a material is a key factor influencing the extraction efficiency, any means to modify the structure to enhance extraction is attractive. As limited information is available on the effect of sample pretreatment prior to extraction on the extractability of a bioactive compound, the effects of selected pretreatment methods, i.e., soaking in citric acid, blanching in water as well as in citric acid, on the sample structure and subsequent microwave-assisted extraction (MAE) were investigated; carrots and β-carotene (as well as carotenoids) were selected as the test material and bioactive compound, respectively. A suitable condition to extract β-carotene in terms of the microwave power and extraction time was determined. Comparison between MAE and Soxhlet extraction was also made. At the optimized condition the contents of β-carotene and total carotenoids extractable from carrots blanched in water (29.74 and 58.04 mg/100 g dry basis) and in citric acid (32.08 and 61.62 mg/100 g dry basis) were significantly higher than those from the untreated carrots (23.26 and 51.79 mg/100 g dry basis). The antioxidant activities of the extracts obtained from carrots blanched in water and in citric acid were also higher than that from carrots with no pretreatment. Comparison between MAE and Soxhlet extraction revealed that the extract from MAE contained lower amounts of β-carotene and total carotenoids and exhibited lower antioxidant activity; the required MAE time was significantly shorter, however.     

Evolution of mechanical properties of parboiled brown rice kernels during impinging stream drying

Information on mechanical properties of parboiled brown rice kernels upon impinging stream drying, which is important for effective control of kernel fissure and head rice yield, is reported. Experiments were performed at the drying temperatures of 130, 150, and 170°C; inlet air velocity of 20?m/s; impinging distance of 5?cm and paddy feed rate of 40?kg_{dry_paddy}/h. Parboiled paddy was dried for up to seven cycles. Between each drying cycle, the paddy was tempered for a period of either 0 (without tempering) or 30?min. The moisture evaporation rate was noted to be very high during the first two drying cycles and rapidly dropped in the later drying cycles. When tempering was included after a particular drying cycle, the drying rate in a subsequent cycle was higher than without tempering. At the kernel moisture contents immediately after drying of 25.3–47.5% (d.b.), the drying temperature and existence of tempering did not affect the mechanical properties although microcracks were formed in the kernels. However, both factors played a more important role on the mechanical properties when the kernels were evaluated at 16% (d.b.). The head rice yield correlated well with the tensile strength of the kernels.     

Effect of pretreatment on surface topographical features of vegetables during drying

It is well recognized that many adverse changes occur to a food product during drying. Various pretreatment methods have thus been introduced to maintain the quality of the product. Among the various qualities, or properties, of a food product surface characteristics are one of the most important as these affect directly the consumer acceptance of the product. In terms of food safety surface characteristics may also be related to the attachment and hence thermal resistance of pathogenic microorganisms on the product surface. In this study attempt was made to investigate changes of the surface topographical features of vegetables as affected by pretreatment (blanching in hot water or soaking in 0.5-1.5% v/v acetic acid solution) and hot air drying (60 °C); cabbage and spring onion were selected as model vegetables to represent different natural topographical features of vegetables. An image analysis technique was used to monitor the changes of vegetable surfaces after pretreatment and during drying. The surface characteristic changes of vegetables were described quantitatively in terms of the relative roughness factor (R). It was observed that the surface characteristic changes, as affected by both pretreatment and drying processes, could be well monitored by the evolution of the R value.