Non-pretreated Samples Research Articles

Prior denaturation and aggregation of whey proteins: is this a useful strategy for increasing the content of these proteins in UHT high-protein dairy beverages?

UHT treatments applied to dairy products have been associated with modifications on the proteins’ structure that may trigger the occurrence of fouling, sedimentation and/or gelation. These issues are particularly relevant regarding formulated whey protein-rich dairy beverages. In this context, this study aimed to evaluate the impact of a two steps preheating treatment coupled with homogenization (pretreatment) prior to UHT treatment to allow an increase of whey protein concentration in UHT high-protein dairy beverage. The pretreatment was applied to 10% w/w protein formulated beverages displaying casein (CN) to whey protein (WP) ratios of 40:60 and 30:70. The pretreated beverages were compared with non-pretreated beverage containing 50CN:50WP ratio. The applied pretreatment induced the denaturation of around 97.8–99.4% of WP. After UHT treatment, despite the higher concentration of WP, pretreated beverages displayed similar particle size distribution and equivalent or lower sedimentation level than the non-pretreated samples. The present study reveals the potential of the pretreatment for allowing the increase of WP content in UHT treated high-protein beverages. The results reinforce the rationalization of process development as a useful strategy for producing stable high-protein products.

Improved accuracy in pentraxin-3 quantification assisted by aqueous biphasic systems as serum pretreatment strategies

Although pentraxin-3 holds promise as a diagnosis/prognosis biomarker of microbial infections and lung cancer, its analysis in human serum can be constrained by matrix effects caused by high abundance proteins – human serum albumin and immunoglobulin G. Aqueous biphasic systems composed of polymers and citrate buffer are here proposed as a serum pretreatment step to improve the accuracy of pentraxin-3 analysis. Binodal curves were determined to identify the compositions required to form two phases and to correlate the polymers' properties and performance in serum pretreatment and biomarker extraction. Aqueous biphasic systems were evaluated regarding their ability to deplete human serum albumin and immunoglobulin G at the interphase. Polymers of relatively high to intermediate hydrophobicity were unveiled as efficient components to deplete high abundance serum proteins. Considering the possibility to extract pentraxin-3 from human serum into the polymer-rich phase, the system composed of polyethylene glycol with a molecular weight of 1000 g·mol−1 simultaneously achieved >93 % of human serum albumin and immunoglobulin G depletion and complete biomarker extraction. The accuracy of analysis of pretreated human serum by enzyme-linked immunosorbent assays outperformed that of a non-pretreated sample, with a relative error of 0.8 % compared to 14.6 %, contributing to boost pentraxin-3 usefulness as a biomarker.

Microstructural modification of papaya tissue during calcium diffusion: Effects on macrostructure level

The microstructural changes in papaya tissue during calcium diffusion, the effect on drying kinetics and texture parameters were investigated. Calcium pretreatment was applied to papaya samples for 3 h, at a solution concentration of 1.5 g Ca(OH)2/100 mL H2O, and a solution temperature of 25 °C; subsequently, the samples were convectively dried at 70 °C, air flow of 1.5 m/s, and a relative humidity of 5 ± 2%. Calcium content was determined using the Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) technique, the microstructure of the samples was analyzed by High-Resolution Scanning Electron Microscopy (HR-SEM), and the elementary analysis was performed by Energy-Dispersive X-ray Spectroscopy (EDS). Effective diffusivity of calcium (DefCa) and moisture (Defw) were calculated during pretreatment and drying, respectively and texture parameters were determined by double compression using a texturometer. The transport mechanism determined during calcium pretreatment was diffusion with a DefCa = 3.10 × 10−10 m2/s. Also, branched calcium microstructures in the cell walls of tissue were observed due to the calcium effect, it was supported by elemental analysis, which showed an increase of calcium in section restructured compared to non-restructured. During drying, Defw = 1.86 × 10−9 m2/s was higher in pretreated compared to non-pretreated samples with Defw = 1.17 × 10−9 m2/s, indicating a higher drying rate and moisture loss. The texture values changed significantly (α ≤ 0.05) due to calcium pretreatment and drying; the calcium microstructures caused higher cohesiveness, springiness, gumminess, and chewiness. Calcium modifies the microstructure and composition of papaya tissue; therefore, drying kinetics and texture parameters depend on this modification.

Effect of surfactant assisted ultrasonic pretreatment on production of volatile fatty acids from mixed food waste

In this study, the potential effect of surfactant assisted ultrasonic pretreatment on mixed food waste was investigated. Surfactants, such as Rhamnolipid, Sodium dodecyl sulfate; Glucopon and Triton X 100 were evaluated in this work. Among them, the maximum solubilization of chemical oxygen demand of 45.5 % and the highest release of soluble COD of 31 g/L were observed for ultrasonication assisted by Triton X 100 at a dose of 0.01 g/g TS in 30 min. The presence of a surfactant also reduced 27.5 % of energy demand when compared to ultrasonic pretreatment alone. Compared to the non-pretreated samples after anaerobic digestion, ultrasonication assisted by Triton X 100 led to 95 % increase of volatile fatty acid titers and 83 % increase of carbon conversion efficiency. Thus, sonication with the addition of Triton X 100 was proven to be highly effective toward increasing digestibility of and yield of volatile fatty acid from mixed food waste.

Effect of Osmotic Dehydration Pretreatment on the Drying Characteristics and Quality Properties of Semi-Dried (Intermediate) Kumquat (Citrus japonica) Slices by Vacuum Dryer.

The effect of osmotic dehydration (OD) pretreatments at different temperatures and immersion times on drying characteristics, total phenolic content (TPC), total antioxidant activity (TAA) (DPPH and CUPRAC methods), and color of kumquat slices dried under vacuum conditions (70 °C-100 mbar) was investigated. The OD pretreatment was performed in a sucrose solution (45 °Bx) at the temperatures of 40 and 50 °C and immersed at times of 30, 60, and 90 min. OD before vacuum drying decreased the total required drying time by up to 70 min compared to the control non-pretreated samples. Page, Modified Page, Henderson Pabis, and Two Terms Exponential models were found to satisfactorily describe the drying behavior of thin layer dried kumquat slices. The minimum and maximum values of effective moisture diffusivity (Deff) for semi-dried kumquat slices were 5.04 × 10−8 to 7.19 × 10−8, respectively. OD treatments induced a decline in TPC (5.30–33.92%) and TAA (23.63–59.34% and 4.17–31.67% for DPPH and CUPRAC assays, respectively) of kumquat slices. It was observed that OD pre-treatment can decrease the gross drying time, and make the color and sensorial attributes of dried kumquats better.

Highly digestible nitrogen-enriched straw upgraded by ozone-urea pretreatment: Digestibility metrics and energy-economic analysis

Ozone is a powerful oxidative gas widely used as a green pretreatment to enhance the delignification of cereal straws. Urea pretreatment can enrich straws with nitrogen to make them more accessible to anaerobic microorganisms. This study aimed to evaluate the effect of ozone-urea pretreatment on the digestibility of wheat straw (i.e., physicochemical, nitrogen enrichment, gas production, nutritional value, and surface chemistry). The results of ozone-urea pretreatment were compared with non-pretreated, ozone-pretreated, and urea-pretreated samples. This pretreatment method outperformed the other methods in terms of digestibility metrics. The ozone-urea pretreatment resulted in a 50% reduction in lignin, a 4.2 times increase in crude protein, a 22.5% increase in bonded organic-N, a 2 times increase in 24 h-gas production, and a 43.67% increase in total digestible nutrients compared to the non-pretreated sample. Based on the total digestible nutrients index, one-tonne ozone-urea-pretreated straw would be 70.6 USD cheaper than the non-pretreated one.

Corrosion protection of carbon steel using a combination of Zr conversion coating and subsequent zinc-rich silicate coating with a flake ZnAl alloy

To improve the corrosion protection properties of zinc-rich silicate coatings on steel, zirconium pretreatment loaded with (3-aminopropyl)triethoxysilane (APTES) 0.025 % (v/v) and the partial replacement of spherical zinc by flake ZnAl alloy were investigated. DC polarization and electrochemical impedance spectroscopy (EIS) show that the zirconium pre-treated layer containing APTES improves the corrosion protection of the bare steel. Zinc-rich silicate coatings containing flake ZnAl with and without pretreatment were evaluated by EIS, salt spray test and pull-off test. Pretreatment with a zirconium conversion layer reduces corrosion products and adhesion loss (from 16.53% to 12.54%) while the performance of corrosion protection significantly increased from 2003 Ω.cm2 to 2640 Ω.cm2 in comparison with the non-pretreated samples. The results show that flake ZnAl pigment (5 wt%) significantly improves corrosion resistance and prolongs the duration of cathodic protection of zinc-rich silicate coatings.

Acclimation of cadmium-induced genotoxicity and oxidative stress in mung bean seedlings by priming effect of phytohormones and proline.

In this research, eight local mung bean (Vigna radiata) varieties were analyzed for their performance against two levels of CdCl2 solution (0.3 and 0.5 mM) alone and priming with gibberellic acid (GA3) (100 μM), salicylic acid (SA) (50 μM) and proline (5 mM) solution prior to Cd exposure. Mung bean seedlings were analyzed for disturbance in cytological, morphological, biochemical and enzymatic parameters under cadmium stress. For cytological studies, 48 h grown mung bean seedlings root tips were used to prepare slides and studied for percent mitotic index (MI%) and to calculate percent C-mitosis, laggard, sticky and fragmented chromosomes, pictures were captured by a Nikon camera (DS-Fi 1 Japan) attached with a microscope. One-week grown mung seedlings were studied for growth traits, malondialdehyde (MDA), protein, proline and antioxidant enzymes. ANOVA and DMR test of this research revealed that all the tested mung bean varieties and treatments were significantly different regarding mitotic index and number of chromosomal aberrations. Both the Cd treatments exhibited increased total chromosomal aberrations with different types and a maximum decrease in MI%. In pretreated samples, GA3, SA and proline serve as mitigating agents that reduce mutagenic effects of Cd in mung bean by increasing MI% and decreasing chromosomal aberrations as compared to non-pretreated samples. Both the Cd treatments showed a decrease in all growth traits. Total proteins were also found to be significantly reduced in a dose-dependent manner in all genotypes. Cd treatment increased the activities of all antioxidant enzymes tested. Cd caused oxidative damage as indicated by elevated levels of MDA content in treated samples in comparison to control. Proline content levels were also high in Cd treated seedlings indicating stress. Results demonstrated that pretreatment with phytohormones and proline before Cd were found to improve all morphological parameters, by altering antioxidant enzymes activities along with a decrease in MDA and proline contents as well. It was further noticed that the performance of GA3 was better at 0.3 mM Cd treatment while SA was found to be a good mitigating agent at 0.5 mM Cd stress in all tested mung bean varieties. This research concluded less deleterious effects of Cd on AZRI-2006 while more sensitivity to NM-51 towards Cd. Priming with phytohormones and proline is a user-friendly, economical, and simple mitigation strategy to reduce Cd toxicity in plants and get better yield from contaminated lands.

Pentixafor PET/CT for imaging of chemokine receptor 4 expression in esophageal cancer \u2013 a first clinical approach

BackgroundExpression of CXCR4, a chemokine (C-X-C motif) receptor that plays a central role in tumor growth and metastasis of circulating tumor cells, has been described in a variety of solid tumors. A high expression of CXCR4 has a prognostic significance with regard to overall and progression-free survival and offers a starting point for targeted therapies. In this context, [68]Ga-Pentixafor-Positron Emission Tomography/Computer Tomography (PET/CT) offers promising possibility of imaging the CXCR4 expression profile. We set out to compare a [18F] fluorodeoxyglucose (FDG)-PET/CT and a [68Ga]Pentixafor-PET/CT in (re-)staging and radiation planning of patients with localized esophageal cancer.Materials and methodsIn this retrospective analysis, ten patients, with adeno- or squamous cell carcinoma of the esophagus (n = 3 and n = 7, respectively), which were scheduled for radio (chemo) therapy, were imaged using both Pentixafor and FDG PET/CT examinations. All lesions were visually rated as Pentixafor and FDG positive or negative. For both tracers, SUVmax was measured all lesions and compared to background. Additionally, immunohistochemistry of CXCR4 was obtained in patients undergoing surgery.ResultsFDG-positive tumor-suspicious lesions were detected in all patients and a total of 26 lesions were counted. The lesion-based analysis brought equal status in 14 lesions which were positive for both tracers while five lesions were FDG positive and Pentixafor negative and seven lesions were FDG negative, but Pentixafor positive. Histopathologic correlation was available in seven patients. The CXCR4 expression of four non-pretreated tumour lesion samples was confirmed immunohistochemically.ConclusionOur data shows that additional PET/CT imaging with Pentixafor for imaging the CXCR4 chemokine receptor is feasible but heterogeneous in both newly diagnosed and pretreated recurrent esophageal cancer. In addition, the Pentixafor PET/CT may serve as complementary tool for radiation field expansion in radiooncology.

Changes in chemical and structural composition of sugarcane bagasse caused by alkaline pretreatments [Ca(OH)2 and NaOH] modify the amount of endoglucanase and β-glucosidase produced by Aspergillus niger in solid-state fermentation

The aim of this study was to evaluate the treatment effects of Ca(OH)2 solutions applied at different concentrations (2.5%, 5%, and 7.5%) on the structural and chemical composition of sugarcane bagasse (SCB). The feasibility of using the SCB as a substrate for endoglucanase and β-glucosidase production by Aspergillus niger through solid-state fermentation was also assessed. Sodium hydroxide (NaOH) 5% was used as a positive control/benchmark. Changes in SCB cell wall compositions was determined using 13C solid-state nuclear magnetic resonance. While cellulosic fiber content and the production of endoglucanase (345.01 ± 139 U.gDM−1) increased using Ca(OH)2 as pretreatment for sugarcane bagasse, hemicellulose, lignin, alkyl C and carboxyl C content decreased. Comparisons between pretreated and non-pretreated SCB revealed that the highest values of β-glucosidase (58.18 ± 9.86 U.gDM−1) occurred in non-pretreated samples. The SCB pretreated with NaOH resulted in the highest delignification values (-49.88%) and the greatest hemicellulose remotion (-53.47%). However, this treatment also increased crystallinity index (CI; + 23.61%) in cellulose and showed the lowest endoglucanase (22.79 ± 11 U.gDM−1) and β-glucosidase (4.71 ± 1.44 U.gDM−1) activities. This study claims that cellulose CI, hemicellulose, and other nutrients (e.g., amino acids) are important variables that should be considered along with delignification, in the substrates selection for cellulase production using filamentous fungi.

Frozen strawberry quality enhancement using high hydrostatic pressure and vacuum infusion with pectin methylesterase and calcium chloride solution

Fresh strawberry(Fragaria x ananassa) is a delicious fruit that is an excellent source of micronutrients and an array of beneficial phytochemicals. Emerging technologies like high pressure freezing and thawing have gained interest recently due to their ability to preserve the structure of the food during storage, albeit the possible shortcomings of degradation of texture and sensory quality. In this study, the effects of high hydrostatic pressure freezing and thawing on the physical quality attributes (texture, drip loss and Degree of Methylation(DM)) of strawberry were investigated. Strawberry samples were infused in a vacuum using pectin methyl esterase(PME) and CaCl2solutionat170 hPa pressure for 5 min at room temperature to improve textural integrity; infused with distilled water; and another group of samples further incubated at 40°C for 20 min. Fresh samples and non-pre treated samples were also studied. All the samples were subjected to high pressure freezing and thawing processes at 200 MPa and the effect of the processing conditions on texture were evaluated. The high pressure processed samples were compared with conventionally frozen and thawed samples.Pectin methyl esterase,CaCl2infusion and incubation gave a relative hardness of 1.5 pre treatment compared to water only infused at 0.5.TheCaCl2and PME-infused samples had a higher relative hardness after one day of storage at -18°C compared to non-pretreated and water-infused samples at 0.3 compared to 0.1,respectively. Pretreated, water-infused, and PME withCaCl2-infused samples showed no significant difference in hardness when measured immediately after conventional thawing and high pressure induced thawing HPIT but are the former are a third less hard compared to the latter upon storage after 3 hours and three months. Galacturonic acid per mg of Alcohol insoluble residues AIR sample for the fresh strawberrywas0.002±2.699E-05 and 0.002±1.070E-05molesfor the one-day vs.three months storage,respectively,for samples conventionally frozen and thawed in duplicate experiments.Therefore,a combination of high-pressure shift freezing (HPSF) with PME and CaCl2infusion improved the texture of the strawberry compared to those that were not pretreated,and gained weight by 15%. The PME and CaCl2-infused strawberry showed less degradation than the non-pretreated and water-infused during both long-and short-time frozen storage. Conventional freezing processes caused more degradation compared to HPSF. Degradation of 3 months conventional freezing was comparable to 1-day storage. For frozen storage, enzyme pretreatment combined with high pressure freezing can be used to enhance the quality of strawberry.

Evolution of quality parameters of high pressure processing (HPP) pretreated albacore (Thunnus alalunga) during long-term frozen storage

The aim of this work was to study the application of high pressure processing (HPP) before freezing for maintaining as much as possible the fresh characteristics of albacore steaks after long-term storage. HPP treatments were applied at 200 MPa for 0–6 min. Then, samples were immediately frozen (−20 °C) and stored (−20 °C) for up to 12 months. Once thawed (4 °C; 24 h), weight losses, color, texture, lipid oxidation (TBARS) and salt-soluble protein content were analyzed.After 12 months of frozen storage, 200 MPa for 6 min minimized thawing loss inherent to freezing and frozen storage and decreased TBARS (53.9%) with respect to the control. However, it resulted in changes in color (higher L*, b* and ΔE values) and texture (higher adhesiveness and springiness) and decreased the salt-soluble protein content with respect to non-pretreated samples. Nevertheless, after cooking, there were no differences in color and texture between HPP pretreated fish and the controls.

Physicochemical and nutraceutical properties of tomato powder as affected by pretreatments, drying methods, and storage period

ABSTRACT This study was carried out to evaluate the effect of different pretreatments, drying methods, and storage period on physicochemical and nutraceutical properties of tomato powder. The results revealed that freeze-dried tomato powder showed significantly (p < .05) higher ash, total sugar, reducing sugar, ascorbic acid, lycopene, β-carotene, lightness (L*), redness (a*), and yellowness (b*) values than hot-air-dried samples. However, pH, titratable acidity, and TSS (oBx) showed non-significant difference (p > .05) between hot-air- and freeze-dried samples. Comparing the different pretreatments sodium metabisulphite 1% treated sample (T2) showed highest total sugar, reducing sugar, rehydration ratio, TSS (oBx), lightness (L*), redness (a*) and yellowness (b*) values than non-pretreated samples (T0) and 0.5% ascorbic acid + 0.5% citric acid-treated samples (T1). While T1 showed the highest ascorbic acid, lycopene, and β-carotene contents than T2 and T0. The results obtained indicated that TSS (oBx), pH, total sugar, reducing sugar, rehydration ratio, ascorbic acid, β-carotene, lycopene, and color parameters (L*, a,* and b*) of both freeze-dried and hot-air dried powdered samples showed decreasing trend, while moisture and titratable acidity showed an increasing trend with the advancement of storage period from 0 to 30 days.

The Effect of Ultrasonication Pretreatment on the Production of Polyphenol-Enriched Extracts from Moringa oleifera L. (Drumstick Tree) Using a Novel Bio-Based Deep Eutectic Solvent

Moringa oleifera L. leaves are a plant tissue particularly rich in polyphenolic phytochemicals with significant bioactivities, and there has been significant recent interest for the production of extracts enriched in these substances. The current investigation is aimed at establishing a green extraction process, using a novel eco-friendly natural deep eutectic solvent, composed of glycerol and nicotinamide. Furthermore, sample ultrasonication prior to batch stirred-tank extraction was studied to examine its usefulness as a pretreatment step. Optimization of the extraction process through response surface methodology showed that the maximum total polyphenol yield (82.87 ± 4.28 mg gallic acid equivalents g−1 dry mass) could be achieved after a 30 min ultrasonication pretreatment, but the difference with the yield obtained from the non-pretreated sample was statistically non-significant (p &lt; 0.05). Extraction kinetics revealed that the activation energy for the ultrasonication-pretreated samples was more energy-demanding, a fact attributed to phenomena pertaining to washing of the readily extracted polyphenols during pretreatment. Liquid-chromatography-diode array-mass spectrometry showed that ultrasonication pretreatment may have a limited positive effect on polyphenol extractability, but the overall polyphenolic profile was identical for the ultrasonication-pretreated and non-pretreated samples.

Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution

We propose the treatment of barley straw with 1-ethyl-3-methylimidazolium acetate [EMIMAcO] ionic liquids (ILs) and subsequent precipitation with antisolvent mixtures, thus allowing the separation of the sugar-rich fractions (cellulose and hemicellulose) from the lignin fraction. For this purpose, different concentration ranges of acetone:water antisolvent mixtures were studied. In all cases, a high recovery percentage and a high and effective separation of fractions was achieved for 1:1 acetone:water. The fractionated lignocellulosic compounds were studied by using infrared spectroscopy, scanning electron microscopy and 1H nuclear magnetic resonance characterization techniques. This method allows the possibility of reusing IL, confirming the versatility of the established method. The fraction rich in cellulose and hemicellulose was subjected to acid hydrolysis (0.2 mol/L H2SO4) for 5 h at 140 °C, obtaining a yield of total reducing sugars of approximately 80%, much higher than those obtained in non-pretreated samples.

Simple, insensitive to environmental matrix interferences method of trace cadmium determination in natural water samples

A simple, fast, and inexpensive anodic stripping voltammetric procedure for trace determination of cadmium in natural water samples containing high concentrations of surface-active substances was described. It was proved that interferences from the organic matrix such as surface-active substances could be removed by the addition of Amberlite XAD-7 resin to the analyzed sample prior to the voltammetric measurement. A renewable mercury film silver-based electrode (Hg(Ag)FE) was used as the working electrode. The following optimum conditions were found: 0.1 mol L−1 acetic acid, accumulation potential of − 0.8 V, and accumulation time of 30 s. The linear range of Cd(II) was observed over the concentration range from 5 × 10−8 mol L−1 to 6 × 10−5 mol L−1, with a correlation coefficient equal to 0.997. The detection limit of Cd(II) for preconcentration time of 30 s was 1.3 × 10−8 mol L−1. The proposed procedure was successfully tested for the detection of cadmium in different non-pretreated and non-deaerated real water samples.

Secondary treated domestic wastewater in reverse electrodialysis: What is the best pre-treatment?

Although Reverse Electrodialysis (RED) is most commonly known as a selective separation technology used for the production of sustainable energy, it can also serve as a valuable pre-desalination tool. By coupling RED to Reverse Osmosis (RO) for seawater desalination: (1) sustainable energy is produced in the RED process and (2) seawater is partially desalinated prior to RO thus, decreasing the energy demand. In this study, secondary-treated wastewater is proposed as the low salinity source in RED and suitable pre-treatment techniques for this effluent are investigated. Although it is generally accepted that RED is less prone to fouling than typical pressure driven membrane processes, results showed that pre-treatment is a key to ensure efficient operation of the wastewater-seawater RED. Both 100 µm filtration and rapid sand filtration proved to be suitable, with an increase in pressure drop of only 0.09–0.18 bar and a permselectivity decrease of only approximately 20% during 40 days of continuous operation. Conversely, River bank filtration did not perform better than the non-pretreated sample. As such, 100 µm filtration and rapid sand filtration are considered suitable, robust, and cost efficient pre-treatment options for wastewater fed RED, enabling the improvement of the hybrid process of RED-RO seawater desalination.

Solar Tunnel Drying: Pretreatment on drying kinetic of plum tomatoes

ABSTRACT: Drying of thin layer tomato was studied using a solar tunnel dryer under the ecological conditions of Isparta, Turkey. During drying process, solar irradiation, drying air temperature, relative humidity, and air velocity were measured constantly in different parts of the dryer. Drying runs were performed using plum tomatoes, characterized by an oval shape, intense red color. The change of tomatoes mass was measured daily. The color measurements of dried products were determined at the beginning and end of experiment. In this study, the fresh tomato samples were sorted, graded, washed in water and then sliced into quarters and halves before pretreated. Sun drying behavior of half and quarter sliced tomatoes pretreated with 10% NaCl solution and non-pretreated was investigated. Results showed that the drying time for pretreated and non-pretreated samples was not significantly different. However, drying time and drying rates were affected by number of tomato slices (quarter and half). Drying characteristic curves were evaluated against thirteen mathematical models and the Midilli et al model was the best descriptive model for solar tunnel drying of thin layer tomato. Color analysis emphasized that if tomatoes are pretreated with 10% NaCl solution, they should be sliced in quarter for better quality.

Effects of prefreezing on the drying characteristics, structural formation and mechanical properties of microwave-vacuum dried apple

The effects of prefreezing on the drying rate, internal structure and mechanical properties of apple fruit processed by microwave-vacuum drying (MVD) were evaluated. The drying rate of the prefrozen sample was approximately 1.2–1.3 times higher than that of the nontreated sample. In the frozen-thawed tissue, damage to the cell wall structure and cell membrane due to ice crystal formation during freezing was confirmed; thus, improvement in the drying rate was suggested to be the result of accelerated water transfer in the tissue. Structural observation using X-ray computed tomography showed that the prefrozen MVD sample had a porous internal structure with larger voids than air dried or nonpretreated samples. Alterations in the mechanical properties, such as higher maximum stress and number of peaks during the puncture test, indicating a softer and crisper texture, were observed in the prefrozen MVD sample.

Sonication and grinding pre-treatments on Gelidium amansii seaweed for the extraction and characterization of Agarose

Various pretreatments methods including sonication and grinding were performed on red seaweed Gelidium amansii for the subsequent extraction of agarose. The agarose products are usually extracted from agar powder products from seaweeds. In this study, the agarose was extracted using a direct polyethylene glycol (PEG) method without the need to first process the agar from seaweed. The agar extract was frozen then thawed and mixed directly with PEG solution to precipitate the agarose. The quality of agarose obtained was evaluated through physico-chemical properties analysis which includes spectral technique (FTIR), melting and boiling point, gel strength and sulfate content. These properties were compared with a non-pretreated sample and it was found that the addition of pretreatment steps improved the quality of agarose but gave a slightly lower yield. The gel strength of pretreated samples was much higher and the sulfate content was lower compared to non-pretreated samples. The best pretreatment method was sonication which gave gel strength of 742 g cm-2 and sulfate content of 0.63%. The extraction of agarose can be further improved with the use of different neutralizing agents. Pretreating the seaweed shows potential in improving the quality of agarose from seaweed and can be applied for future extraction of the agarose.