Freeze-dried Gum Research Articles

Characterization of Khaya Senegalensis Gum: Effects of Drying Methods on the Physicochemical Properties

The study was aimed to assess the effect of drying methods on physicochemical properties of Khaya senegalensis gum. Gum exudates obtained from the bark of Khaya senegalensis plant was extracted and subjected to freeze drying and vacuum oven drying. Gel permeation chromatography, Elemental analysis, attenuated total reflectance Fourier transforms Infra red spectroscopy were used to characterize the gum. The effect of drying methods on the gum samples were assessed based on Differential scanning calorimetry, Scanning electron microscopy, Dynamic vapour sorption, particle size analysis via laser diffraction techniques, colour and density measurements. An average molecular weight of 60 KDa expressed as the Dextran equivalent and a polydispersity of 2.17 with a retention time of 18,485 min was recorded for the vacuum dried gum. The vacuum dried gum occurred as irregular discreet coarse particles, containing both amorphous and crystalline portions due to a glass transition of 65◦ and melting temperature of 182.35◦C. It also displayed excellent flow and compressibility properties whereas the freeze-dried gum appeared flaky, porous with large surface area. The mechanism of water sorption was found to be initial surface adsorption and subsequently bulk absorption for both freeze dried and vacuum dried gum samples. The coarseness, water sorption and retention ability of the vacuum dried gum provides a potential for its use as a disintegrant in solid dosage formulations whereas the freeze-dried gum will be suitable for use as a binding agent due to its smaller particle sizes that enhanced solubility. Furthermore, the presence of nitrogen in Khaya senegalensis gum structure explains its partial solubility and the azo aromatic group suggests biodegradability and candidature for drug delivery to the colon. Keywords: Khaya senegalensis Gum; Average Molecular Weight; Amorphous; Crystalline; Direct Compression Excipient; Disintegrant 2 Freeze and vacuum dried Khaya senegalensis gum characterization

Extraordinary high preservation of the dispersion state of Au nanoparticles during freeze-thawing and freeze-drying with gum arabic

A series of edible and non-toxic substances were screened for their ability to prevent Au nanoparticles (AuNPs) from undergoing aggregation during both freeze-thawing and freeze-drying at as low an additive concentration as possible. Gum arabic was found to be an ideal choice. The addition of 20 µg/mL of gum arabic greatly inhibited the aggregation of AuNPs during freeze-thawing and -drying, whereas polyvinylpyrrolidone was the next best among the tested substances, with approximately 20% aggregation during freeze-drying at a concentration of less than 200 µg/mL. The zeta potential value of the AuNPs indicated the absence of the specific binding of gum arabic to the AuNPs surface. Surface enhanced infrared spectroscopic (SEIRAS) analyses were conducted for the gum arabic solution, frozen and freeze-dried on the Au particles. The results indicated that, in the frozen state, gum arabic molecules were concentrated in remaining unfrozen liquid on the Au coating without any specific orientation toward the Au surface. In contrast, SEIRAS spectra of freeze-dried gum arabic indicated that carboxylic groups in gum arabic molecules preferentially became closer to the Au surface. Considering these findings, during freeze-thawing, we conclude that the high thickening property of gum arabic gum plays an important role in minimizing the mobility and thus the aggregation of AuNPs in the freeze-concentrated regions between frozen ice crystals. The freeze-drying of a gum arabic solution produces a rigid amorphous matrix that has an affinity for the Au surface. The AuNPs were individually separated and immobilized in the freeze-dried matrix of the gum arabic, resulting in the extraordinary inhibition of their aggregation.

Microstructure and reconstitution of freeze-dried gum Arabic at a range of concentrations and primary drying temperatures

Freeze-drying is an energy intensive unit operation used for the production of dehydrated foods, such as instant coffee and dried fruits, and results in high sensorial, nutritional and reconstitution properties of the final products. Understanding the relationships between operating conditions and product quality is essential to design processes that are energy efficient, whilst producing high quality dried foods.In this work, the properties (microstructure and reconstitution) of freeze-dried gum arabic samples (with initial concentrations ranging between 20 and 60% solids by weight) were evaluated. The materials were dried at three different primary drying shelf temperatures, Ts (−20, −30 and −40 °C).Sample temperatures recorded throughout freeze-drying were close to the pre-set Ts, with the exception of the 60% initial concentration system, where the sample was hotter than the shelf by 10–15 °C, in particular on increasing Ts. This was attributed to a combination of local temperature and pressure conditions that may have resulted in partial melting of the material. For the 20–50% systems, the properties of the freeze-dried materials were mainly affected by the initial concentration of the system, with increasing initial concentration generally resulting in lower porosities (ranging between 20 and 40%) and higher reconstitution times (ranging between 0.5 and 10min for 95% reconstitution). Pores were generally needle-shaped and <200 μm. Large (200–1800 μm), circular pores were observed in high initial concentration systems, and they were dominant in the microstructure of the freeze-dried 60% sample. The presence of these large bubbles was linked to the partial melting of the material, which enabled its expansion and puffing. For the 60% system, primary drying temperature had a profound effect on the properties of the freeze-dried solid, with samples dried at higher temperature showing higher porosity (e.g. 60–70% for Ts=−20°C) and faster reconstitution rates (e.g. 3min for 95% reconstitution at Ts=−20°C).Overall, this study demonstrates the significance of formulation and shelf temperature on the porous structure of freeze-dried samples, which directly influences product performance.

Wheat flour and gum cordia composite system: pasting, rheology and texture studies

Abstract Native and acetylated freeze-dried gum cordia (GC) was replaced at 0, 3, 5 and 10% (w/w) of wheat flour, and their pasting and rheological properties were studied. The pasting data indicated a significant (p≤0.05) increase in peak and final viscosities of blends: especially at higher GC concentrations. The shearing profiles signified an increase in shear stress as a function of shear rate confirming a pseudoplastic behavior of the blends (n<1). The consistency coefficient (K) and flow behavior index (n) were estimated using a power law model where higher ‘K’ values strengthened the pasting data. The activation energies (Ea) calculated by Arrhenius equation were observed between 5.7-7.5 and 5.9-8.4 kJ/mol for native and acetylated gels, respectively. The highest hardness was observed for 10% acetylated GC gel while the same concentration of native GC depicted opposite trend.

Effect of drying methods on rheological and textural properties, and color changes of wild sage seed gum

The effect of different drying methods, oven drying (40–80 °C), freeze drying (−40 °C) and vacuum oven drying (100 mbar, 50 °C) on the rheological and textural properties, and color changes of wild sage seed gum were investigated in this study. The results showed that the apparent viscosity of gum solution (0.6 % w/w), was varied from 0.162 to 0.344 Pa × s (60 s−1), and freeze-dried gum exhibited the highest viscosity value among all dried gums. Standard error (SE) and correlation coefficient (R) methods were selected for carrying out the error analysis due to the best fit model and the Heschel-Bulkley’s model was found the suitable to describe the flow behavior of gum solution over the whole experimental range. The amounts of hardness, stickiness, consistency and adhesiveness of wild sage seed gum gel (3 % w/w) were changed from 45.7 to 78.2 g, 9.8 to 17.0 g, 340.4 to 794.8 g.s, and 91.4 to 159.2 g.s at different drying condition. The rise in temperature had a negative effect on the color changes (high ΔE) and brightness (low L*) of gum solution.

Effect of Different Drying Methods on Rheological and Textural Properties of Balangu Seed Gum

The purpose of the present study was to investigate the effect of different drying methods on the rheological and textural properties and color changes in Balangu seed gum. Three drying methods, including air drying (40–80°C), freeze drying, and vacuum drying, were used. The apparent viscosity decreased from 0.161 to 0.056 Pa s with increasing temperature from 40 to 80°C (shear rate = 60 s−1) and freeze-dried gum exhibited the highest viscosity among all dried gums (0.203 Pa s). Different time-independent rheological models (power law, Bingham, Herschel-Bulkley, Casson, and Vocadlo) were used to fit the experimental data and the results revealed that the Herschel-Bulkley model was the most suitable to describe the flow behavior of Balangu seed gum over the whole experimental range (r > 0.98). The hardness values of air dried Balangu seed gum gels varied from 33.1 to 40.4 g and were significantly lower compared to the freeze-dried and vacuum-dried gums (46.9 and 46.6, respectively). The consistency of samples decreased from 386.27 to 245.33 g · s when the drying air temperature increased from 40 to 80°C. The results indicated that the freeze-dried gum exhibited the highest hardness and consistency. The color of air-dried gum was darker (lower L* value) compared to the freeze- and vacuum-dried samples.

Effect of different drying techniques on flowability characteristics and chemical properties of natural carbohydrate-protein Gum from durian fruit seed

BackgroundA natural carbohydrate biopolymer was extracted from the agricultural biomass waste (durian seed). Subsequently, the crude biopolymer was purified by using the saturated barium hydroxide to minimize the impurities. Finally, the effect of different drying techniques on the flow characteristics and functional properties of the purified biopolymer was investigated. The present study elucidated the main functional characteristics such as flow characteristics, water- and oil-holding capacity, solubility, and foaming capacity.ResultsIn most cases except for oven drying, the bulk density decreased, thus increasing the porosity. This might be attributed to the increase in the inter-particle voids of smaller sized particles with larger contact surface areas per unit volume. The current study revealed that oven-dried gum and freeze-dried gum had the highest and lowest compressibility index, thus indicating the weakest and strongest flowability among all samples. In the present work, the freeze-dried gum showed the lowest angle of repose, bulk, tapped and true density. This indicates the highest porosity degree of freeze dried gum among dried seed gums. It also exhibited the highest solubility, and foaming capacity thus providing the most desirable functional properties and flow characteristics among all drying techniques.ConclusionThe present study revealed that freeze drying among all drying techniques provided the most desirable functional properties and flow characteristics for durian seed gum.

Influence of different purification and drying methods on rheological properties and viscoelastic behaviour of durian seed gum

The aim of the present study was to investigate the effects of different purification and drying methods on the viscoelastic behaviour and rheological properties of durian seed gum. The results indicated that the purified gum A (using isopropanol and ethanol) and D (using hydrochloric acid and ethanol) showed the highest and lowest viscosity, respectively. Four drying techniques included oven drying (105°C), freeze drying, spray drying and vacuum oven drying. In the present work, all purified gums exhibited more elastic (gel-like) behaviour than the viscous (liquid-like) behaviour (G″<G′). The current study revealed that all drying methods led to significantly diminish the elastic (G′) and viscous modulus (G″) of durian seed gum. The freeze-dried gum and oven-dried (105°C) gum exhibited the highest and lowest viscous modulus (G″), respectively.

Isolation, purification and characterization of a new gum from Acanthophyllum bracteatum roots

A new gum was isolated from the roots of Acanthophyllum bracteatum (ABG) by warm-water extraction. Purification was carried out by barium complexing to give a yield of 12.4% of pure air-dried or 5.8% of freeze-dried gum. The ABG contained 13.2% moisture, 84.3% carbohydrate, 0.9% protein and 1.5% ash. Its mineral content was comparable to commercial hydrocolloids. Monosaccharide analysis by HPLC showed the presence of galactose, glucose, arabinose, rhamnose and uronic acids in the ratio 16.0:7.2:3.0:1.0:3.1 respectively. The viscosity and pH value of 1% ABG solution at 25 °C were 51.5 mPa s and 6.85 respectively. ABG solutions (5–30 wt%) showed shear-thinning flow behavior at shear rates < 10 s −1. The viscosity decreased as temperature increased, and was highest at the neutral state. ABG had low surface and emulsification properties but moderate foaming capacity and relatively high foaming stability, which suggests that ABG could potentially be used in food systems to improve foaming properties.

Extraction, purification and characterization of durian ( Durio zibethinus) seed gum

This study was carried out to determine the characteristics of pure durian seed gum in terms of moisture and ash content, mineral content, effect of temperature and pH on viscosity and sugar composition of the gum. Durian seed gum isolated from defatted local durian seeds yielded about 18% of light brown crude gum powder. Further purification of durian seed gum was carried out by barium complexing to give a yield of 1.2% of pure air-dried gum or 0.5% of freeze-dried gum. The purified durian seed gum had 17.9% moisture and 29.8% total ash. Mineral content of durian seed gum was comparable to commercial gum except for zinc content which was quite high in durian seed gum. The viscosity of 1% durian seed gum solution was 65 mPa s at a shear rate of 1000 s −1 at 29.8 °C. The viscosity of fully hydrated gum solutions decreased as temperature increase. It was found that increasing the temperature from 10 to 70 °C causing the viscosity to decrease about 34% at shear rate 1000 s −1 and 42% at shear rate 0.93 s −1. The pH of 1% gum solution at room temperature was 6.93, which is quite similar to guar gum. The viscosity of the durian seed gum was found to be highest at the neutral state. Generally, the gum solutions were fairly stable over a wide range of pH (2.0–10.0). Sugar analysis by PC and HPLC revealed the presence of l-rhamnose, glucose and d-galactose sugars in the hydrolyzed durian seed gum. The gum contained l-rhamnose, glucose and d-galactose in the ratio of 3:9:1. The results indicated that durian seed gum is not a galactomannan.