Water sorption isotherms of foods and foodstuffs: BET or GAB parameters?

Water Sorption Isotherm and Critical Water Activity of Amorphous Water-Soluble Carbohydrates Characterized by the Glass Transition Temperature

Water-soluble carbohydrates commonly exist in an amorphous state in foods and undergo glass-rubber transition (glass transition) at the glass transition temperature (Tg). The critical water content (Wc) and critical water activity (awc) are the water content and water activity (aw) at which the glass transition occurs at 298 K (typical ambient temperature), respectively. For amorphous water-soluble carbohydrates, Wc can be predicted from the Tg of anhydrous solid (Tgs) using previously reported equations. However, an approach for predicting awc is still lacking. This study aimed to establish an awc-predictive approach for amorphous water-soluble carbohydrates based on Tgs. First, the water sorption isotherms of four hydrogenated starch hydrolysates were investigated, and the results were analyzed using the Guggenheim-Anderson-de Boer (GAB) model. Second, the effect of Tgs on the GAB parameters (C, K, and Wm) was evaluated using the Tgs values reported in previous literatures. C and Wm decreased and increased logarithmically, respectively, with increasing 1/Tgs. K was fixed to 1 (constant), as it showed little variation. These results enabled the prediction of the GAB parameters from Tgs. The GAB model could then predict awc from Wc, which was determined using the previously established equations. The predicted awc values were in good agreement with the experimentally determined awc. Additionally, we demonstrated that this awc-prediction approach is also applicable to amorphous water-soluble electrolytes and partially water-insoluble carbohydrates. Thus, this approach can be used for the quality control of amorphous water-soluble carbohydrates and carbohydrate-based foods.

Examining the Water-Polymer Interactions in Non-Isocyanate Polyurethane/Polyhedral Oligomeric Silsesquioxane Hybrid Hydrogels

Non-isocyanate polyurethane (NIPU) networks physically modified with octa(3-hydroxy-3-methylbutyldimethylsiloxy)POSS (8OHPOSS, 0-10 wt%) were conditioned in environments of different relative humidities (up to 97%) to study water-polymer interactions. The equilibrium sorption isotherms are of Brunauer type III in a water activity range of 0-0.97 and are discussed in terms of the Guggenheim (GAB) sorption model. The study shows that the introduction of 8OHPOSS, even in a large amount (10 wt%), does not hinder the water affinity of the NIPU network despite the hydrophobic nature of POSS; this is attributable to the homogenous dispersion of POSS in the polymer matrix. The shift in the urethane-derived carbonyl bands toward lower wavenumbers with a simultaneous shift in the urethane N-H bending bands toward higher wavenumbers exposes the breakage of polymer-polymer hydrogen bonds upon water uptake due to the formation of stronger water-polymer hydrogen bonds. Upon water absorption, a notable decrease in the glass transition temperature (Tg) is observed for all studied materials. The progressive reduction in Tg with water uptake is driven by plasticization and slaving mechanisms. POSS moieties are thought to impact slaving indirectly by slightly affecting water uptake at very high hydration levels.

Shelf life prediction of dried garlic powder under accelerated storage conditions

The shelf life of dried garlic powder packaged in high-density polyethylene (HDPE), low-density polyethylene (LDPE), and aluminum laminated pouch (ALP) under accelerated storage temperature (5° to 40 °C) and humidity (70-90% RH) conditions, was predicted using GAB mathematical model. The water activity value reduced significantly from 0.83 to 0.31 as the moisture content reduced. The temperature had a negative effect on color change and the lightness value and whiteness index of garlic powder significantly decreased from 62.21 to 56.06 and 50.67 to 44.91 respectively, when temperature increased from 70° to 90° C. The storage life of garlic powder was 24, 78 and 210 days in LDPE, HDPE, and ALP, respectively under domestic storage conditions (40 °C, 90% RH). Therefore, under industrial storage conditions (5 °C, 70% RH), garlic could be preserved for 1.32, 4.30 and 7.28 years in LDPE, HDPE and ALP, respectively.

Effect of Mixed Particulate Emulsifiers on Spray-Dried Avocado Oil-in-Water Pickering Emulsions

Avocado oil is a very valuable agro-industrial product which can be perishable in a short time if it is not stored in the right conditions. The encapsulation of the oils through the spray drying technique protects them from oxidation and facilitates their incorporation into different pharmaceutical products and food matrices; however, the selection of environmentally friendly emulsifiers is a great challenge. Four formulations of the following solid particles: Gum Arabic, HI-CAP^®100 starch, and phosphorylated waxy maize starch, were selected to prepare avocado oil Pickering emulsions. Two of the formulations have the same composition, but one of them was emulsified by rotor-stator homogenization. The rest of the emulsions were emulsified by combining rotor-stator plus ultrasound methods. The protective effect of mixed particle emulsifiers in avocado oil encapsulated by spray drying was based on the efficiency of encapsulation. The best results were achieved when avocado oil was emulsified with a mixture of phosphorylated starch/HI-CAP^®100, where it presented the highest encapsulation efficiency.

Nonenzymatic Browning of Amorphous Maltose/Whey Protein Isolates Matrix: Effects of Water Sorption and Molecular Mobility

Nonenzymatic browning (NEB) reactions often affect the nutritional quality and safety properties of amorphous food solids. Developing a proper approach to control the NEB reaction has been of particular interest in the food industry. An NEB reaction in an amorphous maltose/Whey protein isolates (WPI) matrix containing L-lysine and D-xylose as reactants were studied at ambient temperatures aw ≤ 0.44 and 45~65 °C. The results indicated that the presence of NEB reactants barely disturbed the water sorption behavior of the matrix. The Guggenheim–Anderson–de Boer (GAB) constants and Qst values of the studied samples were affected by storage conditions as the migration of sorbed water among monolayers occurred. The rate of color changes and 5-hydoxymethylfurfural (5-HMF) accumulation on the matrix were accelerated at high ambient temperatures aw, reflecting the extent of NEB reaction increases. Since the strength concept (S) could give a measure of molecular mobility, the extent of the NEB reaction was governed by the molecular mobility of the matrix as the activation energy (Ea) of 5-HMF production minimized at solids with high S values. We found that the S concept had a considerable potential usage in controlling the NEB reaction on amorphous sugar–protein solids. This data set has practical significance in the comprehensive understanding of manipulating the diffusion-limited chemical reactions on low-moisture food solids.

Hygroscopic Properties of Three Cassava (Manihot esculenta Crantz) Starch Products: Application of BET and GAB Models

This study aimed to compare hygroscopicity properties of three cassava (Manihot esculenta Crantz) products: native starch powder (NS), fermented starch powder (FS), and starch granulate (SG). The analyzed properties were compared based on the statistical evaluation of differences in the course of sorption isotherms and the identification and comparison of parameters in two theoretical models of sorption. Empirical data were generated by means of the static-desiccator method. Measurements were made using AquaLab apparatus. The size, shape, and number of tapioca particles were characterized using a Morphology automatic particle analyzer. The study demonstrated that in-depth exploration of empirical data describing hygroscopicity of samples with the use of mathematical tools allows evaluating their physical parameters. The results obtained were analyzed in terms of correlations between physical and physicochemical properties determining utility traits of cassava starch. The NS and SS featured significantly higher hygroscopicity than SG, as evidenced by the values of all parameters analyzed in this study. The study results provided new information related to the management of the production process, safety, and stability of these products.

Investigation of sorption isotherms of wheat germ for its effect on lipid oxidation

This research aimed to investigate the oxidation and sorption isotherm properties of wheat germ and to determine monolayer moisture content (m₀ ) in particular, because it has a limiting effect on lipid oxidation. This research comprised two stages. The first stage was the determination of sorption properties and m₀ at three temperatures (15, 25, and 35°C). The second stage of the research was to investigate lipid oxidation properties of stored wheat germ at two different temperatures (4 and 25°C) and m₀ for 28 days. As a result, it was determined that wheat germ has a Type II sorption isotherm, Halsey is the best fitting sorption equation, and the average m₀ is 4.25 g moisture per 100 g dry matter. Furthermore, the free fatty acid and peroxide value of wheat germ oil increased with increasing storage moisture content and temperature, determined as 12.63% and 5.01 mEqO₂ /kg on average, respectively. In conclusion, storage of impermeably packaged wheat germ at low temperature and m₀ content is an applicable method for decreasing rancidity and prolonging shelf-life.

Moisture Adsorption potentials and energy models of Gongronema latifolium leaves dried in separate environments

Moisture adsorption isotherm potentials and energy models of Gongronema latifolium leaf grits were investigated. Fresh leaves were dried in sun; passive solar dryer and hot air oven, while proximate composition of the dried and fresh leaves were determined using standard laboratory procedure. Equilibrium moisture content (EMC) of the leaf grits was measured using gravimetric static method. Selected mathematical and statistical models were applied on the experimental data to evaluate data fitting. Energy calculations were done based on the mathematical models. The EMCs of the leaf grits directly increased with water activity (aW) at specific temperatures. Adsorption data was better represented by GAB model than others while differential enthalpy decreased as the EMC of the oven sample increased. Differential entropy of all the samples decreased as the EMC increased. The safest monolayer moisture content varied between 7.1036 and 8.0164 gH2O/100 g solid, below 40°C, within relative humidity of 10%-50%. Sun and oven leaf grits adsorbed more moisture than solar sample. Proximate contents of the dried leaves showed higher values for protein and ash. Overall results indicated that the leaf grits when properly packaged could be used as spice or tea powder to manage household nutrient security in addition to the use as therapeutic foods.

Application of Dynamic Temperature-Humidity Chamber for Measuring Moisture Sorption Isotherms of Biomaterials as Compared to the Conventional Isopiestic Method

Measurement of water activity and moisture sorption isotherms of foods and biomaterials are important to determine the state of water. In this work, a dynamic temperature-humidity (DTH) controlled chamber was used to measure water sorption isotherm and compared with the conventional isopiestic method. Temperature and relative humidity of DTH chamber can be controlled in the range of -15 to 100°C and 0 to 98%, respectively; thus, measurement of water activity at any point can be measured within the above ranges. The DTH chamber method showed high reproducibility as compared with the conventional isopiestic method when measured isotherms of cellulose, lignin, and hemicellulase were compared at 30°C. Finally, isotherm data of cellulose, lignin, and hemicellulase were generated in the temperature range of 10-90°C using DTH chamber, and these were modelled by BET and GAB equations. The model parameters were correlated with the temperature.

The Effect of Chitosan Type on Biological and Physicochemical Properties of Films with Propolis Extract

The aim of the research was to determine the influence of chitosan type and propolis extract concentration on biological and physicochemical properties of chitosan-propolis films in terms of their applicability in food packaging. The films were prepared using three types of chitosan: from crab shells, medium and high molecular weight and propolis concentration in the range of 0.75-5.0%. The prepared polysaccharide films were tested for antimicrobial properties, oxygen transmission rate (OTR) and water vapor transmission rate (WVTR). Moreover, sorption tests and structural analysis were carried out. Microbiological tests indicated the best antimicrobial activity for the film consisting of high molecular weight chitosan and 5.0% propolis extract. Both the type of chitosan and propolis concentration affected transmission parameters-OTR and WVTR. The best barrier properties were recorded for the film composed of high molecular weight chitosan and 5.0% propolis extract. The results of sorption experiments showed a slight influence of chitosan type and a significant effect of propolis extract concentration on equilibrium moisture content of tested films. Moreover, propolis extract concentration affected monolayer water capacity (Mm) estimated using the Guggenheim, Anderson and de Boer (GAB) sorption model. The obtained results indicate that chitosan films with an addition of propolis extract are promising materials for food packaging applications, including food containing probiotic microorganisms.

Application of Different Compositions of Apple Puree Gels and Drying Methods to Fabricate Snacks of Modified Structure, Storage Stability and Hygroscopicity

The aim of this study was to determine the effect of incorporation of apple puree and maltodextrin to agar sol on the sorption properties and structure of the dried gel. The effect of different drying methods on the sorption behaviour of aerated apple puree gels was also observed. The gels with the addition of 25% and 40% concentration of apple puree and with or without maltodextrin were prepared and dried. The foamed agar gel was subjected to freeze-drying, air-drying and vacuum-drying. The sorption properties of dried gels (adsorption isotherms, water uptake in time) were investigated. The relations between the glass transition temperature, water activity and water content were also obtained for some apple snacks. The increase in apple puree in freeze-dried gels increased the hygroscopicity and decreased the glass transition temperature (Tg). The water content at given activity and hygroscopicity were reduced by the addition of maltodextrin, which also caused the increase in Tg. The application of different drying methods enabled obtaining different structures of material. The open-pore, fragile materials were obtained by freeze-drying, the expanded matrix with big holes was characteristic for vacuum-dried gels, but the closed pores with thick walls were created during the air-drying.

Water Uptake as a Crucial Factor on the Properties of Cryogels of Gelatine Cross-Linked by Dextran Dialdehyde

We investigated the water sorption properties of macroporous cryogels of gelatine (Gel) and dextran dialdehyde (DDA) prepared via cryogelation at 260 K and following the freeze drying processes. Water vapour sorption isotherms for aerogels were studied at 293 K by two independent methods: static-gravimetric and dynamic vapour sorption (DVS) over a water activity range of 0.11-1.0. Experimental data were fitted by use of the Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAB) models. The BET model (for a water activity range of 0.1 ≤ p/po ≤ 0.5) was used to calculate the sorption parameters of the studied cryogels (the monolayer capacity, surface area and energy of interaction). In comparison with BET, the GAB model can be applied for the whole range of water activities (0.1 ≤ p/po ≤ 0.95). This model gave an almost perfect correlation between the experimental and calculated sorption isotherms using nonlinear least squares fitting (NLSF). Confocal Laser Scanning Microscopy (CLSM) was used to confirm the structural differences between various DDA:Gel cryogel compositions. Thermogravimetric analysis and DSC data for aerogels DDA:Gel provided information regarding the bonded water loss, relative remaining water content of the material and the temperature of decomposition. Estimation of the amount of bound water in the cryogels after the freeze drying process as well as after the cycle of treatment of cryogels with high humidity and drying was performed using DSC. The results of the DSC determinations showed that cryogels with higher gelatin content had higher levels of bonded water.

Mechanical and Hygroscopic Properties of Molded Pulp Products Using Different Wood-Based Cellulose Fibers

With an increasing interest for molded pulp product (MPP) in the industry, it is important to fully understand how the manufacturing process is different from papermaking. One specific way to differentiate the processes is to compare their resulting products. As the paper industry uses several wood fibers with various pulping processes, it is interesting to compare some of these fibers, to further progress our understanding of the MPP process. In this study, six different wood fibers were used (as received) and analyzed to obtain the sample with the lowest moisture uptake and highest tensile properties. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and fiber analysis module (MorFi) observations were performed, as well as moisture uptake measurements after sorption and tensile tests. We observed significant differences between the fibers tested. Kraft fibers (bleached softwood kraft pulp (BSKP), bleached hardwood kraft pulp (BHKP), and unbleached softwood kraft pulp (USKP)) showed smoother surfaces and less non-cellulosic molecules, such as hemicellulose, lignin, and pectin, in the SEM images. Bleached chemi-thermomechanial pulp (BCTMP) and recycled pulps (R-NPM and R-CBB) both showed non-cellulosic molecules and rougher surfaces. These results were confirmed with the FTIR analysis. With kraft fibers, MPP mechanical properties were lower than non-kraft fibers. Resulting moisture uptake is in between the recycled fibers (lowest moisture uptake) and BCTMP (highest moisture uptake). The removal of non-cellulosic molecules reduces the mechanical properties of the resulting MPP. The incorporation of non-wood molecules, as found in recycled fibers, also reduces the mechanical properties, as well as moisture uptake, when compared with BCTMP.

Effects of glass transition and hydration on the biological stability of dry yeast

The purpose of this study was to determine the effects of glass transition and hydration on the storage stability of baker's dry yeast (Saccharomyces cerevisiae). The glass transition temperature (T_g ) of the yeast decreased with increase in water activity (a_w ), and a_w at which glass transition occurs at 25 °C was determined as the critical a_w (a_wc ). From mechanical relaxation measurements at 25 °C, the yeast exhibited a large mechanical relaxation above the a_wc , and the degree of mechanical relaxation increased gradually with increasing a_w . This behavior corresponded to a gradual increase in molecular mobility with increasing a_w in the rubbery liquid state. Freezable water was observed from a_w ≥0.810, and the proportion of freezable water increased with increasing a_w . Examination of the effect of a_w on the residual biological activity of yeast samples stored at 25 °C for 30 days revealed maximum residual biological activity at a_w  = 0.225 to 0.432. In the lower a_w range, the residual biological activity decreased because of oxidation of lipids. In the higher a_w range, the residual biological activity decreased gradually with increasing a_w . The yeast samples maintained a relatively high residual biological activity, because they could maintain relatively low molecular mobility even in the rubbery liquid state, as suggested by their mechanical relaxation behavior. At a_w ≥0.809, residual activity decreased to a negligible value. This could be explained by the appearance of secondary hydrate water (freezable water). Hydrate water protects yeast cells from lipid oxidation but reduces the T_g . As a result, the yeast cells are stabilized maximally only at the a_wc . PRACTICAL APPLICATION: Although the growth rate of yeast cells becomes negligible below a certain a_w , the biological activity of dry yeast decreases gradually during storage. The fact that dry yeast can be maximally stabilized at the a_wc is practically useful as a criterion for controlling storage stability. In addition, it was found that a remarkable reduction in the molecular mobility, which is otherwise ordinarily increased due to the glass-to-rubber transition, is prevented in yeast. It is possible that the crystallization of amorphous sugar can be prevented by yeast extract. The suggested effect is expected to result in enhanced quality of carbohydrate-based foods.

Effect of the Degree of Substitution on the Hydrophobicity, Crystallinity, and Thermal Properties of Lauroylated Amaranth Starch

In this paper, we consider amaranth starch extracted from the seeds of Amaranthus hypochondriacus L. An amphiphilic character is conferred to the starch by a chemical modification, which involves an esterification by lauroyl chloride at three modification levels. The degree of substitution (DS) after the modification ranged from 0.06 to 1.16. X-ray photoelectron spectroscopy analysis confirmed the presence of fatty acyl chains on the surface of the esterified starches. The hydrophobicity of starches was confirmed by their adsorption isotherms, which showed a decrease in the moisture adsorption of lauroylated as DS increased. X-ray diffraction analysis revealed a higher crystallinity, which was observed in the two samples subjected to the highest levels of modification. A higher crystallinity is related to a higher gelatinization enthalpy. These results are in agreement with the thermal characterization obtained by differential scanning calorimetry (DSC). An inhibition of the retrogradation properties of lauroylated amaranth starches was also observed.

Evaluation of Environmental Impact on Selected Properties of Lime (Tilia Cordata Mill.) Wood

The external and internal factors in the tree development process affect wooden structures and properties. They depend on, for example, a plant species, its age, part and growth conditions. The present study investigated the chemical structure and physical properties of the common urban tree species: small-leaved lime (Tilia cordata Mill.). The properties of trees growing in an urban agglomeration, by a roadside and in a forest, i.e., areas varying in degrees of an environmental stress impact, were compared. Tree-ring width and density, selected hygroscopic properties (sorption hysteresis and isotherms), wood chemical content (percentage content of: holocellulose, cellulose, pentosanes, lignin and substances soluble in 1% NaOH and EtOH) as well as the content of selected chemical elements (Fe, Zn, Cu, Pb, Cd, K, Na, Mg and Ca) were studied. The analysis of the case shows no impact of the environmental stress on the growth patterns characterized by ring width index (RWI). Two-factor analysis of variance (ANOVA) revealed impact significance of growth environment and cambial age on the content of each of the investigated components and chemical elements. There was a relationship demonstrated that for a tree growing in an agglomeration with the highest environmental stress the content of cellulose and lignin was the lowest, whereas the content of substances soluble in NaOH and EtOH was the highest. For mature wood growing under the same conditions, the results corresponded to the highest Zn, Cu, K, Na, Mg and Ca content. It was also shown that the environmental stress affected hygroscopicity which was the consequence of chemical component percentage content. The research proved that Tilia cordata Mill. responded to environmental stress with alternations in its chemical or/and physical properties.

Capsicum pubescens as a functional ingredient: Microencapsulation and phenolic profilling by UPLC-MSE

The aim of the present investigation is to study the effect of inlet temperatures on the physicochemical properties of spray-dried jamun juice powder. The inlet temperatures varied from 140 to 160 °C, whereas other parameters like outlet temperature (80 °C), maltodextrin concentration (25%) and feed flow rate (10 mL/min) were kept constant. Moisture content, water activity, bulk density, solubility, hygroscopicity, colour, powder morphology, particle size and glass transition temperatures were analyzed for the powder samples. Higher inlet temperature increased the moisture content of the powder, and led to the formation of larger particles. Powder samples showed water activity values below 0.3, which is good for powder stability. The colour of the jamun juice powder was mainly affected by inlet temperature, leading to the formation of powders that were significantly brighter and less purple as the inlet temperature increased. Glass transition temperature ranged from 55.85 to 71.78 °C. Powders produced at lower inlet temperatures showed smoother particle surfaces, whereas higher inlet temperature showed spherical particles with some shrinkage as analyzed by scanning electron microscope.

Moisture sorption isotherm and shelf life prediction of complementary food based on amaranth-sorghum grains

The quantity and quality of complementary foods is one of the contributing factors to childhood under nutrition. Complementary food based on amaranth and sorghum grains was formulated. It was deemed to be superior nutritionally to the commonly used complementary foods in Kenya. Knowledge on storage and packaging is important for a long shelf life of the product to be achieved. Water activity and moisture content are key indicators of the stability of dried foods. To establish the proper storage conditions of the product, moisture sorption isotherms at 25 °C, 30 °C and 35 °C were determined over water activity range of 0.11-0.97 and data fitted with six sorption models. Water vapour permeability of common packaging materials was also determined at 25 °C and 35 °C and the data was used to predict the product's shelf life. The product exhibited type two sorption isotherm according to Brunner classification an indication of monolayer-multilayer sorption behavior. The critical storage moisture content of the complementary food corresponding to 0.6 water activity a point of microbiological stability was found to be 7.5%. Based on Heiss-Eichner model, a shelf life of 1423 days at 25 °C can be achieved with product initial moisture content of 5 g/100 g and packaged in 110 µm thick aluminum pouch. The shelf life of the product was shortened two to three fold at 35 °C in comparison to storage at 25 °C.

Regenerated cellulose films with chitosan and polyvinyl alcohol: Effect of the moisture content on the barrier, mechanical and optical properties

The aim of this research was to evaluate the effect of moisture content on the mechanical, barrier and optical properties of films obtained from regenerated cellulose with chitosan and polyvinyl alcohol equilibrated at several relative humidity conditions. The experimental moisture adsorption isotherms were fitted using the Guggenheim-Anderson-DeBoer model. The adsorption isotherm showed a typical type II sigmoidal shape. The highest moisture content (27.53 %) was obtained at a water activity of 0.9. The water vapour permeability values increased up to 6.34·10^-11 g/ m s Pa as the moisture content of the films increased. Tensile strength, percentage of elongation, Young's modulus, burst strength and distance to burst showed a significant plasticizing effect of the water molecules. Results suggest that interactions between film components and water molecules decrease the transmittance in the UV region and the transparency. Consequently, water molecules improve the UV-barrier properties of the films and increasing the opacity.

Environmentally Friendly Films Combining Bacterial Cellulose, Chitosan, and Polyvinyl Alcohol: Effect of Water Activity on Barrier, Mechanical, and Optical Properties

The interest in developing new materials intended for food packaging based on bacterial cellulose is growing in the recent years. Flexible and transparent films from bacterial cellulose-chitosan-polyvinyl alcohol have shown excellent UV-barrier properties. However, this material interacts with ambient moisture modifying its water activity due to its hydrophilic nature. In this work, a study was carried out to evaluate the changes caused by the water activity. Results showed a plasticizing effect of water molecules increasing the water vapor permeability of the samples from 1.86 × 10^-12 to 1.17 × 10^-11 g/m·s·Pa, percentage of elongation from 3.25 to 36.55%, and distance to burst from 0.64 to 5.12 mm. The increase of the water activity decreased the Young's modulus and tensile strength. The values of the UV-barrier were maintained at the wide range of water activity. Consequently, water molecules do not affect the UV-barrier properties of the films.

Phenolics and Antioxidant Capacity of Pitted Olive Pomace Affected by Three Drying Technologies

This study investigated drum-drying's ability to produce dried food-grade olive pomace as a potential food ingredient that is more nutritionally dense than its freeze-dried and hot-air dried counterparts. The pits and skin were removed from fresh olive pomace, and the remaining pulp was dried to <5% moisture through freeze-drying, hot-air drying, and drum-drying at two rotational speeds. The drying treatments had no significant (P ≤ 0.05) effect on the olive pomace's fat or dietary fiber contents but did increase the L^* , a^* , and b^* color parameter values. Although all the drying treatments significantly (P ≤ 0.05) decreased the fresh olive pomace's antioxidant capacity, drum-drying preserved the olive pomace's antioxidant capacity significantly (P ≤ 0.05) better than freeze-drying and hot-air drying. The drum-dried samples had concentrations of caffeic acid and verbascoside that were significantly (P ≤ 0.05) higher than the other dried pomace samples and were not significantly (P ≤ 0.05) different from the fresh pomace. The drum-dried olive pomace contained concentrations of hydroxytyrosol, tyrosol, vanillic acid, luteolin-7-glucoside, and rutin that were not significantly (P ≤ 0.05) different from the dried sample with the highest concentration of each respective phenolic compound. No oleuropein was found in the fresh or dried olive pomace. The results of this study show that drum-drying is an energy efficient method for converting olive pomace into a stable food-grade supplement that preserves its high phenolic, antioxidant, and dietary fiber contents to potentially benefit human health when incorporated into food or supplement products. PRACTICAL APPLICATION: Pitting and drying converts the olive pomace into a stable form that is free of physical hazards and could be incorporated into food products to increase their nutritional quality through olive pomaces' high fiber, antioxidant, and phenolic contents. Drum-drying allows food-grade olive pomace to retain higher amounts of beneficial soluble phenolics and a higher antioxidant capacity than conventional drying methods, thus furthering olive pomace's potential valorization as a food ingredient.