Water sorption and glass transition temperature of spray dried açai (Euterpe oleracea Mart.) juice

Sorption isotherms and glass transition temperature (T_g) of powdered açai juice were evaluated in this work. Powders were produced by spray drying using different materials as carrier agents: maltodextrin 10DE, maltodextrin 20DE, gum Arabic and tapioca starch. The sorption isotherms were determined by the gravimetric method, while the T_g of powders conditioned at various water activities were determined by differential scanning calorimetry. As results, experimental data of water adsorption were well fitted to both BET and GAB models. Powders produced with maltodextrin 20DE and gum Arabic showed the highest water adsorption, followed by those produced with maltodextrin 10DE and with tapioca starch, respectively. With respect to the glass transition temperature, Gordon–Taylor model was able to predict the strong plasticizing effect of water on this property. Both a_w and T_g were used to determine the critical conditions for food storage, at which powders are not susceptible to deteriorative changes such as collapse, stickiness and caking.     

Storage stability of the natural colourant from Justicia spicigera microencapsulated in protective colloids blends by spray‐drying

Muitle (Justicia spicigera), a Mexican native plant, produces a purple aqueous extract (MAE) because of its anthocyanin content. The aim of this work was to microencapsulate MAE by spray‐drying in two different protective colloids blends in a 1:1 weight ratio: gum Arabic‐mesquite gum (GA50‐MD50) and mesquite gum‐maltodextrin DE10 (MG50‐MD50), yielding the microcapsules M_GA50‐MD50 and M_MG50‐MD50. The minimum integral entropy of the microcapsules was determined at 20, 35 and 40 °C, and the resulting water activities (a_W) were 0.555, 0.592, 0.627 for M_GA50‐MD50 and 0.581, 0.587, 0.648 for M_MG50‐MD50, respectively. These a_W temperature sets were considered as the most adequate conditions for achieving maximum storage stability of the microcapsules. Total anthocyanin content (TAC) and total colour change (ΔE) suffered considerable degradation at all storage conditions, but that degradation was significantly inhibited by encapsulating MAE in the biopolymers blends especially that made up by MG50‐MD50.     

Effect of Encapsulating Materials on Water Sorption,Glass Transition and Stability of Juice From Immature Acerola

Immature acerola juice was dehydrated by spray drying, using as encapsulating material maltodextrin DE25, arabic gum, or a mixture of both in different proportions. A constant ratio of 1:1 was kept between juice solids and encapsulating material. The effect of encapsulation materials on water sorption, glass transition, and physical properties of encapsulated immature acerola juice was investigated. The monolayer moisture of the encapsulated juices, calculated according to the GAB theory, varied from 5.11 to 5.73g H₂O/100g of solids (25°C). The glass transition temperature (T_g) of maltodextrin and gum arabic varied from 60 (a_w 0.33) to 38°C (a_w 0.54), and from 62 (a_w 0.33) to 42.6°C (a_w 0.54), respectively. The addition of juice to the encapsulating materials decreased the T_g of the juice powder to 39.5–41.3°C (a_w 0.33) and 1.84–8.05°C (a_w 0.54), but no marked differences were found among the juice powders. The critical a_w, i.e., the point of onset of physical alterations in the encapsulated materials, was higher than the corresponding monolayer values. Stickiness was observed at temperatures close to T_g, and collapse occurred at temperatures of 20°C or more above the T_g. Maltodextrin DE25 and gum arabic offered equivalent contributions to the stability of the system.     

Whey protein-polysaccharide blended edible film formation and barrier, tensile, thermal and transparency properties

BACKGROUND: Films made from different protein (P) or polysaccharide (PS) materials have widely different properties. The objective of this study was to determine whether whey protein isolate (WPI)‐PS blended films possess a combination of properties intermediate and possibly superior to WPI or PS film alone. RESULTS: Oxygen permeability (OP) and tensile strength (TS) for PS‐WPI blended films were intermediate between the OP and TS properties of pure methycellulose (MC), hydroxypropylmethylcellulose (HPMC) or sodium alginate (SA) film and pure WPI film. Starch‐WPI blends gave the weakest films. Water vapor permeability values for all pure and blended films were similar. Blended films made of MC, HPMC or SA with WPI had lower transparency than pure MC, HPMC, SA or WPI films. Differential scanning calorimetry thermograms obtained from the blended films exhibited a single glass transition temperature (T_g) at an intermediate value between the T_g values of the pure films. CONCLUSIONS: Whether properties of PS‐WPI blended films are intermediate to properties of the pure PS and WPI film depends on the particular PS and specific property. In the case of MC or HPMC with WPI, the blended films reflect the higher TS of the PS and lower OP of the WPI. Copyright © 2011 Society of Chemical Industry     

Improving the oxygen barrier of microcapsules using cellulose nanofibres

In this study, the oxygen barrier and physical properties of two maltodextrin/gum Arabic (MD/GA) (3:1 w/w) microcapsules with dextrose equivalence (DE) 26 and 6 were assessed with or without the incorporation of cellulose nanofibres (CNF). The oxygen diffusion coefficient (D_eff) was between 10.6 × 10⁻¹⁵ m² s⁻¹ and 17.3 × 10⁻¹⁵ m² s⁻¹ for all microcapsules. The addition of CNF improved the oxygen barrier of MD/GA microcapsules. The incorporation of CNF did not significantly impact T_g due to the low quantity of CNF present in the microcapsules. Wettability was higher in CNF incorporated microcapsules, and dispersibility was lower only for microcapsules with maltodextrin of DE 26. Spray-dried microcapsules exhibited poor flowability and high cohesiveness due to the moisture content (2.0–2.5%) of the powders. The results suggest that incorporation of CNF can increase the oxygen barrier of MD/GA microcapsules which may lead to better oxidative stability of micronutrients incorporated in the microcapsules.     

Subzero Glass Transition of Waxy Maize Starch Studied by Differential Scanning Calorimetry

A mixture of waxy maize starch and water (1:2, w/w) was heated in a differential scanning calorimeter (DSC) pan to different temperatures to obtain different degrees of gelatinization. Each pan was then quenched to ‐30°C and rescanned, and the subzero glass transition temperature (T_g′) of the content was determined. A three‐phase model of a starch granule—a mobile amorphous phase, a rigid amorphous phase, and a crystalline phase—was used to interpret results and explain the glass transitions in starch. Waxy maize starch had an onset gelatinization temperature (T_o) of 61.5°C, peak temperature (T_p) of 70.3°C, and completion temperature (T_c) of 81.7°C. The T_g′ was clearly noted after the starch and water mixture was heated to T_p and T_c, but was small and barely observable when the mixture was heated up to T_o and immediately cooled to ‐30°C. When the starch and water mixture was heated to 55°C, which was 6°C below the T_o, and held for 2 h, a T_g′ was observed. Moreover, T_g′ began to appear and was observable if the starch and water mixture was heated to 10°C below gelatinization onset temperature (51°C) and annealed for 2 h without any gelatinization. Further holding at ‐7°C showed a clear subzero glass transition of annealed native starch granules.     

Original article: Encapsulation of ascorbic acid in amorphous maltodextrin employing extrusion as affected by matrix/core ratio and water content

Ascorbic acid (AA) was encapsulated in glassy low‐dextrose equivalent maltodextrin matrix by extrusion. The effects of formulation parameters, i.e., core/matrix ratio and water content were mainly investigated on T_g of extrudate. The AA yield, AA content and water content of the products together with extrusion parameters were also determined and compared for different formulations. The T_g of extrudates containing water content from 7.860% to 10.430% ranged from 43.17 to 27.48 °C, and the T_g of extrudates which core to matrix from 1:4 to 1:8 ranged from 35.79 to 41.64 °C. AA yield of all extrudates is above 96%, and with increasing water content, there was a slight decrease in the AA yield. The increased water level and core/matrix ratio reduce specific mechanical energy and die head pressure. X‐ray diffraction and scanning electron microscopy suggested that AA was most likely molecularly dispersed within the maltodextrin indicating the miscibility of AA and maltodextrin.     

The influence of the carrier addition and spray drying temperatures on physicochemical properties of microencapsulated carrot juice powder

The objective of this study was to determinate the influence of carrier addition and spray drying temperatures (160 or 200°C) on physicochemical properties of spray-dried carrot juice powder. As carriers, maltodextrin and gum Arabic in different proportions were used. In powders were determined the following: moisture content, water activity, apparent density, size of particles, colour and carotenoids content. The content of carotenoids in powders prepared from solutions with juice to carrier ratio 2:3 was 324.3–406.6 mg/kg d.m., while in powders with a J:C = 3:2 values ranged from 576.7 to 637.7 mg/kg d.m. The highest content of carotenoids and the most yellow colour were observed in powders with 1:3 gum Arabic to maltodextrin ratio. Powders with the highest amount of gum Arabic have the highest diameter and the lowest water activity. High inlet temperature caused brighter colour of powders, higher dry matter content, lower water activity and apparent density of powders.     

Sweet potato-based pasta product: optimization of ingredient levels using response surface methodology

Sweet potato flour was used for the development of a pasta product. The system known as response surface methodology was used to analyse the effect of sweet potato flour, soyflour, water, Arabic gum and carboxy methyl cellulose (CMC) on quality responses (sensory, solids loss and hardness) of the pasta product. A rotatable central‐composite design was used to develop models for the responses. Responses were affected most by changes in soyflour and gum levels and to a lesser extent by sweet potato flour and water levels. Individual contour plots of the different responses were superimposed and regions meeting the maximum sensory score (33.8), minimum solids loss (16.6%) and maximum texture hardness (5616 g) were identified at 674 g kg^?1 sweet potato flour, 195 g kg^?1 water, 110 g kg^?1 soyflour, 10.6 g kg^?1 Arabic gum and 10.1 g kg^?1 CMC levels.     

X-ray diffraction analysis of lactose crystallization in freeze-dried lactose–whey protein systems

Water sorption, time-dependent crystallization and XRD patterns of lactose and lactose–WPI mixtures were studied with glass transition data. The results indicated that the sorbed water of lactose–WPI mixtures was fractional and water content of individual amorphous components in lactose–WPI mixtures at each a_w from 25 °C to 45 °C could be calculated. Crystallization occurred in pure lactose whereas partial crystallization was typical of lactose–WPI mixtures (protein content ≤ 50%) at intermediate and high a_w (> 0.44 a_w) from 25 °C to 45 °C. The extents of crystallization were significantly delayed by WPI. The T_g values of lactose–WPI systems showed the composition-dependent property in systems and might indicate the occurrence of phase separation phenomena during 240 h storage. XRD showed no anhydrous β-lactose and mixed α-/β-lactose with molar ratios of 4:1 crystals in crystallized lactose–WPI systems (70:30 and 50:50 solids ratios). Reduced crystallization in the presence of WPI was more pronounced possibly because of reduced nucleation and diffusion during crystal-growth. The present study showed that WPI could present an important role in preventing sugar crystallization.     

Stability of Cardamom (Elettaria Cardamomum) Essential Oil in Microcapsules Made of Whey Protein Isolate,Guar Gum,and Carrageenan

The effects of microencapsulating cardamom essential oil (CEO) in whey protein isolate (WPI) alone and combined with guar gum (GG) and carrageen (CG) on microencapsulation efficiency, oil chemical stability, and microcapsule structure were investigated. Freeze‐dried microcapsules were prepared from emulsions containing (w/w): 15% and 30% WPI; 0.1% GG, and 0.2% CG as wall materials with CEO (at 10% of polymer concentration) as core material, and physical properties and chemical stability were compared. Bulk density of microcapsules was highest in WPI without GG or CG and in 30% WPI + GG microcapsules, and was more affected by moisture content (r = ?0.6) than by mean particle diameter (d₄₃; r = ?0.2) and span (r = 0.1). Microcapsules containing only WPI had the highest entrapped oil (7.5%) and microencapsulation efficiency (98.5%). The concentrations of 1,8‐cineole and d‐limonene were used as indicators for microcapsule chemical stability since they were the main components of CEO. Microcapsules retained higher (P ≤ 0.05) concentrations of both components than non‐microencapsulated CEO during 16 wk storage at 20 ºC, but higher loss of both components was noted at 35 ºC. Microencapsulated d‐limonene was reduced faster than 1,8‐cineole regardless of temperature. The 30% WPI and 30% WPI + GG microcapsules retained CEO best throughout storage at both storage temperatures. Scanning electron micrographs revealed that WPI microcapsules had smooth surfaces, were relatively homogenous and regular in shape, whereas GG and CG addition increased visual surface porosity and reduced shape regularity. It was concluded that the best formulation for encapsulating CEO was 30% WPI.     

Liquid and vapour water transfer through whey protein/lipid emulsion films

BACKGROUND: Edible films and coatings based on protein/lipid combinations are among the new products being developed in order to reduce the use of plastic packaging polymers for food applications. This study was conducted to determine the effect of rapeseed oil on selected physicochemical properties of cast whey protein films. RESULTS: Films were cast from heated (80 °C for 30 min) aqueous solutions of whey protein isolate (WPI, 100 g kg^?1 of water) containing glycerol (50 g kg^?1 of WPI) as a plasticiser and different levels of added rapeseed oil (0, 1, 2, 3 and 4% w/w of WPI). Measurements of film microstructure, laser light‐scattering granulometry, differential scanning calorimetry, wetting properties and water vapour permeability (WVP) were made. The emulsion structure in the film suspension changed significantly during drying, with oil creaming and coalescence occurring. Increasing oil concentration led to a 2.5‐fold increase in surface hydrophobicity and decreases in WVP and denaturation temperature (T_max). CONCLUSION: Film structure and surface properties explain the moisture absorption and film swelling as a function of moisture level and time and consequently the WVP behaviour. Small amounts of rapeseed oil favourably affect the WVP of WPI films, particularly at higher humidities. Copyright © 2010 Society of Chemical Industry     

Spray‐drying encapsulation of citral in sucrose or trehalose matrices: physicochemical and sensory characteristics

The potential of the disaccharide trehalose as carrier for producing spray‐dried citral was examined. Some physical and sensory characteristics of citral encapsulated in matrices containing either trehalose or sucrose and maltodextrin (MD) were analysed. They included water sorption, glass transition temperatures (T_g), nuclear magnetic resonance (NMR) relaxation and citral retention during spray‐drying. The glassy state at room temperature (25 °C) was maintained as far as 33% relative humidities (RH) for the spray‐dried trehalose formulation and 43% RH for trehalose–MD; however, for sucrose–MD and for sucrose formulations, the glassy state was limited to RHs lower than 33% and 22%, respectively. Sensory evaluation and gas chromatographic analysis indicated that citral retention after spray‐drying was similar for matrices containing either trehalose or sucrose. However, trehalose formulations had improved physical stability as compared to sucrose.     

Insect‐Resistant Food Packaging Film Development Using Cinnamon Oil and Microencapsulation Technologies

Insect‐resistant films containing a microencapsulated insect‐repelling agent were developed to protect food products from the Indian meal moth (Plodia interpunctella). Cinnamon oil (CO), an insect repelling agent, was encapsulated with gum arabic, whey protein isolate (WPI)/maltodextrin (MD), or poly(vinyl alcohol) (PVA). A low‐density polyethylene (LDPE) film was coated with an ink or a polypropylene (PP) solution that incorporated the microcapsules. The encapsulation efficiency values obtained with gum arabic, WPI/MD, and PVA were 90.4%, 94.6%, and 80.7%, respectively. The films containing a microcapsule emulsion of PVA and CO or incorporating a microcapsule powder of WPI/MD and CO were the most effective (P < 0.05) at repelling moth larvae. The release rate of cinnamaldehyde, an active repellent of cinnamaldehyde, in the PP was 23 times lower when cinnamaldehyde was microencapsulated. Coating with the microcapsules did not alter the tensile properties of the films. The invasion of larvae into cookies was prevented by the insect‐repellent films, demonstrating potential for the films in insect‐resistant packaging for food products. Practical Application : The insect‐repelling effect of cinnamon oil incorporated into LDPE films was more effective with microencapsulation. The system developed in this research with LDPE film may also be extended to other food‐packaging films where the same coating platform can be used. This platform is interchangeable and easy to use for the delivery of insect‐repelling agents. The films can protect a wide variety of food products from invasion by the Indian meal moth.     

Physicochemical, mechanical and thermal properties of brown rice grain with various moisture contents

The effects of moisture content on the mechanical and thermal properties of either a short‐grain variety (Akitakomachi) or two long‐grain varieties (Delta and L201) of brown rice were studied. Total starch contents of the three varieties were comparable, but the amylose content of L201 was significantly higher than that of the other two varieties. The maximum compressive strength of brown rice grain was much higher than the maximum tensile strength. L201 showed the highest maximum compressive and tensile strengths. The phase transition temperatures (glass transition temperature T_g and melting temperature T_m) were examined by differential scanning calorimetry. The T_g and T_m for L201 were higher than those for Delta and Akitakomachi. The maximum compressive strength, maximum tensile strength, T_g and T_m for the three varieties of brown rice grains decreased with increasing moisture content. The T_g of individual brown rice kernels decreased from 53 to 22 °C as moisture content increased from 12 to 25% wet basis. A statistical model was calculated by using linear regression to describe the change in T_g in terms of moisture content.     

Structural,Thermal, Physical,Mechanical, and Barrier Properties of Chitosan Films with the Addition of Xanthan Gum

Films based on chitosan and xanthan gum were prepared using casting technique aiming to investigate the potential of these polymers as packaging materials. Six formulations of films were studied varying the proportion of chitosan and xanthan gum: 100:0 (chitosan:xanthan gum, w/w, C100XG0 film); 90:10 (chitosan:xanthan gum, w/w, C90XG10 film); 80:20 (chitosan:xanthan gum, w/w, C80XG20 film); 70:30 (chitosan:xanthan gum, w/w, C70XG30 film); 60:40 (chitosan:xanthan gum, w/w, C60XG40 film); and 50:50 (chitosan:xanthan gum, w/w, C50XG50 film). The total quantity of solids (chitosan and xanthan gum) in the filmogenic solution was 1.5 g per 100 mL of aqueous solution for all treatments, according to the proportion of each polymer. The films were evaluated by their functional groups, structural, thermal, morphological, physical, mechanical, and barrier properties. All films have presented endothermic peaks in the range of 122 to 175 °C and broad exothermic peaks above 200 °C, which were assigned to the melting temperature and thermal decomposition, respectively. These results demonstrated that films with xanthan gum have the highest T_m and Δ_mH. The films containing higher content of xanthan gum show also the highest tensile strength and the lowest elongation. Xanthan gum addition did not affect the water vapor permeability, solubility, and moisture of films. This set of data suggests the formation of chitosan–xanthan complexes in the films.     

Calorimetric study of the glass transition occurring in aqueous glucose: Fructose solutions

Glass transition temperatures (T_g) for dilute and concentrated glucose: fructose: water solutions have been determined by differential scanning calorimetry. The supplemented phase diagrams (glucose: fructose 1:4, 1:2, 1:1, 2:1, 4:1 (w/w)) are presented and from these the temperature (T_g') and concentration (C'_g) of the maximally freeze-concentrated glass have been determined. Theoretical predictions of T_g for binary (glucose: fructose) and tertiary (glucose: fructose: water) systems according to the Couchman–Karasz and Gordon-Taylor equations are given and discussed. Annealing vitrified glucose: fructose glasses above their T_g allows the glass concentration to approach C'_g as a result of ice formation. Viscosity measurements of fructose and fructose: glucose mixtures allow for a calculation of T_g of the non-aqueous solutions.     

Moisture‐Mediated Interactions Between Amorphous Maltodextrins and Crystalline Fructose

The effects of coformulating amorphous maltodextrins (MDs) and crystalline fructose, a deliquescent solid, on the moisture sorption, deliquescence point (RH₀), and glass transition temperature (T_g) behaviors were determined. Moisture sorption profiles of binary fructose:MD mixtures and individual ingredients were generated using controlled relative humidity (RH) desiccators and by dynamic vapor sorption techniques. Blends exhibited synergistic moisture uptake at RHs below the RH₀ of fructose, attributed to partial dissolution of fructose in plasticized MD matrices without a significant reduction in the RH₀ of the undissolved fructose. Increasing storage temperature decreased the onset RH for moisture sorption synergy. At all storage RHs, the measured T_g (2nd scan) was significantly reduced in fructose:MD mixtures compared to individual MDs, and was related to both the synergistic moisture uptake in the blends and heat‐induced ternary fructose–MD–water interactions in the differential scanning calorimeter. Differences were found between the behavior of fructose:MD blends and previous reports of sucrose:MD and NaCl:MD blends, caused in part by the lower RH₀ of fructose. The enhanced moisture sorption in blends of deliquescent and amorphous ingredients could lead to problematic moisture‐induced changes if storage conditions are not controlled.     

The effect of starch gelatinization and solute concentrations on T g′ of starch model system

The effect of starch gelatinization on glass transitions in a starch/water model system and how the concentrations of added solutes (sucrose and sodium chloride) affect the glass transition temperatures of the gelatinized starch solution was investigated. The starch suspension samples were heat treated in a Differential Scanning Calorimeter (DSC) under different time and temperature regimes to achieve different degrees of gelatinization. The gelatinization characteristics (onset, peak and end temperatures and enthalpy) and the glass transition values of a potato starch were determined using the DSC. The results showed that the starch concentrations had no effect on gelatinization characteristics and the T_g′ of the gelatinized potato starch but had clearly increased their ΔC_p in the T_g′ region. Annealing at a temperature slightly below the T_g′ of −5 °C, led to maximal freeze‐concentration in the total/partial gelatinized starch and a higher T_g′ value at about −3 °C was obtained. The T_g′ values of the totally gelatinized starch samples were slightly lower than those of partially gelatinized samples. The T_g′ of the gelatinized starch decreased with increasing concentrations of sucrose or sodium chloride. Sodium chloride had a stronger depressing effect on T_g′ than sucrose. © 2000 Society of Chemical Industry     

Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: in relation to glass transition

Abstract: Anthocyanins, natural plant pigments in the flavonoid group, are responsible for the red color and some of the nutraceutical benefits of raspberries. This study explores anthocyanin degradation in frozen and freeze‐dried raspberries during storage in relation to glass transition temperatures. Frozen raspberries were stored at ?80, ?35, and ?20 °C, while freeze‐dried raspberries were stored at selected water activity (a_w) values ranging from 0.05 to 0.75 at room temperature (23 °C) for more than a year. The characteristic glass transition temperatures (T′_g) of raspberries with high water content and glass transition temperature (T_g) of raspberries with small water content were determined using a differential scanning calorimeter. The pH differential method was used to determine the quantity of anthocyanins in frozen and freeze‐dried raspberries at selected time intervals. The total anthocyanins in raspberries fluctuated during 378 d of storage at ?20 and ?35, and ?80 °C. Anthocyanin degradation in freeze‐dried raspberries ranged from 27% to 32% and 78% to 89% at a_w values of 0.05 to 0.07 and 0.11 to 0.43, respectively, after 1 y. Anthocyanins were not detectable in freeze‐dried raspberries stored at a_w values of 0.53 to 0.75 after 270 d. First order and Weibull equations were used to fit the anthocyanin degradation in freeze‐dried raspberries. The 1^st‐order rate constant (k) of anthocyanin degradation ranged from 0.003 to 0.023 days^?1 at the selected water activities. Significant anthocyanin degradation occurred in both the glassy and rubbery states of freeze‐dried raspberries during long‐term storage. However, the rate of anthocyanin degradation in freeze‐dried raspberries stored in the glassy state was significantly smaller than the rate of anthocyanin degradation in the rubbery state.