Dry-pasteurization of egg albumen powder in a fluidized bed. II. Effect on functional properties: gelation and foaming

Dry‐pasteurization of egg albumen (EA) powder in a fluidized bed was studied in two experiments. Experiment 1 consisted of two different temperatures (90 and 130 °C) and experiment 2 of two air moisture levels (high and low). Powders were processed from 10 min to 3 h. The reference treatment was traditional pasteurization at 90 °C for 21 h. The fluidized bed treatment effects on gel texture, water‐holding capacity (WHC), protein binding, gel colour, foaming capacity, foam stability and surface pressure were evaluated. Gels of EA powders treated at high temperature and high air moisture levels exhibited higher stress, strain and WHC values than gels of untreated EA powder. The gel colour became significantly darker, greener and less yellow by fluidized bed treatment. Foaming and surface activity properties were un‐affected by the treatments, however, foam stability against liquid drainage correlated positively with surface pressure.     

Novel Radiofrequency‐Assisted Thermal Processing Improves the Gelling Properties of Standard Egg White Powder

Effect of radiofrequency (RF)‐assisted thermal processing on quality and functional properties of high‐foaming standard egg white powder (std. EWP, pH approximately 7.0) was investigated and compared with traditional processing (heat treatment in a hot room at 58 °C for at least 14 d). The RF‐assisted thermal treatments were selected to meet the pasteurization requirements and to improve the functional properties of the std. EWP. The treatment conditions were: RF heating to 60, 70, 80, and 90 °C followed by holding in a hot air oven at those temperatures for different periods ranging from 4 h at 90 °C to 72 h at 60 °C. The quality (color and solubility) and functional properties (foaming properties: foaming capacity and foam stability; and gelling properties: water holding capacity and gel‐firmness) of the std. EWP were investigated. RF‐assisted thermal processing did not affect the color and solubility of std. EWP at any of the treatment conditions. In general, the foaming and gelling properties of RF‐assisted thermally processed std. EWP increased with an increase in temperature and treatment duration. The optimal RF‐assisted treatment conditions to produce std. EWP with similar functional properties as the traditionally processed (hot room processed) std. EWP were 90 °C for ≥8 h. These optimal conditions were similar to those for high gel egg white powder (HG‐EWP, pH approximately 9.5). The RF‐assisted thermal pasteurization improved the gelling properties of std. EWP to the levels of HG‐EWP, leading to newer applications of this functionally improved safe product. The RF‐assisted thermal processing allows the processor to produce a HG‐EWP from std. EWP subsequent to processing while simultaneously pasteurizing the product, thus assuring the product safety.     

Challenges in Radiofrequency Pasteurization of Shell Eggs: Coagulation Rings

A total of 50 different configurations of simple radiofrequency (RF) heating at 27.12 MHz of a shell egg were simulated using a finite element model with the purpose of pasteurizing the egg. Temperature‐dependent thermal and dielectric properties of the yolk, albumen, and shell were measured, fitted, and introduced into the model. A regression equation that relates the top electrode voltage to the gap between the electrodes and vertical position of the egg was developed. Simulation and experimental results had good agreement in terms of temperature deviation (root mean squared error ranged from 0.35 °C to 0.48 °C) and both results demonstrated the development of a “coagulation ring” around the air cell. The focused heating near the air cell of the egg prevented pasteurization of the egg due to its impact on quality (coagulation). Analysis of the electric field patterns offered a perspective on how nonuniform RF heating could occur in heterogeneous food products. The results can be used to guide development of RF heating for heterogeneous food products and further development of RF pasteurization of eggs.     

Effects of ohmic heating on technological properties of whole egg

The aim of this work was to study the effects of different ohmic heating conditions on color, rheology, foaming, and gelling properties of whole egg. Industrial products treated by conventional heat pasteurization and the corresponding raw materials were also evaluated. Ohmic treatments accomplished in a static cell (65.5 °C × 3 min, 70 °C × 1 min, and 67 °C × 4.5 min) increased whole egg apparent viscosity (up to 190%), but also foam overrun (up to 28%) and gel hardness (up to 15%). The performance improvement was confirmed by treatments carried out in a continuous pilot plant (71 °C × 0.6 min, 68 °C × 1.4 min) and the products resulted stable during storage at 4 °C for 30 days. In conclusion, this study demonstrated that ohmic heating is a suitable alternative to conventional pasteurization. Low temperature treatments are preferable to avoid possible rheological issues due to protein denaturation.Industrial relevanceWhole egg is a protein ingredient with multiple technological properties, used in many foods. Due to safety reasons, food manufacturers often use pasteurized liquid egg products, microbiologically safer and easier to handle with respect to shell eggs. In order to satisfy the required sanitary levels for liquid egg products, thermal pasteurization treatments are needed. However, since egg proteins are very sensitive to high temperatures, attention must be paid to avoid coagulation entailing deleterious effects against egg quality. In this study, different ohmic heating treatments were evaluated as milder alternatives to conventional pasteurization. The lab- and pilot-scale experiments and the subsequent statistical analyses of the obtained results contributed to assess the effects of the different ohmic treatments on technological features (e.g. color, rheology, foaming, and gelling properties) of liquid whole egg. This study demonstrated that ohmic heating is a suitable technology for whole egg treatment, paving the way for new opportunities in order to produce safe food ingredients with improved technological functionalities.     

Thermo-mechanical properties of egg albumen–cassava starch composite films containing sunflower-oil droplets as influenced by moisture content

The effect of moisture content on the thermo-mechanical and structural properties of egg albumen–cassava starch composite films containing sunflower oil droplets was studied using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Composite films were prepared by cold gelation, dried in a moisture controlled incubator (83.5%RH) at 25 °C for 8 days and aged at different relative humidity at room temperature (21 ± 1 °C) for 7 days to obtain composite films with moisture contents of 4%, 7%, 11%, 17% and 46% (dry weight basis). In DMA thermograms the magnitude of G′ and G″ increased with increasing temperature in high-moisture samples, decreased and then again gradually increased for intermediate-moisture samples, and decreased in low moisture samples. DSC thermograms indicated two distinct peaks (at 49–53 °C and 79.8 to 132.4 °C) which were attributed to phase transitions and protein denaturation. SEM images indicated that the microstructure of the composite matrix changed with moisture content and heating temperature. Our study confirms that moisture content plays a key role in the thermo-mechanical properties and microstructure of egg albumen–cassava starch composite films containing sunflower oil.     

Optimisation of a pilot‐scale spray drying process for probiotic yoghurt,using response surface methodology

The influence of drying air temperatures, drying air flow rate and feed flow rate on percentage survival rate (% SR) of starter and probiotic bacteria, moisture content, water activity and colour of probiotic yoghurt powder produced using a pilot‐scale spray dryer was investigated. Optimisation of spray drying conditions was achieved based on the desirability value. Results showed that inlet air temperature, drying air flow rate, feed flow rate and outlet air temperature of 150 °C, 478 m³/h, 2 L/h and 63.3 °C, respectively, were optimal conditions to produce powder that meets quality specifications and with a satisfactory% SR.     

Optimization of Convective Dehydration of <Emphasis Type="Italic">Beta vulgaris</Emphasis> for Color Retention

Beta vulgaris or beet root powder is a good natural food colorant since beet contains significant amount of red-colored betalain pigments. This paper reports the process optimization of drying conditions to get beet root powder with maximum retention of red color. Response surface method was used with three factors: five-level central composite design to arrive at optimum drying temperature, sample thickness, and hot air recirculation. Beet powder was evaluated to assess color retention with respect to fresh beet as a control. A 53 °C temperature and 7-mm thickness with 63% air recirculation ratio gave the best product, with 90% retention of red color having acceptable rehydration ratio and final moisture content. Using optimum sample thickness and air recirculation rate, drying process was further improved to reduce drying time and energy consumption. At different temperatures (50 to 120 °C), drying characteristics were studied. Thus, drying time of 6 h was further reduced to 4 h by applying sequential temperature gradient during drying (initial 120 °C gradually reduced to 53 °C) that also resulted in energy savings with the same degree of color retention.     

Rheological Properties of Liquid Egg Products (LEPS)

Rheological properties were determined at 4°C (refrigerated temperature), 25°C (room temperature), 60°C (pasteurization temperature) for liquid whole egg (LWE) and liquid egg yolk (LEY) and 4, 25, 55.6°C for liquid egg white (LEW) by using concentric cylinder viscometer. The shear rate range was 8 to 53.7 s^?1 for LEW and LWE, and 1 to 34 s^?1 for LEY. Selected physical properties (e.g., density) of LEPs were studied at broad range of temperatures from 4°C to 60°C. All liquid egg products (LEPs) exhibited mildly shear thinning (pseudoplastic) behavior. Experimental data of LWE and LEW successfully fitted Herschel-Bulkley model, LEY data were well described by power law model. LEW and LWE showed thixotropy and time-dependency at their pasteurization temperatures (55.6°C for LEW, 60°C for LWE) and considered being time-independent below these temperatures. LEY exhibited time-dependent behavior at 4°C and 60°C. But its rheological behavior showed no thixotropy and time-dependency at room temperature. The density of all three products decreased with increasing temperature. Density data were correlated by polynomial models (r² > 0.99).     

Factors Influencing Ellagic Acid Precipitation in Muscadine Grape Juice During Storage

Ellagic acid sedimentation in white muscadine grape juice was monitored following different processing treatments and storage temperatures. High storage temperatures (40°C) greatly accelerated sediment formation, and pasteurization (100°C, 10 min) resulted in a faster sediment formation than sterile filtration. Sediment also increased substantially after juice was hydrolyzed (121°C and pH 2 for 10 min). Ultrafiltration of juice through a 10,000 or 30,000 dalton membrane resulted in significantly less sediment formation in the juice. Treatment of juice with polyvinylpolypyrrolidone (0.1– 0.2 g/L juice), egg albumen (6–10 mg/L juice) or gelatin (0.05 – 0.4 g/L juice) resulted in a significant reduction of juice phenolics and sediment formation. A commercial pectinase added to the grapes increased sediment formation and total phenolics in the juice. Levels of ellagic acid in juice were very low and did not correlate well with amount of sediment formed.     

Process optimisation of encapsulated pandan (Pandanus amaryllifolius) powder using spray‐drying method

A study on the production of spray‐dried pandan (Pandanus amaryllifolius) powder was conducted and optimised using response surface methodology (RSM). Parameters investigated include inlet temperature (170–200 °C) and feed rate (6–12 rpm), with a preset outlet temperature of 90 °C. The estimated regression coefficients (R²) for the physicochemical characteristic and sensory responses of pandan powder were ≥0.800, except for overall acceptability. Some mathematical models could be developed with confidence based on the results from all responses. An optimum drying process for spray drying represents conditions that would yield acceptably high colour index (such as L value, a value and b value), low moisture content, low water activity (a_w), high solubility and high colour, flavour, odour and overall acceptability for sensory responses. Optimum conditions of 170 °C inlet temperature and 6 rpm feed rate, with a constant outlet temperature of 90 °C, were established for producing spray‐dried pandan powder as an edible colouring and flavouring powder. Copyright © 2005 Society of Chemical Industry     

Loss of essential oil of tarragon (Artemisia dracunculus L.) due to drying

The effect of hot air‐drying on the essential oil constituents and yield in French and Russian tarragon (Artemisia dracunculus L.) leaves was studied. The tarragon leaves were dried at air temperatures ranging from 40 to 90 °C. The drying stopped when the moisture content of the samples reached 10% or for some of the treatments reached 7, 20 and 30%. The essential oil of the fresh and dried leaves was isolated by hydrodistillation and analysed by capillary gas chromatography and gas chromatography–mass spectrometry. The decrease of oil during the drying process was highest at 60 °C drying temperature. For French tarragon the decrease in the amount of oil was significantly lower at 90 °C. The effect of the relative humidity of the drying air at each temperature was not significant. The main compounds were estragole in French tarragon (69%) and sabinene in Russian tarragon (40%). The drying process changed the relative percentage of the constituents in the oil; for instance, the relative percentages of estragole decreased and sabinene increased in French tarragon. Copyright © 2006 Society of Chemical Industry     

The nutritive value of porcine blood plasma concentrates prepared by ultrafiltration and spray Drying

Concentrated solutions of porcine blood plasma proteins, prepared by centrifugation and ultrafiltration⁴ were spray dried directly at air inlet temperatures of 154, 170.3, 225 and 243.2 °C. Spray dried concentrates contained ca 86–90% protein, ca 2–7% moisture and ca 5% minerals. The overall amino acid composition of the plasma proteins compared favourably with that of FAO whole egg protein.¹² Although the values of essential amino acids generally fell below the egg values, the only serious limitations were in the content of isoleucine (less than half of the egg value). The chemical score (CS) and essential amino acid index (EAAI) were 49.1 and 70.1 respectively. Rats fed on a diet containing plasma concentrate as the sole protein source showed a net weight increase. NPU carcass for plasma protein was 65.8 ± 1.9 compared with a value of 72.1 ± 0.4 for a casein control. An inverse correlation between denaturation status of plasma proteins and spray drying temperature was found. The percent denaturation as measured on pH 4.0 filtrates increased from 8.4% at an air inlet temperature of 154 °C to 48.6% at a temperature of 243.2 °C. A similar inverse relationship was found between the available lysine content of plasma proteins and spray drying temperature. A maximum decrease in percent lysine availability of 16% was found at an air inlet drying temperature of 243.4 °C.     

Modeling Gelation of Egg Albumen and Ovalbumin

The Flory gelation theory and a new protein gelation model were used to investigate the aggregation reactions of egg albumen and ovalbumin. Results showed that 178 to 267 ovalbumin monomers were required to establish the initial ovalbumin gel at the gel point temperature, 81°C. The gel point temperature for egg albumen was 72°C by the Instron and 60°C by protein solubility. The values of the activation energy rate constants for the formation of the different aggregates in the pre-gel stage suggested that the larger ovalbumin aggregates were more reactive than the smaller ones.     

Storage stability of coconut milk powder

Spray-dried coconut milk powder prepared with additions of skim milk and dextrin was stored in packages for 6 months at room temperature (30°C and 80% RH). The packaging materials used were aluminum laminate (vacuum and air packed) and polypropylene. The sorption isotherm of the powder showed that the monolayer of water molecules was complete when the relative humidity was 27% which corresponded to a moisture content of 5%. Measurements of water activity, moisture content, peroxide value and solubility index indicated that lipid oxidation is the limiting factor in the stability of the powder. Its maximum shelf-life was 4 months when air or vacuum packaged in aluminum laminates and 1 1/2 months in polypropylene.     

Evaluation of spray drying conditions on properties of microencapsulated oregano essential oil

Response surface methodology (RSM) was employed to investigate variations in powder characteristics with respect to spray drying operating parameters including both feed rates (L min^?1) and inlet temperatures (°C). Inlet temperatures around 180 °C provided the lowest values for moisture. Powder recovery was significantly affected (P < 0.10) by inlet air temperature and feed rate, where a raise in inlet temperature and feed rate resulted in higher powder recovery. No significant difference (P > 0.05) was observed for water activity, solubility and hygroscopicity between treatments. Regarding oil retention, the results showed a significant (P < 0.05) interaction between the two studied factors. A tendency for higher values of oil retention was observed when using combinations of high inlet temperatures/low feed rates and low inlet temperatures/high feed rates. Particle size distribution averaged 2.0, 8.1 and 18.3 μm for D₁₀, D₅₀ and D₉₀, respectively. The morphology of particles showed no cracks in most capsules. The results indicate that high temperature (185 °C) and moderated feed rate (0.63 L min^?1) are the best spray drying conditions.     

Effects of foam-mat drying temperature on physico-chemical and microstructural properties of shrimp powder

This study was carried out to investigate the impact of different drying air temperatures (45, 60, 75, and 90 °C) on the physico-chemical and microstructural properties of foam-mat-dried shrimp powder. Physico-chemical properties such as moisture content, water activity, solubility, water binding capacity (WBC), and color of the powder were determined. The experimental results showed that as the temperature increased, the moisture content, water activity, and WBC of the samples decreased. However, their solubility increased significantly (p < 0.05). Furthermore, the total color difference (ΔE) increased by increasing temperature, yet decreased at 90 °C. The SEM images indicated as the drying temperature increased, the mat structure porosity increased, too, especially at 90 °C.Industrial RelevanceThe demand for ready-to-eat (RTE) and/or ready-to-cook (RTC) meals is gradually growing because they are easy to prepare. The dried shrimp powder can be used for producing formulated seafood and other food products such as soups, sauce, snacks, etc. to increase the protein content and improve the nutritional value of them. Fish and shrimp soup mixes and snacks are examples of dried RTE products. They are popular in Asian countries, due to easy transportation, quality, stability, and long shelf life.     

Rheological Properties of Pasteurized Liquid Whole Egg During Frozen Storage

Effects of pasteurization and frozen storage on the rheological behavior of liquid whole egg (LWE) were studied using a cone and plate viscometer. Homogenized LWE control and LWE heated at 60°C, 64°C or 68°C for 3.5 min were evaluated during 80 days storage at ?24°C. Thixotropic behavior was observed in all frozen samples. Apparent viscosity increased with pasteurization and frozen storage. Unpasteurized LWE exhibited Newtonian behavior throughout storage. Pasteurized LWE flow properties changed from Newtonian to Bingham Plastic during storage. Identification of rheological parameters will help understand the molecular changes that occur during the processing and storage of LWE and help processors monitor LWE quality.     

The significance of critical processing steps in the production of dried egg albumen powder on gel textural and foaming properties

The purpose of the present work was to study the variation in egg albumen functional properties as a function of seven selected processing steps from the initially raw liquid albumen to the final dried egg albumen powder. Albumen samples in six replicates were analysed for dry matter, pH, glucose, triglycerides, albumen gel properties (ie textural stress and Hencky strain, water‐ and protein‐binding capacity and gel colour L*, a*, b*), foaming properties (ie overrun, stability against drainage and bubble breakdown) and surface tension. The gel texture and water‐holding capacity significantly decreased during the processing steps from raw albumen through storage, centrifugation and ion exchange, whereas the final dry‐pasteurisation resulted in increased gel properties. Covalently linked protein polymers formed during the dry‐pasteurisation, as revealed by SDS‐PAGE, may explain this improvement. The foam overrun increased twofold during the three final steps of ultrafiltration, spray‐drying and dry‐pasteurisation compared with the raw albumen; however, the foam stability decreased, ie drainage and foam volume breakdown rates increased. The surface pressure increase was positively correlated with the foam overrun. This paper reveals at which processing steps the control of functional properties of egg albumen powder can take place. Copyright © 2004 Society of Chemical Industry     

Dehydration of red beet root (<Emphasis Type="Italic">Beta vulgaris</Emphasis>) by hot air drying: Process optimization and mathematical modeling

Convective hot air drying was optimized with the objective of maximum color retention of red beet. The process was mathematically modelled as a function of hot air temperature, batch time, and moisture. New semitheoretical model was tested with experimental data (50 to 120°C) and was found better than 9 other reported models. Estimated effective moisture diffusivity was 3.01×10⁻⁹ to 7.21×10⁻⁷ m²/s and it obeyed Arrhenius’s equation. Color and rehydration ratio were used to assess the quality of beet powder. An unusual trend of color minima was also observed; which was attributed to the physical phenomena of surface moisture. The final color of beet was temperature dependent and maximum color retention was achieved at lowest drying temperature. Best drying condition required sequential reduction in temperature (120 to 50°C) resulting in good color retention. This reduced batch time to 4 h compared to 6 h batch of conventional isothermal drying at 50°C.     

Production and characterisation of duck albumen hydrolysate using enzymatic process

Influences of different ultrasound treatments combined with heat pretreatment on enzymatic hydrolysis, emulsifying properties and antioxidant activities of hydrolysates from duck egg albumen were studied. Heat pretreatment at 95 °C for 30 min inhibited both serine and cysteine protease inhibitors effectively. Ultrasonication of heated duck albumen at 60% amplitude for 10 min yielded the highest surface hydrophobicity. Coincidentally, aforementioned pretreatment rendered the hydrolysate with highest degree of hydrolysis (DH) than other pretreatments when Alcalase was used. The resulting hydrolysate showed the highest antioxidant activities including DPPH radical and ABTS radical cation scavenging activities and ferric reducing antioxidant power as well as emulsifying properties when hydrolysis time of 90 min was used. The hydrolysate possessed the peptides with molecular weight of 219–255 Da with the highest ABTS radical scavenging activity. Thus, heat pretreatment, followed by ultrasonication of duck albumen under appropriate condition could increase DH, antioxidant activities and emulsifying properties of duck albumen hydrolysate.