Maximum Foaming Capacity Research Articles

DRYING OF CHERRY LAUREL JUICE USING FOAM MAT DRYING TECHNIQUE AND INVESTIGATING THE EFFECT OF DRYING TEMPERATURE ON DRYING CHARACTERISTICS AND BIOACTIVE COMPONENTS

This study aimed to optimize the foam properties for the foam mat drying (FMD) process and investigate the effect of drying temperatures (60, 70, and 80 °C) on the cherry laurel juice's drying characteristics and bioactive properties. Egg white protein (EWP), carboxymethyl cellulose (CMC), and mixing time (MT) variables were optimized using the Taguchi method to achieve the juice foam with maximum foam capacity and stability. The optimal conditions determined were 10% EWP, 0.3% CMC, and 12 min of MT. The drying times and effective moisture diffusivities (Deff) for 60, 70, and 80 °C were recorded as 160, 120 and 90 min and 6.09×10-9, 7.74×10-9 and 11.33×10-9 m2/s, respectively. As the drying temperature increased, the total phenolic and total monomeric anthocyanin contents, and antioxidant activity values increased, but ascorbic acid content decreased. This research demonstrates that the FMD process can successfully be applied to dry juices with pronounced bioactive properties.

Towards a universal model for the foaming behavior of surfactants: a case study on per- and polyfluoroalkyl substances (PFAS).

Foam fractionation offers a promising solution for the separation of surface-active contaminants from water. Therefore, this work aims to comprehensively investigate foaming behavior and its correlations with the interfacial properties. As a case study, we evaluate foaming of per- and polyfluoroalkyl substances (PFAS), which are one of significant environmental issues worldwide due their pervasive presence in the environment. Since there is no universal model to describe the foaming behavior of surfactants that can be applied to PFAS, this research utilizes dimensional analysis to establish a correlation between the foaming behavior of PFAS solutions-characterized by expansion rate of foaming-and dimensionless numbers that represent both processing and interfacial characteristics. Foaming parameters, such as gas flow rate and aeration time, are varied to study their effect on PFAS foamability. In addition, we study PFAS with different headgroups and with different chain lengths in the presence of electrolytes with different concentrations. Our study elucidates distinct, condition-specific equations for individual PFAS, revealing that long-chain PFAS foaming is significantly influenced by interfacial property-related dimensionless numbers, such as the Boussinesq number. Additionally, the Froude number and Weber number affect the foamability of both long- and short-chain PFAS. Moreover, our study identifies specific trends, including a maximum foaming capacity at a certain Capillary number, aligning with the maximum in dilatational interfacial modulus. The results suggest more studies are needed on bubble interaction and foam film behavior.

ИССЛЕДОВАНИЕ ПЕНООБРАЗУЮЩЕЙ СПОСОБНОСТИ БЕЛКОВОЙ СМЕСИ НА ОСНОВЕ ЭРИТРИТОЛА

The article provides a brief analysis of the use of natural sugar substitutes in the production of finishing semi-finished products. The possibility of reducing both the total calorie content of the product and the consumption of sugar in general, which negatively affects the human body, is shown. The process of foaming is considered as important and determining in the preparation of the finishing semi-finished prod-uct. The purpose of the work is to improve the quality of finishing semi-finished products enriched with non-traditional herbal additives - the sweetener erythritol. The objects of the study were a protein-carbohydrate mixture prepared on the basis of egg white and pectin. A relationship has been established between the intensity of whipping and the foaming properties of a whipped semi-finished product – the basis for the production of a finishing semi-finished product. When whipping 100 g of the recipe mixture at 560 rpm of the mixer, the volume increased by 1.5 times, with a further increase in the intensity of whipping to 1200 rpm, the maximum volume was noted, which increased by 4 times compared to the ini-tial one. With a further increase in the whipping intensity up to 2000 rpm, the structure of the finishing semi-finished product liquefies. The experimental sample of the finishing semi-finished product is charac-terized by the maximum increase in foaming capacity in the pH range of 5.2 – 5.4. At the isoelectric point corresponding to pH 5.5-7.0, protein solutions exhibit maximum foaming capacity at a temperature of 20оC. An analysis of the data obtained shows that at the beginning of the solution churning, the system is actively saturated with air, air bubbles form, and separate. This leads to a sharp increase in the amount of air in the mixture and a strong decrease in the density of the entire churned mass. Having reached the maximum value, the volume concentration of air remains constant for a short time, after which it gradual-ly decreases.

Optimization of pomelo ( Citrus grandis L. Osbeck ) juice foam composition: Effect of foam composition on foam quality

In this study, the effect of pomelo juice foam composition on the foam properties was investigated for the production of foam mat-dried pomelo juice powder. The pomelo juice foam was prepared using maltodextrin (MD), glycerol monostearate (GMS), and carboxymethyl cellulose (CMC) at various concentrations in the range of 2–8%, 0.5–2%, and 5–10%, respectively. A face-centered central composite design was followed. The optimum quality of stable pomelo juice foam was evaluated in terms of minimum foam density, minimum foam collapse, maximum foam stability, and maximum foam capacity. The optimum concentration of the foaming agents as obtained through numerical optimization using design expert 10.0 was 6.027% MD, 1.217% CMC, and 8% GMS with a desirability of 0.777. The foam quality at optimum conditions was as follows: 0.769 g/cc foam density, 92% foam stability, 12.66% foam collapse, and 91.74% foam capacity. Feasibility or incorporation of the developed pomelo juice powder in bakery products, ice cream, yogurt, etc., could be tested for wide applicability. Novelty impact statement The present study aims at optimizing pomelo juice foam composition to produce good quality stable foam so as to convert it into foam mat-dried powder. Foam mat-dried pomelo juice powder has very good reconstitution property and the reconstituted juice is a rich source of vitamin C and other minerals. The findings of the present study would facilitate the production of foam mat-dried pomelo juice powder which has good potential for diet conscious persons.

Foaming and air-water interfacial properties of camel milk proteins compared to bovine milk proteins

The objective of this research was to explore the foaming properties of camel and bovine milk and their derived proteins fractions including sodium caseinates, sweet whey, β-casein, α-lactalbumin and β-lactoglobulin. First, camel and bovine milk proteins were identified by the reversed-phase high-performance liquid chromatography (RP-HPLC) and foaming properties (Foam capacity (FC) and stability (FS)) were analyzed. Afterwards, competitive adsorption of proteins to the air-water interface for both milk protein fractions was characterized using pendant-drop tensiometry parameters and was compared to intrinsic fluorescence results of pure proteins. Experimental results indicated that the maximum FC values were found for camel skim milk, sodium caseinates and β-casein with higher FS values for bovine β-casein. Differences in the stability and the highest tensioactive properties of camel β-casein were explained with the different molecular structure and its higher hydrophobicity when compared to its bovine counterpart. Thus, milk proteins adsorbed layers are mainly affected by the presence of β-casein which is the first adsorbed and the most abundant protein at the air-water contrary to whey proteins (α-lactalbumin and β-lactoglobulin). These globular proteins are involved in the composition of protein layers at air-water interface, giving higher viscoelastic modulus values, but could not compact well at the interface because of their rigid molecular structure. For camel milk, foaming properties and interfacial behavior are mainly maintained by camel β-casein due to its higher hydrophobicity compared to bovine β-casein and the greater exposure of tyrosine residues despite the absence of tryptophan in consistence with the intrinsic fluorescence results. Furthermore, the absence of the β-lactoglobulin leads to the dominance of the α-lactalbumin at the air-water interface which is characterized by lower hydrophobicity than its bovine counterpart leading to lower viscoelastic modulus values than those of bovine whey, and hence to weaker rheological properties of camel milk protein layer at the air-water interface.

Protein isolate from Stauntonia brachyanthera seed: Chemical characterization, functional properties, and emulsifying performance after heat treatment

The seed of Stauntonia brachyanthera is usually regarded as waste after fructus processing. Here, the potential utilization value of the protein isolate (SSPI) from seeds was evaluated by investigating its physicochemical and functional properties. SSPI was a complex protein containing 7 distinct subunits that had high contents of most essential amino acids. The maximum foaming capacity of SSPI was 406.7 ± 41% at pH 9.0, and the water holding/oil adsorption capacities were 4.66 g/g and 9.06 g/g, respectively. SSPI aggregates with a particle size of 154.1 ± 5.2 nm was prepared after heat treatment, which was performed as a Pickering-like stabilizer for the structuring of water-in-oil-in-water emulsions. The outer droplet size of emulsions decreased as the aggregate concentration increased. Emulsion gels could be observed with the increasing aggregate concentration and oil fraction. Further study found that the stabilities of inner water-in-oil droplets and creaming were progressively increased by increasing the aggregate concentration during storage.

Optimizing the extraction of protein from Prosopis cineraria seeds using response surface methodology and characterization of seed protein concentrate

Prosopis cineraria is one of the leguminous trees in arid India, and its pods are known as “Sangri”. The study aims to optimize the extraction condition for soluble protein from Sangri seed flour using response surface methodology considering pH (8–12), extraction temperature (30–60 °C) and time (1–3 h) as variables. The optimized condition suggested employing the isoelectric precipitation method at pH 9.81 for 100 min at 60 °C would lead to the maximum soluble protein of 310 g kg−1. The molecular weight of the seed protein concentrate (SPC) was found to be 26.5 kDa exhibiting an amorphous nature having a crystallinity index value of 0.97. The denaturation heat (ΔH) for SPC was 238.16 J/g with a transition enthalpy of 11.5 J/g of protein. The solubility of SPC is 41.5% at pH 7. The water and oil holding capacity of SPC were 3.87 g/g and 1.4 g/g, respectively; whereas, the maximum foaming capacity of SPC was 40.5% at pH 12. The total phenolic content in the concentrate was 2.8 mg GAE/g with an antioxidant capacity of 3.0 mg AAE/g. During the extraction, the antinutrients such as tannin, saponin, and phytate content were reduced by 95, 50, and 42%, respectively.

Foam mat drying of fig fruit: Optimization of foam composition and physicochemical properties of fig powder

AbstractIn this study, we report an optimization study on fig foam composition and hot air/microwave‐assisted foam mat drying (FMD) at different conditions to produce fig powder. The effects of foam composition on foam stability and capacity were evaluated. The optimum ratio of fig, egg white, carboxymethyl cellulose, and maltodextrin was determined as 52.9, 28.9, 0.8, and 17.4% (wt/wt), respectively, targeting maximum foam capacity and minimum drainage volume, that is, maximum foam stability. The effects of drying methods and their conditions were investigated on the drying rate of fig foam and physicochemical properties of fig powder. Moisture content, water activity, particle and bulk properties, and hydroxymethylfurfural and total phenolic contents of FMD fig powder were analyzed to understand the effect of drying methods and conditions on the physicochemical properties of fig powder.Practical applicationsAlthough fig fruit is generally dried as a whole, the ready‐to‐eat foods in the food market are mostly in powder form. That is why the powdering fig fruit by an appropriate drying method is essential. In this study, we report the foam mat‐dried (FMD) fig fruit powder. The fig foam composition was optimized. The fig foam was dried through hot air and microwave separately. The results showed that the foam capacity and stability of the fig powder highly depend on the foam composition. Microwave drying method was found more efficient than the hot air in the sense of time. Besides, the higher foam thickness provided more hydroxymethylfurfural content in the fig powder. The drying method and conditions were found to be important to produce a high‐quality FMD fig powder.

Effect of ultrasonication on physicochemical and foaming properties of squid ovary powder

Central composite design (CCD) in conjunction with response surface methodology (RSM) was used to optimize the ultrasonication conditions for the improvement of foaming properties of squid ovary powder (SOP). Ultrasonication at amplitude 70% for time 30 min was the optimized condition based on predictive models. Ultrasonication affected physicochemical properties and structure of SOP. Surface hydrophobicity of ultrasonicated SOP was increased by 28%. Solubility was decreased slightly with coincidental decrease in total sulfhydryl group. Nevertheless, ultrasonication had no impact on protein pattern. Mean particle size was reduced by 64.1% for SOP after ultrasonication. Differential scanning calorimetric study revealed that ultrasonication affected transition temperature of proteins in SOP. Foaming capacity (FC) of ultrasonicated SOP was increased by 83.3%, compared to the control. When effect of various whipping times on foam properties was examined, the maximum FC (320%) and the lowest liquid drainage was attained when the ultrasonicated SOP was whipped for 3 min. Ultrasonication also improved the foam properties of SOP by increasing G´ and G´´. Microstructure study revealed that smaller sized bubbles with uniform distribution and thicker lamella were obtained in foam of ultrasonicated SOP. Additionally, foam of ultrasonicated SOP was more stable after 60 min. Thus, ultrasonication under the optimal condition along with appropriate whipping time yielded the foam from SOP with increased foaming capacity and stability.

Polypeptide Profile, Amino Acid Composition and Some Functional Properties of Calabash Nutmeg (Monodora myristica) Flour and Protein Products

AbstractThe aim of this work was to compare the physicochemical and functional properties of calabash nutmeg (Monodora myristica) seed protein flour with those of protein‐enriched products (albumin, globulin, and protein isolate). Defatted M. myristica seed flour (MMF) was used to prepare various protein products. A NaCl extract of MMF was dialyzed against water to obtain the soluble albumin fraction (MMA) and a precipitated globulin fraction (MMG). MMF was also extracted with NaOH, the extract adjusted to pH 4.0 and the precipitated proteins collected as the isolate (MMI). Non‐reducing gel electrophoresis showed that the MMF, MMG and MMI had similar composition that was dominated by 55 and 110 kDa polypeptides while MMA consisted mainly of smaller (<35 kDa) polypeptides. However, under reducing conditions, the 110 kDa polypeptide was not observed. Amino acid composition revealed an Arg/Lys ratio that increased in the extracts (1.92, 2.28 and 2.11 for MMA, MMG and MMI, respectively) relative to that in MMF (1.85). MMA had 67.5–86.5% protein solubility in the pH 4.0–6.0 range while those of MMF, MMG, and MMI were 37.7–63.8, 2.7–69.4 and 3.8–55.1%, respectively. MMA, MMG and MMI were found to be better emulsifiers based on their smaller oil droplet sizes (8–14 μm) compared with the 14–33 μm for MMF emulsion. Maximum foaming capacity was highest for MMI (205%) when compared with MMA or MMG (150%) and MMF (89%). We conclude that protein enrichment led to significantly enhanced emulsion and foam‐forming properties but high solubility may have contributed to reduced emulsion stability.

Physicochemical and functional properties of Moringa oleifera seed and leaf flour

Secondary structure of protein, surface hydrophobicity, and functional properties of defatted Moringa olifeira seed and leaf flour were studied. Protein presented high β-sheet (32.77–41.11%) and β-turn (37.97–39.31%) structures. Water holding and oil absorption capacities of leaf flour were adequate for using in food formulations. Surface hydrophobicity of seed flour increased significantly at pH 9. Leaf protein was more soluble than the seed one, excepted at pH 4–5. Neutral and basic pH favoured emulsifying capacity (EC) of seed flour. The maximum EC was 52.17%. The emulsion stability (ES) was greater at acidic pH and seed flour concentration of 4% (w/v). The maximum ES (53.84%) was observed pH 4 and oil to water ratio of 1/2 (v/v). For applications where high foaming properties are required, it is important to use the seed flour at combined high pH and concentration. The maximum foam capacity and stability (87.50 and 82.50%, respectively) was observed at pH 9 and flour concentration of 4% (w/v).

红萍叶蛋白功能特性研究

本文为了探究红萍作为食品开发利用的可行性，以经脱色、去腥后所得红萍(卡州萍3001(A. caroliniana Wild.3001)为代表)叶蛋白为材料，对其溶解性、持水性、吸油性、起泡性及乳化性等进行测定，结果显示：红萍叶蛋白溶解性、持水力均随温度的升高先升高后降低，在温度为50℃时，溶解性、持水力最大；吸油性随着温度的升高而增大，吸油能力在4.8~6.0 mL/g之间；起泡性及起泡稳定性在叶蛋白浓度为6%时，最大值分别为176.6和72.5；乳化能力及乳化稳定性均随叶蛋白浓度的增大而增大，乳化能力在15~30之间，乳化稳定性在60~80之间。 In order to explore the feasibility about Azolla as food, we test the Azolla leaf protein solubility, water holding capacity, oil absorption, foaming and emulsifying properties. The results show that: The solubility and water holding capacity of Azolla leaf protein first increase and then decrease with the increasing temperature. When the temperature is 50˚C, solubility and water holding capacity are highest; oil absorption increases with the growth of temperature; oil absorption capacity is between 4.8 and 6.0 mL/g. When the leaf protein concentration accounts for 6%, the maximum foaming capacity is 176.6, and the foaming stability is 72.5. The degree of the emulsifying capacity and stability goes up with the increase of leaf protein concentration, with emulsibility between 15 - 30, emulsification stability between 60 - 80.

Physicochemical, Functional and Antioxidant Properties of Diplazium esculentum Leaf Protein Concentrate

Development of plant based low cost protein products is need of the hour. Diplazium esculentum, a sustainable and abundantly available edible species, can be utilized to produce such types of products. The present study aimed to explore the production of Leaf Protein Concentrate from D. esculentum and its assessment for various essential properties for food applications. D. esculentum leaf protein concentrate (DELPC), showed minimum protein solubility (9.36%) at pH 4. Water absorption capacity, oil absorption capacity and bulk density were 1.29±0.02 ml/g, 1.32±0.12ml/g and 0.45±0.01g/ml, respectively. Maximum foam capacity (61.72±2.76%) and foam stability (73.73±2.54%) were at pH 2 and 4 respectively. Maximum emulsion properties were recorded at pH 10. DELPC showed a maximum emulsion capacity (56.57±0.93%) and maximum emulsion stability (54.07±1.65%) at the salt concentration of 0.4M and 0.6M respectively. Mineral contents were found in the range of 84.5 to 312.2 mg/kg. IC50 values of DELPC for DPPH., DMPD·+ and ABTS·+ scavenging were determined as 10.23±0.85, 14.67±1.52 and 7.95±1.04 mg/ml respectively. The study supports the suitability of DELPC for various dietary supplement preparations, or as a food additive, to prevent oxidation in food products or even also in protein rich food where antioxidant character is likewise important. Keywords: Antioxidant, Diplazium esculentum, Functional properties, Leaf protein concentrate.

Effects of environmental factors on functional properties of Chinese chestnut (Castanea mollissima) protein isolates

Chestnut is a nutritious food source. The effects of physical force on the functional properties of chestnut protein isolates were investigated. Maximum protein solubility, emulsion activity, emulsion stability, and foam capacity, as well as minimum protein solubility, emulsion activity, and foam capacity were observed at pH 12 and 4, respectively. The highest foam stability rate was observed at pH 4, particularly after 60 min. At the same ionic strength, the protein in NaCl showed better solubility than CaCl2. The presence of Ca2+ significantly enhanced the foam capacity and stability of chestnut protein, and the maximum foam capacity was 77.3 % at 0.8 mol/L ionic strength of Ca2+. Sugar could enhance foam stability but inhibit foam capacity, and appropriate concentrations (0.05–0.1 mol/L) increased emulsion activity and stability. The chestnut protein isolates had good emulsification and foam properties, and can be used as additives in food products requiring specific functional properties.

Experimental Design and Optimization of Ultrasound Treatment:Functional and Physical Properties of Sonicated Ice Cream Model Mixtures

The aim of this study was to determine the effect of high power ultrasound on functional properties of ice-cream model mixtures. Mixture composed of sucrose, glucose, whole milk powder, whey protein concentrates (WPC) and distilled water was ultrasonically treated according to different parameters. Amplitude of ultrasounds, percentage of WPC in the sample and time of treatment are the three variables considered. Effect of ultrasound parameters on rheological properties (measurement of coefficient of consistency), thermal properties (measurement of initial freezing point) and foaming properties (measurement of maximal foam capacity) was observed. Experiment was designed using model called Central Composite Design (CCD) permitting to consider the significant factors for each property, and results were analyzed and process was optimized through response surface methodology-RSM. Through study, optimal conditions of ultrasound treatment (amplitude, treatment time and percentage of WPC) by which experiment should be performed were obtained. The factor “percentage of WPC” is significant from a rheological and thermal point of view. Regarding foaming properties, the significant factor that is to say affecting most the value of the maximum foam capacity is the duration of ultrasound treatment.

Proximate composition of Karkadeh (Hibiscus sabdariffa) seeds and some functional properties of seed protein isolate as influenced by pH and NaCl

Seeds of an inbred line (B-11-90) of Karkadeh (Hibiscus sabdariffa) were investigated for their proximate composition (AOAC methods), nitrogen solubility and protein isolate (Karkadeh seed protein isolates [KSPI]) functional properties (standard methods). The fat and protein contents of the seeds were 22.43% and 32.46%, respectively. Nitrogen solubility was good in both water and 1.0 M NaCl at alkaline pH rather than at acidic pH, with better solubility at higher pH levels in water than in 1.0 M NaCl. The functional properties of the KSPI were as follows: water absorption capacity, 181 ml/100 g; fat absorption capacity, 110 ml/100 g; bulk density, 0.77 g/ml; and apparent viscosity (at 20°C), 13.42 cps. KSPI showed a maximum foaming capacity at pH 12 and 1.6 M NaCl, a maximum emulsification capacity at pH 11 and 1.8 M NaCl, and a weaker foam stability at neutral pH than at acidic or alkaline pH, with a better foam stability at alkaline pH. The foam stability was considerably improved by treatment with 1.6 M NaCl.

Stabilization of foams solely with polyoxyethylene-type nonionic surfactant

Long-term stability is desirable for many foam-based systems, but achieving it is rather difficult. We report how foams can be stabilized solely with nonionic surfactant of the polyoxyethylene dodecyl ether (C 12EO n ). Effects of concentration and EO chain length of surfactants namely C 12EO 3, C 12EO 5, C 12EO 7 and C 12EO 9 on foaming properties (foamability and foam stability) were considered. The liquid drainage profiles of foams prepared were determined by reading the volume of the liquid drained as a function of time. The microstructure and viscosities on these colloidal systems were studied using optical microscopy and viscosimeter in attempt to explore the stability mechanisms. The experimental results suggest that the foamability goes through a maximum at the concentration of 10 wt.%, respectively, except for C 12EO 7. The optimal concentration of C 12EO 7 displaying maximum foaming capacity is at 1 wt.%. The stability of foams increases with increment of surfactant concentration. Foams stabilized solely by C 12EO 3 and C 12EO 5 at the concentration of 30 wt.%, respectively, exhibit the presence of lamellar liquid crystal adsorbed at the air/liquid interface, and could maintain more than 20 h without occurrence of collapse. In the case of foams generated from C 12EO 7 and C 12EO 9 under same concentration, respectively, there is no any optical fine structure between two air bubbles and thus has a poor stability only for tens of minutes. It is concluded that the stability of foams stabilized solely by C 12EO n surface active agents is attributed to the presence of lamellar liquid crystalline phases located at the gas/liquid interface. The role of liquid crystal in stabilizing foams could be explained in several mechanisms including hydrodynamic drainage, the mechanical strength of the liquid film and the diffusion rate of entrapped gas. The drainage behavior from these foams was well fitted by the empirical equation V t = V max t n /( K n + t n ) and the mechanism of liquid drainage was also discussed.

Characterization of Apple Juice Foams for Foam-mat Drying Prepared with Egg White Protein and Methylcellulose

: Intrinsic stability and rheological properties of apple juice foams for foam mat drying were studied. Foams were prepared from clarified apple juice by adding various concentrations of 2 foaming agents of different nature: a protein (egg white at 0.5%, 1%, 2%, and 3% w/w) and a polysaccharide (methylcellulose at 0.1%, 0.2%, 0.5%, 1%, and 2% w/w), and whipping at different times (3, 5, and 7 min). In general, egg white foams were less stable but showed a higher degree of solidity (stronger structures), higher foaming capacity, and smaller bubble average diameter than methylcellulose foams. Foam stability increased with increasing concentrations of either methylcellulose or egg white. Increasing whipping times increased the stability of egg white foams only. Stability parameters (maximum drainage and drainage half-time) were correlated in terms of rheological parameters of the continuous phase (consistency index and apparent viscosity at 30/s, respectively). The correlations (R2= 0.766 and 0.951, respectively) were considered acceptable because they were independent of whipping time and foaming agent nature and concentration. Results on foam rheology obtained by dynamic and vane tests were in agreement, but the latter method was more sensitive. Optimal concentrations to obtain the most solid foams (0.2% methylcellulose and 2% to 3% egg white, respectively) were the same concentrations required for maximum foaming capacity. Based on this observation and previous models, an empirical expression was proposed to predict the degree of solidity (in terms of inverse phase angle and yield stress) only as a function of foam structural properties (air volume fraction and average bubble size). The model proved to be satisfactory to fit experimental results (R2= 0.848 and 0.975, respectively), independently of whipping time, foaming agent nature and concentration.

Functional properties of a spray-dried porcine red blood cell fraction treated by high hydrostatic pressure

The aims of this study were to evaluate the functional properties of a spray-dried porcine red blood cell fraction (RBC), and the effects of the prior application of high hydrostatic pressure (HHP) on RBC protein functionality (solubility, foaming capacity, foam stability, water-holding capacity and texture properties of heat-induced gels) as well as on its microbiological quality and colour. The application of HHP (400 MPa, 15 min, 20 °C) and later dehydration allowed a dried product to be obtained with a reduction in the mesophilic bacterial counts of 3.2 logarithmic units. The colours of the pressurized and non-pressurized spray-dried RBC were the same, which indicated that both samples presented the same susceptibility to the hem group oxidation provoked by dehydration. The application of HHP increased the denaturant effects of spray-drying on hemoglobin (Hb), especially at pH 7 (isoelectric point; p I) since, after both processes, a decrease in protein solubility at neutral pH was observed. Spray-dried RBC had a maximum foaming capacity at the p I of Hb. The application of HHP decreased the foaming capacity but did not negatively affect the foam stability. Thermal treatment of RBC solutions led to hard and consistent gels at pH 7 whereas, at acid pH, less consistent, more adhesive and more elastic pastes were formed. The latter had higher water-holding capacities than gels at pH 7, in which, the water was retained by capillarity. Neither springiness and adhesiveness nor water-holding capacities of heat-induced gels or pastes were affected by the application of the HHP treatment to the fresh RBC.

Changes in activity coefficient gamma(w) of water and the foaming capacity of protein during hydrolysis.

The changes in the interaction between food proteins and water and in their surface functional property during enzymatic hydrolysis were investigated. Ovalbumin, a soy protein isolate (SPI), and casein were hydrolyzed with trypsin, and the degree of hydrolysis, water activity a(w), and foaming capacity of each hydrolysate were measured. Ovalbumin showed the minimum value for a(w), and the values for SPI and casein progressively decreased during hydrolysis. Therefore, the activity coefficient of water, gamma(w) (=a(w)/x(w), where x(w) is the mole fraction of water) was obtained to remove the influence of mole change and to examine the interaction of protein hydrolysates with water. In order to calculate x(w) in a sample during protein hydrolysis, a method for roughly estimating the number of moles of the protein hydrolysate in a solution was developed. The strategy was to modify the TNBS (2,4,6-trinitrobenzenesulfonic acid) method and to combine this method with the modified Ellman method and the determination of lysine by an amino acid analyzer. During enzymatic hydrolysis, each protein sample showed a minimum gamma(w) value and maximum foaming capacity.