Effect of Lepidium perfoliatum seed gum addition on whey protein concentrate stabilized emulsions stored at cold and ambient temperature

In this study the effect of Lepidium perfoliatum seed gum on the properties of whey protein concentrate (WPC) stabilized corn oil-in-water emulsions at pH 7 was investigated. Various concentrations (0–0.6% w/v) of L. perfoliatum seed gum were used together with 2% (w/v) WPC to emulsify corn oil in water at a ratio of 1:5. Quality attributed such as particle size distribution, creaming profile and coalescence rate during storage at 4 and 25 °C; surface and interfacial tension; zeta potential and viscosity of the emulsions were determined. The results indicated that the addition of L. perfoliatum seed gum had no significant effect on zeta potential but the surface and interfacial tension increased with the rise of gum concentration. It was also found that the addition of L. perfoliatum seed gum to WPC emulsions at a critical concentration of 0.2% (w/v) caused flocculation of oil droplets, which resulted in marked increase in particle size and the creaming rate. However at higher gum concentrations beyond this value, the particle size remained constant, apparently because of the high viscosity of the aqueous phase. At all concentrations tested, emulsions stored at 4 °C were more stable except for those containing 0.2% L. perfoliatum seed gum.     

Intrinsic viscosity and viscoelastic properties of xanthan/guar mixtures in dilute solutions: Effect of salt concentration on the polymer interactions

An oscillating capillary rheometer was used to investigate the dynamic viscoelastic and intrinsic viscosity properties of deacetylated xanthan (0.025%), native xanthan (0.025%), guar gum (0.075%), and xanthan–guar mixtures in dilute solutions. Influence of ionic strength on xanthan conformation and interaction with guar gum was elaborated. As the salt concentration increased, a significant (P < 0.05) decrease in viscosity (η′) and elasticity (η″) values was observed for both native xanthan–guar mixtures and deacetylated xanthan–guar mixtures. In water and 2 mM NaCl solution, the relative viscosity and η″ of both native xanthan–guar mixtures and deacetylated xanthan–guar mixtures were much higher than of those calculated for mixtures assuming no interaction, whereas no pronounced increase was found for polysaccharide mixtures in 40 mM NaCl. The intrinsic viscosities of deacetylated xanthan–guar mixtures in water and 2 mM NaCl were higher, whereas the intrinsic viscosities of native xanthan–guar mixtures were lower than those calculated from the weight averages of the two individually, assuming no interaction. These results demonstrated that intermolecular interaction has occurred between xanthan and guar mixtures in water and 2 mM NaCl, but may not occur in 40 mM NaCl, and mutual incompatibility may occur. The results suggest that the degree of disordering of xanthan played a critical role in xanthan–guar interaction and may explain the differences in η′, η″, and intrinsic viscosity measurements between 2 and 40 mM NaCl.     

Influence of pH and hydrocolloids addition on yam (Dioscorea alata) starch pastes stability

Yam tubers (Dioscorea alata) are a non-traditional starch source that could be used as food ingredient. The stability of yam starch pastes (6/100 g suspension) submitted to different pH conditions during gelatinization and the effect of hydrocolloids addition (guar and xanthan gums) on starch syneresis under refrigeration were analyzed. Changes in pH (3, 5, 6) or the addition of gums (0.1–0.5/100 g suspension) did not affect the starch gelatinization temperature nor the gelatinization enthalpy as determined by differential scanning calorimetry. Rheological behavior was characterized by amylograph profiles and oscillatory rheometry. Amylograms showed that yam starch pastes maintained a high viscosity under heat treatment and mechanical stirring in neutral to slightly acidic conditions. Brabender viscosity increased when gums were added; the effect of guar gum on viscosity was more marked than that of xanthan gum. During refrigerated storage exudate production was observed of pastes without gums. Xanthan gum, at a concentration of 0.5/100 g suspension, showed higher effectiveness than guar gum to reduce exudate production during refrigerated storage. The addition of hydrocolloids could allow yam starch to be used in foods requiring low temperatures.     

Reduced calorie emulsion-based foods: Protein microparticles and dietary fiber as fat replacers

The potential of using microparticulated whey protein (MWP) in combination with either modified starch or locust bean gum (LBG) as fat mimetics to fabricate reduced calorie emulsion-based sauces and dressings was studied. The influence of food matrix composition (protein, polysaccharide, and fat content), ionic strength, and pH on the properties of thermally processed model emulsions (90 °C/10 min) was investigated. Increasing protein concentration (2.5–7.5%) increased the mean (d_3,2) particle diameter due to the formation of large protein aggregates. All MWP-containing systems had a creamy white appearance with high lightness (L* > 75). Addition of fat droplets (5%) further increased their lightness (L* > 90) due to enhanced light scattering. Addition of starch, LBG, or MWP increased emulsion viscosity due to the increased effective volume fraction of the dispersed phase. Addition of calcium chloride (10 mM) and pH adjustment (2–8) caused little change in the physicochemical properties of the mixed systems. Overall, the appearance and rheological properties of the mixed systems were similar to commercial sauces and dressings. This study demonstrates that reduced calorie food emulsions with appearance and consistency similar to those of full-fat versions can be formulated using protein microparticles and polysaccharides.     

An investigation of four commercial galactomannans on their emulsion and rheological properties

Four types of galactomannans, namely fenugreek gum (FG), guar gum (GG), tara gum (TG) and locust bean gum (LBG), were investigated in the present study on their emulsion and rheological properties. The M/G ratios of the four galactomannans were 1.2, 1.7, 3.0 and 3.7, respectively. The results revealed that the M/G ratio, along with molecular weight and intrinsic viscosity, played an essential role on emulsion and rheological properties. Surface activity followed the trend: FG > GG > LBG > TG. Emulsion capacity and stability followed the trend: GG > FG > TG > LBG. Storage modulus (G′) followed the same order as intrinsic viscosity, which was: GG > FG > TG > LBG. By fitting the shear-thinning region of the flow curves into the Power law model, power law index (n) increased with increased concentration. Zero shear viscosity (η_sp)₀ was derived by fitting the Newtonian regions of the flow curves into Cross model, and followed the same order with viscosity based molecular weight (M_v), which is: FG > GG > TG > LBG. Exponents of the four gums were generated from Master curves (log (η_sp)₀ versus log C), which were 4.57, 3.92, 4.31 and 4.19 for FG, GG, TG and LBG, respectively.     

Rheological characterization of experimental dairy creams formulated with locust bean gum (LBG) and λ-carrageenan combinations

The influence of the locust bean gum (LBG)–λ-carrageenan stabilizer combination on the rheology of dairy creams was analyzed. A central composite factorial design was used to choose the LBG–λ-carrageenan ratio, the weight fraction of each gum ranging from 0 to 0.1 g per 100 g cream. Cross’ rheological model was closely fitted to describe the flow curves of the samples and Cross parameters were correlated with gum concentrations. The rheological behaviour of model aqueous gum solutions, with the same pH, ionic strength, and competitive solute concentration as the cream serum, was also examined to analyze gum interactions. Strong interaction of λ-carrageenan with cream components, probably with caseins, may be anticipated based on a great increase in viscosity. The functional role of LBG seems to be associated with an increase in the emulsion shear stability.     

Complex coacervates obtained from lactoferrin and gum arabic: Formation and characterization

Proteins and polysaccharides are the most frequently used hydrocolloids in the food industry, and their interaction can provide products such as complexes coacervates, which can be used as ingredients and biomaterials or in microencapsulation systems. In the present work, the interaction between lactoferrin (0.1, 0.2, 0.3, 0.5 and 1% w/w) and gum arabic (0.1% w/w) with various concentrations of NaCl (0, 0.01, 0.25, 0.3 and 0.5 mol/L) and at various pH values (from 1.0 to 12.0) was studied. The pH for the formation (higher turbidity) of the insoluble complex coacervates (pH_Ø1) varied according to the amount of NaCl used in the system (pH 3.5 to 5.3); these values are below the isoelectric point of lactoferrin (8.0), at which the protein is more positively charged, generating electrostatic binding. At a pH of approximately 2.0, this bond weakens, leading to the solubilization of precipitates, resulting in a sudden decrease in the turbidity (pH_Ø2). Samples containing a lower concentration of lactoferrin (0.1, 0.2 and 0.3% w/w) showed greater turbidity and consequently a higher formation of precipitates or aggregates. Even these samples, which contained a salt concentration of 0.3 mol/L, showed higher turbidity and displacement points of pH_Ø1 and pH_Ø2. The zeta potential and particle size values were used to study the influence of the pH, ionic strength and temperature on the interaction between the biopolymers. It was observed that the formation of macromolecules occurred between the isoelectric point of the protein (8.0) and the pKa of the polysaccharide (2.0), and a certain salt concentration (0.25 mol/L) led to larger particle sizes. It was observed that, at pH 7.0, a concentration of 0.1% gum arabic was able to stabilize the denaturation of the protein in solutions containing 0.1% lactoferrin, resulting in a constant particle size at all temperatures studied.     

Effect of alginate concentrations on survival of microencapsulated Lactobacillus casei NCDC-298

This study reports the tolerance of Lactobacillus casei NCDC-298 encapsulated in different alginate concentrations (2%, 3% or 4%), to low pH (1.5), high bile salt concentration (1% or 2%) and heat processing (55, 60 or 65 °C for 20 min). The release of encapsulated cells in simulated aqueous solution of colonic pH was also assessed. The survival of encapsulated L. casei was better at low pH, high bile salt concentration and during heat treatment as compared to free cells. The survival increased proportionately with increasing alginate concentrations without affecting the release of entrapped cells in solution of colonic pH.     

Effect of gamma irradiation on physicochemical,structural and rheological properties of plant exudate gums

This study was undertaken to determine the effect of gamma irradiation on physicochemical characteristics of acacia, apricot and karaya gum. The moisture and carbohydrate content varied significantly (p ≤ 0.05) from 8.83–11.12 and 77.98–83.08 g/100 g, respectively, in native gums. Protein, fat and ash content also varied significantly among the gums (1.63–2.25, 0.09–1.10 and 3.67–5.72 g/100 g, respectively). Functional properties like water absorption, emulsifying, swelling and solubility index increased with the increase in irradiation dose (0–5 kGy). Viscosity of the aqueous gum dispersions measured using RVA decreased with irradiation under natural and acidic environments. Absorbance of the functional groups like –OH, –COOH, uronic acid and pyranose units increased upon irradiation in acacia and karaya gum as confirmed by FT-IR analysis. Irradiation had a pronounced effect on the rheology of acacia and apricot gums reducing their viscosity. In case of karaya gum, there was a transaction of gel-like solid behaviour to viscous liquid behaviour upon irradiation.     

Encapsulation of Lactobacillus rhamnosus in double emulsions formulated with sweet whey as emulsifier and survival in simulated gastrointestinal conditions

Lactobacillus rhamnosus cultured in sweet whey and harvested in the late log phase was entrapped in the inner aqueous phase of a double water-in-oil-in-water emulsion using concentrated sweet whey as emulsifier. The primary and double emulsion droplets showed practically no changes in their morphology and droplet size with aging time. The viability of the entrapped L. rhamnosus in the double emulsion was compared to that of non-entrapped control cells exposed to low pH and bile salt conditions. The viability of the control cells (initial number = 6.57 ± 0.3 log cfu ml^?1) decreased significantly under low pH and bile salt conditions, and their survival was 71% and 89%, respectively. The survival of the entrapped cells (initial number = 6.74 ± 0.2 log cfu ml^?1) increased significantly under low pH and bile salt conditions, and their survival was 108% and 128%, respectively. It is concluded that the double emulsion protected L. rhamnosus against simulated gastrointestinal tract conditions.     

Temperature shows greater impact on bovine Longissimus dorsi muscle glycogen debranching enzyme activity than does salt concentration

The degradation of glycogen progresses by the co-operation of two enzymes: glycogen phosphorylase (phosphorylase) and glycogen debranching enzyme (GDE). We studied the effect of temperature (4–42 °C) and salt concentration (0–3% NaCl) on bovine M. longissimus dorsi GDE activity. GDE activity (n = 4) decreased significantly with decreasing temperature from about 40–4 °C. GDE exhibited 52% activity at 25 °C and 11% at 4 °C compared to its optimum activity measured at 39 °C. In rapidly chilled meat, the reduction in GDE activity may substantially delay the rate of glycolysis. However, residual GDE activity at 4 °C seems sufficient to enable the attainment of normal ultimate pH if the available time is long enough. An increase in salt concentration from 0% to 2% and to 3% induced a significant (P < 0.001) increase in the ultimate pH of ground bovine meat (n = 6), but showed no effect on GDE activity.     

Influence of main emulsion components on the physical properties of corn oil in water emulsion: Effect of oil volume fraction,whey protein concentrate and Lepidium perfoliatum seed gum

The effect of composition (whey protein concentrate, Lepidium perfoliatum seed gum, and oil content) of corn oil-in-water emulsions on their physical properties, droplet size and viscosity was studied using response surface methodology (RSM). For each response, a second-order polynomial model was developed using multiple linear regression analysis. The results indicated that the response surface models were significantly fitted for all response variables studied. It was shown that all emulsion components greatly influenced the physical properties of emulsion and its overall stability during storage. The main effect of L. perfoliatum seed gum was observed to be significant in most of response surface models. Therefore, the concentration of this gum should be considered as a critical variable for the formulation of emulsions. The overall optimum region resulted in a desirable emulsion was predicted to be obtained by combined level of 0.59% L. perfoliatum seed gum, 6% WPC and 21.95% oil volume fraction.     

Rheological study of xanthan and locust bean gum interaction in dilute solution: Effect of salt

An oscillatory capillary rheometer was used to investigate the effects of NaCl, KCl, and CaCl₂ on visco-elastic properties of xanthan and locust bean gum (LBG) blends in dilute solution. Gums were evaluated for intrinsic viscosity and elastic component. Molecular conformation of the xanthan–LBG complex was assessed by the power-law and Huggins equations. Addition of any of the three salts reduced significantly the intrinsic viscosity and elastic component of the gum blends, with a pronounced effect from divalent ions, compared with monovalent ions. The 60% xanthan–40% LBG blend exhibited the strongest attraction between xanthan and LBG. For the three salts, the attraction weakened when 5-mM salt was added and vanished with the addition of 50-mM salt. The strongest attraction between xanthan and LBG molecules was also evidenced by a positive Huggins miscibility coefficient K_m, and a positive attraction–repulsion coefficient α. With addition of 50 mM of any of the three salts, the coefficient α became negative, suggesting a strong repulsion between the two gums. The power-law coefficient b increased as salt concentration and LBG fraction increased in the blends for the three salts, suggesting a more flexible xanthan–LBG complex dependent on salt concentrations and LBG.     

Heat stability of oil-in-water emulsions formed with intact or hydrolysed whey proteins: influence of polysaccharides

The heat stability of emulsions (4 wt% corn oil) formed with whey protein isolate (WPI) or extensively hydrolysed whey protein (WPH) products and containing xanthan gum or guar gum was examined after a retort treatment at 121 °C for 16 min. At neutral pH and low ionic strength, emulsions stabilized with both 0.5 and 4 wt% WPI (intact whey protein) were stable against retorting. The amount of β-lactoglobulin (β-lg) at the droplet surface increased during retorting, especially in the emulsion containing 4 wt% protein, whereas the amount of adsorbed α-lactalbumin (α-la) decreased markedly. Addition of xanthan gum or guar gum caused depletion flocculation of the emulsion droplets, but this flocculation did not lead to their aggregation during heating. In contrast, the droplet size of emulsions formed with WPH increased during heat treatment, indicating that coalescence had occurred. The coalescence during heating was enhanced considerably with increasing concentration of polysaccharide in the emulsions, up to 0.12% and 0.2% for xanthan gum and guar gum, respectively; whey peptides in the WPH emulsions formed weaker and looser, mobile interfacial structures than those formed with intact whey proteins. Consequently, the lack of electrostatic and steric repulsion resulted in the coalescence of flocculated droplets during retort treatment. At higher levels of xanthan gum or guar gum addition, the extent of coalescence decreased gradually, apparently because of the high viscosity of the aqueous phase.     

Effect of salt concentration and temperature of storage water on the physicochemical properties of fish proteins

Biochemical and physical properties of fish proteins from damaged (filleted and skinned) and undamaged (free of trauma or broken skin) Pacific whiting were investigated during chilling in various salt concentrations at 0.7 to ?1.1 °C. The increase of pH and moisture content were suppressed when chilling water contained higher concentration of NaCl. Conductivities of damaged fish were maximal after 24 h storage, but those of undamaged fish continuously increased throughout 72 h. K-values increased, but rapidly increased at lower salt concentrations. Puncture force and deformation were very low when chilled water contained higher concentration of salt (2–3 g/100 ml). Gel colors were also negatively affected as the concentration of salt increased for chilling water. Our study suggest Pacific whiting may be stored at 0–2 °C, but at 0–1 g/100 ml salt concentration.     

Influence of pH and NaCl on monolaurin inactivation of Streptococcus iniae

Streptococcus iniae, a Gram-positive bacterium, has been recognized as a cause of human and fish streptococcosis. Aquacultured fish are susceptible to infection and have been epidemiologically linked with wound infections of fish handlers. Therefore, there is a need to develop methods of prevention and/or control of this pathogen. This study determined the minimum inhibitory concentration of monolaurin (glycerol monolaurate) against S. iniae strains PW and BU and utilized gradient plates at 37°C to determine the combined influence of pH and NaCl on monolaurin inactivation of S. iniae. The minimum inhibitory concentration of monolaurin against strain PW was 12.4±0.3 μg ml⁻¹ and against strain BU was 12.1±0 μg ml⁻¹. Compared to growth in the absence of monolaurin, the incorporation of 6 μg ml⁻¹ monolaurin into the salt (1.12–6.95%)–pH (4.26–8.88) gradient plates prevented growth of strain PW at pH values <6.00 and strain BU at pH values <6.20, regardless of the salt concentration. The combination of monolaurin with environmental variables such as pH and salt proved to be an effective tool for in vitro control of S. iniae.     

Screening among 18 novel strains of Xanthomonas campestris pv pruni

A screening was made among 18 novel strains of Xanthomonas campestris pv pruni. Yields, viscosity and chromatographic patterns of the biopolymers synthesized in a conventional medium (PM II), were analyzed. Yields varied from 2.3 to 8.3 g l⁻¹. Viscosities of 3% (w/v) aqueous solutions at 25, 45 and 65°C, were determined at 6, 12, 30 and 60 rpm. All biopolymers had pseudoplastic behavior. The biopolymers showed three distinct viscosity patterns when temperature increased: no variation, decrease and increase. Polymers that maintained or increased their viscosity had higher mannose concentrations. Strain 06 was chosen for further studies because it showed a higher viscosity at 6 rpm, 26,000 mPa s at 25°C and 27,000 mPa s at 65°C, and a yield of 4.0 g l⁻¹. The influence of the concentration of biopolymer (1 and 2%) and temperature (25, 45 and 65°C) in the viscosity was also determined. A small increase in viscosity when the temperature was raised was observed at both concentrations. Finally, the influence of fermentation time (24–96 h) on yield, viscosity and chemical composition of the biopolymers, was determined. The biopolymer obtained after 24 h of fermentation showed the higher viscosity, but the highest yield was obtained at 72 h. The biopolymer produced by strain 06 after 48 h of incubation showed similar viscosity and rheological behavior to commercial xanthan.     

Effect of xanthan and guar gums on the formation and stability of soy soluble polysaccharide oil-in-water emulsions

The incorporation of relevant amounts of non-adsorbing hydrocolloids to oil-in-water (O/W) emulsions is a suitable alternative to reduce creaming. The effect of incorporating xanthan gum (XG) or guar gum (GG) in soy soluble polysaccharide (SSPS) stabilized oil-in-water (O/W) emulsions was studied. The emulsions contained 6 wt.% of SSPS, 20 wt.% Perilla seed oil (PSO), an omega-3 vegetable oil, and variable amounts of XG or GG ranging from 0.03 to 0.3 wt.%. The presence of minute amounts of XG or GG in fresh emulsions significantly decreased the emulsion droplet size (EDS) although such low concentrations did not provide enough continuous phase viscosity to arrest creaming. Emulsion microstructure indicated the presence of flocculation even at high concentrations of XG or GG caused by a depletion mechanism. All emulsions with XG or GG exhibited pseudoplastic behavior while the control emulsions showed an almost Newtonian behavior. Emulsion droplet polydispersion generally decreased with increase in the continuous phase viscosity indicating the importance of continuous phase viscosity in the dissipation of shear energy throughout the emulsion during homogenization. The characteristics of the emulsions were closely related to the rheological changes of the continuous phase.     

Effect of germination on the chemical,functional and pasting properties of flour from brown and yellow varieties of tigernut (Cyperus esculentus)

The chemical, functional and pasting properties of flours processed from germinated (0, 24, 48 and 72 h) brown and yellow varieties of tigernut (Cyperus esculentus) seed was studied. Germination decreased carbohydrate (60.50–53.60%) and fat (60.50–53.60%) while protein and ash increased from 8.23% to 12.40% and 3.28% to 4.26%, respectively. In addition, functional properties such as foaming, emulsion, water and oil absorption capacities increased from 7.75% to 12.91%, 14.32–20.25 ml oil/g sample, 2.56–6.97 g water/g sample and 1.14–1.78 g oil/g sample, respectively, with germination. Least gelation of flour samples were improved as a result of germination process. Conversely, bulk density decreased with germination time (0.58–0.50 g/cm³). Trough, peak viscosity, break down, final viscosity, peak time and pasting temperature values were in the range (120.96–203.04 RVU), (145.28–228.11 RVU), (7.85–14.32 RVU), (180.62–324.73 RVU), (5.01.83–6.00 min) and (63.85–65.47 °C), respectively. Our results suggest that the incorporation of germinated tigernut flours may help in enhancing protein calorie delivery with improved functionality in complementary food formulations and baked products.     

Physicochemical,functional and cooking properties of under explored legumes,Canavalia of the southwest coast of India

Nutritionally potential under explored wild legumes viz., Canavalia cathartica and Canavalia maritima are widely distributed in mangroves and sand dunes, respectively, in Southwest coast of India. Physicochemical, functional and cooking properties of dried seeds of these legumes have been evaluated. Seeds and cotyledons of C. cathartica are larger and possessing higher hydration and swelling capacity than that of C. maritima indicating higher permeability and softness. The crude protein of C. maritima and C. cathartica were found to be higher than common pulses. The pH vs. protein solubility profile was almost similar with minimum solubility at pH 4 (27.8–28.1%). C. maritima showed higher oil absorption capacity (1.53 ml/g) as well as water absorption (0.1 M) capacity. The gelation capacity was minimal at 0.1 M NaCl and pH 4 for both the seed flours. Addition of carbohydrates (starch, lactose, maltose and sucrose) reduced the lowest gelling capacity of C. maritima except for maltose in C. cathartica. Emulsifying activity (EA) and emulsifying stability (ES) diminished with increasing concentration of flours. Minimum EA and ES were attained at pH 4 and maximum at pH 10 in both seed flours. Maximum EA for C. cathartica and C. maritima (62% vs. 72.6%) was attained at 0.4 M NaCl. The ES vs. flour concentration, pH and ionic strength profiles did not differ much between C. maritima and C. cathartica. Peak foam capacity (FC) and stability (FS) were achieved at 6% (w/v) of C. maritima flour, while the same was attained at 8% (w/v) of C. cathartica. The FC and FS of the seed flours improved with increasing pH (pH 2–10). C. maritima flour exhibited the better FC (27.7%), while C. cathartica exhibited better FS (44.42%) at pH 10. Although highest FC was attained at 0.4 M NaCl in both flours, C. maritima was found to be superior (30.5% vs. 28.5%). The flour of C. maritima attained the highest FS at 0.2 M NaCl than C. cathartica (0.4 M NaCl). The minimum cooking time for cotyledons of C. cathartica was more and higher gruel solid loss was reported due to its high L/B ratio. The Pearson correlation coefficients revealed that functional properties of seed flours vary due to their chemical composition.