Impact of Sample Aging on Freeze-Thaw Stability of Oil-in-Water Emulsions Prepared with Soy Protein Isolates

The freeze-thaw stability of oil-in-water emulsions prepared with unheated and heated aqueous dispersions of fresh and stored soy protein isolates was evaluated in the absence and presence of glucose or sorbitol (0.75–15.0% w/w). Sample aging had a negative impact of freeze-thaw stability. The cryoprotectant addition enhanced the freeze-thaw stability, but at low concentrations emulsions prepared with unheated soy protein isolates showed better response to freeze-thawing. Nevertheless, at the highest cryoprotectant concentration, a total stabilization was evidenced for all emulsions. The results of this article indicated that the cryoprotectants act on proteins at interfacial level.     

Influence of maltodextrin type and multi-layer formation on the freeze-thaw stability of model beverage emulsions stabilized with β-lactoglobulin

The influences of maltodextrin (MD) addition and multi-layer formation on the freeze-thaw stability of β-lactoglobulin (β-Lg)-stabilized oil-in-water beverage emulsions (0.1 wt% corn oil, 0.006 wt% β-Lg) were investigated. Various beverage emulsions were prepared depending on MD concentration (0–20 wt%), its dextrose equivalent (M150 or M250), and the presence or absence of additional polysaccharides (pectin, alginate, or ι-carrageenan) coatings around the emulsion droplets. All emulsions (β-Lg- and β-Lg-polysaccharide-coated emulsions) were unstable to experimental freeze-thaw cycling in the absence of MD. In the presence of MD, all emulsions containing M250 had better stability to droplet aggregation than those with M150, regardless of MD concentrations and freeze-thawing. The optimum concentrations of M250 required to prevent emulsions destabilization under the freeze-thawing were 6, 15, and 2% for β-Lg-, β-Lg-ι- carrageenan-, and β-Lg-pectin-coated emulsions, respectively. This study implicates practical information to improve freeze-thaw stability of some beverage emulsion products that inevitably go though freezing during processing.     

超声改性大豆分离蛋白与大豆可溶性多糖复合乳化体系的冻融稳定性研究

本实验针对不同超声功率改性的大豆分离蛋白与大豆可溶性多糖形成的复合乳液的冻融稳定性进行研究, 揭示乳液冻融稳定机理与形成乳液复合物结构特性之间的构效关系。对2 次冻融循环处理前后乳液油滴进行共聚焦 观察,研究等温结晶固脂含量、油脂被乳化量的变化和作为乳化剂的大豆分离蛋白不同超声处理（0、200、300、 400、500 W）下二级结构的变化,进而分析其与乳液冻融稳定性的关系。结果表明：乳液经2 次冻融循环处理后 随着超声功率的增加聚结程度降低,400 W超声处理的大豆分离蛋白与大豆可溶性多糖复合乳液最为稳定;等温 结晶条件下不同乳液固脂含量增加速率不同,但最终平衡时总含量相同;油脂被乳化量发生不同程度的变化;不 同超声处理改变了大豆分离蛋白的二级结构,400 W超声处理的大豆分离蛋白无规卷曲结构含量最高。说明不同 超声改性的大豆分离蛋白与大豆可溶性多糖会形成不同结构的复合物,影响了乳液的冻融稳定性,初步明确了 适当的超声处理能够改善大豆分离蛋白的空间结构,促进其与大豆可溶性多糖分子的键合,进而影响大豆分离蛋 白-多糖界面结构特性和乳化体系的冻融稳定性。     

Infrared spectroscopic analysis of structural features and interactions in olive oil-in-water emulsions stabilized with soy protein

Lipid and protein structural characteristics of olive oil-in-water emulsions formulated with various stabilizer systems were investigated using Fourier transform infrared spectroscopy (FT-IR). Proximate composition, water binding and textural properties were also evaluated in these emulsions. Two different olive oil-in-water emulsions were studied: E/SPI prepared with soy protein isolate as a stabilizing system, and E/SPI + SC + MTG prepared with a combination of soy protein isolate, sodium caseinate and microbial transglutaminase as a stabilizing system. Results showed that textural properties (P < 0.05) were dependent on the stabilizing system. E/SPI + SC + MTG emulsion presented greater (P < 0.05) lipid chain disorder, more lipid-protein interactions, and more (P < 0.05) ??-helix and ??-sheet structures. A relationship between textural and structural properties was also observed as a function of the stabilizing system employed in the formulation of emulsions. A more thorough understanding of this connection could help improve the development of food products with appropriate physical properties.     

Utilisation of pectin coating to enhance spray-dry stability of pea protein-stabilised oil-in-water emulsions

In this study, development of pea (Pisum sativum) protein stabilised dry and reconstituted emulsions is presented. Dry emulsions were prepared by spray-drying liquid emulsions in a laboratory spray-dryer. The effect of drying on the physical stability of oil-in-water emulsions containing pea protein-coated and pea protein/pectin-coated oil droplets has been studied. Oil-in-water emulsions (5 wt.% Miglyol 812 N, 0.25 wt.% pea protein, 11% maltodextrin, pH 2.4) were prepared that contained 0 (primary emulsion) or 0.2 wt.% pectin (secondary emulsion). The emulsions were then subjected to spray-drying and reconstitution (pH 2.4). The stability of the emulsions to dry processing was then analysed using oil droplet size, microstructure, Zeta potential, and creaming measurements. Obtained results showed that the secondary emulsions had better stability to droplet aggregation after drying than primary emulsions. To interpret these results, we propound that pectin, an anionic polysaccharide, formed a less charged protective layer around the protein interfacial film surrounding the oil droplets that improved their stability to spray-drying mainly by increasing steric effects.     

Sodium caseinate–maltodextrin conjugate hydrolysates: Preparation,characterisation and some functional properties

Hydrolysates of sodium caseinate (NaCN)–maltodextrin (Md40 or Md100) conjugates were prepared with a limited (<10%) and moderate (>10%) degree of hydrolysis. When assessed in the pH range 2.0–8.0, each conjugate hydrolysate had improved solubility compared to NaCN and their respective native unhydrolysed conjugate. Oil-in-water emulsions containing NaCN (1%, w/w, protein) and various combinations of conjugate hydrolysates (0.2%, w/w) and/or glycerol monostearate (0.07–0.3%, w/w, GMS) were prepared; emulsion storage stability (at 45 °C for up to 20 days) and heat stability (at 140 °C for up to 20 min) was determined by measuring changes in the mean size of fat globules in emulsions. NaCN plus conjugate hydrolysate-stabilised emulsions had improved storage stability compared to a NaCN stabilised emulsion. In general, NaCN plus conjugate hydrolysate-stabilised emulsions were less heat-stable than NaCN or NaCN plus GMS stabilised emulsions; however, emulsions stabilised by NaCN plus one of the conjugate hydrolysates (CH102) had improved heat stability in comparison to the NaCN stabilised emulsion. The results show that hydrolysates of NaCN–Md conjugates have potential for use as emulsification aids in emulsion-based food products.     

Catastrophic inversion and rheological behavior in soy lecithin and Tween 80 based food emulsions

Emulsions inversion occurs in many industrial processes and may be influenced by the formulation conditions, composition and emulsification protocols. In this work, the influence of emulsifiers and stirring on catastrophic inversion (O/W to W/O) was evaluated. Emulsions were prepared with different stirring rates, using soy lecithin and Tween 80, at 2 and 5 wt%. The aqueous phase was distilled water with 1 wt% NaCl and the oil phase was soy oil. These emulsions were analyzed by conductivity, stability, microscopy and rheology assays. The most stable emulsions presented inversion with a smaller amount of the external phase. Rheological analysis showed that, with a higher concentration of emulsifier, it is better to use Tween 80 when lower viscosity is desired, while soy lecithin is more appropriate for higher viscosity products. The oscillatory tests showed that while the emulsions prepared using Tween 80 exhibited concentrated solution behavior, those prepared with soy lecithin exhibited strong gel behavior.     

Emulsifying properties of sweet potato protein: Effect of protein concentration and oil volume fraction

The effect of protein concentrations (0.1, 0.25, 0.5, 1.0, 1.5 and 2.0% w/v) and oil volume fractions (5, 15, 25, 35 and 45% v/v) on properties of stabilized emulsions of sweet potato proteins (SPPs) were investigated by use of the emulsifying activity index (EAI), emulsifying stability index (ESI), droplet size, rheological properties, interfacial properties and optical microscopy measurements at neutral pH. The protein concentration or oil volume fraction significantly affected droplet size, interfacial protein concentration, emulsion apparent viscosity, EAI and ESI. Increasing of protein concentration greatly decreased droplet size, EAI and apparent viscosity of SPP emulsions; however, there was a pronounced increase in ESI and interfacial protein concentration (P < 0.05). In contrast, increasing of oil volume fraction greatly increased droplet size, EAI and emulsion apparent viscosity of SPP emulsions, but decreased ESI and interfacial protein concentration significantly (P < 0.05). The rheological curve suggested that SPP emulsions were shear-thinning non-Newtonian fluids. Optical microscopy clearly demonstrated that droplet aggregates were formed at a lower protein concentration of <0.5% (w/v) due to low interfacial protein concentration, while at higher oil volume fractions of >25% (v/v) there was obvious coalescence. In addition, the main components of adsorbed SPP at the oil–water interface were Sporamin A, Sporamin B and some high-molecular-weight aggregates formed by disulfide linkage.     

Lipid and water crystallization in protein-stabilised oil-in-water emulsions

Phase and state transitions occurring during freezing and thawing of oil-in-water emulsions with different water phase formulations, interfacial compositions and two lipid types were studied as crucial factors affecting emulsion stability. Emulsions containing 0–40% (w/w) sucrose in the water phase at pH 7, and 10, 20, 30, 40% (w/w) dispersed lipid phase (sunflower oil, SO or hydrogenated palm kernel oil, HPKO) with whey protein isolate, WPI, or sodium caseinate, NaCAS, (protein:lipid = 1:10 and 2:10) as emulsifier were prepared. Phase/state behaviour of the continuous and dispersed phases was determined by differential scanning calorimetry (DSC). Emulsion stability and morphology were derived from DSC data, gravitational separation and particle size analysis during 4 freeze-thaw cycles. Systems were stable when only lipid crystallization occurred. DSC data showed that lipid crystallization prior to water crystallization (i.e. emulsions containing HPKO) caused destabilisation at low sucrose concentrations (0, 2.5 and 5% w/w). Emulsions were stable if the dispersed oil phase crystallized after the dispersing water phase (i.e. emulsions containing SO). A concentration of sucrose ≥10% (w/w) in the aqueous phase gave stable emulsions. At 10:1 lipid to protein ratio, WPI showed better stabilising properties than NaCAS at 2.5 and 5% (w/w) sucrose. Double concentration of WPI (lipid:protein = 10:2) at 0% (w/w) sucrose significantly improved systems stability, whereas no positive effect was observed when the concentration of NaCAS was increased. From morphology study, in addition to lipid destabilisation, thickening and flocculation caused instability of the systems. These were extensive in systems containing WPI and were ascribed to interactions between whey proteins during thermal cycling.     

Microencapsulation properties of soy protein isolate: Influence of preheating and/or blending with lactose

Properties and storage stability of spray-dried emulsions stabilized by unheated and preheated (95 °C, 15 min) soy protein isolates, alone or in combination with lactose, were investigated. In general, the heat pretreatment greatly improved retention efficiency (RE), redispersion behavior, glass transition temperature (T_g) and thermal stability of the emulsion powders, but accelerated instability of the reconstituted emulsions. Additional blending with lactose further considerably improved the RE and dissolution behavior, but significantly decreased the stability of reconstituted emulsions and T_g. Storage at 75% relative humidity resulted in considerably increased droplet size of reconstituted emulsions, as well as decreased RE, wettability and T_g, especially in the powders containing lactose. Microscopic observations confirmed that the changes in properties and stability of the powders upon storage were closely related to rupture of particle structure, and/or particle agglomeration. These findings provide fundamental understanding for the development of microencapsulated products using soy proteins as the wall materials.     

Effect of non-meat proteins on hydration and textural properties of pork meat gels enhanced with microbial transglutaminase

The combined effect of incorporation of four non-muscle proteins, NMP (blood plasma, BP; sodium caseinate, SC; soy protein isolate, SPI; gelatin, G) at 2 g/100 g levels on hydration and textural characteristics of pork gels processed without or with 0.6 g/100 g microbial transglutaminase preparation (MTG) was investigated. Addition of SC and BP most favourably affected hydration properties and thermal stability, yielding lower cooking loss and expressible moisture for pork gels. Interactions between NMP and MTG were observed. Improvement of gel strength by addition of transglutaminase was observed for treatments containing SC and BP but not G nor soy isolate. Of the four proteins tested SC was found to be a superior substrate for MTG in enhancing textural properties of a gelled meat system. None of the tested ingredients was able to yield gel cohesiveness equivalent to the control containing 8% muscle proteins. Results of this study indicate a potential for using MTG to improve or modify the functional and textural properties of investigated food proteins (SC and BP in particular) in comminuted meat products.     

Olive oil-in-water emulsions stabilized with caseinate: Elucidation of protein–lipid interactions by infrared spectroscopy

This paper reports a FT-IR study for probing lipid and protein structural changes and their interactions in various oil-in-water emulsions. Two different emulsions were prepared using sodium caseinate, as stabilizer system, without and with microbial transglutaminase (MTG), denominated E/SC and E/SC + MTG respectively. Proximate composition, fat and water binding properties and textural characteristics were also evaluated in the emulsions. Penetration force and gel strength values were used to distinguish different (P < 0.05) textural behaviours depending on the formulation of emulsifying system. E/SC + MTG emulsion showed gel textural behaviour while E/SC lack of this property. The spectral results showed frequency upshifting of the amide I band in going from protein stabilizer systems isolate (the solution used as reference) to their corresponding emulsions, what is attributable to greater protein structural order upon emulsion formation. Enzymatic action of MTG in the sodium caseinate stabilizing system induces structural changes, in terms of lipid chain disorder or lipid–protein interactions and protein secondary modifications, which may reflect the formation of a gel structure in the emulsion. These results could help to choose the stabilizing system that is most suitable and effective for its use in the formulation of food products.     

STABILITY OF OIL-IN-WATER EMULSIONS. 2. Effects of Oil Phase Volume, Stability Test, Viscosity, Type of Oil and Protein Additive

SUMMARY –Stability of oil-in-water emulsions stabilized in sodium caseinate, gelatin and soy sodium proteinate was found to be increased by either an increase in the aqueous phase protein concentration (0.5–2.5%) or oil phase volume (20–50%). Both factors were significantly interrelated. Emulsions stabilized by soy sodium proteinate were generally higher in stability as compared to those stabilized by gelatin or sodium caseinate. With emulsions containing gelatin, greater stability occurred when the stability testing temperature was increased from 37–70°C and when the time interval was decreased from 24 hr to 90 min. Maximum relative viscosities of emulsions stabilized by gelatin and sodium caseinate were 2.0 and 2.5, respectively. Emulsions stabilized by soy sodium proteinate were quite viscous, with relative viscosity from 1.5–30 depending on both protein concentration and oil phase volume. Interchanging the emulsified oil among corn, soybean, safflower and peanut oils did not alter emulsion stability when examined at three concentrations of soy sodium proteinate. Changing the oil to olive oil significantly increased emulsion stability at each soy sodium proteinate level with oil phase volumes of 30, 40 and 50%.     

Pasting behaviour, textural properties and freeze-thaw stability of wheat flour-crude malva nut (Scaphium scaphigerum) gum system

The effect of replacement of crude malva nut gum (CMG) at 0%, 2.5%, 5%, 7.5% and 10% w/w on pasting behaviour, textural properties and freeze-thaw stability of wheat flour was investigated. Replacement of wheat flour by CMG significantly elevated (p < 0.05) the peak viscosity (128-669 RVU), hot paste viscosity (77-363 RVU), breakdown (51-306 RVU) and final viscosity (157-557 RVU) of wheat flour pastes. Pasting temperature (59-85 °C) of the flour decreased with increasing CMG content. The textural parameters including hardness, springiness, cohesiveness, gumminess and chewiness of the mix gels decreased with higher level of CMG. Freeze-thaw stability measurement revealed that wheat gel mixtures containing higher level (7.5% and 10%) of CMG decreased syneresis more than 80% after 3 freeze-thaw cycles, when compared to non-CMG sample. The rate of syneresis depended on CMG concentration and number of freeze-thaw cycles. The results demonstrated that higher viscosity, softer texture and lower syneresis of wheat gel could be attained using CMG.     

β-Conglycinin and glycinin soybean protein emulsions treated by combined temperature–high-pressure treatment

Most studies on functionality of soybean proteins have been made with total protein isolates, with the drawback to limit the knowledge of phenomena due to the important complexity of protein composition. In this study we have tried to better understand the behavior of soy emulsions by using their two partially purified fractions: β-conglycinin (7S) and glycinin (11S). Furthermore, we have assessed the combined effect of temperature (20–60 °C) and high pressure (0.1–600 MPa) on physicochemical, microstructural and rheological properties of oil-in-water emulsions prepared with 7S or 11S proteins at 7% (w/v). Our results show that 7S and 11S emulsions behaved differently under the combined treatments and that 7S protein was responsible for the global properties of soybean emulsions, whereas 11S proteins exerted a negligible effect. From 400 MPa and at 60 °C, we have noticed for 7S emulsions an increase of flocculation and gelation, largely confirmed by confocal microscopy due to aggregation between adsorbed and aqueous 7S proteins. Globally we have evidenced that temperature reinforces the effect of high pressure and that the threshold to obtain some changes is 400 MPa. The very different behavior of 7S and 11S proteins in emulsions under treatments could help to orientate their commercial use as function of planed treatments.     

Physicochemical characterisation and oxidative stability of fish oil and fish oil–extra virgin olive oil microencapsulated by sugar beet pectin

Spray-dried microcapsules were prepared at 25% and 50% w/w oil load from sugar beet pectin-stabilised emulsions (pH 3) containing fish oil, and a blend of fish oil and with extra virgin olive oil (1:1 w/w). Microencapsulation efficiencies were high (≥90%). However, deterioration in microcapsule wall integrity and an increase in oil droplet size were observed during storage (25 °C, 0–3 months). Lipid oxidation increased with both increased oil load (P < 0.05) and storage duration (P < 0.05), but was independent of oil composition (P > 0.05). These results suggest that sugar beet pectin functions poorly as a wall material and its residual metal ions exacerbate omega-3 oxidation, despite the presence of endogenous antioxidants found in extra virgin olive oil. Interestingly, under accelerated storage conditions (OxiPres® at 80 °C, 0.5 bar oxygen pressure), microcapsules containing the oil blend showed the best oxidative stability (P < 0.05), irrespective of oil load. A possible explanation for the superior oxidative stability of the microencapsulated oil blend at high storage temperature is discussed.     

Preparation,characterisation and selected functional properties of sodium caseinate–maltodextrin conjugates

Sodium caseinate (NaCN)–maltodextrin (Md40 or Md100) conjugates were prepared by a Maillard-type reaction by dry heat treatment of mixtures of NaCN and Md at 60 °C and 79% relative humidity for 4 days. Minimal levels of coloured reaction products were formed during conjugate preparation. Conjugation resulted in a 35.6% and a 36.2% loss of available amino groups in the NaCN, and a 17.8% and a 25.7% loss of available reducing groups in Md40 and Md100, respectively. SDS–PAGE and gel permeation chromatography confirmed conjugation. When assessed in the pH range 2.0–8.0 at 20 °C and 50 °C, conjugates had improved solubility compared to NaCN, particularly around the isoelectric point of the protein. The emulsifying properties of NaCN–Md conjugates were assessed in oil-in-water (o/w) emulsions and in model cream liqueurs. The conjugate stabilised o/w emulsions and liqueurs showed improved stability when compared to NaCN stabilised o/w emulsions and liqueurs. These results indicate a potential for these NaCN–Md conjugates as speciality functional food ingredients.     

Thermal behavior of emulsions manufactured with soy protein ingredients

The conformation, denaturation and aggregation behavior of proteins are important factors which dictate their ingredient functions and applications in formulated food products. The effect of variation in pre-treatment temperature (70–90 °C × 30 s), pH (6.4–7.5) and calcium supplementation (450 and 850 mg/L) on heat coagulation time (HCT at 140 °C) of model emulsions (3.6% (w/v) protein) stabilized with soy protein isolate (SPI) and soy protein hydrolysate (SPH) ingredients was determined. Generally, HCT of emulsions was not significantly affected by alteration of constituent pre-heating temperatures. Model emulsions displayed higher HCTs with increasing pH and lower levels of intrinsic ash content. At both supplementation levels, calcium addition led to decreased HCTs. Supplementation with chloride salts caused a greater decrease in HCT compared to supplementation with citrate salts. Furthermore, soy protein hydrolysis was associated with lower emulsion thermal stability. Results demonstrate that modification of ingredient and manufacturing parameters may be a useful approach for enhancing thermal stability properties of soy protein stabilized emulsions.     

Functional egg white–pectin conjugates prepared by controlled Maillard reaction

Changes in the functional properties of egg white (EW) protein/pectin mixtures and their chemical conjugation via the Maillard reaction were investigated. Pectin with high degrees of esterification was conjugated to EW protein at 60 °C and 79% relative humidity for 0, 6, 12, 24 and 48 h. The conjugates were compared with a physical mixture of the two components. There was a significant decrease in the available lysine (free amino groups) of the conjugated protein during incubation with the polysaccharides, negatively correlated to the emulsification properties. Oil–water emulsions prepared using the EW–pectin conjugates showed good stability, with oil droplet mean volume diameters of 0.29–1.2 μm. The conjugates showed higher emulsion viscosity and stability than the raw materials at ambient temperature. Addition of pectin (0.05–0.5% w/v) to EW at concentrations of 1% and 5% w/v had a significant effect on foam volume and stability.     

Functional properties of processed Australian wattle (Acacia victoriae Bentham) seed extracts

Functional properties of water extracts from processed prickly wattle (Acacia victoriae Bentham) seed flours were compared to those of raw flours and an ammonium sulphate precipitate (ASP) containing >77% protein. All extracts formed stable 20% and 50% (v/v) oil-in-water emulsions at concentrations between 1% and 5% (w/v) but the emulsions formed from processed flour at low extract concentrations destabilized by oiling off within 7 days at 25 °C. Comparatively, emulsions formed with 5% raw and processed extracts creamed or broke reversibly. Conversely, ASP-stabilized emulsions were very stable at all concentrations and conditions in this study. However, all extracts and ASP had poor foaming capacity and did not gel even at up to 10% solids concentration. The results indicated that processing of wattle seeds for flavour enhancement or destruction of anti-nutrients led to poorer functionality. The excellent emulsifying and emulsion stabilization properties of ASP could potentially be exploited in processed foods.