Impact of whey protein – Beet pectin conjugation on the physicochemical stability of β-carotene emulsions

The aim of the present study was to investigate the impact of whey protein isolate (WPI)-beet pectin conjugation on the physical and chemical properties of oil-in-water emulsions incorporating β-carotene within the oil droplets. Covalent coupling of WPI to beet pectin was achieved by dry heating of WPI-beet pectin mixtures of different weight ratios at 80, 90, 100 °C and 79% relative humidity for incubation times ranging from 1 to 9 h. It was confirmed by SDS-polyacrylamide gel electrophoresis that WPI covalently linked to beet pectin. The physical and chemical stability of β-carotene emulsions was characterized by droplet size and distribution, transmission profiles using novel centrifugal sedimentation technique, microstructure and β-carotene degradation during the storage. Compared with those stabilized by WPI alone and unheated WPI-beet pectin mixtures, β-carotene emulsions stabilized by WPI-beet pectin conjugates had much smaller droplet sizes, more homogenous droplet size distribution, less change in centrifugal transmission profiles and obviously improved freeze–thaw stability, indicating a very substantial improvement in the physical stability. Rheological analysis exhibited that emulsions stabilized by WPI-beet pectin conjugates changed from a shear thinning to more like Newtonian liquid compared those with WPI alone and unheated WPI-beet pectin mixtures. Degradation of β-carotene in emulsion during storage was more obviously retarded by WPI-beet pectin conjugate than WPI and unheated WPI-beet pectin mixture, probably due to a thicker and denser interfacial layer in emulsion droplets. These results implied that protein–polysaccharide conjugates were able to improve the physical stability of β-carotene emulsion and inhibit the deterioration of β-carotene in oil-in-water emulsions.     

Gel-like pea protein Pickering emulsions at pH 3.0 as a potential intestine-targeted and sustained-release delivery system for β-carotene

In recent years, there is increasing interest in the development of food-grade Pickering emulsions as promising delivery systems for bioactive compounds. Our previous work reported that most of the proteins in pea protein isolate (PPI) at pH 3.0, present in the nanoparticle form, can effectively perform as a kind of food-grade Pickering stabilizers for oil-in-water emulsions (LWT, 2014). The purpose of this study was to further report that PPI-stabilized emulsions at pH 3.0 exhibited great potential to act as intestine-targeted and sustained-release delivery systems for β-carotene. The emulsions were produced by microfluidization at a specific protein concentration of 6.0% (w/v) and varying oil fractions (ϕ) of 0.2–0.6. The results indicated that increasing ϕ was favorable for the gel-like network strengthening of these emulsions. The gel formation was largely related to the droplet flocculation as well as inter-floc attractive interactions. The in vitro simulated digestion results showed that the release of β-carotene during the intestinal digestion of these emulsions could be well modulated by altering ϕ. The gel-like emulsion at ϕ = 0.6 exhibited much lower release of β-carotene, but higher stability towards degradation during the digestion, than that at ϕ = 0.3. The findings provide important information not only for the design of novel delivery systems for lipophilic bioactive components, but also for the development of plant protein-based formulations.     

Emulsion design for the delivery of β-carotene in complex food systems

β-Carotene has been widely investigated both in the industry and academia, due to its unique bioactive attributes as an antioxidant and pro-vitamin A. Many attempts were made to design delivery systems for β-carotene to improve its dispersant state and chemical stability, and finally to enhance the functionality. Different types of oil-in-water emulsions were proved to be effective delivery systems for lipophilic bioactive ingredients, and intensive studies were performed on β-carotene emulsions in the last decade. Emulsions are thermodynamically unstable, and emulsions with intact structures are preferable in delivering β-carotene during processing and storage. β-Carotene in emulsions with smaller particle size has poor stability, and protein-type emulsifiers and additional antioxidants are effective in protecting β-carotene from degradation. Recent development in the design of protein-polyphenol conjugates has provided a novel approach to improve the stability of β-carotene emulsions. When β-carotene is consumed, its bioaccessibility is highly influenced by the digestion of lipids, and β-carotene in smaller oil droplets containing long-chain fatty acids has a higher bioaccessibility. In order to better deliver β-carotene in complex food products, some novel emulsions with tailor-made structures have been developed, e.g., multilayer emulsions, solid lipid particles, Pickering emulsions. This review summarizes the updated understanding of emulsion-based delivery systems for β-carotene, and how emulsions can be better designed to fulfill the benefits of β-carotene in functional foods.     

One-step method for isolation and purification of native β-lactoglobulin from bovine whey

BACKGROUND: The major whey protein β‐lactoglobulin (BLG) has been widely studied for its functional properties. The aim of this study was to develop an efficient, inexpensive and rapid one‐step method for the isolation and purification of BLG while preserving its native structure. RESULTS: BLG was purified from defatted whey obtained from raw cow's milk by anion exchange chromatography. Protein purity and identity were determined using reverse phase high‐performance liquid chromatography and mass spectrometry. Total BLG yield was 80% with protein purity from 97 to 99%. BLG isoforms A and B were separated into fractions of 91 and 99% purity respectively. The structure and native conformation of the isolated BLG were compared with those of standard commercial BLG by circular dichroism spectrometry, susceptibility to various crosslinking enzymes and enzyme‐linked immunosorbent assay inhibition. CONCLUSION: The proposed method is very useful for the rapid preparation of BLG suitable for studying antigenic and molecular characteristics of this protein, as well as the effect of food processing on these properties. The procedure requires only 1 day for the purification of about 300 mg of BLG from a single run using a small column (2.5 cm × 20 cm) of diethylaminoethyl Sephadex and has potential for scaling up. Copyright © 2011 Society of Chemical Industry     

Effects of Maillard reaction conditions on the antigenicity of α-lactalbumin and β-lactoglobulin in whey protein conjugated with maltose

The effects of Maillard reaction conditions (weight ratio of protein to sugar, temperature and time) on the antigenicity of α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) in conjugates of whey protein isolate (WPI) with maltose were investigated. Response surface methodology was used to establish models to predict the antigenicity of α-LA and β-LG and find an optimal reaction condition under which the antigenicity of α-LA and β-LG reduces to minimum value. Conjugating WPI with maltose was an effective way to reduce the antigenicity of α-LA and β-LG. The antigenicity of α-LA decreased from 32.25 μg mL⁻¹ to 10.91 μg mL⁻¹. And the antigenicity of β-LG decreased from 272.4 μg mL⁻¹ to 38.17 μg mL⁻¹. Temperature had the greatest effect on the antigenicity of α-LA, while weight ratio of WPI to maltose was the most significant factor on the antigenicity of β-LG.     

Rheological properties of acid gels prepared from heated milk fortified with whey protein mixtures containing the A,B and C variants of β-lactoglobulin

The effect of fortification of reconstituted skim milk with different levels of a whey protein mixture containing a 1:2 ratio of α-lactalbumin (α-la) and different genetic variants of β-lactoglobulin (β-LG) on the rheological properties of acid milk gels, formed by acidification with glucono-δ-lactone, was investigated. Milk samples were either unheated or heated at 80°C for 30 min before acidification. Acid gels prepared from unheated skim milk had very low G′ values, long gelation times and low gelation pH. Samples prepared from heated milk had markedly higher G′ values, a reduced gelation time and an increased gelation pH. The addition of increasing levels of whey protein mixtures containing β-LG B or β-LG C to the milk prior to heating and acidification caused an almost linear increase in the G′. In contrast, whey protein mixtures containing β-LG A caused a progressive increase in the G′ with added protein levels up to about 0.7% (w/w) but little further change at higher addition levels. A mixture of the A and B variants of β-LG gave an intermediate behaviour between those of the A and B variants. In all samples, the G′ value at 5°C was approximately twice that at 30°C so that the relative differences as a result of the β-LG genetic variants were similar for the two temperatures.     

High pressure homogenization increases the in vitro bioaccessibility of α- and β-carotene in carrot emulsions but not of lycopene in tomato emulsions

Abstract: The correlation between food microstructure and in vitro bioaccessibility of carotenes was evaluated for tomato and carrot emulsions (5% olive oil) subjected to high pressure homogenization (HPH) at varying degrees of intensity. The aim was to investigate whether additional mechanical disruption of the food matrix could be utilized to further increase the carotene bioaccessibility of an already pre‐processed material. The carotene bioaccessibility of the samples was measured after simulated in vitro digestion, carotene release to the oil phase was estimated by Confocal Raman spectroscopy and, to measure active uptake of carotenes, Caco‐2 cells were incubated with the digesta of selected samples. HPH did not notably affect the retention of carotenes or ascorbic acid but significantly increased both the release and micellar incorporation of α‐ and β‐carotene in carrot emulsions 1.5‐ to 1.6‐fold. On the other hand, in vitro bioaccessibility of lycopene from tomato was not increased by HPH under any of the conditions investigated. Instead, the results suggested that lycopene bioaccessibility was limited by a combination of the low solubility of lycopene in dietary lipids and entrapment in the cellular network. Carotene uptake by Caco‐2 cells appeared to be mainly dependent upon the carotene concentration of the digesta, but cis‐trans isomerization had a significant impact on the micellarization efficiency of carotenes. We therefore conclude that HPH is an interesting option for increasing the bioaccessibility of carotenes from fruits and vegetables while maintaining a high nutrient content, but that the results will depend on both food source and type of carotene. Practical Application: A better understanding of the correlation between the processing of fruits and vegetables, microstructure and nutrient bioaccessibility can be directly applied in the production of food products with an increased nutritional value.     

Relation between in vitro lipid digestion and β-carotene bioaccessibility in β-carotene-enriched emulsions with different concentrations of l-α-phosphatidylcholine

In view of consumer health, it is desirable to promote the bioaccessibility of lipid-soluble compounds like carotenoids, while limiting the lipid intake. The objective of this work was to examine the relation between in vitro lipid digestion and β-carotene bioaccessibility of carrot-based model food emulsions containing water, 5% olive oil enriched with β-carotene (from carrots) and different concentrations (1–2–3–4%) of l-α-phosphatidylcholine (PHC), as an emulsifier. The lipid digestion (hydrolysis of triacylglycerols (TAGS) and incorporation of free fatty acids (FFAs) and monoacylglycerols (MAGs) in the micelles) and the β-carotene bioaccessibility (incorporation of β-carotene in the micelles) were studied after an in vitro digestion procedure wherein the stomach phase was mimicked for 2.0 h (37 °C) and the small intestinal phase was mimicked for 1.0 h, 1.5 h and 2.0 h (37 °C) (both end-over-end rotations). As a consequence, not only the influence of the emulsifier concentration, but also the influence of the duration in the small intestinal phase was investigated in this study. The oil droplet size distributions of the emulsions at different stages of digestion were shown to be dependent on the phosphatidylcholine concentration, but independent on the duration in the small intestinal phase (1.0 h–2.0 h). Furthermore, all TAGs were already hydrolysed into FFAs and MAGs after 1.0 h small intestinal phase and the incorporation of FFAs and MAGs into micelles seemed to reach a maximum for all emulsions (approximately 26.5%), independent on the phoshpatidylcholine concentration and thus on the particle size distributions. Finally, the β-carotene bioaccessibility increased with increasing phosphatidylcholine concentration, ranging from 33.2% to 79.8% for a 1% and 4% PHC emulsion respectively. No significant differences in β-carotene bioaccessibility were however noticed for the different durations in the small intestinal phase tested. In conclusion, a higher phosphatidylcholine concentration in emulsions leads to higher β-carotene bioaccessibility while the incorporation of lipids into micelles did not increase.     

Extraction of β-carotene produced from yeast Rhodosporidium sp. and its heat stability

This work determined the characteristics of β-carotene produced from Rhodosporidium sp. isolated from citrus fruits, and an effective extraction method was established. To extract β-carotene from the isolated Rhodosporidium sp., the cell walls were destroyed using dimethyl sulfoxide (DMSO) solution with and without the use of glass beads and a sonicator. Extracted β-carotene was identified by high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) with a β-carotene standard. The yields of β-carotene extracted in DMSO, DMSO and glass beads, and DMSO with a sonicator were 3.371, 5.112, and 3.301 μg/mL, respectively. Isolated β-carotene was relatively heat stable, with 80% of the viable molecules remaining at 80°C.     

Effect of chitosan molecular weight on the stability and rheological properties of β-carotene emulsions stabilized by soybean soluble polysaccharides

In this study, β-carotene emulsions were prepared using a two-stage homogenization process and adsorption of chitosan to anionic droplets coated with soybean soluble polysaccharides (SSPS). Effects of the molecular weights of chitosan on the stability and rheological properties of β-carotene emulsions were investigated. Results demonstrated that the ζ-potential, particle size and rheological properties of emulsions were greatly dependent on the chitosan molecular weight. It was found that the particle size of SSPS-stabilized emulsions increased with the rise of chitosan molecular weight at higher chitosan concentrations (>0.2 wt%). Chitosan molecular weight had a significant impact on the heat and light stability of β-carotene in emulsions. SSPS-stabilized emulsion with the adsorption of medium molecular weight-chitosan (MM-chitosan) was more stable than those with the adsorption of low and high molecular weight-chitosan (LM-chitosan and HM-chitosan). Dynamic oscillatory shear tests indicated that the viscoelasticity could be enhanced by the adsorption of higher molecular weight of chitosan onto the SSPS-coated droplet surfaces.     

Interaction of whey protein with polyphenols from salal fruits (Gaultheria shallon) and the effects on protein structure and hydrolysis pattern by Flavourzyme®

Milk whey can interact with polyphenols leading to the formation of complexes. In this research, whey protein was fortified with salal fruits (SB) extract and the effect on protein structure was investigated. Particle size and tertiary structure analysis indicates α-lactalbumin–ligand interactions when whey is supplemented with SB extract. Circular dichroism spectroscopy suggests conformational changes of α-Lac to a partially unfolded state as indicated by the decrease in α-helix structures. Enzymatic treatment of whey protein mixed with SB revealed differences in the hydrolysis pattern. LC-MS/MS data analysis indicates that a higher number of peptides are released when whey is mixed with SB. Peptides of known bioactivity were identified in all hydrolysates. The supplementation of whey protein with SB extract can influence protein hydrolysis and the release of peptides following enzymatic treatment with commercial proteases which may affect the functional and health-related properties of the hydrolysate.     

Improving the extraction efficiency and stability of β-carotene from carrot by enzyme-assisted green nanoemulsification

In this study, a green solvent (water: ethanol; 98:2) was applied to extract β-carotene (BC) from carrot pomace powder (CP). The low solubility (<5%) of BC was improved (~21%) by enzymatic hydrolysis of CP with a commercial pectinase (61 U/mL, 60 min); enzymatic liquefaction of CP improved the extraction efficiency up to 90%. Also, the nanoemulsions (NEs) based on different surfactants (Lecithin; Lec, Tween 80; T80, Tween 20; T20, and Span 20; S20) enhanced the extraction efficiency of BC. Up to >91%. HPLC data revealed that BC (60%) and α-carotene (29%) were the major carotenoids extracted into micelles of NEs, whereas lutein (9%) and lycopene (2%) as the minor ones. Finally, stability monitoring confirmed that BC in ethanolic extract from CP was completely lost, while BC in NE platform showed good stability of ~25% and 32% as exposed to UV-light and acidic conditions (pH ~ 4), respectively.     

Degradation of β-carotene with the effects of light and sulfur dioxide may be responsible for the formation of white spot in dried apricots

Light and sulfur-induced degradation of -carotene flushing out of cells with the effect of salivary pectolytic enzymes of bugs belonging to the family of Heteroptera have been shown to be responsible for the formation of white spot in dried apricots affecting the product quality adversely. The effects of light and sulfur dioxide on the degradation of -carotene were studied in the model systems. Light-induced degradation rate of -carotene was higher at shorter wavelengths. Sulfur-induced degradation reaction of -carotene followed a second-order rate law with a rate constant of 1687 M^–1 min^–1.At shorter wavelengths, light energy was mainly responsible for the degradation of -carotene while sulfur dioxide was more effective on -carotene degradation at higher wavelengths.     

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.     

A novel glycoprotein emulsion using high-denatured peanut protein and sesbania gum via cold plasma for encapsulation of β-carotene

Due to the instability of β-carotene, a glycoprotein (H/S-P) emulsion was specially prepared using high-denatured peanut protein isolate (HPPI) and sesbania gum by cold plasma (CP). The H/S-P, with multiple hydrophobic and hydrophilic groups present on the surface of HPPI and sesbania gum, was used to stabilize the oil-water interface. Characterization of HPPI and H/S-P emulsion under different protein additions was analyzed. Compared to HPPI emulsion, H/S-P emulsion showed better stability including thermal and salt resistance, smaller particle size, more protein adsorption content, and tough network structure, which was attributed to double-layer structure formation on the oil-water interface. Finally, emulsion with 5% protein addition was selected for embedding β-carotene, with an encapsulation efficiency ≥97.0%. Compared with HPPI emulsion, H/S-P emulsion enhanced the sustained release effect and bioaccessibility for β-carotene in gastrointestinal digestion. The preparation of glycoprotein emulsion by CP had potential applications in the delivery system for fat-soluble nutrients.     

Stability of α-tocopherol, γ-tocopherol and β-carotene during ripening of pasta-filata cheese made from raw and pasteurised milk with different vitamin contents

Ripening stability of α-tocopherol, γ-tocopherol and β-carotene in cheese was evaluated in relation to different milk vitamin content and to the use of either pasteurised or raw milk. Milk from two farms with different management systems was used to obtain different vitamin content. Milk was divided into two parts, of which only one was pasteurised. Four blocks of cheese were made from each batch and ripened for 0, 15, 30, or 60 days at 14–16 °C. There was a notable variation in cheese vitamin levels, with the differences in milk vitamin content due to farm management having the highest impact. Pasteurisation had no effect on cheese vitamin content. Cheese γ-tocopherol and β-carotene content decreased after 30 and 60 days, respectively, whereas α-tocopherol content remained stable. γ-Tocopherol appeared to be the most efficient antioxidant in cheese, followed by β-carotene. Vitamin stability was not influenced by milk vitamin content or pasteurisation.