Food Biophysics

In this research, we studied the relationship between the molecular structure of (R)-12-hydroxyoctadecanamide, (R)-N-propyl-12-hydroxyoctadecanamide, and (R)-N-octadecyl-12-hydroxyoctadecanamide and the thermo-mechanical properties of their 2% (wt/wt) organogels developed using safflower oil high in oleic acid (HOSFO) as the liquid phase. Candelilla wax (CW), a well-known edible gelling additive whose main component is hentriacontane, also was studied for comparative purposes. The results obtained show that the attractive interactions (i.e., hydrogen bonding and dipolar interactions) between amide groups and between hydroxyl groups present in the amides resulted in organogels with higher melting temperature, heat of melting, and crystallization parameters than those found in the CW organogel. The rheological parameters associated to the strength of the amide or CW-based gels developed in HOSFO (i.e., yield stress and elastic modulus) seem to be associated with the nature of amide groups (i.e., primary or secondary amide) and the increase in the length of the self-assembly molecular unit (i.e., L value determined by X-ray diffraction) and therefore to the extent of London dispersion forces along the hydrocarbon chain. The creep and recovery measurements allowed an evaluation among the internal structures of the different organogels and demonstrated that independent of the hydrogen bonding and dipolar interaction provided by the amide and the hydroxyl groups, the increase in the hydrocarbon chain length results in higher organogel resistance to deformation and higher instant recovery capacity. However, the stabilization of the self-assembly unit through polar groups (i.e., –CONH2 in HOA) reduces organogel elasticity but provides a higher extended recovery capacity. The results reported in this investigation showed some relationships between gelator structure and the thermo-mechanical properties of low-molecular-mass organic gelator amides. Our long-term objective is to understand the organogelation process to eventually develop trans-free vegetable oil-based food products with novel textures for the consumers.

Myofibrillar proteins (MPs) are underutilized because of their weak solubility in low-salt conditions. In this research, mixing MPs with sodium alginate (SA) was studied to improve the solubility of MPs, and the effects of pH, mixing ratios (r), and protein preheating were examined. Mixing with SA improved the solubility of MPs at pH 6.5 and 5.5, and the precipitation of MPs was completely inhibited by an MPs/SA ratio of 20 and 5.0, respectively. The solubility of MPs was not improved by mixing with SA at other pHs. The mixing behavior of MPs and SA was greatly influenced by the electrostatic interaction, depletion interaction, and bridging flocculation. Preheating MPs (70 °C, 30 min) reduced the amounts of SA required to inhibit their precipitation and improved the heat stability of MPs/SA mixtures. These improvements may have resulted from the exposure of embedded negatively charged groups, decrease of particle size in MPs, and disulfide crosslinking after preheating. These findings demonstrate an approachable route to obtain soluble forms of MPs, which may find application in liquid products.

The effects of six different polyglycerol esters of fatty acids (PGEs) and two different particle sizes produced using various processing parameters on the physicochemical properties and stability of the β-carotene emulsions during digestion in simulated gastric fluid (SGF) were investigated. β-Carotene emulsions were prepared by high-pressure homogenization using β-carotene (0.1% w/w) in soybean oil as the oil phase and 1% (w/w) PGE in Milli-Q water as the water phase. The particle size of β-carotene emulsions was measured by a laser diffraction technique, and the stability of emulsions was interpreted in terms of the increase in particle size and span value of emulsion droplets and the retention of β-carotene during digestion in SGF. The average particle size ranges of emulsions were 0.17 to 0.27 μm for fine emulsions and 1.16 to 1.59 μm for coarse emulsions. In the prepared β-carotene emulsions, the particle size decreased with increasing polymerization of the glycerol in PGEs, and the higher polymerization of the glycerol also increased the stability of emulsions during digestion in SGF. Although the β-carotene content in the emulsions significantly decreased with increasing digestion period, loss of β-carotene was more severe in unstable emulsions than in stable emulsions, suggesting that the particles incorporated into droplets could provide some protective barrier for decreasing the β-carotene degradation. Therefore, β-carotene emulsions stabilized by PGEs with high polymerization of the glycerol may be useful for further applications in food and drug formulations. Decaglycerol monooleate (MO750) was demonstrated to be the most effective emulsifier in stabilizing β-carotene emulsions in this study.

This work studies saliva foam, and the effect of in vitro orally-processed model foods on this foamy state. It reaches an estimation on the volume fraction of air trapped as bubbles in the saliva of healthy young volunteers, a value close to 0.3. So air bubbles and foam state might be intrinsic colloidal properties of saliva, with implications on its physiological and physicochemical definition and role. It then studies the capacity of mucin to stabilize model saliva, and the role of food protein (here sodium caseinate) to influence this foaming and the resulting foam stability during oral processing in in vitro systems. Synergistic effects are observed between mucin and caseinate in foams in terms of their foaming capacity and foaming stability. These are discussed in relation to their water–air dynamic interfacial tension, while the bubbles are observed with confocal microscopy. The effects of replacement of mucin with caseinate, hence the relevant transitions in interfacial composition, are studied in high internal gas volume fraction foams, with sodium caseinate producing relatively thicker foams, and mucin bringing about higher long-term stability. The above are brought together and discussed in relation to the temporal evolution of foam during the oral processing of foods.

In this work, purification of lactoferrin from whey was performed with high recovery rate. Lactoferrin was then exploited in the preparation of food emulsions. Two tertiary emulsions, formed by olive oil, lecithin, chitosan, and lactoferrin, were compared: both the emulsions showed similar turbidity and stability. In the secondary emulsion formed by oil/lecithin/chitosan, the pH was increased to 9 before addition of lactoferrin. Then, lactoferrin was added, and the pH was stabilized above pH 9. Lactoferrin was found in amounts of 1 to 2.5 mg/ml in the multiple experiments. A fraction of the added lactoferrin was also present in a milky layer above the emulsion layer. This was, to our knowledge, the first study of emulsions made exploiting the interactions between lactoferrin and chitosan. It was noted that chitosan droplets remained soluble, although the hydrocolloid solubility occurs at pH lower than 5.9. These results showed the feasibility of manufacturing lactoferrin-based emulsions as functional foods.

Recovery of high-added-value compounds from seafood waste is a promising area of research. Mussel byssus is a by-product from mussel production for human consumption, which is a potential source of collagen. The goal of this study was to extract collagen from the byssus of Chilean mussel using two methods (acidic and enzymatic) and determine their extraction yields. Acidic extraction was performed by immersing the byssus into distilled water adjusted to pH 4 with HCl at two extraction temperatures (60 or 80 °C) and times (6 or 24 h). For enzymatic extraction, first an enzymatic hydrolysis at two times (4 or 24 h) and pepsin/substrate ratios (1:50 or 4:50) was done. Then, the extraction was conducted at 80 °C for 24 h. All samples were analyzed for total protein, amino acid profile and molecular weight of collagen extracts. Extraction time and temperature had significant effects (p < 0.05) on protein and hydroxyproline contents after acidic extraction, where the higher level of process parameters (80 °C and 24 h) gave the highest protein (6 mg/mL) and hydroxyproline (7.6 mg/g protein) values. Using an enzymatic step before extraction, an increase in protein and hydroxyproline contents was observed, with maximum values of 31 mg/mL and 32 mg/g protein, respectively. The enzyme extraction presented the higher extraction yield, values ranging from 3.86 to 7.56 %. Electrophoretic patterns of collagen presented only β and γ bands, suggesting that this collagen is highly cross-linked at the telopeptide region. These results indicate that the Chilean mussel byssus is a good source of collagen that can be extracted for different purposes.

The effect of low-molecular-weight surfactants (LMS) and sodium caseinate (NaCas) on spray drying of sugar-rich foods has been studied. Sucrose and NaCas were selected as a model sugar-rich food and protein, respectively. Sodium stearoyl lactylate (SSL) and Polysorbate 80 (Tween 80) were chosen as model ionic and nonionic LMS. Sucrose–NaCas solutions with the solids ratio of 99.5:0.5 in the absence and presence (0.01% and 0.05%) of SSL and Tween 80 were prepared. The feed solutions had 25% solid concentration in all cases. The dynamic surface tension (DST) values of the solutions were measured for 100 s and the solutions were subsequently spray dried at inlet and outlet temperatures of 165 and 65 °C, respectively. The glass–rubber temperature (T g-r), the surface elemental composition and amorphous–crystalline nature of the powders were also determined. At these concentrations and experimental time frame, it was found that the proteins preferentially migrated to the air–water interface reasonably swiftly. The addition of LMS resulted in partial or complete displacement of the proteins from the air–water interface. For spray-drying trials with the yield of 82.0%, it was found that 52.0% of the powder particle surface was covered with proteins. The powder recovery was greatly reduced by the LMS concentration and type. At 0.05% on dry solid basis, in the case of nonionic surfactant (Tween 80), the displacement of protein from the surface was such that no powder was recovered. The ionic surfactant (SSL) displaced 2.0% and 29.3% proteins from the droplet surface at concentrations of 0.01% and 0.05%, respectively, resulting in 75.5 ± 1.8% and 30.1 ± 1.4% powder yield. The T g-r results revealed that the amount of protein required for successful spray drying of the sucrose–protein solution depends on the amount of proteins present in the droplet surface but not in the bulk. X-ray diffraction and scanning electron microscopy results confirmed that the powders of both sucrose–NaCas and sucrose–NaCas with 0.01% SSL were mostly amorphous, while those with sucrose–NaCas–Tween 80 (0.01%) and sucrose–NaCas–SSL (0.05%) were crystalline.

Pretreatment of oat protein with ultrasound showed excellent prospects in increasing the efficiencies of enzymatic hydrolysis and inhibitory activities of peptides against angiotensin converting enzyme (ACE). The mechanism of the ultrasound pretreatment on enhancement of protein hydrolysis rate and the characterization of the enzymolysis process was investigated. The Michaelis-Menten model was used to study the effects of ultrasound on the hydrolysis rate. An ordered sequential bi-substrate reaction mechanism model was applied to describe the characteristics of enzymolysis of the protein with ultrasonic pretreatment. The protein concentration and the enzyme loading were factors in this model. The kinetic parameters of the models were estimated by experimental results and evaluated. The results showed that ultrasonic power, time and enzymolysis time greatly influenced the degree of hydrolysis and ACE inhibitory activities of the peptides. The best conditions for hydrolysis and ACE inhibitory activities were 750 W, 20 min of sonication followed by 60 min of enzymolysis. After the treatment, the hydrolysis rate and the ACE inhibitory activities of peptides were significantly (P < 0.001) increased by 32.1 and 53.8 %, respectively compared to the samples without ultrasonic pretreatment. The Michaelis constant K m indicated the ultrasonic treatment enhanced the affinities between the alcalase and oat protein. The enzymolysis kinetic model fitted well the enzyme catalyzed hydrolysis trend for the ultrasonic pretreated oat protein. The model provided a theoretical basis for describing the complex enzymatic process and preparing the ACE inhibitory peptides efficiently.

It is an emerging trend to adopt cholesterol analogues from botanical sterols as membrane stabilizers of liposomes. This work investigated the potential of using purified sterol from camellia oil deodorant distillate as the membrane stabilizer for vitamin C liposomes. At the same time, β-sitosterol, stigmasterol, and cholesterol served as the control. The effect of sterols on vesicle properties, liposomes stability, vitamin C release, and bioavailability was assessed. When purified sterol was incorporated, the properties of these vesicles were comparable to those of the vesicles with β-sitosterol incorporated. However, the incorporation of stigmasterol was not conducive to vesicles dispersion. The storage, thermal, and pH stability, encapsulation efficiency, and bioavailability of vitamin C in liposomes were improved with purified sterol incorporated. In addition, the vitamin C in liposomes containing purified sterol showed a slower release. The release of vitamin C from liposomes containing purified sterols followed a first-order kinetic model. Fickian diffusion governed the release mechanism. The results suggested that purified sterol was a potential replacer for cholesterol as the stabilizer for liposomes, which was beneficial for developing low-cholesterol liposomes.