Unraveling the role of probiotics in affecting the structure of monoglyceride gelled emulsions: A low-field 1H NMR study.

The capacity of monoglyceride (MG) gelled emulsions (MEs) in protecting probiotic cells of Lacticaseibacillus rhamnosus against stresses suffered during food processing, storage, and human digestion has been recently demonstrated. These findings open new perspectives on the possible participation of probiotics in the stabilization of emulsion structure. To unravel this aspect, rheological analysis and Low-Field 1H NMR investigations were performed on MEs having different aqueous phases (water or skimmed milk) and stored for increasing time (1 and 14 days) at 4 °C. Loaded and unloaded samples were considered. Results highlighted that probiotics initially hindered the ability of MG to self-assemble in the multiphase environment, interacting in some way with MG crystalline lamellar structure, as confirmed by rheological and 1H NMR analysis. During storage, an increase of proton compartmentation was observed in loaded MEs indicating the role of probiotics in stabilizing MG structure at a molecular level. Such a result was more evident when the system was composed of milk, suggesting that the presence of milk-native components (i.e., lactose, proteins, and minerals) favored the cell-structure interactions. Such preliminary results could open new perspectives in considering probiotic cells as having an active role in the stabilization of food structure.

Effect of moderate hydrostatic pressure on crystallization of palm kernel stearin-sunflower oil model systems.

Lipid crystallization under moderate hydrostatic pressure treatments (200 MPa, 20 °C, 1-24 h) was studied in palm kernel stearin (PS 100%) and its blends with sunflower oil (PS 80, 90 % w/w). Hyperbarically-crystallized samples exhibited significantly higher firmness, elastic modulus and critical stress values as compared to those of the samples crystallized at atmospheric pressure. These data indicate that moderate hydrostatic pressure favored the formation of a higher amount of small palm kernel stearin crystals as compared to those formed at atmospheric pressure. Pressurization did not affect fat polymorphism, but was able to enhance nucleation instead of crystal growth. This work clearly demonstrated the efficacy of moderate hydrostatic pressure in steering lipid crystallization, opening interesting possible applications of high-pressure processing technology in the fat manufacturing sector.

Oleogelation of extra virgin olive oil by different gelators affects lipid digestion and polyphenol bioaccessibility.

The possibility to steer extra virgin olive oil (EVOO) digestion and polyphenol bioaccessibility through oleogelation was investigated. EVOO was converted into oleogels using lipophilic (monoglycerides, rice wax, sunflower wax, phytosterols) or hydrophilic (whey protein aerogel particles, WP) gelators. In-vitro digestion demonstrated that the oleogelator nature influenced both lipid digestion and polyphenol bioaccessibility. WP-based oleogels presented ∼100% free fatty acid release compared to ∼64% for unstructured EVOO and ∼40 to ∼55% for lipophilic-based oleogels. This behavior was attributed to the ability of WP to promote micelle formation through oleogel destructuring. Contrarily, the lower lipolysis of EVOO gelled with lipophilic gelators compared to unstructured EVOO suggested that the gelator obstructed lipase accessibility. Tyrosol and hydroxytyrosol bioaccessibility increased for WP oleogels (∼27%), while liposoluble-based oleogels reduced it by 7 to 13%. These findings highlight the deep effect of the gelator choice on the digestion fate of EVOO components in the human body.

Role of the polyphenol content on the structuring behavior of liposoluble gelators in extra virgin olive oil.

The role of polyphenols in affecting the structural and rheological properties of oleogels was investigated. Polyphenols were selectively removed from extra virgin olive oil (EVOO), and the resulting oils at three different polyphenol levels were gelled by using 10% (w/w) of monoglycerides (MG), rice wax (RW), sunflower wax (SW), and a mixture of ß-sitosterol/γ-oryzanol (PS). The structural characteristics of oleogels were assessed by visual appearance, rheology, polarized light microscopy, calorimetry, XRD, and FTIR. Polyphenol content differently affected oleogel characteristics depending on network features. While EVOO-polyphenols did not influence PS- and SW-based oleogels, they reinforced MG- and RW-based oleogel network. As polyphenol content increased, the critical stress and melting temperature also increased, concomitantly with changes in crystal morphology. This was attributed to the capacity of polyphenols to form additional junction points in the crystalline network.