Phytosomes consist of a phytochemical bound to the hydrophilic choline head of a phospholipid. Their use in food products is gaining interest. However, literature on the use of food‐grade solvents, crude plant extracts as opposed to pure compounds, and unrefined phospholipids to prepare phytosomes is limited. Furthermore, studies on compound stability are lacking. This study aimed to develop nano‐phytosome vesicles prepared from inexpensive food‐grade ingredients to improve the stability of polyphenolic compounds. Cyclopia subternata extract (CSE) was selected as a source of phenolic compounds. It contains substantial quantities of C‐glucosyl xanthones, benzophenones, and dihydrochalcones, compounds largely neglected to date. The effect of process conditions on the complexation of CSE polyphenols with minimally refined food‐grade fat‐free soybean lecithin (PC) was studied. The PC:CSE ratio, sonication time, and reaction temperature were varied. This resulted in phytosomes ranging in vesicle size (113.7–312.7 nm), polydispersity index (0.31–0.48), and zeta potential (−55.0 to −38.9 mV). Variation was also observed in the yield (93.5%–96.0%), encapsulation efficiency (3.7%–79.0%), and loading capacity (LC, 1.3%–14.7%). Vesicle size and LC could be tailored by adjusting the sonication time and PC:CSE ratio, respectively. Chemical interaction between the lipid and the phenolic compounds was confirmed with nuclear magnetic resonance. Phytosomal formulation protected the compounds against degradation when freeze‐dried samples were stored at 25 and 40°C for 6 months at low relative humidity. The study provided valuable information on the importance of specific process parameters in producing food‐grade phytosomes with improved phenolic stability.

Phenolic compounds are known to degrade and/or undergo changes during food production and storage. Reaction kinetic modeling is generally used to define kinetic parameters of a food system and predict changes during thermal processing and storage. Data for phenolic acids and flavonoids, such as anthocyanins and flavan-3-ols, have been reviewed in detail, but the flavonoid sub-classes, dihydrochalcones and flavanones, have been mostly neglected. Other neglected phenolic classes are xanthones and benzophenones. The stability of these types of compounds is important as they are present in fruits and exposed to heat when processed into juice and jam. Other sources of the compounds are herbal teas, which are also subjected to thermal processing, either during the primary processing of the plant material, or the production of extracts for use as food ingredients. The theoretical background is given to understand the review of literature on these classes/sub-classes. Results of research on kinetic modeling are discussed in detail, while research on compound stability without the application of reaction kinetic modeling is briefly mentioned to provide context. The studies discussed included those focusing on heating during the processing and storage of model solutions, liquid foods, plant material, dried extracts, and extracts formulated with other food ingredients.

Green rooibos extract (GRE), shown to improve hyperglycemia and HDL/LDL blood cholesterol, has potential as a nutraceutical beverage ingredient. The main bioactive compound of the extract is aspalathin, a C-glucosyl dihydrochalcone. The study aimed to determine the effect of common iced tea ingredients (citric acid, ascorbic acid, and xylitol) on the stability of GRE, microencapsulated with inulin for production of a powdered beverage. The stability of the powder mixtures stored in semi-permeable (5 months) and impermeable (12 months) single-serve packaging at 30 °C and 40 °C/65% relative humidity was assessed. More pronounced clumping and darkening of the powders, in combination with higher first order reaction rate constants for dihydrochalcone degradation, indicated the negative effect of higher storage temperature and an increase in moisture content when stored in the semi-permeable packaging. These changes were further increased by the addition of crystalline ingredients, especially citric acid monohydrate. The sensory profile of the powders (reconstituted to beverage strength iced tea solutions) changed with storage from a predominant green-vegetal aroma to a fruity-sweet aroma, especially when stored at 40 °C/65% RH in the semi-permeable packaging. The change in the sensory profile of the powder mixtures could be attributed to a decrease in volatile compounds such as 2-hexenal, (Z)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, (E,Z)-2,6-nonadienal and (E)-2-decenal associated with “green-like” aromas, rather than an increase in fruity and sweet aroma-impact compounds. Green rooibos extract powders would require storage at temperatures ≤ 30 °C and protection against moisture uptake to be chemically and physically shelf-stable and maintain their sensory profiles.

Aspalathin, a C‐glucosyl dihydrochalcone, could have beneficial effects in the gut through the modulation of the microbiome. However, aspalathin is susceptible to oxidative degradation. The effect of electrospraying conditions on encapsulation of an aspalathin‐rich fraction prepared from green rooibos (GRAF; 40% aspalathin, m/m) with Eudragit S100 (ES100), a pH‐sensitive release polymer, was investigated to enhance the stability of aspalathin. Electrospraying conditions were varied according to a central composite design, using ES100 concentrations of 1–6% (m/m), GRAF concentrations of 5–25% (m/m, relative to polymer concentration), and voltages of 10–25 kV. The varying conditions produced nanoparticles ranging in yield (60.3–83.7%), encapsulation efficiency, (20.5–81.8%), loading capacity (1.0–14.9%), particle size (183–260 nm), and polydispersity index (0.35–0.74). The GRAF nanoparticles and nanoparticles prepared with pure aspalathin were evaluated for stability and release of aspalathin at fixed pH–time combinations (pH 6.8, 5 min; pH 2, 120 min; pH 4, 60 min; and pH 7, 120 min), simulating the pH and residence/transit time at various locations of the orogastrointestinal tract. Nanoencapsulation decreased aspalathin degradation at all pH‐time combinations (1.9–2.7 times less degradation; p < 0.05), except for pH 7, 120 min (p ≥ 0.05), thus offering protection from the pH of the upper gastrointestinal tract. Additionally, the parallel artificial membrane permeability assay and the Caco‐2 monolayer model indicated that the low membrane permeability of aspalathin after nanoencapsulation was maintained that would limit absorption, ideal for delivery in the gut. Thus, nanoencapsulated aspalathin holds potential for the regulation of gut microbiota.