Handling wine pomace: The importance of drying to preserve phenolic profile and antioxidant capacity for product valorization.

Four different wine grape pomaces (GP) (Vitis vinifera) varieties, Auxerrois, Pinot Blanc, Gamay and Pinot Noir, and obtained from white, rosé or red wine vinification, were considered for possible valorization in food supplement industry. Stabilization of GP by drying is paramount prior to further processing in the valorization chain, as GP might suffer spoilage over time. The objectives of this work were therefore to: evaluate the effect of microbiological spoilage and drying on the polyphenol profile and antioxidant capacity of GP; define a drying procedure by comparing kinetics of freeze-drying (FD) and vacuum oven (VO) (at 60 °C and 40 °C). Microbiological spoilage led to significant losses (P < 0.01) of antioxidant capacity (40% to 87%) and total phenolic content (70% to 90%), while drying had no significant effect. FD and VO at 60 °C drying kinetics exhibited similar drying curves, and a dry weight (DW) plateau was reached by 48 hr. In contrast VO at 40 °C required 170 hr to reach similar DW values, pointing out the importance of temperature when opting for VO technology. Antioxidant capacity of GP extracts did not differ between drying methods. Interestingly, GPs from white and rosé wines (AUX, PB, and GAM) had up to 3.5 times higher content (P < 0.001) of total polyphenols compared to PN, obtained from red wine. These results reinforce the importance of drying of GP as a pretreatment, which otherwise could result in significant product degradation. Additionally, we propose white and rosé GP as more interesting sources for valorization, with higher phenolic content, compared to red wine GP.

Influence of soy and whey protein, gelatin and sodium caseinate on carotenoid bioaccessibility.

Proteins could alter carotenoid bioaccessibility through altering their fate during digestion, due to emulsifying properties of resulting peptides, or influencing access of digestion enzymes to lipid droplets. In this investigation, we studied whether whey protein isolate (WPI), soy protein isolate (SPI), sodium caseinate (SC) and gelatin (GEL), added at various concentrations (expressed as percentage of recommended dietary allowance (RDA): 0, 10, 25 and 50%) would influence the bioaccessibility of lycopene, ß-carotene or lutein, added as pure carotenoids solubilized in oil, during simulated gastro-intestinal (GI) digestion. Protein and lipid digestion as well as selected physico-chemical parameters including surface tension, ζ-potential and micelle size were evaluated. Adding proteins influenced positively the bioaccessibility of ß-carotene, by up to 189% (p < 0.001), but it resulted in generally decreased bioaccessibility of lutein, by up to 50% (p < 0.001), while for lycopene, the presence of proteins did not influence its bioaccessibility, except for a slight increase with WPI, by up to 135% (p < 0.001). However, the effect depended significantly on the type of protein (p < 0.001) and its concentration (p < 0.001). While ß-carotene bioaccessibility was greatly enhanced in the presence of SC, compared to WPI and GEL, the presence of SPI strongly decreased carotenoid bioaccessibility. Neglecting individual carotenoids, higher protein concentration correlated positively with carotenoid bioaccessibility (R = 0.57, p < 0.01), smaller micelle size (R = -0.83, p < 0.01), decreased repulsive forces (ζ-potential, R = -0.72, p < 0.01), and higher surface tension (R = 0.44, p < 0.01). In conclusion, proteins differentially affected carotenoid bioaccessibility during digestion depending on carotenoid and protein species, with both positive and negative interactions occurring.

Whey protein isolate modulates beta-carotene bioaccessibility depending on gastro-intestinal digestion conditions.

Carotenoids are lipophilic phytochemicals; their intake has been associated with reduced chronic diseases. However, their absorption depends on emulsification during digestion and incorporation into mixed micelles, requiring digestive enzymes, gastric peristalsis, bile, and dietary lipids. In this study, we investigated whether whey-protein-isolate (WPI), a commonly consumed protein source, can modulate ß-carotene bioaccessibility in vitro, especially under incomplete digestive conditions, i.e. under low digestive enzyme concentrations. Thus, amounts of pepsin, pancreatin, bile, co-digested lipids and kinetic energy and gastric digestion time were modified, and WPI at concentrations equivalent to 0/25/50% of the protein recommended dietary allowance (approx. 60 g/d) were added to ß-carotene dissolved in oil. WPI enhanced bioaccessibility by up to 20% (p < 0.001), especially under higher simulated peristalsis or reduced amount of dietary lipids. Conversely, they impaired bioaccessibility to one third (p < 0.001) under incomplete digestive conditions. WPI modulated ß-carotene bioaccessibility depending on digestive conditions.

Two competing reactions of tetrabutylammonium alginate in organic solvents: Amidation versus γ-lactone synthesis.

Biocompatibility and thickening properties predetermine alginates as ingredients in food, cosmetic and pharmaceutical products. Further chemical modifications are often desired for a product optimization. The introduction of hydrophobic groups can be realized by employing organic tetrabutylammonium alginate (TBA-Alg) solutions. The synthesis of alginic acid alkyl amides from TBA-Alg with 2-chloro-1-methylpyridinium iodide (CMPI) as a coupling agent, however, has so far not resulted in a high degree of amidation. The analysis of the coupling reaction revealed the formation of mannuronic acid γ-lactone structures, which required a conformation change from (1)C4 to (4)C1. The opening of the γ-lactone required a high excess of butylamine. In the case of CMPI, triethylamine had to be added prior to the coupling agent in order to suppress the assumed alginic acid formation. The degrees of amidation achieved were up to 0.8, and for propylphosphonic anhydride as the coupling agent up to 1. The molecular weights of the alginic acid butyl amide were ≥35kDa.

Synthesis enhancements for generating highly soluble tetrabutylammonium alginates in organic solvents.

The adaptation of alginates to food and pharmaceutical specifications is limited to aqueous chemistry due to the insolubility of sodium alginate (Na-Alg) and the insufficient solubility of tetrabutylammonium alginate (TBA-Alg) in organic solvents. In the present investigation, these restrictions were resolved by optimizing the solubility of TBA-Alg by improving its synthesis from Na-Alg via heterogeneous acidification with hydrochloric and formic acid, followed by neutralization with tetrabutylammonium hydroxide. The best acidification results were achieved with formic acid, because the reaction controlling solubility of the by-product in the acidic solvent was improved in comparison to hydrochloric acid. The solubility of TBA-Alg in polar aprotic organic solvents improved by increasing the degree of TBA substitution (DSTBA), decreasing the molecular weight of TBA-Alg and increasing the relative permittivity of the solvent. The best TBA-Algs, with DSTBA=0.95 and relative high molecular weights, gave optically clear solutions with a turbidity of about 1 NTU.