Structure, controlled release mechanisms and health benefits of pectins as an encapsulation material for bioactive food components.

Encapsulation of food and feed ingredients is commonly applied to avoid the loss of functionality of bioactive food ingredients. Components that are encapsulated are usually sensitive to light, pH, oxygen or highly volatile. Also, encapsulation is also applied for ingredients that might influence taste. Many polymers from natural sources have been tested for encapsulation of foods. In the past few years, pectins have been proposed as emerging broadly applicable encapsulation materials. The reasons are that pectins are versatile and inexpensive, can be tailored to meet specific demands and provide health benefits. Emerging new insight into the chemical structure and related health benefits of pectins opens new avenues to use pectins in food and feed. To provide insight into their application potential, we review the current knowledge on the structural features of different pectins, their production and tailoring process for use in microencapsulation and gelation, and the impact of the pectin structure on health benefits and release properties in the gut, as well as processing technologies for pectin-based encapsulation systems with tailor-made functionalities. This is reviewed in view of application of pectins for microencapsulation of different sensitive food components. Although some critical factors such as tuning of controlled release of cargo in the intestine and the impact of the pectin production process on the molecular structure of pectin still need more study, current insight is that pectins provide many advantages for encapsulation of bioactive food and feed ingredients and are cost-effective.

Zinc availability from zinc-enriched yeast studied with an in vitro digestion/Caco-2 cell culture model.

BACKGROUND: Organic zinc sources for the treatment of zinc deficiency or as a supplement to a specific diet are increasingly needed. Zinc-enriched yeast (ZnYeast) biomass is a promising nutritional supplement for this essential micronutrient. However, these products are not yet authorized in the European Union and a clear position from the European Food Safety Authority on the use of ZnYeast as a zinc supplement is pending, demanding more data on its bioavailability. OBJECTIVE: The study aimed to produce a ZnYeast based on a Saccharomyces genus (S. pastorianus Rh), characterize its zinc enrichment quota, cellular distribution of zinc, and evaluate its zinc bioavailability after human digestion by comparing it to commonly used inorganic and organic zinc supplements (ZnO, ZnSO4, zinc gluconate, and zinc aspartate). METHOD AND MAIN FINDINGS: The zinc-enriched S. pastorianus Rh contained 5.9 ± 1.0 mg zinc/g yeast, which was predominantly localized on the cell surface according to its characterization on the microscale with scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX). Combined experiments with a human in vitro digestion model and the in vitro intestinal cell model Caco-2 showed that intestinal zinc bioavailability of digested yeast biomass was comparable to the other zinc supplements, apart from ZnO, which was somewhat less bioavailable. Moreover, zinc released from digested ZnYeast was available for biological processes within the enterocytes, leading to mRNA upregulation of metallothionein, a biomarker of intestinal zinc status, and significantly elevated the cellular labile zinc pool. CONCLUSIONS: Our findings demonstrated that ZnYeast represents a suitable nutritional source for organically bound zinc and highlighted optimization strategies for future production of dietary ZnYeast.

Influence of the Carboxylic Function on the Degradation of d-Galacturonic Acid and Its Polymers.

Past investigations have shown high browning potential during the caramelization of sugar acids in comparison to reducing sugars. However, no approaches to elucidate the chemical mechanisms have been made. Therefore, this study aims to clarify the reasons for the high browning potential by measuring the mutarotation velocity and the elimination of CO2 during the heat treatment of uronic acids. Performed polarimetric experiments show that the mutarotation velocity of d-galacturonic acid exceeds that of d-galactose by a factor of nearly 4.5. However, the ring opening velocity is not the only parameter that differs between the two carbohydrate structures. Measurements of the release of CO2 of heated d-galacturonic acid at 60 °C show a steady increase, and after 48 h, 6% of degraded d-galacturonic acid has eliminated CO2. CO2 release was also found during the heating of pectin, indicating a decarboxylation reaction during thermal degradation. One of the degradation reactions postulated for the release of CO2 leads to α-ketoglutaraldehyde, which is responsible for the formation of several chromophoric substances.

Composition of Quillaja saponin extract affects lipid oxidation in oil-in-water emulsions.

Quillaja saponin extract comprises both, surfactants and phenolic compounds, which makes it interesting, in particular, for the formulation of sensitive functional food ingredients and its protection against oxidation. The aim of this study was to investigate the antioxidant effect of Quillaja saponin extract in oil/water emulsions. Emulsions stabilised by Quillaja saponin showed decreased oxidation stability due to naturally occurring metals but stability increased to a great extent when a chelating agent was added. Antioxidant efficiency of the saponin extract was determined photometrically by 2,2'-diphenyl-1-picrylhydrazyl (DPPH) assay and by the use of electron paramagnetic resonance spectroscopy (EPR). EPR spectroscopy applying stable hydrophilic and hydrophobic radicals is advantageous, especially for characterisation of antioxidant efficiency at the interface. The extract showed antioxidant activity towards radicals in both environments, aqueous and hydrophobic, indicating the importance of phenolic compounds for the antioxidant properties of Quillaja saponin extract and their presence at the interface facilitated by saponin molecules.

Interfacial properties of Quillaja saponins and its use for micellisation of lutein esters.

Natural food colourants, colouring foods and bioactive food ingredients need to be solubilised for their incorporation in food. Aim of the present study was to investigate the micelle-forming properties of saponins from Quillaja saponaria Mollina (QS) in order to solubilise a lutein ester extract for its incorporation in food matrices. QS showed a high surface activity and functionality with respect to micellisation as derived from interfacial tension measurements and subsequent data fitting to the classical Frumkin model. The composition of the aqueous phase affected the lutein ester incorporation as revealed by particle size, zeta potential and colour measurements. In terms of morphology of lutein ester loaded saponin micelles (LMS), cryo-TEM micrographs showed depending on the composition of the medium both, spherical and elongated branched micelles.