Extrusion of apple pomace increases antioxidant activity upon in vitro digestion.

Apple pomace, a by-product of juice production, is a high-fibre, high-polyphenol functional food ingredient. Extrusion (barrel moisture 15%, 20% or 30%) of apple pomace, followed by drying, allows it to be supplied in a convenient form. Extrusion caused degradation of the apple pomace cell wall structure. Water solubility was significantly increased by extrusion but oil holding capacity was reduced. Total extractable polyphenols, measured as gallic acid equivalents, were reduced by extrusion (barrel moisture 30%) but were not affected by extrusion at lower barrel moisture contents (15% or 20%). However, individual sub-groups of extractable flavanols, flavonols, phenolic acids and dihydrochalcones were increased by extrusion. There was little effect of extrusion on the release of total polyphenols from the matrix into the supernatant, as measured by total extractable polyphenols (measured as gallic acid equivalents) released during in vitro digestion. There was a marked increase in total flavanols, phenolic acids and dihydrochalones released into the supernatant during the gastric phase but changes in flavonoids were less obvious. The changes in the bioaccessibility of individual polyphenols released during intestinal digestion were dependent on the type of polyphenol and extrusion conditions. The antioxidant activity, as measured using oxygen radical absorbance capacity (ORAC) of the bioaccessible nutrients released upon in vitro intestinal digestion, was significantly enhanced by extrusion (from 78.2 to 400-500 µmol Trolox equivalents per mL at the ileal phase). The increased ORAC may be attributed in part to the increased release of individual polyphenols.

In situ quantification of ß-carotene partitioning in oil-in-water emulsions by confocal Raman microscopy.

Confocal Raman microscopy (CRM) was able to quantify the ß-carotene concentration in oil droplets and determine the partitioning characteristics of ß-carotene within the emulsion system in situ. The results were validated by a conventional method involving solvent extraction of ß-carotene separately from the total emulsion as well as the aqueous phase separated by centrifugation, and quantification by absorption spectrophotometry. CRM also enabled the localization of ß-carotene in an emulsion. From the Raman image, the ß-carotene partitioning between the aqueous and oil phases of palm olein-in-water emulsions stabilized by whey protein isolate (WPI) was observed. Increasing the concentration of ß-carotene in an emulsion (from 0.1 to 0.3g/kg emulsion) with a fixed gross composition (10% palm olein:2% WPI) decreased the concentration of ß-carotene in the oil droplet. CRM is a powerful tool for in situ analyses of components in heterogeneous systems such as emulsions.

Synbiotic microcapsules that enhance microbial viability during nonrefrigerated storage and gastrointestinal transit.

A Bifidobacterium infantis strain was microencapsulated within a film-forming protein-carbohydrate-oil emulsion. This novel encapsulant incorporated prebiotics and substantially protected the bacterium during nonrefrigerated storage and gastrointestinal transit. The dried microcapsules were small (15 to 20 microm), had low water activity (0.2 to 0.3), and rapidly released the bacteria in simulated intestinal fluid.