In vitro bioaccessibility of beta-carotene from heat-processed orange-fleshed sweet potato.

Orange-fleshed sweet potato (OFSP) is currently promoted in parts of sub-Saharan Africa as a biofortified staple food with large potential to provide considerable amounts of provitamin A carotenoids. However, the bioaccessibility of provitamin A carotenoids from OFSP has not been widely investigated, especially not as an effect of different preparation methods. In this study, we used an in vitro digestion model to assess the bioaccessibility of beta-carotene from differently heat-processed OFSP. The fraction of carotenoids transferred from the food matrix to a micellar phase obtained after microfiltration and to a supernatant obtained after low-speed centrifugation was investigated. The percentage of accessible all-trans-beta-carotene in the micellar phase varied between 0.5 and 1.1% in the heat-processed OFSP without fat and between 11 and 22% with the addition of 2.5% (w/w) cooking oil. In comparison with the micellar phase, the percentage of accessible all-trans-beta-carotene in the supernatant phase was significantly higher (P < 0.001), between 24 and 41% without fat and between 28 and 46% with fat. These results support the importance of fat for an improved micellarization of beta-carotene. Overall, the high in vitro bioaccessibility of beta-carotene from heat-processed OFSP indicates that sweet potato might be a promising dietary approach to combat vitamin A deficiency.

Phytate degradation by human gut isolated Bifidobacterium pseudocatenulatum ATCC27919 and its probiotic potential.

The growing awareness of the relationship between diet and health has led to an increasing demand for food products that support health above and beyond providing basic nutrition. Probiotics are live organisms present in foods, which yield health benefits related to their interactions with the gastrointestinal tract. Phytases are a subgroup of phosphatases that catalyse the desphosphorylation of phytate, which reduces its negative impact on mineral bioavailability, and generates lower inositol phosphates. The aims of this investigation were to (i) study the ability of the probiotic candidate Bifidobacterium pseudocatenulatum to degrade phytate in synthetic medium, to (ii) identify the lower inositol phosphates generated, to (iii) study its survival under conditions mimicking gastrointestinal passage and finally to (iv) assess adhesion of the bacteria to Caco-2 cells. The first steps of InsP(6) degradation by B. pseudocatenulatum phytate-degrading enzyme/s were preferentially initiated at the DL-6-position and 5-position of the myo-inositol ring. It suggests that the main InsP(6) degradation pathway by B. pseudocatenulatum by sequential removal of phosphate groups was D/L-Ins(1,2,3,4,5)P(5) or D/L-Ins(1,2,3,4,6)P(5); D/L-Ins(1,2,3,4)P(4); to finally Ins(1,2,3)P(3) and D/L-Ins(1,2,4)P(3)/D/L-Ins(1,3,4)P(3). This human strain also showed a notable tolerance to bile as well as a selective adhesion capacity (adhesion to control surfaces was zero), to human intestinal Caco-2 cells comparable to the commercial probiotic B. lactis. The phytate-degrading activity constitutes a novel metabolic trait which could contribute to the improvement of mineral absorption in the intestine as a nutritional probiotic feature with potential trophic effect in human gut.

Prolonged transit time through the stomach and small intestine improves iron dialyzability and uptake in vitro.

The iron dialyzability and uptake in relation to transit time through the stomach and small intestine was investigated using a dynamic in vitro gastrointestinal model in combination with Caco-2 cells. Three test meals were evaluated, consisting of lactic fermented vegetables with white (I) or whole meal bread (II) and of sourdough-fermented rye bread (III). Three transit times were tested (fast, medium, and slow transport). Iron dialyzability and absorption differed significantly between medium and slow transit time for meal I and between fast and medium transit time for meal III. For meal II, high in phytate, the iron dialyzability and absorption were low irrespective of transit time. The meals could be ranked with respect to iron dialyzability and uptake in the order I > III > II. Although the in vitro models used have limitations compared to in vivo experiments, the results suggest that an increased transit time may improve iron availability.

Pathway of dephosphorylation of myo-inositol hexakisphosphate by phytases of legume seeds.

Using a combination of high-performance ion chromatography analysis and kinetic studies, the pathway of dephosphorylation of myo-inositol hexakisphosphate by the phytases purified from faba bean and lupine seeds, respectively, was established. The data demonstrate that the legume seed phytases under investigation dephosphorylate myo-inositol hexakisphosphate in a stereospecific way. The phytase from faba bean seeds and the phytase LP2 from lupine seeds degrade phytate by sequential removal of phosphate groups via D-Ins(1,2,3,5,6)P(5), D-Ins(1,2,5,6)P(4), D-Ins(1,2,6)P(3), and D-Ins(1,2)P(2) to finally Ins(2)P, whereas the phytases LP11 and LP12 from lupine seeds generate the final degradation product Ins(2)P via D-Ins(1,2,4,5,6)P(5), D-Ins(1,2,5,6)P(4), D-Ins(1,2,6)P(3), and D-Ins(1,2)P(2).