Adrien Servent

Changes in antioxidant activity during the ripening of jujube (Ziziphus mauritiana Lamk)

Phenolic compounds from jujube fruits and related antioxidant activities were investigated during the ripening stages. Three different antioxidant assays, including ORAC, FRAP and DPPH, were monitored on crude jujube extract (CJE). Jujube fruits were additionally fractionated into three selective fractions F1, F2, and F3. However, only the FRAP assay gave the relative antioxidant activity for the three fractions. Furthermore, HPLC-ESI-MSMS (Q-Tof) and GC-MS were used to identify the compounds in each purified fraction. Using FRAP, F1 mainly composed of lipids, exhibited the lowest antioxidant activity (≈0.080±0.015mmol trolox/100g, p<0.05). F2, rich in flavanols and flavonols, displayed 50-fold higher activity (4.27±0.11mmol trolox/100g). Remarkably, F3 with an elevated content of condensed tannins (polymeric proanthodelphinidins), exhibited the highest antioxidant activity (25.4±0.35mmol trolox/100g). The presented results showed that the phenolic profiles of the fruits were influenced by their developmental stage. Furthermore, during ripening, the antioxidant activity may be more impacted by the flavanols and condensed tannins. The purified condensed tannins of jujube fruits may be used as natural antioxidant extracts.

Culinary practices mimicking a polysaccharide-rich recipe enhance the bioaccessibility of fat-soluble micronutrients

This study was carried out to assess the impact of heat processing of a complex emulsion on the behavior of fat soluble micronutrients (FSM) in a traditional Tunisian dish. A simplified recipe involved, dried mucilage-rich jute leaves, tomato paste and olive oil, followed by a cooking treatment (150min). Hydrothermal pattern and viscosity were monitored along with the changes of FSM content and the bioaccessibility (called micellarization, using an in vitro digestion model). Partitioning of carotenoids differed according to their lipophilicity: lycopene, β-carotene and lutein diffused to the oil phase (100%, 70% and 10% respectively). In contrast with the poor carotenes/tocopherol bioaccessibility (0.9-1%), the highest micellarization was observed for lutein (57%) and it increased with heating time and viscosity change. Domestic culinary cooking practices probably increase the bioavailability of carotenes mainly by their diffusion to the oil phase, facilitating their in vivo transfer into micelles.

Effects of Blanching on Flavanones and Microstructure of Citrus aurantium Peels

Water and steam blanching were investigated as pretreatments of bitter orange peels in order to modulate their bitterness before further formulation processing such as osmotic treatment and drying. The fruit pieces were water blanched at 95xa0°C for 10xa0min and at 85xa0°C for 60xa0min and steam blanched at atmospheric pressure during 5xa0min. The kinetics of water inflow and bitter flavanone losses were established from the variation of moisture and bitter compound contents during the blanching process. The whiteness and the citrus color indexes were adopted to evaluate respectively the color of the flavedo and the albedo. Thin sections of fresh and treated peels were resin embedded for light microscopy evaluation and optical porosity determination. Results revealed that water blanching could partially debitter the peels by removing about 38 and 48xa0% of bitter flavanones (naringin, neohesperidin, neoeriocitrin) respectively at 95 and 85xa0°C. The citrus color index and the whiteness index decreased during the process denoting a flavedo discoloring and an albedo darkening. By contrast, the steam blanching showed good retention of bitter compounds. The color of the flavedo was unaffected by steaming while the whiteness index decreased. At microscopic level, the water-blanched peels exhibited an extreme swelling of the cell walls and slight disintegration of the tissue. Contrariwise, the steam blanching maintained the structure of the peels and brought about the shrinkage of the albedo tissue and the decrease of porosity.

Processed Z. Mauritiana Lamk in the Formula of High Nutritional Value Cake

The nutritional value of jujube fruits Ziziphus mauritiana Lamk was processed through an optimized traditional cake procedure. The characteristics of jujube fruit polysaccharides from an accession known as P3 were determined for each of the 5 ripening stages. Therefore, the content of the Alcohol Insoluble Materials, Water Soluble Polysaccharide and Galacturonic Acid was determined at each ripening stage. The degree of methylation (DM) of jujube pectins was less than 50% therefore was classified as low methoxylated pectin (LM). Using the 3rd and the 5th ripening stage, the impact of the drying and cooking was evaluated on selected nutritional characteristics, including vitamin C, total phenolics content and antioxidant capacity. Remarkably, using the fruits from the 3rd stage, the drying process decreased the vitamin C content (74.5%, p<0.05) whereas an increase of 20% (p<0.05) was observed for the cake. Interestingly, the antioxidant activity was unchanged during the drying process. In contrast, after the cooking process the phenolics content and the antioxidant capacity had both increased, by 64% and 30% (p<0.05) respectively. Overall, our results indicated that stage 3 fruits would exhibit higher nutritional qualities than stage 5 fruits. We strongly recommend stage 3 fruits of accession P3 for food applications, including jujube cake processing.

Bioaccessibility of Biofortified Sweet Potato Carotenoids in Baby Food: Impact of Manufacturing Process

Orange-fleshed sweet potato (OFSP), a biofortified crop rich in β-carotene, can be used as a component of baby food recipes in order to tackle vitamin A deficiency in children <6 years old. In this work, the impact of formulation (addition of pumpkin, oil, and egg yolk) and industrial heat processing (pasteurization, sterilization) on carotenoid content and bioaccessibility was evaluated in an OFSP-based baby puree. A commercial OFSP baby food product from Brazil and a homemade OFSP puree were used as references. The losses of all-trans-β-carotene ranged from 16 to 21% (pasteurization, homemade) to 32% (sterilization). Because of higher particle sizes and despite a higher content in carotenoids, the homemade puree had a lower bioaccessibility (i.e., micellar transfer using in vitro digestion: 0.50%) compared with the sterilized and commercial purees (5.3–6.2%). Taking into account bioaccessibility and applying a 50% conversion to retinol, a 115 g baby portion of the sterilized OFSP-puree formulated with 2% oil provided 31.4% of the daily vitamin A requirement (RDA) for children under 6 years. In comparison, 115 g of homemade OFSP-puree provided only 3.5% of the RDA. Addition of pumpkin to OFSP did not improve the percentage of RDA. Interestingly, the incorporation of an emulsifier (egg yolk powder) before cooking could improve the percentage of provision by a factor of 2.7. These results showed that reaching a balance between formulation and processing is determinant to maximize carotenoid bioaccessibility of carotenoids from OFSP-based baby food.

Effects of Osmotic Treatments on Modulating Bitter Flavanones Glycosides Contents and Microstructure of Citrus aurantium Peels

This study investigated the use of wet and dry osmotic dehydration for modulating the bitter taste of Citrus aurantium peels, imparted by the predominance of flavanones glycosides in their albedo; namely naringin, neohesperidin, and neoeriocitrin. For this purpose, the peels were subjected to dehydration-impregnation by soaking (DIS) in 40°Brix sucrose solution at 25xa0°C and in 60°Brix sucrose solutions at 25 and 50xa0°C and to dry osmotic dehydration (DOD) at 25xa0°C for 6xa0h. The peels had not shown the immediate dewatering phenomena in the DIS process but rather an imbibition of sucrose solution, reflected in water and sugar gains. Such a tendency has shown to be ascribed to the porous structure of the albedo which fostered the capillary inflow of external liquid. The imbibition was observed during 6xa0h of treatment in low concentrated sucrose solution whereas in high concentrated ones, it was followed by the dewatering phenomenon thereby inducing an increase of pore volume together with a decrease of cells size. Conversely, in the DOD process, the expected cross transfers of water and sugar were markedly observed. The water was removed from both albedo and flavedo. Indeed, the essential oil cavities exhibited elongation of their shape in line with shrinkage of the peel. The two techniques allowed loss of bitter compounds and gain of sucrose. Nonetheless, The DIS gave rise to higher gain of sucrose and losses of flavanones glycosides than DOD.