Drying And Browning Of Date Pulp During Hot Air And Microwave Drying

The present work is a part of our scientific project about the valorisation of the common dates grown in southern Algeria. The principal aim was to study the drying ability of the fruit pulp with the view to produce food powders, which can easily take the place of many synthetics ingredients (white sugar, colorant like caramel) in many food preparations. The specific structure of the date pulp was also described: presence of two edible constitutive tissues (outside pigmented and inside white) that can influence the technological proprieties (as drying) of the whole fruit. The pigmented and white part weights were significantly different ( p ≤ 0.05). Results reveal the preponderance of white part, which can favourably influence the heat processing such as drying since the coloured pulp is already pre-browned compared with the white part. Hot air (60°C) and microwave (MW) (350W) drying kinetics of date ( Phoenix dactylifera L.) pulp pieces from Mech-Degla variety were investigated. Colour change (browning) was also analyzed during these drying processes using absorbance measurement at 420nm of the hydro alcoholic extract from pulp pigmented part. The latter has a heterogeneous initial colour in the same fruit. Three shades can be noticed: yellow, beige and brown related to the optic densities (at 420nm) of 0.92, 1.5 and 1.93 respectively. The minimal moisture contents reached by means of MW and hot air drying are about 8 (during 5 min) and 5 % dry basis (during 165 min) respectively. On the other hand, the MW drying could be considered instantaneous but it involves a few scorched spots on pulp pieces what may be due to the non uniformity of the initial date pulp colour or to the inadequacy of the chosen power. In addition, the applied model strongly fit the experimental data for convective air drying (R 2 = 0.995; MRE = 6.71%) compared to MW drying (R 2 = 0.94; MRE = 18.4%

Some physicochemical and morphological characterizations of three varieties of Algerian common dates

The date palm is a typical plant of the arid and semi arid areas. Unfortunately in fact they are not all the varieties that profits from an economic interest except for Deglet-Nour. Thus, it represents a danger to the genetic inheritance and the biodiversity. The three varieties studied in this work are: Mech-Degla, Degla-Beida and Frezza, which are common varieties cultivated in the south of Algeria. They are characterized by a good availability and an interesting aptitude for the conservation. In this work (included in our project consisting in the valorization of the common local dates) were presented only the obtained first results. The morphological characteristics (weight of whole date, pea of pulp (pulpit), weight of the seed, length and width of whole date and the seed, pulp/seed ratio, pulp/date ratio, seed/date ration) are given. The physicochemical parameters studied are: pH, ashes, flavonoid, minerals and antioxidant activity. All three varieties are particularly rich in minerals (K, Ca, Na, Zn, Fe, Cu and Mn), in flavonoïd. Concerning the antioxidant activity, different cultivars is endowed with an extraordinary capacity (61.82, 61.56 and 61.61% respectively for Mech-Degla, Degla-Beida and Frezza). © EuroJournals Publishing, Inc. 200

Drying and browning of date pulp during hot air and microwave drying.

The present work is a part of our scientific project about the valorisation of the common dates grown in southern Algeria. The principal aim was to study the drying ability of the fruit pulp with the view to produce food powders, which can easily take the place of many synthetics ingredients (white sugar, colorant like caramel) in many food preparations. The specific structure of the date pulp was also described: presence of two edible constitutive tissues (outside pigmented and inside white) that caninfluence the technological proprieties (as drying) of the whole fruit. The pigmented and white part weights were significantly different (p ≤ 0.05). Results reveal the preponderance of white part, which can favourably influence the heat processing such as drying since the coloured pulp is already pre-browned compared with the white part. Hot air (60°C) and microwave (MW) (350W) drying kinetics of date (Phoenix dactylifera L.) pulp pieces from Mech-Degla variety were investigated. Colourchange (browning) was also analyzed during these drying processes using absorbance measurement at 420nm of the hydro alcoholic extract from pulp pigmented part. The latter has a heterogeneous initial colour in the same fruit. Three shades can be noticed: yellow, beige and brown related to the optic densities (at 420nm) of 0.92, 1.5 and 1.93 respectively. The minimal moisture contents reached by means of MW and hot airdrying are about 8 (during 5 min) and 5 % dry basis (during 165 min) respectively. On the other hand, the MW drying could be considered instantaneous but it involves a few scorched spots on pulp pieces what may be due to the non uniformity of the initial date pulp colour or to the inadequacy of the chosen power. In addition, the applied model strongly fit the experimental data for convective air drying (R2 = 0.995; MRE =6.71%) compared to MW drying (R2 = 0.94; MRE = 18.4%

Some technologic proprieties of common date (Phoenix dactylifera L.) fruits

Mech-Degla, Degla-Beida and Frezza are the common (or dried) varieties studied in this research. On average, their water and sugar contents are of 15 and 80% dry basis (db), respectively. In this paper we report on their technological abilities. The experimental study consist the following: complementary vacuum (200 mbars) air-drying at 60°C, soaking in citrus juices, double fermentation (alcoholic and acetic) and water-alcohol extract preparation. The three previously quoted varieties show an interesting drying ability since they water content has been reduced to 5-7% (db) without apparent browning, which allows the possibility to produce first fruit powder then tablets. In order to formulate biologic vinegar and to optimize the traditional process as has traditionally applied in Algerian Sahara, the dates have been submitted to the spontaneous double fermentation: alcoholic and acetic. Using oxygenation during 4 h after 14 days of anaerobic fermentation, the acetic acid content reaches a value above 7 g/100 mL (in the Mech-Degla case). The swelling power (more than 50% in relation to the initial fruit`s weight) of Mech-Degla dates immerged in citrus juices as well as the brix degree variation in liquid phase (on average 25%) were also analyzed. Results indicate also the possibility to produce the dates in their auto induced syrup. In addition, the water-alcohol extract obtained reveals an antioxidant activity of about 52