New Researches in Biotechnology - Facultatea de Biotehnologii ...

Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011Gel samples were prepared using concentrations of inulin powder (23.5–25 g), agar-agar(1.0–2.5 g) sucrose (28 g) and water (145 g).Agar-agar was swollen in cold water, and then the mixture was heated until agar-agar wasdissolved in water. Agar-agar/water solution was boiled for 5 minutes at a temperature of100 °C, and then sucrose and citric acid added to the solution. Solution was cooled down to85 °C and inulin powder was added, mixture stirred and kept for 5 minutes at thetemperature 85 °C.Subsequently, the obtained agar–agar/water with inulin powder, sugar and citric acid washot–filled in polystyrene containers (150 ml), which were covered with lids and cooleddown to 18 °C. To compare results of experimental gels the control samples were preparedusing only agar-agar or inulin powder. The analyses of the structure were carried out on thenext day after all kinds of gel samples were prepared.Gel strength (hardness)The gel strength (hardness) was characterised by cutting force. The texture was determinedby using the Texture Analyser Model TA.XT Plus (Stable Micro Systems, UK) equippedwith a load cell of 50 kg. The gel samples were positioned on a platform and cut using wirecutter (A/BC). The testing conditions were cross-head movement at a constant speed of1 mm s -1 , a trigger point of 0.09 N, distance 13 mm. The average values of tenmeasurements are reported.Preparing of microscopic samples of inulin and agar-agar powder suspended in water, andexperimental gels (Table 1)Structure of agar-agar and inulin powder dissolved in water, control gel samples with agaragar,inulin as well as gel samples with both polysaccaharides were analysed under thetriocular microscope Axioskop 40 (epifluorescence, excitation 450–490 nm, emission>500 nm). Pictures were taken by digital compact camera Canon PowerShot A620 via16 × 10 or 16 × 40 magnification of the microscope.The samples of experimental gels were cut in a 5 µm layer by device Microm HM315.Preparations were placed on a glass slide.Table 1. Recipes of the samples for analysis of microstructure and texture (g)Ingredients Samples1 2 3 4 5 6Agar 2 - 2.5 2 1.5 1Inulin - 24 23.5 24 24.5 25Water 145 145 145 145 145 145Sugar - - 28 28 28 28Citric acid - - 1 1 1 1Total 147 169 200 200 200 200Microsoft Excel software was used for the research purpose to calculate mean values andstandard deviations of the experimental data obtained in the research.72