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A9-P: THERMAL ANALYSIS OF WHEY PROTEIN’S CREAMS

S. Ostojić, M. Kićanović, S. Zlatanović, M. Pavlović, D. Aranđelović and B. Simonović

Institute of General and Physical Chemistry, Studenski trg 12/V P.O. Box 551 11000 Belgrade, Serbia

 

Whey proteins are well known for their high nutritional value and versatile functional properties in food products. Estimates of the worldwide production of whey indicate that about 700,000 tones of true whey proteins are available as valuable food ingredients [1].

This work focused on influence of xylitol on thermal properties of prepared whey creams and influence of xylitol, as a humectant [2, 3], on water activity (aw) of whey creams. Water activity (aw) of prepared creams was determined by thermoanalytical techniques [4].

Eight oil-in-water emulsion formulations (creams), made of whey protein isolates (Davis co) with different xilitol concentrations (2%, 4% and 8%) and/without ascorbic acid (500mg/kg) added, were analyzed by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC scans were performed in temperature range from 233K to 523K, with heating rate of 5 K/min in inert atmosphere (N2). Thermo gravimetric analysis of whey creams was conducted in temperature range from 298K to 973K, with heating rate of 10 K/min in inert atmosphere. Obtained DSC curves of prepared whey creams indicate influence of different concentrations of xylitol added, on thermal stability of creams, according to peak temperature maximum (Tm), enthalpies of transitions (ΔH) and shapes of thermal transitions. TGA curves reflected influence of xylitol added, on weight loss during heating up to 973K. All of whey creams lost 99% of total mass on 823K. Water activity (aw) is an important factor affecting stability of food over storage, microbial stability and properties of food during manufacture [3, 4].

Water activity (aw) of prepared creams was determined by thermo analytical techniques: thermogravimetry (TGA) was used to determine water content (moisture) and differential scanning calorimetry (DSC) was used for determination of freezing point depression [4]. Obtained results for water activity (aw) varied in the range of 0.830-0.912 which is in agreement to xylitol concentration in sample.

References

1. J.N. de Wit, J. Dairy Sci., 1998, 81, 3, 597-608.
2. C. Severini, M. Rosaria, A. Derossi, A. Bevilacqua, R. Guiliani, Int. J. Food Sci. Technol., 2008, 43, 1041-1046.
3. M.F. Gliemmo , Carmen A. Campos, Lia N., Gerschenson, J. Food Eng., 2006, 77, 761–770.
4. V.M. da Silva,, L.A.Silva, J.B.de Andrde, Quim. Nova., 2008, 31, 4, 901-905.