Rheological and thermophysical properties of starch model suspensions with addition of sugar or whey protein concentration

Škrob ima široku primjenu u prehrambenoj industriji: u proizvodnji preljeva, juha i umaka, pri konzerviranju, u proizvodnji slastica, mliječnih proizvoda itd. Svrha ovog rada bila je ispitati utjecaj dodataka saharoze, fruktoze, laktoze, glukoze i WPC-a u koncentraciji od 5% i 10% s obzirom na suhu tvar, na termofizička i reološka svojstva modelnih sustava krumpirovog, tapiokinog i pšeničnog škroba u koncentraciji od 10% (s obzirom na suhu tvar). Primjenom rotacijskog viskozimetra (Rheometric Scientific RM-180) izmjerena je viskoznost modelnih suspenzija krumpirovog, tapiokinog i pšeničnog škroba pri 20°C, sa ili bez dodataka saharoze, fruktoze, laktoze i glukoze, te koncentrata proteina sirutke (WPC-a). Diferencijalnom termičkom analizom (DTA) određivana je temperatura početka i završetka smrzavanja modelnih sustava krumpirovog, tapiokinog i pšeničnog škroba sa ili bez dodataka saharoze, fruktoze, laktoze i glukoze, te koncentrata proteina sirutke (WPC-a), te temperatura početka i završetka odmrzavanja modelnih sustava. Svi uzorci pokazali su i zadržali svojstva nenewtonske tekućine, dilatantnog tipa (n>1). Utvrđene su veće promjene prividnog viskoziteta i koeficijenta konzistencije (k) kod dodatka šećera i WPC u udjelu od 10%, a manje kod dodataka od 5%. Došlo je do pomaka u temperaturi smrzavanja modelnih sustava škrobova sa dodacima šećera i WPC-a ka nižim vrijednostima temperature u odnosu na modelne suspenzije škroba bez dodataka. Do pomaka u početnim temperaturama odmrzavanja došlo je kod modelnih sustava škrobova sa različitim dodacima u odnosu na modelni sustav bez dodataka.Starch is widely used in food industry: the production of dressings, soups and sauces, in preservation, in the manufacture of confectionery, dairy products etc. The purpose of this study was to examine the effect of supplements of sucrose, fructose, lactose, glucose and WPC in concentration of 5% or 10% (considering per dry matter), on thermophysical and rheological properties of model system of potato, tapioca and wheat starch in a concentration of 10 % (considering per dry matter). Using a rotational viscosimeter (Rheometric Scientific RM-180) the viscosity of model suspensions of potato, tapioca and wheat starch with or without added sucrose, fructose, lactose, glucose or whey protein concentrate (WPC's) at 20 °C was measured. With differential thermal analysis (DTA) the temperature of beginning and end of freezing of potato, tapioca and wheat starch model with or without added sucrose, fructose, lactose, glucose or whey protein concentrate (WPC's) was measured. Also, the temperature of melting of model systems was measured. All samples showed and retained properties of non-Newton fluid characteristics, dilatant type (n> 1). Major changes were observed at apparent viscosity and consistency coefficient (k) at 10% concentration of sugar or WPC-s and less in 5% concentration of additions. There has been a shift in freezing temperature in starch models with additives of sugar and WPC to lower temperature values, compared to the model of starch suspensions without additives. A shift in the initial temperatures values has occurred in starch model systems with various additions as compared to the model system without additives