Rapid visco analyser

The pasting property was determined using a Rapid Visco Analyser (RVA) (Newport Scientific, Warriewood, Australia), as described in AACC 44-31A [23 ]. About 2.5 g of the sample was weighed into a dry empty canister and 25 mL of distilled water was dispensed into the container. The solution was thoroughly mixed, and the canister fitted into the RVA, according to the manufacturer’s instructions. The slurry was heated from 50 to 95 °C with a holding time of 2 min, and then, cooled to 50 °C with 2 min holding time. The rates of heating and cooling were maintained constant at 11.25 °C/min. Peak viscosity, trough, breakdown, final viscosity, set back, peak time, and pasting temperature were obtained from the pasting profile with the aid of Thermocline for Windows Software (TCW, v. 2.3, Warriewood, Australia).

The pasting properties were measured according to the method of AOAC (2005) . For determination of pasting properties, a rapid visco analyser (Newport Scientific Pty Ltd, Australia) were used. Approximately 3g of smples were taken and dispersed in aluminum canister containing distilled water. For moisture correction the following equation were applied.
Where M_1, denotes the weight of corrected sample (g); M_2, denotes weight of sample (3 g), W₁, denotes actual moisture content of sample (%); W_2, denotes corrected water volume (mL), and 25 mL is the volume to suspend 3 g of sample. The suspension of flour-water was kept at 50°C for 1 min and heated up to 95°C and kept for 10 min. The parameters of starch viscosity such as Pasting Viscosity (PV), Pasting Temperature (PT), Final Viscosity (FV), Break down (BD) and Set Back (SB) were measured and the results were expressed as Rapid Visco Units (RVU).

Stirring number was determined using a Rapid Visco Analyser (Newport Scientific, Warriewood, NSW, Australia), in accordance with the AACC International Method 22-08.02. A sample of 4 g WWF and 3.5 g WF (dry basis), respectively, was used for the measurements. The flour was added into a canister containing 25 mL distilled water and was gently dispersed by hand using the Rapid Visco Analyser (RVA) paddle. Shortly after, the canister was loaded onto the RVA to initiate the test. The temperature was held at 95 °C. The sample was stirred at 960 rpm for the first 10 s, which was subsequently reduced to 160 rpm for the remaining 170 s of the test. The FN was calculated from the SN values, as defined by its apparent viscosity in rapid visco units (RVU), based on Tordenmalm et al. [14 ].

A Rapid Visco Analyser (Newport Scientific, Warriewood, NSW, Australia) was employed to prepare the white sauce, using a formulation based on that given by Arocas et al. [15 (link)] with minor modifications. The white sauce consisted of skimmed milk (91.25%, w/w), white flour (6% w/w), vegetable oil (2.5% w/w) and table salt (0.25% w/w). The skimmed milk for the white sauce mixture containing xanthan (0.15% w/w) was reduced to 91.1% (w/w). The w/w ratio of all other ingredients used was the same as that without xanthan. The pre-weighed ingredients were transferred to the RVA canister prior to making the white sauce. The canister was loaded onto the RVA and was heated from 50 to 95 °C in 4 min, held at 95 °C for 3 min, cooled to 70 °C in 4 min and maintained at 70 °C for 3 min. The mixture was stirred at 960 rpm for 10 s, and then the speed was reduced and maintained at 200 rpm for the remaining time. The white sauce was maintained at 70 °C using a water bath for 2 min to settle down the white sauce emulsion before performing subsequent analyses. Commercial white sauce powder (Gravox White, Seven Hills, NSW, Australia) was mixed with skimmed milk in proportion (w/w) as per the manufacturer’s instructions to acquire a total of 25 g, and was prepared by the same procedures as detailed above.