New RVA method for pregelatinized starches

Modifications made to starches need to be monitored and characterized. The RVA can be used to test the properties of pregelatinized starches simply and quickly. 

Pregelatinized starch is a modified starch which easily takes up water and swells at room temperature. It is used in instant desserts, allowing the food to thicken when cold water is added. Other applications include cold prepared foods such as dairy products, beverages, including reduced sugar varieties, confectionery, cold mixes such as fruit and cream fillings, glazes, frostings and icing for bakery products and snacks, instant foods, soups, sauces, dressings and as a binder and texturizer in meat products. There are also industrial and pharmaceutical applications for pregelatinized starches.

Method

Rapid and uneven swelling of pregelatinized starch can cause dispersion problems (clumping) during testing. A cold initial temperature and cold solvent (distilled water) slow the rate of water uptake by the starch. This also differentiates samples.

Superfine (castor) sugar is used as a dispersion aid without significantly affecting the curve shape. The better dispersal is due to even distribution of small water-absorbing sugar granules between sample particles.

 

RVA Profile

Time

Type

Value

00:00:00

Temp.

15°C

00:00:00

Speed

960 rpm

00:00:10

Speed

160 rpm

00:02:00

Temp.

15°C

00:07:43

Temp.

95°C

00:10:00

Temp.

95°C

00:15:00

Temp.

25°C

00:20:00

End

 

Table 1. Idle Temperature: 15±1°C. Time Between Readings: 4 s

 

 

Figure 1. Effect of dispersion aid on RVA pasting curves of pregelatinized starch. Sugar improved the dispersion of the sample, without affecting curve shape. The higher overall viscosity when sugar was added indicates that it was successful in dispersing the sample throughout the water.

Results

The Final Viscosity (cP) is the RVA Pregel Starch Index. The Cold Peak (peak prior to heating) (cP) is the RVA Cold Swelling Index. The Hot Peak (peak after commencement of heating and prior to cooling and holding) (cP) may also be recorded. Cold viscosities increase through a pregelatinization effect, and then eventually decrease through granule rupture and dextrinization.

Conclusion

RVA applications include monitoring consistency of starches between production batches, trouble-shooting product manufacture and quality control of starches used in food manufacture.