1School of Wine and Food Science, Charles Sturt University, Wagga Wagga, NSW 2678, Australia
2School of Science and Technology, Charles Sturt University, Wagga Wagga, NSW 2678, Australia
3ENITIAA Nantes, IT3 GPA, Rue de la, Géraudière, BP 82225 NANTES CEDEX 3, France
4Sunrice, Leeton 2705 Australia
5CRC for Sustainable Rice Production, Yanco, Australia
It is of often necessary to store rice for long periods, particularly in years of drought when rice supply is limited. Rice storage, especially at higher temperature, has been found to cause quality changes even though the total protein and starch content remains almost unchanged (Chrastil, 1990; Sowbhagya & Bhattacharya, 2001). Different rice cultivars appear to change at different rates during storage (Zhou et al, 2002). This paper compares the changes that occur in 12 commercially growth Australian Rice cultivars following nine months storage.
Methods and materials
Brown rice (Oryza sativa L.) samples from twelve cultivars (Amaroo, Doongara, Illabong, Jarrah, Koshikari, Kyeema, Langi, Millin, Opus, Paragon, Quest and Reiziq) were stored in airtight jars at 37°C and 4°C.
Rice grain was removed from the glass containers after the designated storage period and ground immediately using a Cyclone Sample Mill (UDY Corporation, Fort Collins, CO) using a 1mm sieve screen. Rice flour samples were analyzed using a Rapid Viscosity Analysor (RVA) after 1, 3, 6, 9 months of storage. The standard Newport RVA rice method was used to analyse samples in duplicate.
The pasting properties changed following storage at 4°C and 37°C, however, samples stored at 4°C showed relatively minimal change (data not shown) compared to samples stored at 37°C. Generally the changes in all cultivars followed a similar trend (with the exception of Illabong), however, they appeared to change at different rates (Figure 1.). Figure 1 shows there are changes in Peak Viscosity (PV), Breakdown (BD), Final Viscosity (FV) and Setback (SB). Generally, there is a very slight increase in PV, a noticeable increase in FV and SB, and a decrease in BD. The maximum change appeared to occur after 6 months of storage. After 6 months, the change in parameters appeared to slow down or reverse. The cause of this trend is not known.
Figure 1. Peak Viscosity, Final Viscosity, Breakdown and Setback values of 12 rice cultivars following 9 months storage. Amaroo , Doongara, Illabong, Jarrah, Koshihikari, Kyeema, Langi, Millin, Opus, Paragon, Quest, Reiziq
There appears to be a genetic basis to rice ageing as each cultivar changes at a different rate following storage. This suggests that it may be possible to breed rice cultivars which have particular storage characteristics. Further work is needed to understand the non-linear trend of the ageing process and the reason why the trend observed in Illabong samples is different to other cultivars.
The authors wish to thank Sunrice. and CRC for Sustainable Rice Production for providing funding.
Chrastil, J., (1990), Protein- Starch Interactions in Rice Grains. Influence of Storage on Oryzenin and Starch, J. Agric. Food Chem. 38: 1804- 1809.
Bhattacharya, K. R., Sowbhagya, C. M. and Indudhara Swamy, Y. M., (1978), Importance of insoluble amylose as a determinant of rice quality, J. of Sci. of Food and Agric. 29: 359- 364.
Zhou, Z., Robards, K., Helliwell, S. & Blanchard, C., (2002), Ageing of Stored Rice: Changes in Chemical and Physical Attributes, J. of Cereal Sci. 35: 65- 78.