51B-7

A. KRAMER, Nordic Sensor Technologies, One Exchange Place, Suite 1000, Jersey City, NJ 07302, C. C. Grimm, Food Processing and Sensory Technology, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, and E. T. Champagne, Food Processing & Sensory Quality, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd., New Orleans, LA 70124.

Justification: The concept of rice quality varies greatly from country to country and ethnicity. What a producing country deems acceptable may be unacceptable for an importing country. With the continued expansion of world trade there is a need for a rapid instrumental method to assess rice quality.

Objective: To determine the ability of an electronic nose to differentiate between types of rice and changes in the headspace of rice over time.

Method: Rice varieties, including waxy and non-waxy rice, from two different crop years were analyzed. Five grams of milled rice were placed in 20 ml vials and sealed with a screw cap equipped with a Teflon liners. Samples were held at room temperature until analyzed and then raised to 50C during sampling. The headspace was purged from the sample vial using purified air at 60 ml/min. The electronic nose was a Nordic Sensor Technology instrument, model # 3320, equipped with 10 MOSFET type and 12 MOS types sensors. Cycle times of seven minutes were employed and raw data files generated. Rice samples were concurrently analyzed by solid-phase microextraction GC/MS.

Results: Data was analyzed using principle component analysis. Plotting of the primary component against the second resulted in readily discernable groups, with the primary component containing as much as 90% of the variability in the data set. Confidence in the analyses was obtained by comparing multiple vials containing the same sample against a single sample analyzed multiple times. However, multiple analyses on the same vial over an extended time period (days) resulted in non-reproducible data. Both varietal differences and aging differences could be observed, however varietal differences were small relative to aging. The 1997 rice samples did not necessarily overlay the 1998 samples of the same variety. This results in a unique grouping for each rice sample for each year.

Significance: An electronic nose has been used to detect gross differences in the volatile compounds found in the headspace of rice. The current method suggests that the electronic nose may be more suited to monitoring shelf-life relative to varietal differences.