Quantitation of 2‐acetyl‐1‐pyrroline in aseptic‐packaged cooked fragrant rice by HS ‐ SPME / GC ‐ MS

Aseptic‐packaged cooked rice ( APCR ) is a rice‐based food product with a rapidly increasing market size, and APCR made of fragrant rice ( FR ) has recently appeared on the market. The fragrance of FR is produced by a combination of odoriferous compounds, among which 2‐acetyl‐1‐pyrroline (2 AP ) has been identified as the most important contributor to overall aroma. This study describes the development of a method to quantify 2 AP in FR ‐based APCR using headspace solid‐phase microextraction ( SPME ) coupled with gas chromatography–mass spectrometry ( GC ‐ MS ). The recovery of 2 AP spiked into APCR was lower than 10%, which suggests significant matrix effects and inappropriateness of external standard‐based calibration. For standard addition calibration method, up to 1,000 ng of 2 AP were spiked into APCR containing 0% to 100% FR . Subsequent regression analyses of recovered peak area ( Y ) as a function of the amount of 2 AP spiked ( X ) yielded highly linear calibration curves ( R 2  > 0.9917) with consistent slopes ( RSD  = 2.7%), regardless of FR composition. Y ‐intercepts, however, which represent the amount of 2 AP in APCR without spiking, increased linearly ( R 2  = 0.9898) in proportion to the composition of FR in the APCR . The amount of 2 AP in APCR , determined by extrapolating the standard addition calibration curves, also increased linearly ( R 2  = 0.9963) as a function of FR composition. Practicality of developed method was tested by monitoring 2 AP contents in APCR under realistic storage conditions, which successfully demonstrated 38% and 60% 2 AP reductions in APCR of 20% FR after 1 and 2 months of storage at 25°C, respectively. The present study demonstrates that a standard addition method, whereby up to 1,000 ng of 2 AP standard is spiked into 4 g of APCR containing 5%–100% FR in a 20‐mL headspace vial followed by SPME / GC ‐ MS , may serve as an effective means of quantitating 2 AP in fragrant rice‐based APCR .