OPTIMIZATION OF THE NUTRITIONAL, FUNCTIONAL, AND SENSORY PROPERTIES OF RAW AND PROCESSED LEGUMES, GRAINS, AND SPECIALTY CROPS
Location: Processed Foods Research
Title: Shelf-life of infrared dry-roasted almonds
Submitted to: Journal of Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 2012
Publication Date: December 12, 2012
Citation: Yang, J., Pan, Z., Takeoka, G.R., Mackey, B.E., Bingol, G., Brandl, M., Garcin, K., Mchugh, T.H., Wang, H. 2012. Shelf-life of infrared dry-roasted almonds. Journal of Food Chemistry. 138(1):671-678 DOI: 10.1016/j.foodchem.2012.09.142.
Interpretive Summary: Almonds are California’s largest tree nut crop in total dollar value and acreage. In 2010, California almond production was 1.65 billion pounds which had a value of $2.69 billion. Almonds are traditionally processed using hot air (HA) at temperatures ranging from 129.5°C to 154.5°C. In this study we investigated the shelf-life of almonds processed by infrared (IR), sequential infrared and hot air (SIRHA), and hot air (HA). The quality of roasted almonds produced with SIRHA and HA was similar immediately after roasting and after three months of storage. We believe that SIRHA processing is an effective method for producing pasteurized almonds with similar quality as HA. In addition, SIRHA processing has the potential to lower production costs due to reduced roasting time compared with conventional hot air processing.
Infrared heating was recently used to develop a more efficient roasting technology than traditional hot air roasting. Therefore, in this study, we evaluated the shelf-life of almonds roasted with three different approaches, namely infrared [IR], sequential infrared and hot air [SIRHA], and regular hot air [HA]. Nine medium roasted almond samples produced by the aforementioned heating methods were processed at three different temperatures (130°C, 140°C and 150°C), packed in paper bags and then stored at 37°C for three, six or eight months. Shelf-life of the roasted almonds was determined by measuring the changes in color, peroxide value, moisture content, water activity, flavor components and sensory quality. No significant difference was observed in moisture content and water activity among the almond samples processed with different roasting methods and stored under the same conditions. GC/MS analysis showed that aldehydes, alcohols, and pyrazines were the main flavor components of almonds. Aliphatic aldehydes such as hexanal, (E)-2-octenal, and nonanal were produced as off-flavors during storage. Although the overall quality of roasted almonds produced with SIRHA and HA heating was similar during the first three months of storage, their peroxide value and concentration of aliphatic aldehydes differed significantly for different roasting methods and increased significantly in all roasted samples during storage. We postulate that hexanal and nonanal might be better indicators of the shelf life of roasted almonds than the current standard, peroxide value.