Foods: Walnuts

Although nuts have been a staple food in many countries for generations, their status in the United States as a chief food crop is relatively recent. The main suppher of Knglish walnuts, filberts, and almonds had been Europe. However, pecans and black walnuts are indigenous to North America, and the United States is the principal producer of pecans. Other U.S. nuts, such as beech, butternut, white walnut, American chestnut, chinquapins, hickory, picon, and northern California black walnut, are utilized mainly for local consumption. Chestnuts and chinquapins are susceptible to the chestnut blight fungus, Endothiaparasitica which has virtually destroyed the American chestnut (152). 

A sensitive qualitative detection method for walnut using PCR was also developed (Yano et ah, 2007). For detection of walnuts with high specificity, the primer pair was designed based on walnut matK genes. Trace amounts of walnuts in commercial food products can be qualitatively detected using this method. 

Doi, H., Shibata, H., Shoji, M., Sakai, S., and Akiyama, H. (2008). A reliable enzyme linked immuno-sorbent assay for the determination of walnut proteins in processed foods. /. Agric. Food Chem. 56, 7625-7630. 

Sakai, S., Adachi, R., Akiyama, H., Teshima, R., Doi, H., and Shibata, H. (2010a). Determination of walnut protein in processed foods by enzyme-linked immunosorbent assay interlaboratory study. /. AOAC Int. 93,1255-1261. 

Yano, T., Sakai, Y., Uchida, K., Nakao, Y., Ishihata, K., Nakano, S., Yamada, T., Sakai, S., Urisu, A., Akiyama, H., and Maitani, T. (2007). Detection of walnut residues in processed foods by polymerase chain reaction. Biosci. Biotechnol. Biochem. 71, 1793-1796. 

This method is relatively easy to use for anhydrous systems, but not for emulsions, foods, or biological media where the presence of water is detrimental. The method has been applied for determining antioxidant activity of both individual natural polyphenols and vegetable extracts. Methods based on this one have been used to evaluate the peroxide value in walnuts (Wilson-Kakashita and others 1995), mango seeds (Joseph 1995), almonds (Uthman and others 1998), and coconut cream powder (Yusof and others 2007). 

Almeida IF, Fernandes E, Lima JLFC, Costa PC and Bahia, MF. 2008. Walnut (Juglans regia) leaf extracts are strong scavengers of pro-oxidant reactive species. Food Chem 106(3) 1014-1020. 

While the declaration should be for the food as sold, data can be given for the food after preparation if instructions for preparation are given. A nutritional analysis of unshelled walnuts has a limited value for example. 

A Waldorf salad uses a simple method to prevent fruit from browning. This type of salad usually consists of diced apples, celery, and walnuts, covered with a mayonnaise dressing. The dressing keeps the air away from the food ingredients. Without air, the fruit does not turn brown. 

A direct effect of vasoactive amines on the organism which are not degraded in GI tracts due to the lack of mono- and diaminooxidase (MAO and DAO) or their blockade by medicines or alcohol. This group of amines includes tyramine (in Cheddar, emmental, roquefort cheeses, pickled fish, and walnuts), phenylethylamine (in chocolate), serotonin (in bananas), octopamine (in lemons), and histamine (in fermented foods, e.g., blue cheeses, but also in strawberries, tomatoes, wines, and in mackerel that have not been stored properly [scombrotoxin illness]). 

Teuber, S.S. and W. R. Peterson. Systemic allergic reaction to coconut (Cocos nucifera) in 2 subjects with hypersensitivity to tree nut and demonstration of cross-reactivity to legu-min-like seed storage proteins new coconut and walnut food allergens. J Allergy Clin Immunol 1999 103(6) 1180-1185. 

Cerda, B., Tomas-Barberan, F. A., and Espin, J. C. (2005) Metabolism of antioxidant and chemo-preventive ellagitannins from strawberries, raspberries, walnuts, and oak-aged wine in humans Identification of biomarkers and individual variability, J. Agric. Food Chem. 53 227-235. 

Method. The sample is spotted on to a TLC plate (silica gel) followed by 2 d of a solution of TFA (50% in chloroform, prepared fresh each day). The reaction is allowed to proceed for 5 min, after which time the plate is dried with a stream of nitrogen or air. The plate is then developed with chloroform—acetone (in various ratios such as 9 1 or 4 1), benzene-ethanol-water (43 35 19) or ethyl acetate-methanol-water (96 3 1). The plate is removed from the tank and dried in the dark. The spots are observed visually under UV light at long wavelength. The derivative of aflatoxin Bt appears blue, while the derivative of aflatoxin Gi is green. This confirmation technique has been applied to peanuts, brazil nuts, pistachio nuts, walnuts, barley, corn and other foods. 

McDonald s introduced a fruit and walnut salad in 2005 in an effort to offer healthier items on their menu. Researchers believe that fast food restaurants, such as McDonald s and Burger King, play a major role in Americans weight gain. 

Robotham, J.M., Teuber, S.S., Sathe, S.K., and Roux, K.H. 2002. Linear IgE epitope mapping of the English walnut (Juglans regia) major food allergen, Jug r 1. J Allergy Clin Immunol 109( 1) 143—149. 

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