French-fried potatoes, volatiles

A sample of french fried potatoes weighing 100.0 g was extracted with the volatile organic solvent hexane. After separation and evaporation of the hexane, 6.25 g of cooking oil was recovered. What was the percent oil in the potatoes Show your calculations. 

The occurrence of pyridines in food has been reviewed (16). 2-Alky1-pyridines were proposed to form from the corresponding unsaturated n-aldehydes with ammonia upon heat treatment (17, 18). Table I lists pyridines Identified in the volatiles of fried chicken (19) and french fried potatoes (7). 

The oxidation products of lipids include volatile aldehydes and acids. Therefore, lipids are one of the major sources of flavors in foods. For example, much of the desirable flavors of vegetables such as tomatoes, cucumbers, mushrooms, and peas (Ho and Chen, 1994) fresh fish (Hsieh and Kinsella, 1989), fish oil (Hu and Pan, 2000) and cooked shrimp (Kuo and Pan, 1991 Kuo et al., 1994), as well as many deep-fat fried foods such as French-fried potatoes (Salinas et al., 1994) and fried chicken (Shi and Ho, 1994), are contributed by lipid oxidation. LOX-catalyzed lipid oxidation produces secondary derivatives, e.g., tetradecatrienone, which is a key compound of shrimp (Kuo and Pan, 1991). The major difference between the flavors of chicken broth and beef broth is the abundance of 2,4-decadienal and y-dodeca-lactone in chicken broth (Shi and Ho, 1994). Both compounds are well-known lipid oxidation products. A total of 193 compounds has been reported in the flavor of chicken. Forty-one of them are lipid-derived aldehydes. 

Carlin J.T., Lin Q.Z., Huang T.C., Ho C.T. and Chang S.S. (1986) Identification of alkyloxazoles in the volatile compounds from French-fried potatoes. J. Agric. Food Chem. 34, 621-3. 

Potato flavor is greatly influenced by methods of cooking or preparation. Raw potato contains the characteristic earthy aroma component, 2-ixo-propyl-3-methoxypyrazine. A character impact compound common to boiled and baked potatoes is methional (3-[methylthio]propanal). Baked potatoes contain Maillard products such as 2-ethyl-3-methylpyrazine (earthy, nutty) and 2-ethyl-6-vinylpyr-azine (buttery, baked potato) (34). In potato chips and French-fried potatoes, the potato flavor character of methional is modified by volatile aromatics from frying oils, such as ( , )-2,4-decadienal, and thermally generated alkyl oxazoles possessing lactone-like flavors (34,39). The pyrazines 2-ethyl-3,5-dimethyl and 2,3-diethyl-5-methylpyrazine are described as potato chip like (40). 

During storage of food products, volatile compounds produced by lipid oxidation cause rancidity, especially if the lipids contain linolenic acid. Dark flours become easily rancid on storage. Crackers and other durable bakery products should be stored in an inert gas atmosphere or be protected by antioxidants. Roasted products, such as peanuts, may change their agreeable flavor if stored in air therefore, they are stored either in nitrogen or under reduced pressure. Fried products are most sensitive to oxidative rancidification, especially Med products with weak flavor, such as fried bread, French fries, or potato chips. Dry and deep-frozen products are generally rather sensitive to oxidation because of easier access of air into the inner layers of the food product. 

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