Frying flavor from

Frying of food is an old and traditional means to prepare food quickly and enjoy the preparation for culinary delight. Fried foods are tasty because of the fried food flavor and the pleasant mouth feel produced by the oil absorbed in the fried food. This increases the salivation process that helps release of oil the soluble flavors from the fried food, making it very appealing to the taster. Fried food is popular in North and South America, Mexico, Europe, India, China, Japan, Malaysia, and elsewhere. 

The term processed flavor is used in different contexts to describe (a) products where the natural raw materials lack a characteristic flavor profile and the desired aromatic profile is achieved only by deliberate processing (e.g., coffee) (b) flavorings created as a result of Maillard and other related reactions between amino acids and sugars (e.g., meat-like flavors) (c) flavorings resulting from controlled enzymatic reactions (e.g., enzyme-modified dairy products) (d) products made by fermentation (e.g., wines, vinegar) and (e) products of thermal reactions of lipids (e.g. French fry flavor). 

This complex unit operation involves significant microstructural changes in fact, most of the desirable characteristics of fried foods are derived from the formation of a composite structure a dry, porous, crispy and oily outer layer or crust, and a moist cooked interior or core, whose microstructures form during the process (Bouchon et al., 2001). The high temperatures (around 160 and 180°C) cause water evaporation, which is transferred from the food towards the surrounding oil, whereas oil is absorbed by the food replacing part of the released water. This process results in products with a unique flavor-texture combination (Mellema, 2003). 

Many nitrogen- and sulfur-containing heterocycles have been identified in the aroma fractions of foods [214]. In roasted products (e.g., coffee) and heat-treated foods (e.g., baked bread or fried meat), these heterocycles are formed from reducing sugars and simple or sulfur-containing amino acids by means of Maillard reactions [215, 216]. Their odor threshold values are often extremely low and even minute amounts may significantly contribute to the aroma quality of many products [217, 218]. Therefore, N- and N,S-heterocyclic fragrance and flavor substances are produced in far smaller quantities than most of the products previously described. 

Heat-generated flavors, due to the formation of lactones and methyl ketones from hydroxy and keto add precursors, which occur in trace quantities in milk lai. These flavors arc considered to be desirable in fried and baked goods and are partly responsible for the unique condiment properties of butler in food preparation. However, they are undesirable in dried whole milk and evaporated milk where the objective is to make a bland product as much like fresh milk as possible. 

Interest in the influence of lipids on pyrazine formation has recently been generated by the identification of long-chain alkyl-substituted heterocyclic compounds in foods and in model systems. Pyrazines in this category include 2-heptylpyrazine isolated from french fried potato flavor (7), and 2-methyl-3(or 6)-pentylpyrazine and 2,5-dimethyl-3-pentylpyrazine, isolated from extruded zein/corn amylopectin/corn oil systems (8, 9). Only the involvement of lipids or lipid-decomposition products in the formation of these compounds could account for the long-chain alkyl substitution on the pyrazine ring. 

Sample b c roasted (bread, coffee, peanut, walnut, malt), burnt, popcorn, slightly rancid, heated cooking oil Sample ds heated cooking oil, deep-frying fat, solvent, old paint Since the panel found no difference between samples b and c in the triangle test, it was not possible to ask for two distinct "profiles" in the descriptive test. However, it was evident that samples b and c were the most attractive oils from a flavor point of view. There were similarities with sesame oil and Swedish crispbread. 

Frying temperature was found to be the crlterial parameter that determined the flavor quality in Chinese pork bundle. Cooked meat aroma increased as the heating temperature varied from 134°C to 172°C., as shown in Figure 3. Below 130°C neither cooked meat aroma nor brown color developed. Slightly higher temperatures have been reported for the optimum flavor formation in fried potato chips at 180°C (2), and roasted beans at 200°C (3). 

Pyridine and its derivatives. The most unique pyridine derivative isolated from processed food is l,lt,5,6-tetrahydro-2-ace-topyridine. This compound was prepared by roasting proline and dihydroxyacetone at 92°C in presence of sodium bisulfate, and exhibited a strong odor reminiscent of freshly backed soda crackers (82). 2-Ethylpyridine and 2-pentylpyridine were reported in volatile flavor components of shallow fried (83). Pyridine, 2-methylpyridine, 3-methylpyridine, 2-ethylpyridine, 3-ethylpyri-dine, 5-ethyl-2-methylpyridine, 2-butylpyridine, 2-acetylpyridine, 2-pentylpyridine, 2-hexylpyridine, 3-pentylpyridine, 5-methyl-2-pentylpyridine, and 5-ethyl-2-pentylpyridine were identified in the volatiles of roasted lamb fat (8H). 2,5-Dimethylpyridine and... 

Several of the alkylthlazoles identified in french fried potato flavor, such as 2,4-dlmethyl-5-propylthiazole, 2,4-dimethyl-5-pentyl-thlazole, 2-butyl-4-methyl-5-ethylthiazole and 2-butyl-4-propylthia-zole have a strong characteristic sweet, sulfury and green aroma (33). This aroma characteristic is quite distinctive and is present in a large number of the fractions generated from the gas chromatographic fractionation of the french fried potato flavor isolate. It is probably an important part of the total french fried potato flavor. 

In most parts of the world, both cooking and salad oils from soybeans are refined to have bland taste and light color. For other oils, distinct flavors and dark colors may be acceptable. Important distinctions between salad oils, cooking oils, and frying... 

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