Changes in the Frying Medium During Deep‐frying of Food Rich in Proteins and Carbohydrates

Abstract

Changes in the f j i n g medium (rapeseed oil) during controlled deep-frying of slicedpotatoes and codfillets and oil heated without them were compared. Fifteen f j i n g cycles were conducted each day for five days. Results showed that oil after f j i n g of cod fillets contained 10% less triacylglycerol (TAG) polymers and 40% less TAG dimers than other oils. Other parameters (iodine and anisidine values and absolption value at 233nm) showed that less thennooxidative products formed duringfjling of food rich in proteins. Oil after f j i n g of cod fillets was darker and its acid value was significantly higher than that for other oils. Content of TAG polymers and dimers for oil afterfjling of slicedpotatoes and oil heated without food was equal. The relative loss of C18:2 acid and decrease in iodine value showed that oil after heating without food underwent more intensive thermooxidative transformation than other oils.

Effects of convective and microwave roasting on the physicochemical properties of cocoa beans and cocoa butter extracted from this material

“…Changes in the absorption of 1% solutions of analyzed samples of fat (E 1% 1cm ) at λ5233 and 270 nm determine the content of secondary oxidation products in fats, especially those containing aldehydes and ketones (Tynek et al, 2001). Data contained in Table 5 indicate relatively small changes, which confirm previous conclusions on changes in fatty acids in the tested samples subjected to heating.…”

“…It may also be the antioxidant effects of products formed during the heating of biological material, e.g. as a result of the Maillard reaction (Tynek et al, 2001) For other variants of roasting the Pv was found to be in the range of 2,0-2,3 mmol O 2 /kg fat. The relatively low value of Pv (Pv 5 2.0 mmol O 2 /kg fat) for cocoa butter extracted from microwave roasted beans can be caused by a different method of heating the bean, short process time (t 5 12.5 min), and similarly as in roasting at T 5 140°C, the presence of antioxidant substances in the cocoa butter.…”

“…Measurements were taken on a Genesis Milton Roy Uv-vIS apparatus. The determination was based on the work of Tynek and Drozdowski (Tynek et al, 2001). Color change was measured by determining the absorption of a 10% (E 10% 1cm ) sample solution in hexane, in visible light.…”

“…Measurements were taken on a Genesis Milton Roy Uv-vIS apparatus. The determination was based on the work of Mancini-Fiho et al (Tynek et al, 2001). …”

“…, RH50,4%, t535 min (3) -cocoa butter extracted from convectively roasted bean kernel T5135°C, v51,0m s 21 , RH55,0%, t560 min (4) -cocoa butter extracted from convectively roasted bean kernel T5140°C, v50,5m s 21 , RH50,35%, t510 min 1 T5140°C, v51,0m s 21 , RH50,35%, t520 min (5) -cocoa butter extracted from microwave roasted bean kernel M5700 W, t512,5 min layer that prevents the penetration of oxygen (Mujumdar, 1995, Tynek et al, 2001. Also Albi and coworkers (Albi et al, 1997) in their studies on vegetable oils heated by convection and microwave methods obtained an increase in (E 1% 1cm ) value at λ 5 233 and 270 nm.…”