COMPARISON OF WET-CHEMICAL METHODS FOR DETERMINATION OF LIPID HYDROPEROXIDES

Five methods for determination of lipid hydroperoxides were evaluated, including two iodometric procedures involving a titration and a spectrophotometric micro method, and three other spectrophotometric methods namely the ferro, International Dairy Federation (IDF) and FOX2 (ferrous oxidation in xylenol orange). Peroxide values determined in a range of food products by these five methods gave different results. The ferro method required large amounts of solvent (50 mL/sample); the FOX2 method had a low range (0.005–0.04 μmol hydroperoxide); the end point detection of the titration method was subjective and required a large amount of sample (1 g); and the micro method was sensitive to interruptions during execution. Therefore, only the modified IDF method was chosen for further testing and validation. Stability tests of the standard curve showed a variation coefficient of 4% and within runs the highest variation was 5.9% (for blank) and a maximum of 9.6% between runs variation for the lowest concentration. Among the antioxidants tested, only ethylenedi-aminetetraacetic acid (EDTA) affected the peroxide determinations.     

Low-temperature Blanch Improves Textural Quality of French-fries

Potatoes, CV. Alpha, were sorted (specific gravity), peeled, cut, and blanched at four temperatures (55—70°C) for several times (0—60 min.) before frying in vegetable oil (200°C, 4 min). Multiple puncture (raw potatoes) and single puncture and Texture Profile Analysis (TPA) of French-fries were used. Limpness angle and oil retention (Carver press) were also evaluated. Firmness and some TPA parameters (chewiness, cohesiveness) were increased (>200%) by blanch. Limpness and oil content were reduced by treatment. Improvement of French-fries texture resulted after blanching for 30—45 min. at 60—65°C.