Protein quality, antigenicity, and antioxidant activity of soy-based foodstuffs

Commercial soy-based foodstuffs, including beverages ( n = 15), cow's milk supplemented with soy isoflavones ( n = 1), snacks ( n = 1), and biscuits ( n = 2), were analyzed to find any link between alterations in protein quality, safety (antigenicity), functionality (antioxidant activity), and food processing. Protein content was analyzed by the Kjeldhal method and available lysine by OPA assay. Chromatographic (RP-HPLC) and electrophoretic (SDS-PAGE) protein profiles were obtained to monitor modifications in the structure of soy allergens. The antigenicity was estimated by immunoblotting against soy total antibodies. Total phenol content was measured by Folin-Ciocalteu, while peroxyl radical scavenging activity of the sample was determined by ORAC FL assay. Protein content did not differ of those declared by the producers. Lysine availability was higher in liquid soy beverages compared to that in other soy foodstuffs studied here. 7S and 11S soy allergens were detected by RP-HPLC and SDS-PAGE, respectively. Both data indicated changes in soy protein patterns due to processing of instant powdered soymilk, soy snacks, and biscuits. Immunoblotting assay showed modifications in the antigenic response of these foodstuffs based on soy, suggesting that their processing had altered the structure of soy allergens. RP-HPLC, SDS-PAGE, and immunoblotting resulted in adequate analytical approaches for detecting changes in protein structure due to processing and adulteration. Protein quality, antigenicity, and antioxidant activity of soy products can be affected as a function of the intensity of the thermal processing.     

Acidified peel of litchi fruits selects for postharvestPenicillium decay

Litchi fruits are fumigated after harvest with sulfur dioxide (SO₂) to prevent their rapid browning. SO₂ blocks enzymatic activity but bleaches the fruits and, if this process is followed by dipping the fruit in dilute hydrochloric acid, the appealing red color is regained. Hot water brushing (HWB) is among the alternative methods that were developed to replace the use of SO₂. HWB reduced fungal population size on the surface of the fruit peel after treatment but did not eliminate fruit infection after storage. Whereas untreated fruits were infected with a variety of fungal species,Penicillium sp. was the only fungus that developed on the pericarp after storage in fruits that had been dipped in 1.5M HCl. Fruit treated by HWB followed by handling and storage under sterile conditions suffered greater decay than fruit stored under non-sterile conditions but with more ventilation. APenicillium sp. isolated from litchi grew well in liquid medium acidified to the pH range reported for SO₂ and HCl-treated litchi fruits. Morphological analysis identified fungal isolates asP. aurantiogriseum. Internal transcribed spacer sequence analysis of five isolates suggested a sequence similarity toP. commune. Our data support the hypothesis that dipping litchi fruit in hydrochloric acid eliminates infection by common opportunistic fungi and selects forPenicillium species that tolerate low pH. http://www.phytoparasitica.org posting April 30, 2004.     

Effect of bread making on formation of Maillard reaction products contributing to the overall antioxidant activity of rye bread

This paper reports the effects of flour extraction rate on antioxidant activity, early, fluorescent and coloured Maillard reaction products in rye flour, crumb, crust and bread. Extent of the reaction was determined by analyses of furosine, fluorescence compounds and browning while antioxidant properties were measured by Folin reaction, Trolox Equivalent Antioxidant Capacity (TEAC) and Oxygen Radical Antioxidant Capacity (ORAC_FL) assays. Antioxidants present in rye flours and breads scavenged peroxyl and ABTS radicals and reduced Folin-Ciocalteu reagent. Data indicated that baking favoured the formation of antioxidant compounds. In controversy, milling to obtain white rye flour negatively affected bread quality.