Effect of extrusion cooking on the physicochemical properties, resistant starch, phenolic content and antioxidant capacities of green banana flour.

Green banana flour was extruded through a co-rotating twin-screw extruder with constant barrel temperature. The objectives of this study were to determine the effect of extrusion cooking variables (feed moisture, FM, 20% and 50%; screw speed, SS, 200 and 400rpm) and storing of the extruded flours at 4°C for 24h on the physicochemical properties, resistant starch (RS), pasting properties and antioxidant capacities. Extrusion cooking at higher FM and lower SS increased the amylose content, which was expressed in highest RS content. Water adsorption index (WAI) and pasting properties were increased, while water solubility index (WSI), total phenolic content (TPC) and antioxidant activities (FRAP, ABTS(+), DPPH) in free and bound phenolics were decreased compared to the other extruded samples. Storing the extruded flours at 4°C for 24h prior to oven drying was the main factor leading to a further increase in the content of amylose, RS, TPC and WSI values, as well as pasting properties - in particular peak viscosity. Compared to native banana flour, extrusion cooking caused significant changes in all studied properties of the extruded flours, except for soluble DF and antioxidant capacity (ABTS(+) and DPPH) of bound phenolics.

Effect of thermal heating on some lignans in flax seeds, sesame seeds and rye.

Consumption of lignan rich food is presumed to have positive effects on human health. As numerous foods are consumed mainly in processed form it is important to investigate the changes of the lignan content during processing. To this end, unheated and heated sesame seeds, sesame products, rye grains, rye flour, rye bread and flax seeds were extracted by sonication with ethanol/water (70:30, v:v) or sodium methoxide. The extracts were additionally hydrolysed enzymatically (ß-glucuronidase/arylsulphatase, cellulase), the compounds separated on a reversed phase column by gradient elution and detected by UV/ESI-MS in the negative ionisation multiple reaction monitoring mode (MRM). Secoisolariciresinol, lariciresinol, pinoresinol, 7-hydroxymatairesinol, syringaresinol, isolariciresinol, secoisolariciresinol diglycoside, lariciresinol monoglycoside, pinoresinol mono-, di- and triglycoside, sesaminol, sesaminol triglycoside, sesamolinol and sesamolinol diglycoside were identified. Moderate heating at 100°C did not degrade the lignan aglycones and glycosides in dry foods. In contrast, heating was responsible for the better extractability of the lignans. If samples with high moisture content were heated, the degradation of the lignans in sesame seeds and rye was observed already at 100°C. Higher roasting temperatures caused degradation of aglycones and glycosides. Especially at 250°C, lignans were degraded rapidly in sesame seeds and rye but not in flax seeds.

Uncommonly high levels of 3-deoxyanthocyanidins and antioxidant capacity in the leaf sheaths of dye sorghum.

Extracts from leaf sheaths of farmers' varieties of dye sorghum cultivated and used in Benin as a source of biocolorings were analyzed for their anthocyanidin and phenolic contents, as well as their antioxidant capacity. The aim was to identify and quantify the types of anthocyanin and phenolic acids. The total anthocyanin content of the leaf sheaths ranged from 13.7 to 35.5 mg of cyanidin 3-glucoside equivalent/g of dry matter (DM), with an average of 27.0 mg/g. The total anthocyanin content is 90 times higher than levels usually reported in fruits and vegetables. Anthocyanin consisted essentially of apigeninidin and luteolinidin, two 3-deoxyanthocyanidins with many applications in food, beverage, and pharmaceutical industries. The apigeninidin content of the leaf sheaths was 30 times higher than that in cereal bran and ranged from 14.7 to 45.8 mg/g, with an average of 31.3 mg/g. The amount of luteolinidin ranged from 0.4 to 2.4 mg/g, with a mean of 1.2 mg/g. The total phenolic content expressed as gallic acid equivalent averaged 95.5 mg/g. The free phenolic acids identified were benzoic acid, p-coumaric acid, and o-coumaric acid at amounts of 801.4, 681.6, and 67.9 µg/g, respectively. The leaf sheaths of dye sorghum have an antioxidant capacity [3.8-5.6 mmol of Trolox equivalent (TE)/g of DM] much higher than that reported for cereal bran and fruits and vegetables.

Functional properties of gluten-free pasta produced from amaranth, quinoa and buckwheat.

The use of amaranth, quinoa and buckwheat for the production of gluten-free pasta was investigated in the present study. The aim of the work was to produce pasta of good textural quality, in particular, low cooking loss, optimal cooking weight and texture firmness. The results demonstrated that pasta produced from amaranth had decreased texture firmness and cooking time, while pasta from quinoa mainly showed increased cooking loss. In buckwheat pasta the least negative effects were observed. By combination of all three raw materials to one flour blend in the ratio of 60% buckwheat, 20% amaranth and 20% quinoa, dough matrix was improved. After decreasing dough moisture to 30%, addition of an increased amount of egg white powder of 6% and addition of 1.2% emulsifier (distilled monoglycerides) texture firmness as well as cooking quality of gluten-free pasta produced from such a flour blend reached acceptable values comparable to wheat pasta.

Phytochemical profile of main antioxidants in different fractions of purple and blue wheat, and black barley.

Two pigmented wheat genotypes (blue and purple) and two black barley genotypes were fractionated in bran and flour fractions, examined, and compared for their free radical scavenging properties against 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (Trolox equivalent antioxidant capacity, TEAC), ferric reducing antioxidant power (FRAP), total phenolic content (TPC), phenolic acid composition, carotenoid composition, and total anthocyanin content. The results showed that fractionation has a significant influence on the antioxidant properties, TPC, anthocyanin and carotenoid contents, and phenolic acid composition. Bran fractions had the greatest antioxidant activities (1.9-2.3 mmol TEAC/100 g) in all four grain genotypes and were 3-5-fold higher than the respective flour fractions (0.4-0.7 mmol TEAC/100 g). Ferulic acid was the predominant phenolic acid in wheat genotypes (bran fractions) while p-coumaric acid was the predominant phenolic acid in the bran fractions of barley genotypes. High-performance liquid chromatography analysis detected the presence of lutein and zeaxanthin in all fractions with different distribution patterns within the genotypes. The highest contents of anthocyanins were found in the middlings of black barley genotypes or in the shorts of blue and purple wheat. These data suggest the possibility to improve the antioxidant release from cereal-based food through selection of postharvest treatments.

Effect of thermal treatment on the quality of cloudy apple juice.

Apple juice from eight different varieties of apples was heated at high-temperature (60-90 degrees C) and short-time (20-100 s) (HTST) combinations. To determine the effect of heating conditions on enzymatic browning and cloud stability in apple juices, the activity of polyphenol oxidase and pectinesterase was analyzed and correlated with the thermal treatment conditions and the quality of the juice. Additional investigations included the measurement of pH value, soluble solid content, titratable acidity, color, and turbidity after 3 and 6 months. The results showed that HTST treatment at 80 degrees C already inactivated polyphenol oxidase, whereas pectinesterase activity was reduced to half and could even at 90 degrees C not be inactivated completely. In fact, highest residual pectinesterase activity was found at 60 degrees C. Heating at 70 degrees C caused stable pectinesterase activity and even a slight increase for 50 and 100 s heating times. Turbidity and lightness increased after HTST treatment. In particular, differences in cloud stability between the varieties were measured. HTST parameters did not correlate with the residual cloud stability after 6 months. The sensory evaluation revealed that only a few combinations were distinguishable. The best stability of cloud and color in relation to heat impact was achieved by HTST treatment between 70 degrees C/100 s and 80 degrees C/20 s.