Chemical studies of anthocyanins: A review

Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review

A critical review of methods for characterisation of polyphenolic compounds in fruits and vegetables.

Phenolic compounds are well-known phytochemicals found in all plants. They consist of simple phenols, benzoic and cinnamic acid, coumarins, tannins, lignins, lignans and flavonoids. Substantial developments in research focused on the extraction, identification and quantification of phenolic compounds as medicinal and/or dietary molecules have occurred over the last 25 years. Organic solvent extraction is the main method used to extract phenolics. Chemical procedures are used to detect the presence of total phenolics, while spectrophotometric and chromatographic techniques are utilized to identify and quantify individual phenolic compounds. This review addresses the application of different methodologies utilized in the analysis of phenolic compounds in plant-based products, including recent technical developments in the quantification of phenolics.

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Techniques for analysis of plant phenolic compounds.

Starch is the major energy component of grains. Wheat contains 77% of DM as starch, corn and sorghum contain 72%, and barley and oats contain 57 to 58%. In vitro systems have provided valuable data on kinetic aspects of starch digestion. Molecular biological techniques have provided a clearer picture of the ruminal microbial milieu. Proportions of starch fermented in the rumen can be predicted satisfactorily for a variety of grains and processing methods. Compared with dry rolling, steam processing (flaking or rolling) increases ruminal digestibility of starch (percentage of intake) from 52 to 78% for sorghum, from 75 to 85% for corn, and six percentage units or less for other grains. Recent research provides new insight into pancreatic function and intestinal glucose transport systems. The capacity to digest starch in the intestine ranges from 45 to 85% of starch entering the duodenum, with that capacity apparently limited by the supply of pancreatic amylase. There is evidence that amylase secretion may be enhanced by increasing duodenal entry of protein. Capacity for active transport of glucose across of gut wall does not seem to limit the amount of starch digested that is absorbed as glucose. For ruminants eating medium- to high-concentrate diets, about 30% of their total glucose need comes from glucose absorption, 50% from organic acid absorption (substrates for hepatic gluconeogenesis), and 20% from other sources. When glucose absorption from the gut increases, ruminants generally adjust (decrease) gluconeogenesis to meet their need; that need is directly linked to DE intake. In terms of overall ME yield, grain starch is best used when it is fermented in the rumen. However, close coordination of protein and starch supply to the duodenum may improve capture of starch in the form of glucose.

Starch utilization by ruminants: from basics to the bunk.

https://www.afritradomedic.com/pdf/about_sorghum/AwikaAnthocyanidins2004Final.pdf

Anthocyanins from black sorghum and their antioxidant properties

The effects of plant color, pericarp thickness, pigmented testa, and spreader genes on phenols and antioxidant activity levels of 13 sorghum genotypes were evaluated. Total phenols, condensed tannins, flavan-4-ols, and anthocyanins were measured. Antioxidant activity levels using the 2,2‘-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl assays were evaluated. Sorghums with a pigmented testa and spreader genes (B1B2S) had the highest levels of phenols and antioxidant activity. In addition, sorghums with purple/red plants (PQ) and thick pericarp (z) genes had increased levels of phenols and antioxidant activity. Sorghums with a black pericarp had higher levels of flavan-4-ols and anthocyanins than the other varieties. This suggests that genes for plant color, pericarp thickness, presence of a pigmented testa, and spreader genes increase phenols and antioxidant activity levels. This information can be useful in the production of sorghums with increased phenols and antioxida...

Phenolic Compounds and Antioxidant Activity of Sorghum Grains of Varying Genotypes

There is increasing interest in natural food colorants with functional properties. Anthocyanins from black, brown (containing tannins), and red sorghums were characterized by spectrophotometric and HPLC techniques. The antioxidant activity and pH stability of the anthocyanins were also determined. Sorghum brans had 3-4 times higher anthocyanin contents than the whole grains. Black sorghum had the highest anthocyanin content (average = 10.1 mg/g in bran). The brown and red sorghum brans had anthocyanin contents of 2.8-4.3 mg/g. Only 3-deoxyanthocyanidins were detected in sorghum. These compounds are more stable to pH-induced color change than the common anthocyanidins and their glycosides. Additionally, crude sorghum anthocyanin extracts were more stable than the pure 3-deoxyanthocyanidins. The antioxidant properties of the 3-deoxyanthocyanidins were similar to those of the anthocyanins. Pigmented sorghum bran has high levels of unique 3-deoxyanthocyanidins, which are stable to change in pH and have a good potential as natural food pigments.

Properties of 3-deoxyanthocyanins from sorghum.

The effects of grain type and processing on ruminal starch digestion are well documented but poorly understood at the biochemical and molecular levels. Waxy grains have starches high in amylopectin and are more readily digested than nonwaxy grains. However, the composition of the endosperm cell matrix and the extent to which the starch granules are embedded within it also affect starch digestion rates. Continued work is needed to determine the influence of specific cell matrix proteins, protein-starch interactions and cell wall carbohydrates on starch availability. The microbial populations that metabolize starch are diverse, differing in their capacities to hydrolyze starch granules and soluble forms of starch. Surveys show that the amylases are under regulatory control in most of these organisms, but few studies have addressed the types of amylolytic enzymes produced, their regulation and the impact of other plant polymers on their synthesis. Research in these areas, coupled with the development and use of isogeneic or near-isogeneic grain cultivars with biochemically defined endosperm characteristics, will enhance our ability to identify mechanisms to manipulate ruminal starch digestion.

Starch Hydrolysis by the Ruminal Microflora

Three white food sorghums, ATx631*RTx436, ATxARG*RTx436, and SC283-14, were decorticated, milled into flour and processed into 100% sorghum noodles. Flour, water, and salt (1%) were preheated using a hotplate or a microwave oven. The mixtures were put through a forming extruder to produce noodles. Extruded noodles were dried by three methods: air-dry method (23°C, 48 hr); one-stage (60°C, 30% rh, 3 hr), or two-stage (60°C, 100% rh for 2 hr followed by 60°C, 30% rh for 2 hr). Noodles were evaluated dry and after cooking. Sorghum flours with smaller particle sizes yielded better noodles. The microwave preheating method yielded better noodles than the hot-plate method. Stronger and firmer noodles, dry or cooked, were prepared using two-stage drying compared with the other drying methods. Fine flour that was preheated using a microwave oven and dried using the two-stage method gave the best noodles with moderate (10%) dry matter loss. Optimized processing conditions yielded sorghum noodles with good ...

Ralph D. Waniska

Papers

Anthocyanins from black sorghum and their antioxidant properties

Phenolic Compounds and Antioxidant Activity of Sorghum Grains of Varying Genotypes

Properties of 3-deoxyanthocyanins from sorghum.

Starch Hydrolysis by the Ruminal Microflora

Cooking Characteristics and Quality of Noodles from Food Sorghum