Evaluation and modification of processing techniques for recovery of anthocyanins from colored corn

Color is the most important indicator of taste and flavor, both vital sensory properties of food and beverages. The processing industry commonly uses artificial food colorants derived from petroleum or coal, called coal tar dyes. These dyes may cause attention-deficit/hyperactivity disorder, genotoxicity, neurotoxicity and/or carcinogenicity. In an era of “natural ingredients”, there is increasing customer pressure for exploring natural alternatives of synthetic dyes. Anthocyanins can be used as a replacement of synthetic FD&C Red 40 dye. However, their recovery from conventional sources is uneconomical due to higher inputs and lower economic value of the processing residues. The potential of using colored corn as a viable source of anthocyanins was explored. Anthocyanins containing purple and blue corn were fractionated using laboratory scale wet milling, dry milling and dry grind processes; coproduct yields were compared with those from conventional yellow dent corn. In wet milling, starch yields of colored corn were 6.7 to 8.7% less than conventional yellow dent corn on dry basis (db). In dry milling, large grit yields of colored corn were <25% (db), implying a softer endosperm composition. In the dry grind process, mean final ethanol concentrations for colored corn were 2.7% (v/v) less than those from yellow dent corn. Colored corn may be used in all three processes; however, with some yield differences. Colored corn coproducts from three processes were analyzed for anthocyanin content. Corn processing can generate coproducts with disproportionately higher anthocyanin contents. Location of pigments in colored corn kernels differed. Anthocyanins in the blue and purple corn were located in the aleurone and pericarp, respectively. Purple corn contained 13 times higher anthocyanins compared to blue corn. For purple corn, 80% of the anthocyanins were found in steepwater from wet milling and 48% in pericarp from dry milling process. Corn processing was tailored in such a way so as to recover coproducts with maximum anthocyanin concentrations while other fractions, which remain unaffected, could be further utilized. To increase anthocyanin recovery, dry milled purple corn pericarp was steeped using different combinations of wet milling chemicals. In the treatment containing SO2 (0.2%), lactic acid (0.5%) and water, 22.9 g anthocyanins/kg pericarp was quantified while the treatment containing only water recovered 7.1 g anthocyanins/kg pericarp. Although addition of SO2 facilitated higher anthocyanin extraction, it had a bleaching effect on the final extract color. Cyanidin-3-glucoside and its acylated form were the most dominant anthocyanins in treatments containing SO2 and lactic acid while the condensed forms were most abundant in the treatment containing only water. A 100 g dry milling protocol was developed which allowed estimation of coproduct yields for corn hybrids with low standard deviations of means. Crude oil contents of large and medium grits from hard endosperm varieties were comparable to those reported for similar lab scale studies. Due to the absence of a roller milling step, true sized large grits were recovered. This protocol should be helpful in estimating dry milling characteristics of newly developed colored corn varieties with relatively small amounts of material

Cascading effects of polyphenol-rich purple corn pericarp extract on pupal, adult, and offspring of tobacco hornworm (Manduca sexta L.)

A major bottleneck in the commercialization of plant-based pest management compounds is that the extraction methods are complex, time-consuming, and even highly expensive. Using a recently developed inexpensive extraction and quantification methodology to isolate polyphenols (including anthocyanins and condensed tannins) from purple corn pericarp, we examined their effects on Manduca sexta, a common insect herbivore. Following up on our previous work which demonstrated the negative impacts of polyphenol-rich extract on larval stages, we further examined whether there are any cascading effects on subsequent life stages (pupal and adult) including any possible transgenerational effects. Our results show that polyphenol-rich purple corn extract-fed caterpillars had significantly lower pupal mass and survival. Moreover, adult moths also had lower mass when eclosed from caterpillars reared on the extract diet. To test whether there were any transgenerational effects, we allowed male and female adults fed on purple corn extract diet and control diet to mate and lay eggs in a full factorial experiment. We found that purple corn extract-fed adult pair laid a lower number of eggs compared to other treatments. In addition, we also found that second instar M. sexta caterpillars hatched from eggs laid by any mating combination with at least one parent reared on purple corn extract gained significantly lower mass compared to caterpillars with both parents reared on the control diet. Taken together, our results show that there are cascading negative effects for feeding purple corn pericarp extract on pupal, adult, and second generation of M. sexta, reaffirming its potential application as a cost-effective and environmentally friendly pest deterrent

Polyphenol-Rich Purple Corn Pericarp Extract Adversely Impacts Herbivore Growth and Development

Plant secondary metabolites such as terpenes, phenolics, glycosides, and alkaloids play various functional roles including pigmentation, foliar and floral volatile synthesis, hormonal regulation, and direct and indirect defenses. Among these, phenolic compounds are commonly found in plants, but vary in the distribution of their specific compounds among plant families. Polyphenols, including anthocyanins and tannins, are widely distributed and have been well documented for their roles- primarily in plant pigmentation and also in plant defenses. However, commercialization of such compounds for use in insect pest management is severely hampered by expensive, inefficient, and time-consuming extraction protocols. Using a recently developed inexpensive and easy extraction method using the byproducts of pigmented (purple) corn processing, we examined whether the crude pericarp extract rich in polyphenols can affect the growth and development of tobacco hornworm (Manduca sexta L.) caterpillars. Our findings show that purple corn pericarp extract negatively affected M. sexta egg hatching and larval mass gain and prolonged developmental time compared to regular yellow corn extract or an artificial control diet. We also found that these effects were more severe during the early stages of caterpillar development. These results conclusively demonstrate that purple corn pericarp, an inexpensive by-product of the corn milling industry, is a valuable product with excellent potential as an insect antifeedant

Comparison of Hermetic Storage of Wheat with Traditional Storage Methods in India

India is among the countries experiencing high postharvest losses. Four hermetic bags, two metallic bins, and two gunny bag (also known as jute or burlap bag) piles each containing 1 tonne of wheat were instrumented with temperature, relative humidity, and carbon dioxide sensors. Representative samples from each structure were collected each month and tests for moisture, germination, insect-damaged grain, and milling yield were performed. After nine months, wheat stored in hermetic bags had higher germination (87%) and lower insect-damaged grain percentages (0% to 0.33% with a mean value of 0.2%). Hermetic bags with deliberately introduced Rhyzopertha dominica successfully eliminated the pests. Gunny bag piles had infestations; metallic bins also were infested. Wheat moisture content in all structures varied depending upon ambient conditions; moisture variation was largest in gunny bag piles. Milling yields were lowest for gunny bag piles. Hermetic bags can be an effective and environmentally friendly solution for reducing storage losses of wheat in India

Comparison of Hermetic Storage of Wheat with Traditional Storage Methods in India

India is among the countries experiencing high postharvest losses. Four hermetic bags, two metallic bins, and two gunny bag (also known as jute or burlap bag) piles each containing 1 tonne of wheat were instrumented with temperature, relative humidity, and carbon dioxide sensors. Representative samples from each structure were collected each month and tests for moisture, germination, insect-damaged grain, and milling yield were performed. After nine months, wheat stored in hermetic bags had higher germination (87%) and lower insect-damaged grain percentages (0% to 0.33% with a mean value of 0.2%). Hermetic bags with deliberately introduced Rhyzopertha dominica successfully eliminated the pests. Gunny bag piles had infestations; metallic bins also were infested. Wheat moisture content in all structures varied depending upon ambient conditions; moisture variation was largest in gunny bag piles. Milling yields were lowest for gunny bag piles. Hermetic bags can be an effective and environmentally friendly solution for reducing storage losses of wheat in India

Sonoprocessing improves phenolics profile, antioxidant capacity, structure, and product qualities of purple corn pericarp extract

For the first time, purple corn pericarp (PCP) was converted to polyphenol-rich extract using two-pot ultrasound extraction technique. According to Plackett-Burman design (PBD), the significant extraction factors were ethanol concentration, extraction time, temperature, and ultrasonic amplitude that affected total anthocyanins (TAC), total phenolic content (TPC), and condensed tannins (CT). These parameters were further optimized using the Box-Behnken design (BBD) method for response surface methodology (RSM). The RSM showed a linear curvature for TAC and a quadratic curvature for TPC and CT with a lack of fit > 0.05. Under the optimum conditions (ethanol (50%, v/v), time (21 min), temperature (28 °C), and ultrasonic amplitude (50%)), a maximum TAC, TPC, and CT of 34.99 g cyanidin/kg, 121.26 g GAE/kg, and 260.59 of EE/kg, respectively were obtained with a desirability value 0.952. Comparing UAE to microwave extraction (MAE), it was found that although UAE had a lower extraction yield, TAC, TPC, and CT, the UAE gave a higher individual anthocyanin, flavonoid, phenolic acid profile, and antioxidant activity. The UAE took 21 min, whereas MAE took 30 min for maximum extraction. Regarding product qualities, UAE extract was superior, with a lower total color change (ΔE) and a higher chromaticity. Structural characterization using SEM showed that MAE extract had severe creases and ruptures, whereas UAE extract had less noticeable alterations and was attested by an optical profilometer. This shows that ultrasound, might be used to extract phenolics from PCP as it requires lesser time and improves phenolics, structure, and product qualities