In addition to specific plants, staple crops also pro­vide phytochemicals at large scale, as coproducts of well-developed, comprehensive food production pro­cesses, which may be considered as the first generation of biorefineries.

Soybean processing involves multitier steps yielding multiple streams. The major soybean products include oil, feedstuff, and fermented soy food. Minor products include full-fat soy flours, soy concentrate, soy protein iso­lates, and lecithin. Phytochemicals that can be produced as coproducts from soybean processing include caroten­oids, isoflavones and saponin; protease inhibitors from protein fractions; as well as lecithin, phytosterols, and tocopherols from oil. Soybean processing in general consists of preparatory steps (cleaning, drying, mechanic disruption or grinding, or conditioning) and oil-extraction steps (mechanical pressing or solvent extraction, refining, bleaching, and hydrogenation). Coproducts are prepared by extractive distillation, adsorption, membrane filtration, and super — or subcritical fluid extraction (Kannan et al., 2012; Zijlstra et al., 2012) (Figure 20.5).

One of the two major corn processings is wet milling. Wet milling yields major products ranging from starch, starch-fermented ethanol (first-generation bioethanol), Wet or Dried Distillers Grains (residues from ethanol fermentation) or Dried Distillers Grains and Solubles or Stillage (WDDG or DDG, DDGS, which are widely used as feed), and steep liquor. Phytochemicals that might be generated as coproducts include flavonoids, phytosterols, carotenoids, polyamine-hydroxycinnamic acid amide conjugates (Rausch, 2012; Moreau et al., 2009) from steep liquor, steeped corn, oil-extracted resi­dues, stillage, or unfermented residues, although their production has not been widely integrated in current corn wet milling factories. Corn wet milling process include mechanic disruption, liquid extraction (steep­ing, acidic, basic or SO2 impregnation), screening, oil pressing, evaporation, centrifugation, fermentation and distillation. Corn dry milling is another major corn pro­cessing, mainly geared for bioethanol production. The process does not have steeping and germ-processing (oil extraction) as the wet milling does, resulting in sep­aration and enrichment of most corn phytochemicals in unfermented residues and stillage (Rausch, 2012; Rausch and Belyea, 2006) (Figure 20.6).

Vegetable oil production involves multitier, multi­phase steps (Figure 20.7). Major plant sources for vege­table oils include palm, soybean, rapeseed, sunflower seed, peanut, cotton seed, coconut, and olive, and (to less extent) corn, hazelnut, grape seed, sesame, flax seed, safflower, rice bran, etc. Besides oil and cake (or meal, oil-extracted residues), other coproducts come from mechanically or chemically separated substances prior to oil extraction as well as refining by-products. Degumming and deodorizing of crude vegetable oils result in the production of lecithin and tocopherols or phytosterols, respectively. General processes of vegetable oil production include feedstock disruption by mechanical, chemical or enzymatic means, mechani­cal pressing, phase separation, solvent extraction, and refining (degumming, neutralizing, bleaching and deo­dorizing) (Panpipat et al., 2012; Febrianto and Yang, 2011; Muth et al., 1998; Dunford, 2012).

Postharvest processing of wheat, rice, oat, or other cereals generates not only flour or milled rice, bran, and germ as primary products, but also gluten, fiber, bran oil, or other phytochemicals as secondary products. The processing mainly comprises different levels of mill­ing and fractionation (air classification, sieving, etc.), sometimes also with extraction (Kraus, 2006).