Dry Beans and Pulses Production, Processing, and Nutrition. Группа авторов

Dry Beans and Pulses Production, Processing, and Nutrition - Группа авторов


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per 100 seed count will vary from 48–56 g/100 seed for the large‐seeded kidney bean to 15–16 g/100 seed for the small white classes. Navy bean seeds weighing 17–19 g/100 seeds are common. Alternatively, black beans are generally selected to a size of about 500–550 seeds/100 g.

      Source: Smoliak et al. (1990), Kandel and Endre (2019).

Commercial market class Seeds/Pound
Black 2,100–2,500
Cranberry 900–1,000
White kidney 825–1,280
Great northern 1,300–1,600
Light/dark red kidney 800–1,000
Navy 2,200–2,400
Pink 1,300–1,600
Pinto 1,200–1,600
Small red 1,300–2,000
Yellow 1,000–1750

      US standard sieves are used to screen beans for grade standard specifications. The United States Department of Agriculture (USDA) standards for dry beans (USDA 2017a) state that “well‐screened” beans “shall mean that the beans are uniform in size and are practically free from such small, shrivelled, underdeveloped beans, splits, broken beans, large beans, and foreign material that can be removed readily…through use of sieves.” Sieves are to be constructed of 0.319‐inch‐thick metal with perforated round holes. Sizes are specified as a 30/64 sieve (0.4687 inch on a 11/64‐inch center); a 28/64 sieve (0.4375 inch on 19/32‐inch center); and a 24/64 sieve (0.0319 inch on a 17/32‐inch center). All rows of perforations are to be staggered. The screening is conducted in commercial operations (see Chapter 4), and these sieve specifications are used during USDA grading procedures to the assess sample uniformity for size.

      Commercial market classes have characteristic seed shapes that range from spherical to elongated (e.g., navy beans are generally characterized by a small round seed whereas kidney beans have elongated seed that resemble the human kidney). Similar to seed size, seed shape is under genetic control; however, deviations may occur due to stressed growing conditions (i.e., water availability and temperature profiles throughout the growing season).

      Commercial classes are also characterized by their seed coat color. Seed coat color is defined by the pigmentation underlying the testa and may be distributed throughout the testa as a solid or mottled pattern. The appearance will range from glossy (shiny) to a matte (dull) finish. The glossy finish is associated with the presence of a lipid layer on the surface of the testa. The P locus is known as the ground factor for all seed coat color genotypes (Bassett 2007).

Schematic illustration of general classification of phenolic compounds.

      Source: Adapted from Luthria and Pastor‐Corrales (2006).

      In recent years, interest in the antioxidant capacity of plant foods and specifically the phenolic content of dry beans (Wu et al. 2004; Xu and Chang 2009; Giusti et al. 2019) has intensified. There is increasing evidence that flavonoids consumed in native foods convey health benefits in human diets through their antioxidant activity (Frankel et al. 1993; Hertog et al. 1993). Condensed and hydrolyzable tannins of high molecular weight also have been shown to be effective antioxidants with even greater activity than simple phenolics (e.g., flavonoid monomers) (Hagerman et al. 1998). Although exceptionally high levels of antioxidant capacity have been reported in raw dry beans (Wu et al. 2004), further work on the retention of these properties in prepared (cooked or canned) beans is warranted.

      The genetics of black bean pigmentation has been studied by various researchers and summarized by Hosfield (2001). Feenstra (1960) isolated 18 different compounds from 12 experimental lines. These pigment compounds were identified as anthocyanins, flavonol glycosides, and leucoanthocyanidins. The secondary plant metabolites known as flavonoids are water‐soluble phenolic compounds that possess the basic structural C15 skeleton of flavones. Beninger et al. (1998) reported that the pigments responsible for the wide variation in the color of bean seed coats are flavonoids.


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