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The composition of tepary beans Phaseolus acutifolius var. latifolius was determined; starch (41%) and protein (26.3%) were the predominant components. The physical, physicochemical, rheological, structural and nutritional properties of the isolated starch and its suitability in food products were evaluated. Starch granules were spherical to oval with a typical legume starch birefringence pattern. They appeared smooth and showed a normal distribution of diameters (range 15.5 - 59.9 μ; mean 33.5 μ). Tepary starch had an amylose content of 30.7% and a gelatinization temperature range of 70.5 - 84.0°C. Other physicochemical values were as follows: phosphorus, 0.01%; iodine binding capacity, 6.14%; alkali number, 8.97; inherent viscosity, 2.44 ml/g; water binding capacity, 82.1%; swelling power, 13; solubility, 17.9%; and sag, 6.26%. Fractionation provided an amylose fraction with a β-amylolysis of 76.3%, limiting viscosity of 83.5 ml/g and a DP(η) of 618. Amylopectin (iodine binding capacity, 0.88%) had a DP(η) of 1094, limiting viscosity of 91.1 ml/g and CL, OCL, and ICL values of 33, 22 and 10 glucose units, respectively. Gelatinization of tepary starch was a single-step process. Pasting viscosity was stable when starch suspensions were cooked at 95°C for 15 min; viscosity progressively increased when pastes cooled to 50°C. At 4 and 6%, tepary starch pastes resembled a type C viscosity pattern, whereas at 7% and above, pasting behavior exhibited a type B pattern. Pastes were stable at pH 5 to 9 but showed faster breakdown and no retrogradation at pH 3. Addition of sucrose and salt changed rheological behavior; 2% oil had no effect on pasting. Sensory evaluation of tepary starch vanilla pudding established its consumer acceptability. In vitro determination indicated that raw tepary starch was poorly digested (8%). Digestibility improved (from 8 to 82%) upon cooking. Raw corn starch was more digestible (25.6%) than tepary starch. Freeze-drying reduced the hydrolysis of all materials evaluated (i.e. 8.64 to 3.21%, 8.03 to 2.63% and 25.6 to 17.8% for tepary flour, tepary starch and corn starch, respectively). Autoclaving decreased the digestibility of tepary flour (8.64 to 5.72%), and tepary starch (8.03 to 7.38%), but it slightly improved that of corn starch (25.6 to 27.7%).

An investigation was made of physicochemical and functional properties of a polysaccharide, arabinogalactan (TAG), found in the tepary bean, Phaseolus acutifolius var. latifolius, an arid adapted legume with substantial protein and starch content. TAG has specific functional and sensory properties which could be of value in foods and industrial products. The polysaccharide was isolated by a sequence of steps depending on initial extraction by trichloroacetic acid. Isolated TAG was obtained from bean flour in 3.7% yield and contained 3.6% protein; fractional precipitation provided further purification and gave fractionated TAG in 1.8% yield with a protein content of 0.9%. The purified product was composed primarily of two monosaccharide monomers, arabinose and galactose, in the ratio 2.07:1.00. Fractionated TAG was separated further by gel filtration and showed the presence of two arabinogalactans in the ratio of 9:4 with similar properties and approximate molecular weights of 500,000 and 30,000. The influence of concentration, temperature, pH and presence of sugars and electrolytes on the viscosity of fractionated TAG was studied. The specific viscosity at 1% w/v (17.84), was much greater than that of larch arabinogalactan (0.08) or soluble starch (0.39). Optical rotation measurements of temperature dependent conformational changes gave evidence for the maintenance and stabilization of the native conformation of TAG by guar gum in a mixed gel. No synergism was observed. TAG in 4% concentration produced oil in water emulsions with excellent stability over at least five months. Loaf and crumb characteristics of wheat bread were influenced by TAG at a supplementation level of 0.2%. Sensory evaluation indicated excellent color, flavor, aroma, mouthfeel, texture and overall acceptability. Substantial advantages were also afforded by TAG supplementation of rice flour bread which is formulated specifically for gluten-allergic people. Significant improvements were found in loaf and crumb quality and in sensory properties. The inclusion of TAG in a variety of other foods could be expected to enhance rheological properties as well as improve thickening, emulsification, emulsion stabilization, gas-holding and dough-raising.

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The responses of the tepary bean (Phaseolus acutifolius) to in vitro tissue culture systems were documented. Tests were conducted to identify the optimal auxin and cytokinin combinations required for optimal callus growth. Regeneration experiments were conducted to: (1) determine the effect of explant source and age on regeneration, (2) effect of callus age on regeneration, (3) the cultivation status of the explant source, and (4) the effects of nutritional additives on somatic embryogenesis. The callus was easily induced and maintained in all hormonal medias except those containing IAA and 6BA. The results for regeneration were most promising from cultures derived from immature cotyledon tissue. Ammonium Chloride, glutamine and Absisic acid appeared to have little affect on embryogenesis, however the addition of kinetin enabled the embryos to develop to the torpedo stage. Callus age and cultivative status of explant source had no effects on plantlet regeneration.