Effects of chemical additives on the heat inactivation of trypsin inhibitor (TI), lipoxygenase and urease in soybeans were investigated. The nutritional value of soybeans increases when antigrowth factors, such as TI, are inactivated. Inactivation of lipoxygenase enhances palatability and storage stability. Heat inactivation of antinutritional factors during immersion cooking of dry soymeats was studied without additives. Processing time was varied from 15 min to 2 hr over a temperature range of 120–212 F. The experiments were repeated, with the addition of NaOH or HCl to the cooking water. Without additives, lipoxygenase proved to be the most heat labile and TI, the least. With either acid or base additives, the initial inactivation of urease and lipoxygenase was accelerated significantly; however, while TI inactivation was accelerated by base, it was retarded by acid addition.

Oxidation of soybean lipids catalyzed by lipoxidase was prevented by heat treatment of soybean meats, which were then ground to give a full‐fat soy flour free of rancid odor and flavors. Our previous studies showed that lipids in cracked, dehulled, soybeans rapidly oxidized after the lipoxidase system was activated by increasing moisture content to 20%. A series of experiments are reported in which various heat treatments were evaluated for effectiveness of lipoxidase deactivation. Dry heat to 212 F, steaming, or both, deactivated lipoxidase to give flours that had low values of peroxide, conjugated diene and free fatty acid and had good flavors after 2 years’ storage. Wet heat alone was also an effective treatment, whereas wet heat preceded by dry heat at 180 F gave poor flavor stability after 2 years. Gas liquid chromatography studies gave evidence that the rapid formation of volatiles in full‐fat soy flours was catalyzed by an enzyme system. A 10 member taste panel was able to detect significant flavor and odor differences between oxidized and nonoxidized samples.

The bioavailability of zinc (Zn) and magnesium (Mg) from soy protein products freeze‐dried at different pH's was investigated. Soy concentrates and isolates were produced by both acid precipitation (acid soy) or acid precipitation with subsequent neutralization to pH 7.0 (neutral soy). The bioavailability studies involved feeding growing rats isonitrogenous and isocaloric diets based on egg white (with added ZnCO3 or MgCO3) or soy product (substituted in egg white diets to provide equivalent Zn or Mg). Linear regression analysis related amount of Zn (or Mg) in diet to: rat growth (zinc studies), log tibia Zn (or Mg), or serum Mg. Experiments I, II, IV, and V compared the availability of endogenous Zn or Mg from these soy products with ZnCO3 or MgCO3. Experiment III measured the effect of the presence of the acid or neutral soy in rat diets upon the availability of supplemental Zn as ZnCO3. Results of experiments I, II, and IV testing the bioavailability of endogenous zinc showed growth for rats on acid soy was equal to growth from ZnCO3 and greater than from neutral soy. Log tibia zinc analysis demonstrated zinc from both acid and neutral soy products to be less available than ZnCO3 Zn added (Experiment III) to either soy product was highly available. Mg (Experiment V) was highly available from all soy products. It was concluded that neutralization of soy products may result in decreased availability of endogenous Zn but not endogenous Mg.

Full-fat soy flours prepared by the extrusion process were shown to have good nutritive value, flavor, and stability. A flour cooked to a nitrogen solubility index (NSII of 30 stored well, but the addition of tertiary butyl hydroguinone was necessary to prevent rancidity in flours cooked to 19 and 11 NSI values. The 30 NSI flour was more yellow than a commercial flour cooked to the same degree by a different process. When soy flours were compared in bread to 3 and 6% nonfat dry milk on an equivalent protein, fat, and reducing sugar basis, baking properties were similar. At 15 and 20% levels of soy flour, loaf volume decreased less with the extruded products than with nonextrusion-processed soy flour.

A processing method for preparing full-fat soybean flours for human consumption by a new extrusion-cooking method was developed. Biological evaluations were made of samples produced experimentally by this method to determine the best conditions for preparing a product of maximum nutritive value and stability. Twelve processed full-fat soybean flours, prepared under different conditions, were evaluated by means of chemical analyses, biological assays, available lysine content, organoleptic and bacteriological test s~ and oxidative stability storage tests. Flour of high nutritive value and good stability can be prepared by preheating unextraeted soybean flakes or grits to 200-212F, premixing and adding sparge steam at 212F to adjust moisture content to 18-21%, extruding for 1-1.5 rain with final extrusion temp reaching 250-290F, cooling, drying and grinding. Clinical testing of the flour with infants up to 12 months of age has begun in two Far Eastern countries on a fairly extensive scale,

Even though it is well established that both underheated and overheated meals are of inferior nutritive value, comparatively little is known of the fundamental nature of the changes brought about in the protein and how these correlate with the processing conditions during toasting. In the present study we examined the interrelation of several factors in the commercial desolventizing‐toasting process for toasting soybean meal and determined how these relate to protein quality of the meal. A total of 48 test runs were made in the pilot plant from two cultivars of soybeans (one high and one low in protein) that were dehulled, flaked, and defatted in a continuous extractor using hexane. The solvent‐wet flakes were desolventized and toasted under a variety of conditions. In a simulation of commercial operation, independent variables such as moisture, temperature and time of toasting were mathematically converted to equations for computer fitting of the data, which were used to predict several dependent measurements. Quality of the meal was improved by increasing heating time, jacket steam pressure and moisture content. Moisture level in the toasting operation was directly affected by the hexane level in the feed material to the toaster.

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A method is reported for removingepi‐progoitrin, the major glucosinolate, from crambe seed meal. Defatted meal was cooked and water extracted or treated with soda ash and then water extracted. Although soda ash aided destruction and removal of glucosinolate factors, there was a 28% reduction in total lysine. In animal feeding tests designed to reflect differences due to toxic factors, soda ash treated and water extracted meals gave the best results. No toxicity was apparent in rats and chicks fed these meals in nutritionally adequate diets. The rat diet included 30% crambe meal for 90 days; the chick diet, 20% crambe meal for 4 weeks. Pathological examinations in both series showed no organ damage.