Cholesterolemic effects of the lysine/arginine ratio in rabbits after initial early growth

The lysine/arginine ratio has been directly associated with serum cholesterol levels. Male, New Zealand rabbits with a mean weight of 2.1 kg were fed, ad libitum, one of three diets containing 14% vegetable oil and 20% protein from casein, soy or almonds with lysine/arginine ratios of 2.2, 0.9, or 0.3, respectively. At the end of three weeks for phase 1, the serum cholesterol level of the casein group (154 +/- 25 mg/dl, mean +/- SD) was twice the level and significantly greater (p less than 0.02) than either of the plant protein groups (soy 70 +/- 7, almond 78 +/- 6 mg/dl). During phase 2, the almond diet was supplemented with L-lysine to increase the lysine/arginine ratio from 0.3 to 3.0 while casein remained as the high, and soy the low lysine/arginine ratio control diets. Serum cholesterol levels remained high for the casein, and low for the soy groups, while lysine supplementation significantly increased (p less than 0.05) the serum cholesterol level in the almond protein group (from 78 +/- 6 to 101 +/- 10), but not greater than the casein group. Growth was similar for rabbits fed soy or casein diets throughout the study, but lower (p less than 0.02) for the almond group. Thus, growth rate was not related to the effect of dietary protein on levels of serum cholesterol. While there is a direct relationship between hypercholesterolemia and the absolute amount of dietary lysine and with the lysine/arginine ratio, the data suggest that this is only a partial explanation for the effect of proteins on the control of serum cholesterol levels.     

Separate effects of dietary protein and fat on serum cholesterol levels: another view of amino acid content of proteins

Casein or soy protein with vegetable or animal fat were used to determine the dietary protein or fat effects and their possible interaction on serum cholesterol levels. Young, male New Zealand white rabbits with a mean weight of 2.1 kg were divided into groups of six and fed one of four different diets containing 20% of the calories as protein, 30% as fat (according to dietary guidelines for the United States) and 50% as carbohydrate. The diets contained casein or soy (lysine/arginine ratio = 2.2 or 0.9, respectively) as the protein sources with fat from either almond oil or butter. There was no significant difference in weight gain among the diet groups. Total serum cholesterol level was highest among animals fed the diet containing butter with casein (177 +/- 25 mg/dl) or soy protein (189 +/- 50 mg/dl), it was intermediate in animals fed the vegetable oil with casein (121 +/- 14 mg/dl), and lowest in the soy protein with vegetable oil group (58 +/- 12 mg/dl). There was a significant difference in serum cholesterol levels due to the protein effect when vegetable oil was used (p less than 0.05) but not with butter. There was also a significant fat effect on serum cholesterol when the diet contained soy protein (p less than 0.005) but not when the protein was casein. No significant interaction was observed between the dietary fat and protein sources on serum cholesterol levels, which suggests that dietary protein and fat independently affect the levels of serum cholesterol. Thus, dietary protein has a significant effect on serum cholesterol levels and may be a factor in the low levels of serum cholesterol observed among vegetarians and in humans of Third World countries where the diets is primarily of vegetable origin.     

Soy and corn flour precooked with microwaves and its use in the preparation of arepas]

Unhusked corn and soy grits were used as raw material, with a particle size ranging between 10 and 20 mesh (ASTM). The results obtained in this study reveal that microwave heating is effective in destroying the antinutritional factors present in soybeans. The trypsin inhibitor activity, in effect, was reduced to a 76% inactivation. The hemagglutinating titer was labile to the heating process, showing values of +8 to +3 for the full-fat soy flour and precooked soy flour, respectively. The quality of soy protein was measured by the protein efficiency ratio (PER) showing values of 2.63 for the precooked soy flour, and 2.46 to 2.21 for the precooked corn:soy blends (70:30 and 50:50). These uncooked blends present values of 1.17 and 1.04. The enriched corn:soy flour had a PER value of 1.60, in comparison to casein (PER = 2.90). The microwave heating improved the digestibility of the soy flour and blends. There were no significant differences (P less than or equal to 0.05) in relation to the functionality of the precooked flour and mixtures. The results obtained revealed that the applied process markedly improve the functional properties and nutritional value of the enriched flour, and of the "arepas" prepared from them.     

Effects of soy proteins containing trypsin inhibitors in long term feeding studies in rats

Pancreatic hypertrophy that occurs in rats fed raw soy flour containing about 1200 mg tripsin inhibitor (TI)/100 g diet was reversed by switching the rats to control diets or to diets containing 30% toasted defatted soy flour. No pancreatic hypertrophy occurs in rats fed commercial, edible grade soy flours, concentrate or isolate from time of weaning to adulthood (ca. 300 days). TI content of the soy diets ranged from 178–420 mg/100 g. Except for pancreas enlargement in rats fed raw soy flour, gross and microscopic examination of pancreata revealed no abnormalities. The gross appearance of heart, kidney, spleen, and liver was normal. Soy flour, protein concentrate, and protein isolate in a formulated corn-soy diet provided optimum growth and maintained body weight only if supplemented with vitamin B-12 in long term feeding studies with rats. In the absence of such supplementation, rats fed soy diets initially grew at a rate equal to or greater than those fed a comparable corn-casein control diet; but, with continued feeding for ca. 300 days, body weight of rats fed the casein control was significantly greater than that of the soy flour-fed rats. Those fed soy isolate ceased to grow; and rats fed soy concentrate lost weight. No significant differences were found in organ weights between groups fed soy products and casein, except for increased kidney, liver, and testes weights relative to body weight with the group fed soy concentrate. Supplementation of the soy diets with vitamin B₁₂ stimulated growth to the greatest extent, calcium pantothenate or riboflavin had an intermediate effect, other vitamins had little or no effect; whereas a complete mineral mix was detrimental. Supplementation of the soy diets with vitamin B₁₂ stimulated growth to the greatest extent, calcium pantothenate or roboflavin had an intermediate effect, other vitamins had little or no effect; whereas a complete mineral mix was detrimental. Supplementation of the control diet was without effect. The dietary protein level in these diets was 20%, with casein or soy protein representing 75% of total protein. When fed continuously to rats from weaning to adulthood, properly processed soy protein products, when balanced with essential nutrients, can provide growth comparable to corn-casein diets.     

Increased In Vitro and In Vivo Digestibility of Soy Proteins by Chemical Modification of Disulfide Bonds

To improve protein digestibility of aqueously extracted soy proteins, an effective chemical treatment under mild conditions is needed. Soy proteins, including storage protein glycinin and antinutritional factors such as trypsin inhibitors, are rich in disulfide bonds. Reduction of these disulfide bonds by incubating soy proteins with sodium sulfite and sodium metabisulfite at 55 °C showed no net increase of free sulfhydryl groups after dialysis to remove the residual reducing agent. However, the in vitro digestibility measured by trypsin hydrolysis using the pH-Stat method was significantly increased. Sodium metabisulfite (SMBS) was more effective in increasing in vitro digestibility than sodium sulfite at the same molar concentration. The digestibility of soy protein treated by 0.5 mmol SMBS/g soy flour at 55 °C was more than doubled compared to that of the control without reduction treatment. Large-scale testing of soy proteins treated with SMBS for an in vivo animal feeding study showed similar in vitro digestibility by trypsin, e.g., the degree of hydrolysis of the treated sample was 8.5% compared to 1.6% of the control. These soy proteins were further evaluated using a chick growth model. The protein efficiency ratio (PER) increased by 57% when the chicks fed SMBS-treated soy were compared to the chicks fed raw soy flour. SMBS-fed chicks did not display any pancreatic hypertrophy compared to those fed with raw soy control. These results indicate that there is great potential to use safe chemicals and mild temperature to inactivate the antinutritional factors in soybeans and thus improve digestibility of soy proteins that are extracted with low-temperature aqueous process.     

Separating Oil from Aqueous Extraction Fractions of Soybean

Previous research has shown that enzyme-assisted aqueous extraction processing (EAEP) extracts 88–90% of the total soybean oil from extruded full-fat soy flakes into the aqueous media, which is distributed as cream (oil-in-water emulsion), skim, and free oil. In the present work, a simple separatory funnel procedure was effective in separating aqueous skim, cream and free oil fractions allowing mass balances and extraction and recovery efficiencies to be determined. The procedure was used to separate and compare liquid fractions extracted from full-fat soy flour and extruded full-fat soy flakes. EAEP extracted more oil from the extruded full-fat soy flakes, and yielded more free oil from the resulting cream compared to unextruded full-fat soy flour. Dry matter partitioning between fractions was similar for the two procedures. Mean oil droplet sizes in the cream and skim fractions were larger for EAEP of extruded flakes compared to non-enzymatic AEP of unextruded flour (45 vs. 20 μm for cream; 13 vs. 5 μm for skim) making the emulsions from EAEP of extruded flakes less stable. All major soy protein subunits were present in the cream fractions, as well as other fractions, from both processes. The cream could be broken using phospholipase treatments and 70–80% of total oil in the extruded full-fat flakes was recovered using EAEP and a phospholipase de-emulsification procedure.     

Functional properties of hydrothermally cooked soy protein products

The effects of hydrothermal cooking on the functional properties of defatted soy flour, aqueous alcohol washed soy protein concentrate, and soy protein isolate were determined in samples that were treated at 154°C by infusing steam under pressure for 11, 19, 30, and 42 s, and then spray dried. Hydrothermal cooking increased the nitrogen solubility index (NSI) of the concentrate from 15 to 56% and altered the solubility profile from a flat profile to one more typical of native soy protein. Hydrothermal cooking also improved foaming and emulsifying properties of the concentrate. For isolate, hydrothermal cooking also improved NSI and foaming and emulsifying properties, although the improvements were less dramatic than with concentrate. NSI and emulsifying properties of the flour were improved by some processing conditions, but foaming properties were not improved by hydrothermal cooking. Dramatically increased protein solubility of concentrate and modestly improved protein solubilities of flour and isolate by hydrothermal cooking, which will also inactivate trypsin inhibitors and microorganisms, have considerable practical significance to protein ingredient manufacturers and those who use these ingredients in foods and industrial products.     

Structure,Protein Interactions and In Vitro Protease Accessibility of Extruded and Pressurized Full-Fat Soybean Flakes

The objectives of the present study were to determine how extrusion (barrel temperature of 100 °C) and high-pressure processing (HPP, 200 and 500 MPa, 15 min, 25 °C) of full-fat soybean flakes (FFSF) modified the structure of soybean cotyledon cells, the protein interactions and the in vitro protease accessibility. Cellular disruption of the cotyledon cells was only observed for extruded FFSF. Extrusion and HPP at 500 MPa favored formation of insoluble protein aggregates, in which oil was entrapped. High pressure size exclusion chromatography (HPSEC) and extraction methods using buffers containing SDS and 2-mercaptoethanol suggested that noncovalent interactions were the main forces in protein aggregate formation during HPP 500 MPa and extrusion. Intermolecular cross-linking by disulfide bonding was also involved in insoluble aggregates, but at a lesser extent than noncovalent interactions. Extrusion and HPP 500-MPa treatment enhanced the proteolytic attack, while treatment at 200 MPa had no impact. Drastic changes in the peptide profile of the extracted proteins were, however, only observed for the enzyme-treated 500-MPa FFSF. Optimal oil and protein extraction yields required cellular disruption of cotyledon cells and hydrolysis of protein aggregates, which were obtained with enzyme-assisted aqueous extraction of extruded FFSF.     

Germination of soybeans and its modifying effects on the quality of full-fat soy flour

Usually, full-fat soy flour has some disadvantages in flavor, odor and stability. A soybean germination process was developed to improve the quality of full-fat soy flour. Advantages of the process were evaluated determining protein dispersibility index (PDI), trypsin inhibitor (TI) and lipoxygenase activities, milling capacity, odor and flavor score during the different stages of the process. In the final stages of the process, a marked decrease in lipoxygenase and TI activities were observed. The PDI increased with germination time in unheated soybeans. Odor and flavor scores improved substantially. Milling capacity dropped as germination time was increased.     

Flaking and extrusion as mechanical treatments for enzyme-assisted aqueous extraction of oil from soybeans

Flaking and extruding dehulled soybeans were evaluated as a means of enhancing oil extraction efficiency during enzyme-assisted aqueous processing of soybeans. Cellulase, protease, and their combination were evaluated for effectiveness in achieving high oil extraction recovery from extruded flakes. Aqueous extraction of extruded full-fat soy flakes gave 68% recovery of the total available oil without using enzymes. A 0.5% wt/wt protease treatment after flaking and extruding dehulled soybeans increased oil extraction recovery to 88% of the total available oil. Flaking and extruding enhanced protease hydrolysis of proteins freeing more oil. Treating extruded flakes with cellulase, however, did not enhance oil extraction either alone or in combination with protease. Discrepancies in oil extraction recoveries were encountered when merely considering crude free fat because some oil became bound to denatured protein during extrusion and/or sample drying. Bound fat was unavailable for determination by using the hexane extraction method, but was accounted for by using the acid hydrolysis method for total oil determination. Oil extraction recovery from extruded soybean flakes was affected by oil determination methods, which was not the case for unextruded full-fat soy flour.     

Interaction between dietary proteins and lipids in the regulation of serum and liver lipids in the rabbit. Effect of fish protein

Purified diets varying in dietary protein, namely casein (CA), soy protein (SP), fish protein (FP), and lipid origin (corn oil (CN), coconut oil (CO)) were fed to rabbits to evaluate the effects of protein and fat source, as well as protein-lipid interactions, on serum total, lipoprotein and hepatic lipid levels. Dietary proteins and lipids exerted a separate effect on serum total cholesterol (C), very low-density lipoprotein cholesterol (VLDL-C), and low-density lipoprotein cholesterol to high density lipoprotein cholesterol (LDL-C/HDL-C) ratio. Hence, CA increased serum cholesterol compared to SP, while coconut oil enhanced serum and VLDL-C, and decreased LDL-C/HDL-C compared to corn oil. Dietary proteins interacted with dietary lipids to modulate HDL-C levels. Thus, FP maintained a high level of HDL-C regardless of lipid origin, compared to CA and SP whose HDL-C levels were decreased by corn oil, compared to coconut oil. A dietary protein-lipid interaction was also observed in the regulation of liver cholesterol levels. Coconut oil, compared to corn oil, decreased liver cholesterol in rabbits fed FP, whereas hepatic cholesterol concentration was unaltered by dietary lipid source in CA- and SP-fed rabbits. These results demonstrate that dietary proteins act synergistically with dietary lipids to regulate cholesterol metabolism in the rabbit. This work was presented in part at the 74th Annual FASEB meeting held in Washington, D.C., April 1–5, 1990.     

High temperature performance of soy-based adhesives

We studied the high temperature performance of soy meal processed to different protein concentrations (flour, concentrate, and isolate), as well as formulated soy-based adhesives, and commercial nonsoy adhesives for comparison. No thermal transitions were seen in phenol-resorcinol-formaldehyde (PRF) or soy-phenol-formaldehyde (SoyPF) or in as-received soy flour adhesive during differential scanning calorimetry scans heating at 10?°C/min between 35 and 235?°C. Heat flow rates decreased in the order soy flour (as received)?>?SoyPF?>?PRF?>?emulsion polymer isocyanate (EPI). In thermogravimetric analysis (TGA) scans from 110 to 300?°C at 2?°C/min, total weight loss decreased in the order soy flour (as-received)>SoyPF?>?PRF?>?casein?>?maple?>?EPI. For bio-based materials, the total weight loss (TGA) decreased in the order soy flour (as-received) > concentrate, casein?>?isolate. Dynamic mechanical analysis from 35 to 235?°C at 5?°C/min of two veneers bonded by cured adhesive showed 30–40% decline in storage modulus for maple compared to 45–55% for the adhesive made from soy flour in water (Soy Flour) and 70–80% for a commercial poly(vinyl acetate) modified for heat resistance. DMA on glass fiber mats showed thermal softening temperatures increasing in the order Soy Flour?<?casein?<?isolate?<?concentrate. We suggest that the low molecular weight carbohydrates plasticize the flour product. When soy-based adhesives were tested in real bondlines in DMA and creep tests in shear, they showed less decrease in storage modulus than the glass fiber-supported specimens. This suggests that interaction with the wood substrate improved the heat resistance property of the adhesive. Average hot shear strengths (ASTM D7247) were 4.6 and 3.1?MPa for SoyPF and Soy Flour compared to 4.7 and 0.8?MPa for PRF and EPI and 4.7 for solid maple. As a whole, these data suggest that despite indications of heat sensitivity when tested neat, soy-based adhesives are likely to pass the heat resistance criterion required for structural adhesives.     

Effects of dietary casein and soy protein on metabolism of radiolabelled low density apolipoprotein B in rabbits

Rabbits fed semipurified diets containing casein have elevated plasma cholesterol levels compared to those fed soy protein. As part of continuing studies on the mechanism of casein-induced hypercholesterolemia, two groups of six rabbits were fed these diets for 14 to 16 weeks. Animals fed the casein diet were found to have significantly higher plasma concentrations of protein, cholesterol, triacylglycerol, phospholipid and apolipoprotein B (apo B) associated with low density lipoprotein (LDL) than those fed the soy protein diet. Kinetic studies showed that the fractional catabolic rate of LDL-apo B was significantly lower in animals fed casein than in those fed soy protein regardless of whether the tracer LDL was obtained from donors fed casein or soy protein. The production rate of LDL-apo B was higher in casein-fed animals but this was not statistically significant. These results show that the efficiency of removal of LDL is significantly reduced in animals fed casein compared to those fed soy protein, and that the source of LDL did not affect the efficiency of its subsequent removal. The acumulation of LDL in casein-fed animals is consistent with down-regulation of the LDL receptor.     

Dietary proteins modulate the effects of fish oil on triglyceridemia in the rat

Sprague-Dawley rats were fed purified diets varying in both protein (20%) and lipid (11%) content for 28 d to verify the independent and interactive effects of dietary proteins and lipids on serum and hepatic lipids, and on tissue lipoprotein lipase (LPL) activity in both fasted and postprandial states. These diets consisted of either casein-menhaden oil, casein-coconut oil, soy protein-menhaden oil (SPMO), soy protein-coconut oil, cod protein-menhaden oil, or cod protein-coconut oil. A randomized 3×2 factorial design was used. A significant protein-lipid interaction was seen on serum triglyceride levels: menhaden oil, compared with coconut oil, induced a decrease in serum triglyceride levels when combined with soy protein but not when combined with cod protein and casein. The lower serum triglyceride concentrations observed in the SPMO-fed rats could be the result of decreased hepatic triglycerides when soy protein was compared with casein and when menhaden oil was compared with coconut oil. Total LPL activity in the heart was higher in menhaden oil-fed rats than in coconut oil-fed rats in the postprandial state. The higher LPL activity in the heart could, however, explain only 10% of the reduction of serum triglycerides, contributing slightly to the lowering effects of SPMO diet on serum triglycerides. Therefore, the present results indicate that dietary proteins can modulate the effects of fish oil on triglyceridemia in the rat, and that could be mainly related to specific alterations in hepatic lipid concentrations.     

Dietary protein effects on gallstone formation

Semipurified lithogenic diets for hamsters contain casein as the protein source. Since substitution of soy protein isolate for casein reduces serum cholesterol concentrations in several species, we studied replacement of casein by soy protein for effects on gallstone formation. Feeding soy protein consistently resulted in a significantly reduced incidence of gallstones. Switching to a soy-based diet after induction of gallstones resulted in dissolution of a significant percentage of the stones. Partial substitution of soy for casein gave results intermediate between 100% casein and 100% soy. The lysine/arginine ratio of the proteins may be responsible for the observed differences in cholelithiasis. The reduction in lithogenicity associated with feeding soy protein appears to be mediated primarily through decreased secretion of cholesterol into bile.     

Effect of the quality and quantity of dietary proteins on vitamin A depletion rate, and biological availability of vitamin A precursors

The effect of quantity and quality of protein from cereal and legume sources on the rate of vitamin A depletion was evaluated through changes in retinol serum levels and liver stores in male and female Wistar strain rats. A total of 64 animals were distributed into four groups and fed ad libitum with diets adequate in all nutrients, except vitamin A. The protein in the diets was derived from 91% common maize (Diet A); 91% Opaque-2 maize (Diet B), 64% common maize plus 27% precooked common black bean flour (Diet C), and 64% Opaque-2 maize with 27% bean flour (Diet D). The total depletion period lasted 60 days and four rats per group were sacrificed at 15, 30 and 60 days. A total of 4 animals were sacrificed at 0 day to count with a basal serum and hepatic retinol concentration value. The 16 depleted remaining rats were used for the carotene bioavailability study with dehydrated carrots. During the first 15 days the greater rate of depletion was observed in animals fed the highest protein quality diet made from Opaque-2 maize and beans (Diet D), which also caused the greatest weight increase. The least depletion rate and lowest weight gain was obtained with the common corn diet (Diet A). Diets B and C caused intermediate depletion rates, with Diet B (Opaque-2 maize) being more effective than Diet C in spite of its lower protein content. At the end of 60 days all groups presented depletion levels not statistically different. Thus, these results confirm that protein quantity and quality from basic staple foods influence mobilization of retinol liver reserves. The 16 remaining depleted rats were then divided into four groups and fed a standard 14% casein diet to which 25, 50 and 75% of the retinol requirements was added to obtain a reference standard biological response. The fourth group was fed with an amount of dehydrated and ground carrot containing 67.1 mg % of total carotenoids. After seven days, serum and hepatic retinol were obtained, from which a regression equation of liver retinol to diet retinol was calculated (microgram % liver retinol per 100 g of rat) = 2.47 + 0.063 (microgram retinol/g diet) (r = 0.585). From this equation the bioavailability of carrot carotenoids was established with a value of 21.8% comparable to the FAO/WHO value previously reported.     

Nutritional effects of mustard seed protein detoxified with aqueous isopropanol in young rats

The effect of removing anti‐nutritional factors from n‐hexane‐extracted mustard meal using 80% isopropanol (to reduce thioglucosides, phenolics, etc.) on growth, food efficiency ratio, serum and liver lipid profiles and protein content of young rats was examined. For this n‐hexane‐extracted mustard meal was extracted with 80% isopropanol giving a fraction with 68% protein and low residual thioglucoside (0.5%) as well as phenolic (0.3%) content. This isopropanol‐extracted mustard seed protein fraction reduced the growth of young rats slightly when compared with casein. The food efficiency ratio between rats fed isopropanol‐extracted mustard seed protein or casein did not differ, nor did the protein composition affect serum total cholesterol, triglyceride, HDL‐cholesterol, LDL‐cholesterol, VLDL‐cholesterol and LDL‐C/HDL‐C ratio. However, rats fed isopropanol‐extracted mustard seed protein showed a significantly lower (p<0.05) liver cholesterol concentration than rats fed casein. Liver triglyceride and phospholipid concentrations did not differ between rats fed the two proteins, nor was serum protein affected. This study indicates that extraction of hexane‐extracted mustard meal with 80% isopropanol reduced a number of anti‐nutritional factors like thioglucoside and phenolics. Furthermore the nutritional quality of mustard seed protein fraction is comparable to casein in respect to growth, food efficiency ratio, serum lipid and protein concentrations and organ weights.     

Interaction between dietary protein and fat in triglyceride metabolism in the rat: Effects of soy protein and menhaden oil

The objective of the present study was to determine the mechanisms by which dietary proteins interact with dietary lipids in the regulation of triglyceridemia in rats. Male Sprague-Dawley rats (n=56) were subjected to 28-d experimental diets containing different combinations of proteins (20% w/w) and lipid sources (14% w/w): (i) casein-menhaden oil, (ii) casein-beef tallow, (iii) soy protein-menhaden oil, and (iv) soy protein-beef tallow. Significant protein-lipid interactions were observed on triglyceridemia and hepatic cholesterol in fasted rats. The combination of casein and beef tallow was associated with high plasma TG and hepatic cholesterol concentrations, which were reduced by substitution either of soy for casein or of menhaden oil for beef tallow. Therefore, triglyceridemia and liver cholesterol remained low with soy protein feeding, independently of the lipid source, as well as with menhaden oil feeding, regardless of the protein source. The menhaden oil diets reduced plasma cholesterol, hepatic TG, and TG secretion compared with beef tallow diets independently of the dietary protein source. Modifying the source of dietary proteins and lipids had no effect on post-heparin plasma lipoprotein lipase activity. These results demonstrate that soy protein can lower rat triglyceridemia relative to casein when associated with beef tallow consumption, whereas menhaden oil can attenuate hypertriglyceridemia when rats are fed casein. The data further suggest that part of the hypotriglyceridemic effect of soy protein in the rat may be mediated by reduced hepatic lipid synthesis, as is the case for menhaden oil.     

Effects of various dietary animal and vegetable proteins on serum and biliary lipids and on gallstone formation in the hamster

The objective of this study was to determine the effects of various dietary animal (casein, bovine albumin and egg albumin) and vegetable (soy, cottonseed and peanut) proteins on serum and biliary constitutents and gallstone formation in the hamster. Eighty-four hamsters (60±5g) were assigned to either a control group (Purina rat chow) or to one of the 6 experimental groups. Experimental diets contained 20.0% protein. With the exception of hamsters fed egg albumin, gallstone incidence was greater among hamsters fed animal proteins. Hamsters fed egg albumin exhibited a lower concentration of total serum cholesterol and HDL-cholesterol than most of the other experimental groups. There were no significant differences between experimental groups for either HDL₃-cholesterol concentration or VLDL-LDL-cholesterol concentration. Bile acid concentrations within the vegetable protein-fed groups were significantly higher than within the animal protein-fed groups. Casein- and bovine albumin-fed hamsters showed a significantly higher percentage of biliary cholesterol in the bile fluid. As the percentage of biliary cholesterol increased, the percentage of bile acids was found to decrease. Preliminary reports of portions of this work were presented at the 74th Annual Meeting of the American Oil Chemist’s Society in May 1983 in Chicago.     

Effects of feeding formaldehyde treated,full fat soybean flours on milk fat polyunsaturated fatty acids

Raw, commercial, and extrusion cooked full fat soy flours were treated with formaldehyde and then fed to dairy cows. This treatment protected the polyunsaturated fats of the soy from hydrogenation by microbial action in the cow’s rumen. With all of these materials, higher than usual amounts of polyunsaturated fats were incorporated into the milk. In a screening test limited to one cow, an advantage as measured by milk yield, fat yield, protein, solids-not-fat, and increased milk fat C18:2 was seen for the formaldehyde treated, full fat soy flour. The percentage of linoleic acid more than doubled in the milk fat of cows receiving the protected products. Only very slight quantities of formaldehyde (0.1–0.2 ppm) were found in the milk. The efficiency of transfer of the C18:2 from the feed to milk was ca. 37%. This represented a marked improvement over previous trials in which we fed expensive safflower oil-casein-formaldehyde supplements.