Peanut flour

Nut Products. Peanut products iaclude peanut flour, Hpoproteia, proteia, milk, and partially defatted peanuts (109). Pecan butter is made from dry roasted meats, ground to a very fine state, and mixed with salt (2% of final weight), hydrogenated fat (1.5%), and the antioxidant butylated hydroxyanisole (BHA) (131). 

The edible oilseed protein industry is comparatively small and is restricted to peanut and soybean proteins. One company manufactures partially defatted peanut flours made by hydraulic pressing. The products contain 40—42% protein. Production estimates for edible soybean proteins in the United States in 1993—1994 (56) and wholesale prices as of November 1995 are given in Table 15. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

Commercial peanut flours were also evaluated for their performance in preparation of peanut chips (2). The following processing treatments were employed ... 

Gel electrophoretic patterns of water-soluble proteins in the five peanut flours were determined as previously described (2) and show considerable differences in protein character (Figure 2). In... 

Figure 1. Peanut flours and chips prepared from the flours. Reproduced with permission from Ref. 2. Copyright 1980, Institute of Food Technologists.

The protein content of cookies was markedly influenced by the addition and protein content of the various legume flours (Figure 4). Each increment of peanut flour raised the total protein content in cookies by 1.5%. Increases of 1.4% occurred with soy flour and 0.5% with cowpea flour. 

Follow-up studies utilized finely-milled legume flours and the addition of soybean flour as a fat-control agent in an effort to improve doughnut quality (5). The legume products and doughnuts prepared from them are shown in Figure 5. On a dry weight basis, peanut flour from solvent extracted peanuts (PF-SE) contained 0.9% fat and 54.4% protein while cowpea flour (CF) contained 1.4% fat and 25.5% protein. Peanut flour from partially defatted untoasted peanuts (PF-PD-U) contained 34.5% fat and 34.9% protein while peanut flour from partially defatted peanuts toasted at 160°C contained 34.4% fat and 37.6% protein. 

Figure 5. Representative doughnuts prepared from peanut flour-solvent extracted (PF-SE), peanut flour-partially defatted-untoasted (PF-PD-U), peanut flour-partially defatted-toasted (PF-PD-T), and cowpea flour (CF). WFR = wheat flour reference,...

Defatted flours are especially attractive as protein sources, since 10-12% substitution of wheat flour with 50% protein flour will raise total protein content of typical wheat breads by approximately 50%, and 25% substitution will almost double the protein content of cookies. Preparation of protein-enriched breads has been reported in the literature using soy flours and protein concentrates (25), peanut flours and peanut protein concentrates C26, 27), glandless cottonseed flours, concentrates and isolates (28), sunflower seed flours and seed protein concentrates (27) and sesame flours and protein concentrates (26). 

Some legumes, including raw soy or peanut flour are known to contain certain antinutritional factors such as proteinase inhibitors and hemagglutinins or lectins (21,22). These factors can be inactivated, for the most part, by moist heat, during processing. Interestingly, peanut flour contained more trypsin inhibitor and lectin than did soy flour (22). 

Sunflower and soy flours were obtained from the Food Protein R D Center, Texas A M University, College Station, Tex. alfalfa leaf protein from the Western Regional Research Center, U.S. Department of Agriculture, Berkeley, Calif. and peanut flour from Gold Kist, Inc., Lithonia, Ga. 

The best method for evaluation of the color problem is to prepare a food product containing the protein flour. Biscuits were routinely used as the model food system. Figure 5 illustrates the color of biscuits prepared with lOOZ wheat flour and with 20Z plant-protein products. The color of the biscuits prepared with soybean and peanut flours shows that these ingredients do not cause a serious color problem. However, sunflower, alfalfa leaf, and cottonseed flours do produce a discoloration in this model food system. The L and b values generally reflect this visual evaluation. 

Other Protein Components. Other protein components In complex food systems and In protein Ingredient preparations may Interfere with or modify gelation reactions. Protein Interaction between whey protein and casein upon heating has a profound Influence on the characteristics of the casein gel structure In cheesemaking. Similarly protein Interactions are Important to meat structures. Protein-protein Interaction between soy and meat proteins has also been demonstrated with heat treatment (28). While concrete Interaction data have not been collected on protein gels formed from protein combinations, gelation properties of whey proteln/peanut flour blends have been Investigated GU) ... 

Peanut Seed. Ramanatham et al. (21) studied the influence of such variables as protein concentration, particle size, speed of mixing, pH, and presence of sodium chloride on emulsification properties of peanut flour (50% protein) and peanut protein isolate (90% protein). Emulsions were prepared by the blender... 

Data in Table I show that emulsion capacity of peanut flour decreased with increasing flour or protein concentration while emulsion viscosity increased. This phenomenon was also demonstrated by McWatters and Holmes (2D. A decrease in flour particle size increased emulsion capacity and viscosity appreciably. Increasing the rate of mixing, however, decreased emulsion capacity but increased viscosity. Increased speeds produce greater shear rate, which decreases the size of the oil droplet thus, there is an increase in the surface area of the oil to be emulsified by the same amount of soluble protein (23, 24). 

Beuchat et al. (24) also examined the nitrogen solubility profiles for enzymatically hydrolyzed and control peanut flour samples in 0.03M Ca2+ (as CaCl2). Solubilities of controls between pH 2.0 and 5.0 in 0.034 Ca solutions were similar to those noted for water however, very little increase in nitrogen solubility of controls was noted in the pH 5.0 tc 11.0 range. 

A concentration of 0.03M Ca2+ has been prescribed as a minimum in the formulation of imitation milk. Evidence from the study reported by Beuchat et al. (24) suggests that enzymatic hydrolysis of peanut flour modifies protein to the extent that it is highly soluble in 0.03M Ca2+ at a pH range normally associated with fluid milk. Further studies are required to assess the effect of enzyme-induced proteolysis on organoleptic properties of hydrolyzed peanut protein solutions. 

Changes in soluble proteins of peanut flour caused by proteolytic enzyme digestion as detected by gel electrophoresis... 

Sekul et al. (29) studied the nitrogen solubility properties of enzyme-hydrolyzed peanut proteins. A deionized water dispersion of peanut flour (1 10, w/v) was treated with papain (0.5% total volume) at 45OC for 15 min. Solubility was tested over a range of pH 1 to 9. In general, papain treatment improved solubility at all levels examined except pH 2 and 8 (Figure 6). 

The effects of fungal fermentation on the moisture adsorption and retention properties of defatted peanut flour have been reported (28). At 8 and 21OC, little difference was noted between the moisture contents of freeze-dried ferments and untreated samples equilibrated at relative humidities ranging from 14 to 75%. However, marked changes were noted above 75% equilibrium relative humidity (ERH), where the control samples did not adsorb as much moisture as did the ferments. These differences were attributed to an increased ratio of exposed hydrophilic to hydrophobic groups resulting from fermentation. 

Beuchat (60) investigated the performance of enzyme-hydrolyzed defatted peanut flour in a cookie formula. Flour slurries were treated with pepsin at pH 2.0, bromelain at pH 4.5, and trypsin at pH 7.6. After readjustment to pH 6.9, materials were freeze-dried, pulverized (60-mesh), and then substituted for wheat flour at 5, 15, and 25%. Adjustment of peanut flour to pH 2.0, as well as treatment with pepsin at this pH, greatly improved the handling characteristics of dough in which these flours were incorporated. Use of peanut flours treated at pH 4.5, with or without bromelain, and at pH 7.6, with or without trypsin, improved handling properties of cookie dough. These doughs did not tend to crumble... 

Enzyme hydrolysis of peanut flour also altered the physical characteristics of baked cookies (60). With the exception of the bromelain hydrolysate, the use of peanut flour in cookies resulted in increased specific volume when compared to the 100% wheat flour control. Untreated peanut flour substitution reduced the diameter and increased the height of cookies however, treatment with proteolytic enzymes reversed the behavior. As evidenced by substantial increases in spread ratios, the diameter of cookies containing treated flours increased proportionately more than did the height. These data promote the feasibility of decreasing or increasing the spread of cookies through the addition of various amounts of untreated or enzyme-treated peanut flour. 

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