Pea Protein Concentrate Research Articles

DIGESTIBILITY OF PEA PROTEINS BY PRE-RUMINANT CALVES

Two milk replacers, formulated to provide one-half the dietary protein from either pea protein concentrate (PPC) or pea protein isolate (PPI), were compared with a milk replacer based on reconstituted skim milk (SM). The milk replacers were fed to pre-ruminant Holstein-Friesian calves aged 3–23 days and dry matter and protein digestibilities were determined. The mean protein digestibilities of the SM (control) and PPI milk replacer were 84.0 and 75.4%, respectively (the difference was not statistically significant), and were greatly superior to that of the PPC milk replacer (47.5%). The PPC contained, on dry matter basis, 61.2% protein, 5.5% starch and 9.8% total sugars. The sugars detected were sucrose (3.7%), raffinose (1.5%), stachyose (3.3%) and verbascose (2.5%). The PPI contained 92.8% protein and less than 1.0% starch or total sugars; the only sugar detected was sucrose (0.7%). Lactose was the only sugar present in SM. Although other factors cannot be ruled out, it was concluded that starch and oligosaccharides were mainly responsible for the poor digestibility of the pea proteins in the PPC milk replacer.

Storage Stability Studies on Pea Flour, Protein Concentrate and Starch

Flour (PF), protein concentrate (PPC) and starch (PS) from field peas (Pisum sativum) were examined for changes during a one year storage period at four moisture levels ranging from 3.8 to 13.6% and temperatures of 7, 21 and 30°C. The standard plate, coliform, yeast and mold and psychrotroph counts usually decreased to less than 10,000/g during the storage period. Odor and flavor changes under the most unfavorable storage conditions were probably largely due to lipid changes. Color variations during storage appeared to be caused by enzymatic or non-enzymatic browning near the surface of the glass storage containers.

The Supplementation of Pea Protein Concentrate with DL-Methionine or Methionine Hydroxy Analog

A series of three experiments was conducted with weanling male rats to study the effect on growth of supplementing a protein concentrate obtained from field peas (Pisum sativum) with DL-methionine or methionine hydroxy analog (MHA) before or after processing of the concentrate. Protein efficiency ratio (PER) was greater (P<0.05) when pea protein concentrate (PPC) was supplemented with 1.0% than with 0.5% methionine. Supplementing PPC with 1.0% methionine or an equivalent amount of MHA gave PER values that were higher (P<0.05) than PER for the unsupplemented protein, but not significantly different from each other. Neither form of supplement was adversely affected by processing of the PPC. It was concluded from these rat growth trials that MHA could be used effectively to supplement the supply of sulfur amino acids in PPC. The ability of PPC to meet rat and human essential amino acid requirements is considered.

EFFECTS OF VARIOUS HEAT AND pH TREATMENTS ON DIGESTIBILITY OF PROTEIN IN PEA PROTEIN CONCENTRATE (PISUM SATIVUM)

Pea protein concentrate (PPC) was subjected to various cooking and acid or alkali treatments in order to improve the digestibility of pea protein for use in calf milk replacers. Treatment effects were assessed by in vitro digestion with rennin, pepsin and calf abomasal fluids. Oven heating at 95–246 C for 5 min to 15 h or steam heating at 1.06 kg/cm2 for 4 h failed to improve digestibility. Treatment of PPC in an aqueous medium at pH values from 2 to 12 for 5 h at 37 C resulted in higher digestibility. A pH of 2.0 or 10.6 was most effective. Acid or alkali hydrolysis of PPC at 110 C for 4–5 h increased digestibility, but adversely affected amino acid content. Rennin was consistently less effective than pepsin or abomasal contents in digesting PPC. The pH of abomasal contents from young calves fed milk replacers may be too high for effective pepsin activity. These factors could account for the low digestibility of non-milk proteins by calves under 2 wk of age.

PROTEIN LEVELS IN DEVELOPING AND MATURE PEA SEEDS

Nine cultivars of peas (Pisum sativum L.) were grown in 1971 and 1972 to study the changes in percent crude protein levels during maturation. Percent protein was found to vary with years, cultivars, and stages of maturity. The year × cultivar, year × maturity, and cultivar × maturity interactions were also important. On a dry weight basis, pea protein concentration as determined by the Kjeldahl method showed a decrease with increasing pea seed maturity through the canning stage. The correlation coefficient between the Kjeldahl and Udy dye-binding methods of protein determination was 0.86 at the mature seed stage, and negligible at the canning stage. There was a highly significant correlation (r = 0.91) between protein concentration at the canning and mature stages of seeds (Kjeldahl method). The correlation coefficient between protein values obtained by the dye-binding method of Ashworth et al. and the Kjeldahl method was lower than between the Kjeldahl and Udy methods.

DIGESTIBILITY OF PEA PROTEIN CONCENTRATE AND ENZYME-TREATED PEA FLOUR IN MILK REPLACERS FOR CALVES

In an experiment involving enzymatically hydrolyzed pea flour (HPF) and pea protein concentrate (PPC) to provide half the dietary protein in milk replacers, the pea protein was found to be about 25% digestible by calves under 2 wk of age and 65 to 70% digestible by calves 3 wk of age. The younger calves digested 42 to 53% of the pea starch; older calves digested 63 to 84%. The digestibility of dry matter, protein, energy and ether extract increased with calf age (P &lt; 0.01). In the second trial, involving PPC at 7.7, 15.4 and 23.1% of the dry matter in milk replacers, and providing 19, 33 and 46% of the dietary protein, the digestibility coefficients for dry matter, disregarding calf age, declined from 90 to 86% as PPC increased from 15.4 to 23.1%, but the low and intermediate PPC diets were equally well digested. The reduction was due mainly to the corresponding reduction in protein digestibility. Digestibility coefficients for dry matter, protein, energy, ether extract and nitrogen-free extract for milk replacer diets containing 23.1% PPC exceeded 81% with calves over 14 days old. The third experiment involved feeding the control milk replacer until the calves were 2 wk old, then commencing the feeding of PPC and HPF replacers, using formulas similar to those of the first experiment. The digestibility coefficients were similar to those of the first experiment, indicating that the observed improvement in older calves was primarily a function of calf age and not markedly influenced by the formula of the diet. These studies indicate that PPC and HPF are not satisfactory ingredients in milk replacers to be fed to calves under 2 wk of age, but, though less digestible than milk, are effectively digested thereafter.

STUDIES WITH MICE ON THE NUTRITIONAL VALUE OF PEA PROTEIN CONCENTRATE

A protein concentrate containing 60% protein was obtained from field peas (Pisum sativum) by stirring pulverized peas in dilute aqueous CaO solution at pH 9.3 and room temperature for 15 min, followed by centrifuging off the starch and drum drying the protein-rich supernatant fraction. Feeding experiments with mice showed that the protein and energy yielding fractions of pea protein concentrate (PPC) were less digestible than those of egg, fish protein concentrate (FPC) or casein. The digestion coefficients for energy in PPC, egg, FPC and casein were 80, 89, 89 and 90%, and for protein were 88, 91, 91, and 93%, respectively. Biological value of PPC protein was markedly inferior to the other proteins because of methionine deficiency, when the test protein constituted the only dietary source of protein. Supplementation with methionine in PPC diets containing 15% protein produced growth rates and biological values equal to those with egg, FPC, or methionine-supplemented casein.