Allergenicity, trypsin inhibitor activity and nutritive quality of enzymatically modified soy proteins

Two ultrafiltered soy flour protein fractions were evaluated; the first was obtained by hydrolysis (0.5-3 kDa, F(0.5-3)), and the second was an enzymatically methionine-enriched fraction (1-10 kDa, F(1-10)E). Amino acid profiles, protein quality, allergenicity (against soy-sensitive infant sera) and trypsin inhibitor activity were determined. Fraction F(1-10)E fulfilled amino acid requirements for infants, whereas the F(0.5-3) fraction was methionine deficient. Both fractions were similar in net protein utilization, and F(1-10)E digestibility was comparable with casein and higher (P?相似文献   

Free amino acid content in standard infant formulas: comparison with human milk

OBJECTIVE: To compare the concentration of non-protein nitrogen (NPN) and free amino acids (FAA) in powdered and liquid commercial formulas with that in human milk. METHODS: The non-protein nitrogen and FAAs in pooled breast milk was compared with that in 11 protein-modified starting infant formulas (seven powdered, four liquid whey-predominant formulas) and one powdered soy-formula. Human milk was collected at the end of each feeding (hindmilk) over 24 hours in a group of 40 healthy lactating women after delivery of full-term infants at age one month. RESULTS: In human milk glutamic acid plus glutamine and taurine were the prevalent amino acids, accounting for around 50% total FAA. In the analysed formulas the total FAA fraction was 10% or even less than in human milk, mostly represented by taurine, while methionine was high in soy formula. The sum of glutamic acid and glutamine in all the formulas was much lower than in human milk. CONCLUSIONS: Breastfed infants are supplied with FAA, mainly glutamic acid and glutamine, compared to formula-fed counterparts. The different FAA intake might be the origin of some functional differences at the enteral level between breast- and formula-fed infants.     

Allergenicity,trypsin inhibitor activity and nutritive quality of enzymatically modified soy proteins

Two ultrafiltered soy flour protein fractions were evaluated; the first was obtained by hydrolysis (0.5–3 kDa, F_0.5–3), and the second was an enzymatically methionine-enriched fraction (1–10 kDa, F_1–10E). Amino acid profiles, protein quality, allergenicity (against soy-sensitive infant sera) and trypsin inhibitor activity were determined. Fraction F_1–10E fulfilled amino acid requirements for infants, whereas the F_0.5–3 fraction was methionine deficient. Both fractions were similar in net protein utilization, and F_1–10E digestibility was comparable with casein and higher (P?<?0.05) than F_0.5–3 or soy isolate. Allergenicity of SF was reduced to 21.5% with the hydrolysis in F_1–10E and it was not detected in F_0.5–3. Residual trypsin inhibitor activity with respect to soy flour was 8.1%, 3.3% and 1% for hydrolysate, F_1–10E and F_0.5–3, respectively. Both fractions presented high nutritive quality and reduced or null allergenicity. The trypsin inhibitor activity decreased along processing and could be a useful indicator for production of hypoallergenic proteins.     

Methionine fortification of a soy protein formula fed to infants

Data from study of nine normal full-term infants fed a soy isolate-based formula unsupplemented with methionine were compared with similar data from study of 10 similar infants fed the same formula supplemented with L-methionine and with data from previous studies of larger groups of infants receiving various other feedings. Food intake, growth, and serum chemical values were studied from 8 through 111 days of age. In addition, nitrogen balance studies were carried out. Statistically significant differences were as follows: lesser weight gain per 100 kcal by infants fed the unsupplemented soy isolate-based formula than by infants fed milk-based or other soy isolate-based formulas; lesser serum concentrations of albumin at age 28 days by infants fed the unsupplemented soy isolate-based formula than by breast-fed infants; greater serum concentrations of urea nitrogen by infants receiving the unsupplemented soy isolate-based formula than by those receiving the same formula supplemented with L-methionine. A number of other differences was noted but were not statistically significant. The results suggest that normal infants fed a formula providing 2.25 /100 kcal of a soy protein isolate not fortified with methionine performed less well during the first 6 weeks of life than did breast-fed infants and infants fed milk-based formulas or other soy isolate-based formulas fortified with methionine. The limiting nutrient appears to have been methionine.     

Free Amino Acid Content in Standard Infant Formulas: Comparison with Human Milk

Objective: To compare the concentration of non-protein nitrogen (NPN) and free amino acids (FAA) in powdered and liquid commercial formulas with that in human milk.

Methods: The non-protein nitrogen and FAAs in pooled breast milk was compared with that in 11 protein-modified starting infant formulas (seven powdered, four liquid whey-predominant formulas) and one powdered soy-formula. Human milk was collected at the end of each feeding (hindmilk) over 24 hours in a group of 40 healthy lactating women after delivery of full-term infants at age one month.

Results: In human milk glutamic acid plus glutamine and taurine were the prevalent amino acids, accounting for around 50% total FAA. In the analysed formulas the total FAA fraction was 10% or even less than in human milk, mostly represented by taurine, while methionine was high in soy formula. The sum of glutamic acid and glutamine in all the formulas was much lower than in human milk.

Conclusions: Breastfed infants are supplied with FAA, mainly glutamic acid and glutamine, compared to formula-fed counterparts. The different FAA intake might be the origin of some functional differences at the enteral level between breast- and formula-fed infants.     

Formulation, nutritive value and sensory evaluation of a new weaning food based on sweet corn (Nutrimaiz) dehydrated pulp

The objective of the present work was to develop a formulation for complementary infant and child feeding employing linear programing as a mathematical model for optimization. High lysine/high tryptophan sweet corn pulp in the dehydrated form was used as the main ingredient. The restrictions imposed on the model were nutrient requirements, adequate protein/energy ratio and minimum cost. The formula derived by the computer (FC) matched the amino acid requirements, the protein/energy ratio (NDPCal%) and was rated high in laboratory tests in terms of sensory qualities. The cost determined for this formula was competitive in relation to commercial products used for the same purpose. Formula A, which contained 5% more sweet corn pulp and 10% less whole powdered milk, did not differ in nutritional, sensorial and functional properties from the formula FC and was chosen for the field acceptability trial because of its lower cost. Formula A had protein efficiency ratio and Biological Value similar to casein for the rat but protein digestibility and net protein utilization were statistically lower (p less than 0.05) for formula A than for casein. Acceptability tested on children who were 8-18 months of age ranged from 80-90%, average value 87%.     

Differences in protein digestibility and quality of liquid concentrate and powder forms of milk-based infant formulas fed to rats

Protein and amino acid digestibility and protein quality of liquid concentrate and/or powder forms of infant formulas were studied by rat balance and growth methods. Casein plus methionine (control) and eight formulas were fed to weanling rats as the sole source of protein in diets containing 8% protein (nitrogen X 6.25). Values for true digestibility of protein, lysine, methionine, or cystine (85-92%) in liquid concentrates were up to 13% lower than those in powders. Similarly, the 2-wk relative protein-efficiency ratio values (64-85%) or the relative net protein ratio values (78-94%) of liquid concentrates were up to 25% lower than those for powders. Lower levels of bioavailable lysine and methionine plus cystine in liquid concentrates compared with powders (prepared by the same manufacturer) would suggest that inferior protein quality of liquid concentrates may be due to more heat treatment involved in their preparation.     

Nutritional benefits of soy protein and soy fiber.

Soy protein and soy fiber are common ingredients in many foodstuffs. Various kinds of soy protein, including soy flour, soy-protein concentrate, and isolated soy protein, are currently used in human foods. Soy proteins are used in infant formulas and enteral nutrition products, as ingredients in meat products, and as protein supplements. Although it is a plant protein, the protein quality of soy protein is excellent. Soy fiber is used in enteral nutrition products and some bakery goods. Research shows that soy fiber provides the important health benefits usually associated with dietary fiber, including improved laxation and cholesterol-lowering ability. This review provides background information on soy protein and soy fiber and their use in human foods.     

Effect of reducing the phytate content and of partially hydrolyzing the protein in soy formula on zinc and copper absorption and status in infant rhesus monkeys and rat pups

BACKGROUND: Although soy formulas have been designed to meet the nutrient requirements of human infants, they also contain phytate, which may negatively affect trace element absorption. OBJECTIVE: We evaluated the effect of removing phytate on zinc and copper absorption and status in infant rhesus monkeys and suckling rat pups and evaluated differences between intact and partially hydrolyzed soy protein. DESIGN: In monkeys, regular and low-phytate soy formulas were fed exclusively for 4 mo and whole-body absorption and retention of 65Zn, 67Cu, 59Fe, 54Mn, and 47Ca were determined at different time points with a whole-body counter. Subsequently, zinc and copper absorption from several human infant formulas and the effect of phytate concentration were evaluated in suckling rat pups by using 65Zn and 64Cu. Finally, infant rhesus monkeys were fed low-phytate formulas with intact or hydrolyzed soy protein for 4 mo and plasma zinc and copper were measured monthly. RESULTS: In the first monkey study, zinc absorption at 1 mo was higher from low-phytate soy formula (36%) than from regular soy formula (22%), whereas there was no significant difference between groups in the absorption of other minerals. Plasma copper was significantly lower in monkeys fed low-phytate soy formula from 2 to 4 mo. In rat pups, zinc absorption was significantly higher from low-phytate soy formula (78%) than from regular soy formula (51%) and hydrolysis of the protein had no significant effect. Phytate content or protein hydrolysis did not significantly affect copper absorption. In the second monkey study, plasma copper concentrations were highest in monkeys fed the low-phytate, hydrolyzed-protein soy formula. CONCLUSION: Reducing the phytate content and partially hydrolyzing the protein in soy formula had a beneficial effect on zinc and copper absorption and status in infant rhesus monkeys.     

Noncoagulating Enteral Formula Can Empty Faster From the Stomach

Background: The gastric accumulation of enteral formulas in tube‐fed patients leads to an increased risk of vomiting and regurgitation. Gastric secretion–induced coagulation of proteins in enteral formulas might lead to gastric accumulation of solid protein particles that further increase the risk of upper digestive intolerance. This study used magnetic resonance imaging to noninvasively assess the half‐emptying time (t₅₀) of enteral formulas differing in protein composition. Methods: Three isocaloric (450 kcal) and isovolumetric (300 mL) enteral formulas, 1 with a noncoagulating P4 protein blend and 2 with coagulating casein‐dominant protein blends, were compared in a double‐blind, randomized, 3‐way crossover study in 21 healthy volunteers. Gastric content emptying curves were fitted with the LinExp model to compute t₅₀ and the parameter κ with κ > 1 reflecting the accumulation of gastric secretion. t₅₀ and κ were compared between all 3 enteral formulas. The formula that emptied fastest was identified by an ordinal mixed model using the ranks of t₅₀. Results: As indicated by values for κ > 1, all enteral formulas induced gastric secretion. No differences were detected for t₅₀. However, the noncoagulating formula emptied fastest in 74% of all participants (P = .004). Conclusion: This study demonstrates that a noncoagulating enteral formula can empty faster from the stomach compared with coagulating formulas in a large cohort of healthy volunteers. Investigations on the efficiency of the noncoagulating P4 protein blend in patients requiring tube feeding will further elucidate its potential for reducing upper digestive intolerance during enteral nutrition. Trial NTR2979.     

Soy protein in relation to human protein and amino acid nutrition

The nutritional value of processed soy protein (isolated soy proteins and soy-protein concentrates) in human protein and amino acid nutrition is evaluated on the basis of a review of studies of growth and nitrogen balance in infants, children, adolescents, and adults. Findings show that well-processed soy-protein isolates and soy-protein concentrates can serve as the major, or even sole, source of protein intake and that their protein value is essentially equivalent to that of food proteins of animal origin. The importance of the sulfur amino acid content of soy protein for practical human nutrition is also examined from nitrogen-balance data. Under conditions of an anticipated normal usage of soy protein, methionine supplementation is not only unnecessary but may even be undesirable for young children and adults. However, for newborns, the data suggest that modest supplementation of soy-based formulas with methionine may be beneficial. Soy proteins have also been found to be of good quality to include in hypocaloric diets for weight reduction in obese subjects. Finally, the data indicate that soy proteins are well-tolerated and of good acceptability.     

Effect of pulsed electric field on the rheological and colour properties of soy milk

The effects of pulsed electric field (PEF) treatments on rheological and colour properties of soy milk were evaluated. Flow behaviour, viscosity and rheological parameters of PEF-treated soy milk were monitored using a controlled stress rheometer. For PEF treatments, electric field intensity of 18, 20 and 22 kV cm(-1) and number of pulses of 25, 50, 75 and 100 were used. For the measurements of rheological properties of soy milk shear rates between 0 and 200 s(-1) was used. The rheological behaviour of control and the PEF-treated soy milk were described using a power law model. The PEF treatments affected the rheological properties of soy milk. Apparent viscosity of soy milk increased from 6.62 to 7.46 (10(-3) Pa s) with increase in electric field intensity from 18 to 22 kV cm(-1) and increase in the number of pulses from 0 to 100. The consistency index (K) of soy milk also changed with PEF treatments. Lightness (L*), red/greenness (a*) and yellowness/blueness (b*) of soy milk were affected by PEF treatments.     

A double-blind clinical trial comparing the gastrointestinal side effects of two enteral feeding formulas

Adequate enteral nutritional support is often limited by gastrointestinal (GI) side effects. In this pilot clinical trial we compared an enteral nutrition formula based on soy hydrolysate (study formula, SF) against a widely used intact casein formula (control formula, CF) for the incidence of GI side effects in a completely randomized double blind design. Twenty-three nonsurgical hospitalized patients requiring enteral nutritional support and free of GI symptoms were randomly assigned to receive either the CF or the SF for 6 days continuously. Both formulas were isotonic, low in residue, lactose free and isocaloric, but differed in the type and concentration of protein and the concentration of medium-chain triglycerides. After randomization both groups were comparable in demographic characteristics, and nutritional status, but there were more patients on antibiotics in the CF group. The amount of formula infused per day and the route of administration were equivalent. The number of bowel movements per day was 1.0 +/- 0.5 for the CF group and 0.6 +/- 0.3 for the SF group (p less than 0.05). The incidence of diarrhea was 10.8% days for the CF group and 6.2% for the SF group (p = NS). High gastric residuals occurred in 16.9% of days in the CF group and 3.3% in the SF group (p less than 0.05). Vomiting incidence was 10.8% in the CF group and 1.5% in the SF group (p less than 0.05). After adjustment for the use of antibiotics as a covariate, the differences in number of bowel movements, vomiting and incidence of high residuals became less significant (p less than 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of the fiber content of enteral feedings.

The importance of dietary fiber in maintaining optimum bowel function has been shown in feeding studies, and many enteral formulas now contain dietary fiber, usually as soy polysaccharide (SP). Generally only total dietary fiber (TDF) values are given on the label or in product literature, with no indication of insoluble dietary fiber (IDF) and soluble dietary fiber (SDF) content. Often product literature highlights the amount of SP contained in the formula, not the TDF. The method used to determine TDF content usually is not specified, making it impossible to compare products on a TDF basis. We compared the dietary fiber content of commercially available enteral formulas objectively to help clinicians make informed choices when selecting fiber-containing formulas. Fiber-containing formulas by suppliers were freeze-dried and total, water-soluble, and water-insoluble dietary fiber measured by the Association of Official Analytical Chemists (AOAC) approved method. TDF per 1000 mL ranged from 4.0 to 9.9 g for blenderized formulas and from 7.2 to 20.3 g in formulas containing SP. IDF values per 1000 mL ranged from 2.0 to 5.4 g for blenderized product, and the soy formulas ranged from 5.5 to 16.9 g. SDF values per 1000 mL ranged from 2.0 to 4.5 g in blenderized products, and in soy formulas SDF ranged from 1.7 to 3.8 g. Differences in physiological effects of fiber-containing enteral formulas may be because of differences in fiber composition.     

Effect of enteral diets on whole body and gut growth in unstressed rats

The composition of enteral feeding formulas may have different effects on total body and gut growth. We studied the growth effects in rats of a complex solid fiber-based diet (Prolab Rodent Diet) with that of three isocaloric and isonitrogenous commercially available liquid feeding formulas which differ in their type of protein (Osmolite HN, an intact protein formula; Reabilan HN, a peptide formula; and Vivonex-TEN, an amino acid formula). Total body weight gain was greatest with the rodent diet (93 +/- 2 g/10 days), followed by the peptide diet (72 +/- 5 g/10 days) and intact protein diet (58 +/- 8 g/10 days). Weight gain was significantly lower on the amino acid diet (43 +/- 7 g/10 days). Proximal and mid gut mass was comparable with all four diets, but distal gut mass was significantly lower with the amino acid diet. Somatomedin C levels on the rodent diet (13.3 +/- 1.8 nM), and the peptide diet (14.0 +/- 3.3 nM) were significantly higher than somatomedin C levels on the amino acid diet (8.0 +/- 1.0 nM). Somatomedin C levels on the intact protein diet (9.6 +/- 1.4 nM) were intermediate between the rodent diet and amino acid diet. We conclude that growth effects vary with different enteral diets (unrelated to total calories and protein) and may result from differences in the generation of tissue growth factors.     

Trophic effects of different enteral diets in the rat intestine

The trophic effect of 4 commercial diets compared to chow was studied in 50 rats. The 4 commercial diets were: a free amino acid diet, a diet based on soy protein hydrolysate and two diets based on intact protein with and without extra fibre added. Bowel weight, mucosa weight and DNA content were measured after 7 days of treatment. The enteral formula based on a soy protein hydrolysate had a significant growth stimulating effect on the proximal small bowel compared to rat chow. In the ileum and in the colon all diets without fibre supplementation caused significantly lower bowel weights than rat chow.     

The digestion of protein in young pigs and the utilization of dietary methionine

Forty pigs between 23 and 51 d of age were given ad lib. diets containing wheat and one of five protein concentrates: meat meal A, meat meal B, soya-bean meal, milk and lupins (Lupinus augustifolius). Twenty of these pigs were given indigestible markers from 51 to 56 d of age and were killed at 56 d of age. The diets containing meat meals A and B, soya-bean meal and milk contained 2.3 g total methionine/kg and the diet containing lupins contained 2.1 g/kg. A further forty pigs of the same age were given the same diets supplemented with 1 g synthetic methionine/kg. The weight gains and feed conversion ratios of the pigs given the diets containing 2.1-2.3 g methionine and 3.1-3.3 g methionine/kg were not significantly different. The weight gains of the pigs given lupins (2.1 g methionine/kg) were less than those of the pigs given the diets containing 2.3 g methionine/kg. The apparent digestibility of dry matter (DM) and nitrogen was less for the diets containing the meat meals (0.75 and 0.78 respectively) than for those containing the other protein concentrates (0.80 and 0.84). The retention times in the large intestine of the diets containing soya-bean meal and lupins were 965 and 1083 min which were greater than those of the diets containing the other protein concentrates, mean 732 min. The major site of N digestion and absorption for the diet containing milk was the area of the small intestine 25-50% of total length from the pylorus, while for the other protein concentrates the major site was 50-75% of its total length from the pylorus. The digestion and absorption of N in the large intestine was less (3.4%) for the diet containing milk than for those containing the other protein concentrates (7.5-11.3%). The apparent digestibility of the methionine to the ileum for the five diets ranged from 0.74 to 0.86 while the calculated retention of the apparently-absorbed methionine was 1.00. It was suggested that methionine digestibility could be used as an indicator of availability. The calculated retention of apparently absorbed N in the carcass was 0.71 for the pigs given the diet containing milk and 0.51-0.58 for the pigs given the other diets.     

Requirement for sulfur-containing amino acids in infancy

A series of studies designed to define the requirement of normal infants for sulfur-containing amino acids (methionine, cystine) was conducted with formulas providing 3.0, 2.8, 2.6, 2.2 or 1.8 g of isolated soy protein per 100 kcal. The formulas were fed with or without a methionine supplement. Adequacy of the diet was determined by measurement of growth, serum chemical indices and nitrogen balance. Nitrogen balance demonstrated a beneficial effect of methionine supplementation only at the lowest protein concentration (1.8 g/100 kcal). However, measurement of weight gain and/or serum concentrations of urea nitrogen and albumin clearly showed a beneficial effect of methionine supplementation at protein concentrations of 2.2 and 2.6 g/100 kcal. Intakes of sulfur-containing amino acids of 435 and 495 mumol/100 kcal therefore appear inadequate. At higher intakes of protein (2.8 and 3.0 g/100 kcal) there was no beneficial effect of methionine supplementation. Possible exceptions were male infants provided with 3.0 g protein per 100 kcal, in whom weight gain between 8 and 56 d of age was significantly (P less than 0.05) greater with than without a methionine supplement. Based on intakes of sulfur-containing amino acids from the formula providing 2.8 g of isolated soy protein per 100 kcal without methionine supplementation, we conclude that for male infants older than 56 d the requirement for sulfur-containing amino acids is no more than 588 mumol/100 kcal when intake of methionine is 264 mumol/100 kcal. However, it seems possible that such intake fails to meet the requirement in male infants less than 56 d of age. For female infants, regardless of age, 533 mumol/100 of sulfur-containing amino acids per 100 kcal meet the requirement when intake of methionine is 239 mumol/100 kcal.     

Microbial contamination of enteral feeding formulas and diarrhea

Twenty-five medical and surgical patients receiving liquid ready-to-use sterile enteral formulas were evaluated prospectively to investigate the relation of diarrhea to serum albumin level, total lymphocyte count, delayed hypersensitivity to purified protein derivative, antibiotic therapy, administration rate and site of enteral formula, and microbial contamination of enteral feeds. Formulas were administered to 6 patients with hang times of up to 6 h by pump-assisted continuous drip and to 19 patients with hang times of up to 3 h as a bolus feeding. Samples of formulas for microbial culture were obtained aseptically before and after feeding on the first and eighth day of the study period. The incidence of microbial contamination of the formula before and after feeding was 1 of 49 samples (2.0%) and 10 of 48 samples (20.8%), respectively. There were 2 patients with diarrhea, which occurred on the second day. Formula samples from 2 patients (100%) with diarrhea and 2 samples from 23 patients (8.7%) without diarrhea were contaminated with 10(4) cfu/mL or more, respectively. A significant difference (P = 0.04) was detected between the two groups. The other factors studied showed no significant association with the incidence of diarrhea. In conclusion, contaminated formula appears to play a significant role in the etiology of diarrhea in patients receiving enteral feeding.     

Vitamin plasma levels in long-term enteral feeding patients

Plasma levels of vitamins were determined in eight patients who were nourished with long-term enteral feeding using commercial formulas. The type and quantity of the formula were individually tailored to the patients' needs. Caloric intake (mean +/- SEM) amounted to 1564 +/- 97 kcal/day. Vitamins intake from the formulas, expressed as percent of Recommended Daily Allowances (RDA), was as follows: pantothenic acid, 222 +/- 44%; vitamin B12, 206 +/- 34%; vitamin C, 376 +/- 51%; thiamine, 207 +/- 34%; niacin, 207 +/- 34%; riboflavin, 207 +/- 34%; pyridoxine, 222 +/- 17%; biotin, 113 +/- 13%; vitamin A, 93 +/- 4%; and folic acid, 104 +/- 14%. Plasma levels of thiamine, riboflavin, pyridoxine, pantothenic acid, folic acid, and vitamin B12 were within normal limits in all patients. Two patients had lower than normal plasma levels of nicotinic acid despite the high intake. Plasma biotin levels were above normal in all patients, with a mean of 931 +/- 140 pg/ml (N: 200-500 pg/ml). Ascorbic acid levels were within or above normal, but no correlation with intake was found. Carotene levels were measured in five patients and found to be below the lower limit of normal, a reflection of lack of intake from the enteral formulas. The plasma vitamin A levels were normal in all patients. It is concluded that feeding with commercial enteral formulas results in normal plasma levels of vitamins in patients maintained on these formulas for over 6 months. The excessive amounts of vitamins in the formulas do not result in elevated plasma levels, except for Biotin.