Jean Mauron

The availability of lysine, methionine and tryptophan in condensed milk and milk powder. In vitro digestion studies

Abstract 1. 1. Destruction and inactivation of α-amino groups, tryptophan, tyrosine, methionine and lysine were determined in fresh and boiled milk and in preserved milk manufactured according to four widely used processes: i.e., spray-dried and roller-dried milk powders, sweetened condensed, and evaporated milks. 2. 2. No destruction of tryptophan, tyrosine, or methionine occurred in any milk. 3. 3. A 6% destruction of α-amino groups was noted in a slightly scorched roller-powder milk (roller-powder milk B ). 4. 4. No destruction of lysine was apparent in boiled milk, whereas a slight destruction took place in spray-dried milk (3.6 %) and sweetened condensed milk (4.8%). Destruction was appreciable in evaporated milk (8.4%) and average roller-dried milk A (13%), while in roller-powder B it was considerable (26.6%). 5. 5. Inactivation of the same amino acids was measured by an in vitro digestibility test, which is described in detail. 6. 6. No inactivation of tryptophan and tyrosine was found in any milk. 7. 7. Thirteen per cent of the α-amino groups was inactivated in roller-powder B. 8. 8. Methionine was slightly inactivated in roller-dried milks only. 9. 9. Lysine was inactivated in evaporated milk (11.2%), roller-milk powder A (20%), and B (45.8%). 10. 10. There is a close correlation between destruction and inactivation of lysine ( r = 0.992). Both are attributed to a sugar-amine condensation. 11. 11. The sum of destruction and inactivation gives the total deterioration of lysine. 12. 12. Availability of lysine was computed by deducting total deterioration from 100 (availability in fresh milk taken as 100). 13. 13. Lysine availability ( y ) in industrial milks can be estimated from lysine destruction ( x ) using the regression equation: y = 109.58 − 3.099 x .

Relationship between in vitro lysine availability and in vivo protein evaluation in milk powders.

Abstract 1. 1. The protein efficiency ratios of a series of roller-dried milk powders submitted to heat treatments of varying intensity were determined and compared to that of the corresponding spray-dried powders. The protein level of the diets was kept at 10%. 2. 2. Lysine deterioration in the same roller powders as measured by the in vitro digestion procedure already described ranged from 18.3 to 72.4%. 3. 3. Maximum protein efficiency was obtained with spray-dried milk plus methionine. The decrease in protein efficiency in the roller powders ranged from 2.8 to 82.4%. Protein efficiency in roller powders could be almost completely restored by an adequate lysine supplement. 4. 4. It was found that a methionine addition to the milk diets increases the sensitivity of the rat assay to lysine deterioration, so that, in case of small lysine deterioration, the difference between spray powder and roller powder becomes significant in the presence of methionine only. 5. 5. An excellent correlation ( r = 0.991) was found between in vivo decrease of protein efficiency and in vitro lysine deterioration. 6. 6. With the methionine-supplemented diet, the regression of decrease in protein efficiency ( y ) on lysine deterioration ( x ) is: y = −31.71 + 1.54 x 7. 7. The regression line with unsupplemented diet is: y = −56.94 + 1.89 x 8. 8. The properties of these regression lines, which allow a very good prediction of the in vivo protein value from an in vitro enzymic test, are discussed.

Availability of the true Schiff's bases of lysine. Chemical evaluation of the Schiff's base between lysine and lactose in milk.

During the heat-treatment of milk, the Maillard reaction which takes place between the epsilon-amino group of lysine and lactose leads to the formation of two well-defined chemical types : the Schiff’s base in equilibrium with its aldosylamine form and the deoxyketose (Amadori product). Rat growth assays showed that the synthetic e-N-deoxyketosyl-L-lysine was not utilized as a source of lysine and that the true Schiff’s bases resulting from the reaction of lysine with aromatic aldehydes were 100% utilized indicating that the Schiff’s base ⇄ aldosylamine are also 100% utilized.

Phosphatidyl choline and avoidance performance in 17 month-old SEC/1ReJ mice

Male SEC/1ReJ mice aged 6 or 17 months were fed diets containing 0, 2, 4, and 8% added phosphatidyl choline. After 4 days on the test diets they were given 5 daily sessions of 100 trials each in the shuttle-box. The younger mice rapidly acquired an avoidance response and reached high, stable levels of performance. The older mice learned more slowly and reached significantly lower performance levels (p less than 0.01). Phosphatidyl choline had no effect on performance of young mice, while in the older mice the highest dose level of phosphatidyl choline increased avoidance performance by nearly 30% (p less than 0.05).

Effects of early malnutrition on Swiss white mice: Avoidance learning after rearing in large litters

Abstract Mice were undernourished by rearing in litters of 20 pups per mother, weaned onto stock diet and their shuttle-box avoidance performance measured at 2 months of age. The mice from these large litters learned the avoidance response more slowly than controls (mice reared in litters of 5). In a second experiment, avoidance performance was measured after nutritional rehabilitation until 2, 4 or 6 months old. No significant improvement was observed in the previously malnourished mice. In the controls, performance was high at 2 and 4 months but by 6 months had fallen almost to the same level as the test group.

Micronutrient intake and status in rural Democratic Republic of Congo

Vitamin, mineral and trace element intakes were assessed in a rural African population using a novel dietary survey method, and compared with status measurements. In addition to the previously described protein deficiency, multiple micronutrient deficiencies were observed. Although vitamin A intakes were generally satisfactory, some low plasma retinol concentrations were observed in adults, due perhaps to the very low protein intakes or infectious diseases. Vitamin B1, B2 and niacin intakes were clearly inadequate, and for the two former were confirmed by status measurements. Whilst B6 intake was low, B6 status was adequate, probably resulting from lower requirements because of low protein intakes. B12 intake was low in some age groups, whereas that of folate was satisfactory. Fe, Cu and Mg intakes appeared to be adequate. Intakes of phosphorus and iodine were low for children and adolescents; those of Zn and Ca were clearly inadequate, except for Zn in women. Dietary interventions to prevent or treat malnutrition in this region should address several micronutrients in addition to protein.

The effects of chlordiazepoxide on avoidance performance of mice subjected to undernutrition or handling stress in early life

This experiment compared the effects of (i) “early undernutrition” by rearing in large litters and (ii) an early handling stress, on avoidance learning in Swiss white mice. The two treatments, the first leading to permanent physical stunting and the second not, had similar and additive detrimental effects on avoidance performance. Treatment with the minor tranquillizer Chlordiazepoxide improved performance in all groups but had a proportionately greater effect on previously undernourished, handled mice. Thus the poor avoidance performance of mice reared in large litters appears to be largely independent of the growth stunting effect and more closely related to an elevated stress response produced by stress in early life.

The effects of different amino acid diets on a fast-induced performance decrement in mice.

In mice subjected to long uninterrupted avoidance sessions (1,500 trials) a clear decrement of performance was evident after the first 500–600 trials. Mice subjected to a 24 h fast showed a more rapid decrement of performance during the session following the fasting period than that evident in the same group fed ad libitum.When the effects of feeding casein, glucose or different amino acids were assessed, only casein, glucose or serine prevented the impairment of performance while the most toxic amino acids, i.e. histidine, methionine and tryptophan diminished the performance below that obtained by fasting. Casein, glucose and serine were the only diets that maintained blood glucose levels within the normal range. Feding experiments showed that serine was the most acceptable aminoacid to the mice indicating that it was unique in maintaining performance because it is the only amino acid that is both palatable and readily gluconeogenic.

Is the adult protein-energy malnutrition syndrome the same as that described in the infant?

Protein-energy malnutrition, a multi-factorial disease, has been described predominantly in the infant. It was the aim of this research to give a biochemical assessment of the adult form and to compare it to the infantile syndrome within the same socio-cultural context of central Zaïre (Kwilu region). Thirty-four children, 22 women and 2 men suffering from marasmic kwashiorkor at the hospital of Yasa-Bonga (Kwilu) were submitted to a complete set of 7 anthropometric and 60 biochemical tests. The control values were taken from healthy well-fed children and adults from Yasa-Bonga; for certain parameters, rural adult control values were also obtained. Dyspigmentation was found in all patients, children and adults alike. The other symptoms were, in decreasing order of importance : oedema, dermatitis, apathy and liver enlargement, often accompanied by associated secondary pathology. In the children, all anthropometric indices were well below normal. In serum, total protein, albumin, prealbumin, ceruloplasmin and haemoglobin were reduced; the alpha 1, alpha 2 and beta-globulins were slightly reduced in infants but not much modified in adults, whereas gamma-globulins were slightly increased in adults only. IgG and IgM were increased in both infants and adults, the enhancement was less pronounced for IgA. Essential amino acids in serum were reduced in the patients and most non-essential amino acids raised, with the exception of tyrosine and arginine which were reduced like the essential amino acids. Some ratios (phenylalanine/tyrosine, serine/threonine, and non-essential/essential amino acids) proved to be very sensitive parameters for this type of protein-energy malnutrition. No differences were found in the amino acid levels between adult and infant patients, with the exception of alanine which was higher in the adults. Alanine levels were also high in the rural adult controls as compared to the European controls, probably due to the extremely high carbohydrate (manioc) diet. Serum electrolytes were normal in adult patients, with the exception of low Ca, whereas in children P and Mg were also low. Total lipids and cholesterol were reduced in adult and infant patients. The urinary excretion of all parameters measured (N, urea, creatinine, hydroxyproline, electrolytes, trace elements and some vitamins) was reduced in the patients with only small differences between adults and infants.(ABSTRACT TRUNCATED AT 400 WORDS)

Dietary intake measurement in rural zaire: Macro-nutrients

Abstract A modified dietary survey method by weighing was employed to evaluate nutrient intakes in a poor rural community of Western Zaire. Energy intakes of children (4–11 years), equivalent to 1.1 times basal metabolic rate (BMR) were inadequate for normal growth and activity. Intakes of adolescents (11–18y) were marginal (1.5 BMR). Adult women and men had energy intakes corresponding to 2.0 and 1.5 BMR respectively. These amounts were compatible with the intensive physical activity of women and lighter activity of men on one hand, and with their small body size on the other. Mean daily protein intakes, after correction for digestibility and amino acid score according to FAO/WHO/UNU (1985) recommendations, were 0.63, 0.60 and 0.47 g/kg for children, adolescents and adults, respectively and corresponded to only 50 to 70% of recommended levels, and were thus in accordance with the commonly observed clinical and biochemical signs of protein depletion. Protein and fat accounted for only 4.5% and 9%, respectively, of energy intake. This situation is the result of the high consumption of cassava combined with the poor availability of foods rich in protein and fat. Dietary protein inadequacy, unlikely when energy requirements are met in populations with cereal food staples, can be a major problem in root tuber consuming populations.