In vitro digestibility of weaning food
based on sweet potato (products).

Digestibilidad in vitro de la comida de destete en base de (harina de) camote. resumen


The aim of this protocol was, to find out if the invented weaning food, based on yellow or white sweet potato, cause some digestive problems, and if they do so, find out if there's a causal relation between the possible problems of the formulas and the possible digestive problems of the sweet potato (flours) used and/or with the process of preparing the formulas. These tests were done in vitro, with a-amylases and a protease and the fermentation of the colon was simulated by an anaerobic incubation with an active inoculum obtained from feces of babies between 6 months and 2 years. This protocol was a compilation of different other previous used protocols and adapted to the different conditions of the digestive tract of babies. An in vivo digestibility test was set up to compare the results and predict if the in vivo method could be replaced by the in vitro protocol.

The blank, white wheat flour, didn't show the digestibility percentages as ought to be, which is apparently due to the interference of the other ingredients in the "100%" white wheat flour with the enzymes used. Therefore the blank isn't used in the comparison of the results.

Results show, that formula f2 (with white sweet potato flour) is well degradable, comparing to the other formulas and the standard weaning food (Gerber). The third formula (also with white sweet potato flour) has a similar overall digestibility with the Gerber mixture, though it showed a lower maltose diffusion peak, which is apparently due to the lower content of milk powder and/or higher amount of (partly other) flours, which might have lowered the enzyme activity.
Formulas f1 and f4, both made with yellow sweet potato (the first with the fresh roots, the second with flour), are less degradable than f2 and f3. Also yellow sweet potato flour is less degradable than the white variant. It seem that there's a causal relation between the lower digestibility of the yellow sweet potato formulas and the yellow sweet potato. Though there's just a relation between the gas production and the sediment. The maltose diffusion of the flours have no effect on the graphs of the formulas, neither there's a relation with the percentages of the starch digestion and the dietary fibre contents.
Between the two formulas made with yellow sweet potato, the is also a difference in digestibility detected, on the benefit of f4. F1, with the fresh yellow sweet potato, has poorer digestibility due to the lower activity of the enzymes. This is possibly caused by the larger amounts of dietary fibre present and the larger substrate particles (i.e. the flour should have smaller particles because of the different processing). This low enzymatic degradation caused an increased fermentation with micro-organisms that produce a lot of gas and a considerable amount of sediment.
Taking the previous mentioned aspects into account, formula f2 has a future for implementation, and f3 might have. Strong thoughts have to be made continuing with the use of yellow sweet potato, and definitely the fresh roots, in spite of the very nice appearance of the formula.

Comparing the in vitro results with the in vivo ones, the in vivo results show a 20% higher energy digestion rate. A reason for these differences apparently lies in the lower amounts of enzymes used by trying to simulate the digestive tract of babies better.
Further comparing of the two different protocols is difficult because different aspects of the digestibility were analyzed, the in vivo test couldn't contain a blank, didn't contain a standard and wasn't done in duplo.

The in vitro protocol needs further improvement regarding to the losses of material during the pH setting, transfer to the dialysis tubes and the stirring with the spatula. A concession to this problem is using a stronger initial dilution, but it never can be extinguished.
Depending on the present laboratory equipment, a stronger dilution of the enzyme solution can be made (and add more solution), or less strong enzymes could be used. Further the practical feasibility depends on the possibilities of the laboratory.

Don't hesitate to contact me if you'd like more information and the results + conclusions.

* I've carried out this 5-months research project at the Centro Internacionál de la Papa (Social Science and Physiology Departments) in Lima, Peru (1996).