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Influence of the design of a product on in vitro mineral availability of homogenized weaning foods
Innovative Food Science & Emerging Technologies 2 Ž2001. 181᎐187
Influence of the design of a product on in vitro mineral availability of homogenized weaning foods A.B. OlivaresU , C. Martınez, G. Lopez, G. Ros ´ ´ Area de Nutricion ´ y Bromatologıa, ´ Veterinary Faculty, Uni¨ ersity of Murcia, 30071-Murcia, Spain Received 23 July 2000; accepted 29 December 2000
Abstract The influence of the design of the product Žpercentage of main ingredients used in the formulation of the product. on mineral content and their ‘in vitro’ bioavailability, such as total dietary fibre ŽTDF. and phytic acid ŽPA. of a meat-based infant weaning food was studied. Phosphorus, Ca, Zn and Fe concentration and ‘in vitro’ availability of Ca, Fe and Zn changed depending on the percentage of rice flour, carrot, pea puree and chicken liver in the weaning foods. Also TDF contents depends on the design of the product, and both, FA and TDF, reduce the mineral bioavailability. Increasing pea puree and carrot in the formulation of the weaning food could increase P and Ca content. On the other hand, carrot supplies high TDF, therefore contributing to reduction of Ca availability. Iron content was positively correlated with the percentage of chicken liver. Percentage of carrot and pea puree included in the formulation of the weaning foods analysed determined the differences in Fe availability as significant positive regression coefficients Ž bs 0.676, P- 0.05 and bs 0.622, P- 0.05, respectively. were found. Using the in vitro availability values we have performed Cluster analysis and principal components analysis ŽPCA. to establish the best combination of percentages of raw ingredient which provides the highest mineral availability. 䊚 2001 Elsevier Science Ltd. All rights reserved. Keywords: Mineral availability; Phytate; Fibre content; Weaning foods
1. Introduction During the past decades there has been an increase in the consumption of manufactured infant foods in industrialised countries. An important proportion of these foods are the so-called beikost, defined by Fomon Ž1974. as additional foods which are different to human milk and formulas used in infant nutrition as supplementary feeding. At the age of 6 months, the majority of European infants begin to eat semi-solid foods as complementary alimentation, where homogenised infant foods play a very important role in nutrition. The authorities of some countries have recommended that certain trace element levels in infant foods should be studied ŽKirpatrik, Conacher,
U
Corresponding author.
Meranger, Dabeka, Collins & Mckenzie, 1980. and the improved techniques should be established for assessing trace element status ŽGibson, 1990.. Specific research programs have been developed to critically assess priorities for the study of micronutrients in the European Community ŽCEC, 1994.. Fulfilling trace element requirements depends not only on the intake but also on the relative availability of the elements to the organism. Availability is particularly important for trace elements because many factors affect absorption and assimilation. The amount of element absorbed depends not only on the chemical form of the mineral in the food, but also on other components in that food and in the rest of the diet such as phytate and fibre. Phytic acid, myo-inositol hexaphosphate, is of widespread occurrence in plant foods such as cereal grains and legume seeds. The formation of mineral᎐phytate complexes in the gastrointestinal tract
1466-8564r01r$ - see front matter 䊚 2001 Elsevier Science Ltd. All rights reserved. PII: S 1 4 6 6 - 8 5 6 4 Ž 0 1 . 0 0 0 2 5 - X
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A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187
is a major mechanism by which phytate reduces the mineral bioavailability. The use of phytatermineral molar ratios has become more widespread as a method for predicting the risk of mineral deficiency, in particular Zn. Davies, Carswell and Mills Ž1985. proposed the application of a phytate = CarZn ratio as a more accurate predictor of the risk of Zn deficiency. According to this author the upper limit for phytate = CarZn molar ratios in humans must not exceed 0.5. On the other hand, one of the most important properties of dietary fibre is the cation exchange. The reduced mineral availability and electrolyte absorption associated with some diets high in fibre are undoubtedly due to the binding of minerals and electrolytes on fibre sources, leading to increased faecal excretion of minerals and electrolytes. The number of free carboxyl groups on the sugar residues and the uronic acid content of polysaccharides appear to be related to the cation exchange properties of fibres ŽSchneeman, 1986.. Previous papers ŽSantaella, Martınez, Ros & Periago, ´ 1997; Periago, Ros, Rincon 1997; Rincon, ´ & Martınez, ´ ´ Ros, Periago, Martınez & Ros, 1996. have dealt with ´ meat-based weaning food design of different brands and stressed the effect of the design on mineral content and availability. To further elaborate on the same idea, this work was undertaken to evaluate how the combination of key ingredients determine the ‘in vitro’ availability of the main divalent cations of nutritional interest ŽFe, Zn, Ca and P. in weaning foods, and to clarify if such influence could be due to phytic acid and fibre content variations. In addition, we would try to obtain an optimal formulation with a combination of the main ingredients which would lead to maximum Fe, Zn and Ca in vitro bioavailability and the minimum of antinutrients. This could be an important improvement from a nutritional point of view. The key ingredients selected were those that provide a high amount of cations and also may have a reasonable amount of dietary fiber, peas and carrots ŽPeriago et al., 1997. or PA. Only chicken liver would provide minerals of high quality for nutritional purposes.
2. Materials and methods 2.1. Experimental design A randomized 4 = 3 Žingredients = percentages. factorial experimental design was used to obtain 25 types of homogenised weaning foods Ž250-g jars. designed from the combination of different percentages of the four main ingredients Žcarrot, rice flour, pea puree and chicken liver. as is shown in Table 1. All samples were supplied by Hero S.A. ŽAlcantarilla, Murcia, Spain..
Table 1 Design of weaning foods Weaning food No.
Ingredients % Carrot
Rice
Pea
Chicken liver
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
5.70 5.70 5.70 5.70 5.70 5.70 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 7.64 7.64 7.64 7.64 7.64 7.64
7.20 8.00 8.00 8.00 8.00 8.80 7.20 7.20 7.20 7.20 8.00 8.00 8.00 8.00 8.00 8.80 8.80 8.80 8.80 7.20 8.00 8.00 8.00 8.00 8.80
2.00 1.40 2.00 2.00 2.60 2.00 1.40 2.00 2.00 2.60 1.40 1.40 2.00 2.60 2.60 1.40 2.00 2.00 2.60 2.00 1.40 2.00 2.00 2.60 2.00
1.00 1.00 0.15 1.85 1.00 1.00 1.00 0.15 1.85 1.00 0.15 1.85 1.00 0.15 1.85 1.00 0.15 1.85 1.00 1.00 1.00 0.15 1.85 1.00 1.00
2.2. Methods
Zn, Fe, Ca and P contents in the weaning foods were estimated by inductively coupled plasma atomic spectrometer ŽICP-AES. model JY 70 Plus. Samples were dry-ashed in porcelain crucibles according to the AOAC method 985.35 Ž1999.. Then 5 ml of 25% HCl and 2 ml of HNO3 were added. The solution was placed in a 50-ml volumetric flask, and the level made up with deionised water. Estimation of Fe, Zn and Ca availability were carried out by the method of Miller, Schricker, Rasmussen & van Campen Ž1981.. This ‘in vitro’ technique consists of peptic digestion at pH 2.0 and 37⬚C for 2 h, pH adjustment with NaHCO3 and, after addition of bile salts, pancreatic digestion with dialysis at pH 7.0 and 37⬚C for 3 h. Minerals were determined in the dialysates by ICP, and expressed as the percentage of the amount of minerals present in the food sample. Total dietary fibre ŽTDF. was determined following the enzymatic᎐gravimetric method described by Prosky, Asp, Schweizer, de Vries and Furda Ž1988. and adapted by the AOAC as the official method 985.29 ŽAOAC International, 1999.. Phytic acid content was analysed following the
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187
method described by Plaami and Kumpulainem Ž1991.. Phytic acid was extracted with H 2 SO4 and precipitated as a phytate ferric complex. The complex was converted to ferric hydroxide by adding NaOH and boiling, releasing phytic acid as soluble sodium phytate. After these procedures, phytate phosphorus was measured according to Chapman and Pratt, Ž1961. using a UV-VS Spectrophotometer ŽHitachi Model U-2000.. The determination of PA = CarZn molar ratio was calculated according to Fordyce, Forbes, Robbins and Erdman Ž1987. as a predictor of Zn bioavailability. 2.3. Statistical analysis One-way analysis of variance ŽANOVA. was included in the data treatment to study the variation of the data referring to mineral content and mineral availability in the different combination of ingredients. To investigate relationships between variables, regression and correlation analyses were carried out. Cluster analysis and principal components analysis ŽPCA. were performed to find the combination of percentages of raw ingredients which provide the highest mineral availability. All analyses were performed in triplicate. Statistical analysis of the data was performed using SPSS version 8.0 ŽSPSS Inc. Chicago, I.C.. 3. Results and discussion 3.1. Mineral elements Phosphorus, Ca, Zn and Fe concentrations observed for weaning foods are presented in Table 2. The design of the product determined significantly Ž P- 0.05. the mineral content ŽTable 4.. Phosphorus was the most abundant in the weaning foods analysed, Žranging from 53.79 to 75.96 mgr100 g., followed by Ca with levels between 5.73 and 8.76 mgr100 g. Phosphorus and Ca content calculated as the average of the 25 samples were 62.66 mgr100 g and 7.59, respectively, which suppose an 56.96 and 7.02% of the RDI ŽCommittee on Dietary Reference Intakes, 1997. calculated from an intake of 250 g of weaning food per day. There was a positive correlation Ž r s 0.500, P- 0.01. between Ca and P concentrations, depending on the P content of pea puree Ž r s 0.418, P- 0.01., carrot Ž r s 0.382, P0.01. and chicken liver Ž r s 0.340, P- 0.05.; and Ca with percentages of pea puree Ž r s 0.340, P- 0.05., rice flour Ž r s 0.384, P- 0.01. and carrot Ž r s 0.544, P- 0.01.. We should point out that the ingredient added in the formulation is pea puree and not the whole seed, as fibre content and other antinutrients are reduced during industrial treatment ŽCantoral, Fernandez-Quintela, Alfredo Martınez & Macarulla, 1995; ´ Vidal, 2000.. Zinc concentrations ranged between 0.35 and 0.48
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Table 2 Mineral content mgr100 g wrw Weaning food
P
Ca
Zn
Fe
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
53.79" 4.23 60.11" 1.71 56.69" 2.82 62.24" 0.67 61.29 " 0.38 60.36" 0.48 57.74" 0.33 55.97" 1.08 60.31" 2.64 64.17" 1.36 59.10" 2.08 62.50" 1.47 64.82" 9.29 65.62" 0.43 75.96" 4.92 61.42" 1.54 62.80" 0.12 64.89" 0.33 69.26" 0.70 66.62" 0.08 66.40" 0.35 60.56" 1.21 64.18" 0.66 67.12" 0.79 62.59" 7.21
5.73" 0.05 7.23" 0.28 6.72" 0.02 7.37" 0.09 8.17" 0.24 7.93" 0.50 7.10" 0.007 7.74" 0.19 7.30" 0.12 8.29" 0.056 6.62" 0.042 6.92" 0.30 6.94" 0.019 7.82" 0.59 7.92" 0.072 7.73" 0.028 8.19" 0.16 8.13" 0.37 8.39" 0.042 7.68" 0.37 7.28" 0.27 7.95" 0.47 7.89" 0.007 8.76" 0.28 7.98 " 0.11
0.45" 0.007 0.39" 0.02 0.36" 0.02 0.47" 0.0 0.48" 0.007 0.43" 0.0 0.42" 0.007 0.41" 0.007 0.42" 0.0 0.42" 0.07 0.35" 0.007 0.44" 0.0 0.41" 0.007 0.45" 0.012 0.47" 0.0 0.42" 0.0 0.44" 0.0 0.38 " 0.007 0.44" 0.03 0.43" 0.007 0.48" 0.02 0.44" 0.007 0.46" 0.007 0.47" 0.0 0.45" 0.0
0.37" 0.007 0.40" 0.98 0.34" 0.0 0.39" 0.007 0.34" 0.0 0.35" 0.007 0.32" 0.0 0.25" 0.0 0.38" 0.007 0.30" 0.007 0.20 " 0.0 0.37" 0.007 0.29" 0.0 0.24" 0.007 0.36" 0.007 0.29" 0.007 0.22" 0.012 0.31" 0.014 0.29" 0.0 0.40" 0.0 0.37" 0.0 0.28" 0.0 0.51" 0.0 0.43" 0.0 0.38" 0.007
mgr100 g, with an average value of 0.43" S.D. mgr100 g Žbased on the 25 different formulations. which will cover 14% of the RDA wNRC ŽNational Research Council., 1991x, calculated from an intake of 250 g of weaning food per day. This micromineral is especially important in children’s development because a lack of it will cause delay in growth. The type of meat has been reported to have a great influence over Zn content in weaning foods ŽSantaella et al., 1997., and for instance our research group revealed that Zn content is considerably higher than in chicken meat. For that reason, chicken liver was included into the formulation, and it was effective, increasing or getting a positive correlation between Zn content and chicken liver percentages Ž r s 0.298, P- 0.05.. Iron is one of the most studied trace elements in infant nutrition, since Fe deficiency is particularly prevalent in infants and is a major nutritional problem in the world today. In fact Fe food fortification is generally considered to be the best long-term strategy to combat Fe deficiency ŽHurrell, 1994; Martınez, Lopez, Ros, Vidal & Abellan, ´ ´ ´ 2000.. In our samples, Fe content ranged from 0.20 to 0.51 mgr100 g, the average content was 0.38 mgr100 g, therefore supposing 8.25% of the RDA wNRC ŽNational Research Council., 1991x calculated for an intake of 250 grday. The measured iron content of a food does not necessarily reflect the amount, which is absorbed when the food is eaten. The availability of iron depends on
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187
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many factors, haem iron from meat being the most available form. Liver has been described as one of the main sources of Fe. In our study, Fe content and percentage of chicken liver were positively correlated Ž r s 0.510, P- 0.01.. Therefore a reasonable form of rising iron content in weaning foods would be increasing the percentage of this ingredient in the formulation of the product, which is, at the same time, a highly available form of this micronutrient. 3.2. In ¨ itro mineral a¨ ailability Percentage of mineral dialysability, PA and TDF contents and PA = CarZn molar ratio are given in Table 3. In vitro methods based on the determination of the amount of dialysable minerals under simulated physiological conditions have shown reasonably good correlation with in vivo availability and can be used for a relative prediction of the bioavailability of minerals ŽWolters, Schreuder, van den Heuvel, van Lonkhuijsen, Hermus & Voragen, 1993.. Modern nutrition programs have recommended increased intake of TDF. However, this fact can be especially controversial in children, since a high TDF content as well as PA have been demonstrated to bind Ca, Fe, Zn and other metals, resulting in low mineral availability. In this study, percentages of the main ingredients in the formulation of weaning foods resulted in a significant Ž P- 0.05. influence of Ca, Zn and Fe availability
ŽTable 4.. The values obtained for Ca availability ranged from 6.03 to 23.01%. The utilisation of this mineral is at a maximum from milk and milk products in children, since lactose appears to increase Ca absorption by infants. On the other hand, lactose, at levels normally present in milk, does not have a significant effect on Ca absorption by healthy adults consuming normal diets ŽMiller & Berner, 1989.. Calcium availability in other foods is considerably low, especially in plants, due to the fact that this mineral is linked to inhibitors such as oxalates, phosphates, TDF and PA ŽMiller, 1993.. However, the values obtained in vitro may be underestimated with respect to in vivo bioavailability because the Ca linked to uronic acids can be released by bacterial enzymes during digestion in the colon for absorption in the large intestine. In our study, a negative correlation was found between Ca availability and TDF Ž r s y0.330, P- 0.05., and although a negative correlation coefficient was also found between Ca availability and PA content it was not statistically significant. TDF content in the weaning foods could be reduced lowering carrot percentage as this ingredient seems to supply the main quantity of this antinutrient. The percentage of Zn dialyzable ranged from 1.75 to 7.10%. The bioavailability of zinc is influenced by other dietary components. Phytates form insoluble complexes with Zn and this is more pronounced if there is excess calcium in the diet ŽCOMA report, 1995.. That is the
Table 3 In vitro availability of Ca, Fe and Zn, phytate content ŽPA., total dietary fibre ŽTDF. and PA = CarZn molar ratio in weaning foods Weaning food
Ca Ž%.
Fe Ž%.
Zn Ž%.
PA Žmgrg.
TDF Ž%.
Ratio PA = CarZn
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
22.08" 8.79 23.01" 3.97 22.88" 0.90 11.99" 1.39 9.55" 0.04 8.12" 0.94 10.02" 3.27 13.19" 0.38 10.26" 2.02 13.02" 0.49 12.80" 2.40 12.87" 0.07 9.90 " 0.11 10.64" 0.26 9.59" 0.12 6.03" 1.27 11.95" 0.88 12.96" 0.07 13.14" 1.50 9.37" 0.78 17.53" 0.61 15.25" 0.94 12.49" 0.71 9.88" 1.24 16.37" 0.43
5.82" 3.92 2.11" 0.01 3.03 " 0.65 2.32" 0.09 3.03" 1.13 1.83" 0.25 1.84" 0.22 6.30" 0.07 2.53" 0.30 3.82" 0.30 5.14" 0.17 3.46" 0.18 2.87" 0.59 3.47" 0.49 3.57" 0.30 1.39" 0.15 5.12" 0.20 2.49" 0.33 3.95" 0.02 3.54" 0.11 4.06" 0.07 5.35" 0.23 3.10" 0.13 3.06" 0.09 4.53" 0.04
3.24" 1.59 3.36" 0.28 7.10" 0.70 3.62" 0.14 3.01" 0.09 2.45" 0.96 1.75" 0.64 5.41" 0.04 4.18" 0.90 4.46" 0.04 4.32" 0.55 5.06" 0.03 3.49" 0.24 3.68" 0.07 3.31" 0,08 2.78" 0.06 3.52" 0.09 3.60" 0.40 4.23" 0.18 3.83" 0.34 4.34" 0.52 5.28" 0.45 4.14" 0.18 3.66" 0.27 3.53" 0.47
1.42" 0.36 1.15" 0.32 0.97" 0.05 1.64" 0.53 1.78" 0.07 1.94" 0.12 0.98" 0.01 1.44" 0.08 1.70" 0.07 1.44" 0.08 1.22" 0.97 1.63" 0.21 1.58" 0.06 2.13" 0.03 1.03" 0.27 0.64" 0.25 1.77" 0.26 0.19" 0.08 1.50" 0.07 0.84" 0.02 1.09" 0.69 1.61" 0.41 0.95" 0.07 1.02" 0.29 1.90" 0.31
0.55" 0.01 0.44" 0.01 0.49" 0.02 0.48" 0.01 0.98" 0.02 0.25" 0.01 0.56" 0.04 0.72" 0.02 0.55" 0.03 0.73" 0.01 0.88" 0.01 0.96" 0.02 0.82" 0.02 0.75" 0.01 0.86" 0.02 0.91" 0.03 0.66" 0.02 0.59" 0.01 0.88" 0.02 0.89" 0.02 0.79" 0.01 0.68" 0.01 0.70" 0.01 0.66" 0.02 0.55" 0.01
0.26 0.26 0.24 0.35 0.39 0.46 0.25 0.44 0.44 0.39 0.34 0.38 0.36 0.48 0.24 0.16 0.45 0.05 0.36 0.21 0.24 0.41 0.19 0.26 0.45
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187 Table 4 One-way analysis of variance of mineral content and mineral availability Source of variance Mineral content Iron Zinc Calcium Phosphorus Mineral availability Iron Zinc Calcium
F
Significance
24 24 24 24
39.508 18.395 13.623 4.983
0.000 0.000 0.000 0.000
24 24 24
6.439 10.578 12.600
0.000 0.000 0.000
d.f.
reason why Davies et al. Ž1986. proposed the application of a PA = CarZn molar ratio as a predictor of the risk of Zn deficiency. According to this research the upper limit in humans must not exceed 0.5. All samples studied presented lower ratios, which means that Zn availability is not compromised in these weaning foods. Iron availability showed the lowest values among all
185
the minerals analysed Žfrom 1.39 to 6.30%.. Iron is most readily absorbed from foods rich in haem, particularly red meat but also other meats and meat products. Non-haem iron, present in plants, is less well absorbed. Phytic acid from cereals, legumes and other vegetables, tannin in tea and polyphenols in spinach, coffee, and other vegetables bind to iron and hinder iron absorption. It is a matter of concern that diets commonly used during weaning may provide inadequate absorbable iron ŽCOMA report, 1995.. Percentages of rice included in the formulation of the weaning foods analysed determined differences in Zn and Fe availability as significant negative Pearson correlation coefficients were found Ž r s y360, P- 0.05 and r s y281, P0.05, respectively.. In fact, it has been previously stated that rice flour is the main ingredient, which increases phytic acid content in weaning foods ŽRincon ´ et al., 1996.. However, we could not find a clear relationship between PA content and Fe and Zn availability. To determine the influence of antinutrients on avail-
Table 5 Cluster analysis, conglomerates final centres, significant levels and samples into each group Mineral availability
Conglomerates final centres 1
2
3
4
Significant level
Fe Ca Zn
4.65 16.38 4.38
3.61 11.49 3.90
3.65 22.66 4.57
1.69 8.06 1.86
0.026 0. 0.013
Samples
21, 22, 25
The rest
1, 2, 3
6, 7, 16
Fig. 1. Graphic representation of principal components analysis based on mineral availability.
186
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187
Fig. 2. Graphic representation of principal components analysis based in mineral availability and TDF and FA contents.
ability of minerals, regression analysis was performed. Negative regression coefficients were found between phytic acid and TDF and Ca dyalizable although only with the last one was statistically significant Ž bs y0.356, P- 0.05.. TDF also showed negative effects on Zn dialysability Ž bs ᎐0.003. although was not statistically significant. A Cluster analysis and factorial study were performed since, none of the 25 samples showed values higher than the others to Ca, Fe and Zn availability. The aim of two statistical analyses was the selection of a combination of different percentages with the optimal values of Fe, Ca and Zn availability. A Cluster analysis was used to obtain four homogeneous groups of samples determined by the distance between conglomeration final centres and means of Fe, Ca and Zn availability. Table 5 shows these distances, the rate of significance for three variables and the samples of each group. The four groups were significant at P- 0.05 to Fe and Zn availability and P- 0.01 to Ca availability. The groups 1 Žsamples 21, 22 and 25. and 3 Žsamples 1, 2 and 3. were the relative higher percentages to mineral availability. A principal components analysis of samples Žgrouped in previously describe four groups by mineral availability . and Fe, Zn, Ca availability, phytic acid and dietary fiber, calculated by means of alternative least squares was carried out and plotted in Figs. 1 and 2, respectively. These figures represented a bi-dimensional scaling defined by two factors where the association between samples or variables is determined by its position in the graph and their relative distances Žor dissimilarities . with the other elements. When both fig-
ures were overlapping, half of the samples were in the positive side of factor 1 with a great rate of proximity to the parameters of selection ŽFe, Ca and Zn availability. than the other half. This second analysis allows the selection of samples into each group by means of their behaviour Žproximity or distance. with respect to mineral bioavailability Ž P- 0.01.. Thus, we may select samples 3 and 22 since these represent the combination of ingredients Žpea puree, carrot, rice flour and chicken liver. which make infant weaning foods with the optimal Fe, Zn and Ca availability.
Acknowledgements To Hero Spain S.A. ŽMurcia, Spain. for providing the samples analysed in this study. References AOAC International Ž1999.. Official Methods of Analysis, 16th ed. Washington DC, USA: Association of Official Analytical Chemist. CEC, & Moller, S. Ž1994.. Progress report of R and D projects and concerted action. Second framework programme Ž1988᎐93.. Luxembourg: Office for Official Publications of the EC. Cantoral, R., Fernandez-Quintela, A., Alfredo Martınez, J., & ´ Macarulla, M. Ž1995.. Estudio comparativo de la composicion ´ y el valor nutritivo de semillas y concentrados de proteına ´ de leguminosas. Archi¨ os Latinoamericanos de Nutricion, ´ 3Ž45., 242᎐248. Chapman, H. H., & Pratt, P. C. Ž1961.. Methods of Analysis for Soils, Plant and Water. Davis: Division of Agricultural Science, University of California. COMA report Ž1995.. Department of Health. Weaning and the weaning diet. Report on Health and Social Subjects N⬚45. London: Her Majesty’s Stationery Office.
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187 Committee on Dietary Reference Intakes Ž1997.. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride, Washington, DC National Academy Press. Davies, N. T., Carswell, A. J. P., & Mills, C. F. Ž1985.. The effects on variation in dietary calcium intake on the phytate᎐zinc interaction in rats. In: C. F. Mills, I. & Bremmer, J. K. Chester, Trace Elements in Man and Animals, Žp. 465.. Aberdeen, Scotland. Fomon, S. J. Ž1974.. In: W. B. Saunders, W.B., Infant Nutrition, 2nd ed. Philadelphia, USA. Fordyce, E. J., Forbes, R. M., Robbins, K. R., & Erdman Jr., J. W. Ž1987.. Phytate = calciumrzinc molar ratio: are they predictive of Zn bioavailability? Journal of Food Science, 52, 440᎐444. Gibson, R. S. Ž1990.. Essential trace elements and their nutritional importance in the 1990s. Journal of the Canadian Dietetic Association, 51, 292᎐296. Hurrell, R. F. Ž1994.. Prospects for improving iron fortification of foods. In: S. Fomon & S. Zlotkin, Nutritional Anemias, Žpp. 193᎐208.. New York: Raven Press. Kirpatrik, D. C., Conacher, H. B., Meranger, J. C., Dabeka, R., Collins, B., Mckenzie, D. D. et al. Ž1980.. Canadian Institute of Food Science and Technology Journal, 4, 154. Martınez, C., Lopez, G., Ros G., Vidal, M. L., & Abellan, ´ ´ ´ P. Ž2000.. Use of haem iron concentrate in the fortification of weaning foods. Journal of Agricultural and Food Chemistry. In Press. Miller, D. D. Ž1993.. Calcium in the diet. Food sources, recommended intakes and nutritional bioavailability. Ad¨ ances in Food and Nutrition Research, 33, 103᎐155. Miller, D. D., & Berner, L. A. Ž1989.. Is solubility in vitro a reliable predictor of iron bioavailability? Biological and Trace Element Research, 19, 11. Miller, D. D., Schricker, B. R., Rasmussen, R. R., & van Campen, D. Ž1981.. An in vitro method for estimation of iron bioavailability from meal. American Journal of Clinical Nutrition, 34, 2248᎐2256.
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NRC ŽNational Research Council. 1991. 1st Spanish edition of 10th original edition of National Research Council. Ediciones Consulta, S.A. Barcelona, Espana. ˜ Periago, M. J., Ros, G., Rincon, F., & Martınez, C. Ž1997.. Nutritio´ nal meaning of dietary fibre and phytic acid in meat-based homogenised weaning foods. Food Research International, 30 Ž3r4., 223᎐230. Plaami, S. P., & Kumpulainem, J. Ž1991.. Determination of phytic acid in minerals using ICP-AES to determine phosphorus. Journal of Association of Official Analytical Chemists, 74, 32᎐36. Prosky, L., Asp, N. G., Schweizer, T. F., de Vries, J. W., & Furda, I. Ž1988.. Determination of insoluble, soluble and total dietary fibre in foods and food products: interlaboratory study. Journal of Association of Official Analytical Chemists, 71, 1017᎐1023. Rincon, M. C., & Ros, F. Ž1996.. ´ F., Ros, G., Periago, M. J., Martınez, ´ Design of product as source of variance in the composition of meat-baset infant beikost. Meat Science, 43Ž2., 99᎐109. Santaella, M., Martınez, I., Ros, G, & Periago, M. J. Ž1997.. Assess´ ment of the role of meat cut on the Fe, Zn, Cu, Ca and Mg content and in vitro availability homogenised beikost. Meat Science, 45Ž4., 473᎐483. Schneeman, B. O. Ž1986.. Dietary fibre: physical and chemical properties, methods of analysis, and physiological effects. Food Technology, 40 Ž2., 104᎐110. Vidal, M. L. Ž2000.. Harina hidrolizada de guisante Ž Pisum sati¨ um L. como sustancia enriquecedora de alimentos. Doctoral Thesis. Wolters, M. G., Schreuder, H. A., van den Heuvel, G., van Lonkhuijsen, H. J., & Voragen, A. G. Ž1993.. A continuous in vitro method for estimation of the bioavailability of minerals and trace elements in foods: application to breads varying in phytic acid content. British Journal of Nutrition, 69, 849᎐861.
Influence of the design of a product on in vitro mineral availability of homogenized weaning foods A.B. OlivaresU , C. Martınez, G. Lopez, G. Ros ´ ´ Area de Nutricion ´ y Bromatologıa, ´ Veterinary Faculty, Uni¨ ersity of Murcia, 30071-Murcia, Spain Received 23 July 2000; accepted 29 December 2000
Abstract The influence of the design of the product Žpercentage of main ingredients used in the formulation of the product. on mineral content and their ‘in vitro’ bioavailability, such as total dietary fibre ŽTDF. and phytic acid ŽPA. of a meat-based infant weaning food was studied. Phosphorus, Ca, Zn and Fe concentration and ‘in vitro’ availability of Ca, Fe and Zn changed depending on the percentage of rice flour, carrot, pea puree and chicken liver in the weaning foods. Also TDF contents depends on the design of the product, and both, FA and TDF, reduce the mineral bioavailability. Increasing pea puree and carrot in the formulation of the weaning food could increase P and Ca content. On the other hand, carrot supplies high TDF, therefore contributing to reduction of Ca availability. Iron content was positively correlated with the percentage of chicken liver. Percentage of carrot and pea puree included in the formulation of the weaning foods analysed determined the differences in Fe availability as significant positive regression coefficients Ž bs 0.676, P- 0.05 and bs 0.622, P- 0.05, respectively. were found. Using the in vitro availability values we have performed Cluster analysis and principal components analysis ŽPCA. to establish the best combination of percentages of raw ingredient which provides the highest mineral availability. 䊚 2001 Elsevier Science Ltd. All rights reserved. Keywords: Mineral availability; Phytate; Fibre content; Weaning foods
1. Introduction During the past decades there has been an increase in the consumption of manufactured infant foods in industrialised countries. An important proportion of these foods are the so-called beikost, defined by Fomon Ž1974. as additional foods which are different to human milk and formulas used in infant nutrition as supplementary feeding. At the age of 6 months, the majority of European infants begin to eat semi-solid foods as complementary alimentation, where homogenised infant foods play a very important role in nutrition. The authorities of some countries have recommended that certain trace element levels in infant foods should be studied ŽKirpatrik, Conacher,
U
Corresponding author.
Meranger, Dabeka, Collins & Mckenzie, 1980. and the improved techniques should be established for assessing trace element status ŽGibson, 1990.. Specific research programs have been developed to critically assess priorities for the study of micronutrients in the European Community ŽCEC, 1994.. Fulfilling trace element requirements depends not only on the intake but also on the relative availability of the elements to the organism. Availability is particularly important for trace elements because many factors affect absorption and assimilation. The amount of element absorbed depends not only on the chemical form of the mineral in the food, but also on other components in that food and in the rest of the diet such as phytate and fibre. Phytic acid, myo-inositol hexaphosphate, is of widespread occurrence in plant foods such as cereal grains and legume seeds. The formation of mineral᎐phytate complexes in the gastrointestinal tract
1466-8564r01r$ - see front matter 䊚 2001 Elsevier Science Ltd. All rights reserved. PII: S 1 4 6 6 - 8 5 6 4 Ž 0 1 . 0 0 0 2 5 - X
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is a major mechanism by which phytate reduces the mineral bioavailability. The use of phytatermineral molar ratios has become more widespread as a method for predicting the risk of mineral deficiency, in particular Zn. Davies, Carswell and Mills Ž1985. proposed the application of a phytate = CarZn ratio as a more accurate predictor of the risk of Zn deficiency. According to this author the upper limit for phytate = CarZn molar ratios in humans must not exceed 0.5. On the other hand, one of the most important properties of dietary fibre is the cation exchange. The reduced mineral availability and electrolyte absorption associated with some diets high in fibre are undoubtedly due to the binding of minerals and electrolytes on fibre sources, leading to increased faecal excretion of minerals and electrolytes. The number of free carboxyl groups on the sugar residues and the uronic acid content of polysaccharides appear to be related to the cation exchange properties of fibres ŽSchneeman, 1986.. Previous papers ŽSantaella, Martınez, Ros & Periago, ´ 1997; Periago, Ros, Rincon 1997; Rincon, ´ & Martınez, ´ ´ Ros, Periago, Martınez & Ros, 1996. have dealt with ´ meat-based weaning food design of different brands and stressed the effect of the design on mineral content and availability. To further elaborate on the same idea, this work was undertaken to evaluate how the combination of key ingredients determine the ‘in vitro’ availability of the main divalent cations of nutritional interest ŽFe, Zn, Ca and P. in weaning foods, and to clarify if such influence could be due to phytic acid and fibre content variations. In addition, we would try to obtain an optimal formulation with a combination of the main ingredients which would lead to maximum Fe, Zn and Ca in vitro bioavailability and the minimum of antinutrients. This could be an important improvement from a nutritional point of view. The key ingredients selected were those that provide a high amount of cations and also may have a reasonable amount of dietary fiber, peas and carrots ŽPeriago et al., 1997. or PA. Only chicken liver would provide minerals of high quality for nutritional purposes.
2. Materials and methods 2.1. Experimental design A randomized 4 = 3 Žingredients = percentages. factorial experimental design was used to obtain 25 types of homogenised weaning foods Ž250-g jars. designed from the combination of different percentages of the four main ingredients Žcarrot, rice flour, pea puree and chicken liver. as is shown in Table 1. All samples were supplied by Hero S.A. ŽAlcantarilla, Murcia, Spain..
Table 1 Design of weaning foods Weaning food No.
Ingredients % Carrot
Rice
Pea
Chicken liver
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
5.70 5.70 5.70 5.70 5.70 5.70 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 6.67 7.64 7.64 7.64 7.64 7.64 7.64
7.20 8.00 8.00 8.00 8.00 8.80 7.20 7.20 7.20 7.20 8.00 8.00 8.00 8.00 8.00 8.80 8.80 8.80 8.80 7.20 8.00 8.00 8.00 8.00 8.80
2.00 1.40 2.00 2.00 2.60 2.00 1.40 2.00 2.00 2.60 1.40 1.40 2.00 2.60 2.60 1.40 2.00 2.00 2.60 2.00 1.40 2.00 2.00 2.60 2.00
1.00 1.00 0.15 1.85 1.00 1.00 1.00 0.15 1.85 1.00 0.15 1.85 1.00 0.15 1.85 1.00 0.15 1.85 1.00 1.00 1.00 0.15 1.85 1.00 1.00
2.2. Methods
Zn, Fe, Ca and P contents in the weaning foods were estimated by inductively coupled plasma atomic spectrometer ŽICP-AES. model JY 70 Plus. Samples were dry-ashed in porcelain crucibles according to the AOAC method 985.35 Ž1999.. Then 5 ml of 25% HCl and 2 ml of HNO3 were added. The solution was placed in a 50-ml volumetric flask, and the level made up with deionised water. Estimation of Fe, Zn and Ca availability were carried out by the method of Miller, Schricker, Rasmussen & van Campen Ž1981.. This ‘in vitro’ technique consists of peptic digestion at pH 2.0 and 37⬚C for 2 h, pH adjustment with NaHCO3 and, after addition of bile salts, pancreatic digestion with dialysis at pH 7.0 and 37⬚C for 3 h. Minerals were determined in the dialysates by ICP, and expressed as the percentage of the amount of minerals present in the food sample. Total dietary fibre ŽTDF. was determined following the enzymatic᎐gravimetric method described by Prosky, Asp, Schweizer, de Vries and Furda Ž1988. and adapted by the AOAC as the official method 985.29 ŽAOAC International, 1999.. Phytic acid content was analysed following the
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method described by Plaami and Kumpulainem Ž1991.. Phytic acid was extracted with H 2 SO4 and precipitated as a phytate ferric complex. The complex was converted to ferric hydroxide by adding NaOH and boiling, releasing phytic acid as soluble sodium phytate. After these procedures, phytate phosphorus was measured according to Chapman and Pratt, Ž1961. using a UV-VS Spectrophotometer ŽHitachi Model U-2000.. The determination of PA = CarZn molar ratio was calculated according to Fordyce, Forbes, Robbins and Erdman Ž1987. as a predictor of Zn bioavailability. 2.3. Statistical analysis One-way analysis of variance ŽANOVA. was included in the data treatment to study the variation of the data referring to mineral content and mineral availability in the different combination of ingredients. To investigate relationships between variables, regression and correlation analyses were carried out. Cluster analysis and principal components analysis ŽPCA. were performed to find the combination of percentages of raw ingredients which provide the highest mineral availability. All analyses were performed in triplicate. Statistical analysis of the data was performed using SPSS version 8.0 ŽSPSS Inc. Chicago, I.C.. 3. Results and discussion 3.1. Mineral elements Phosphorus, Ca, Zn and Fe concentrations observed for weaning foods are presented in Table 2. The design of the product determined significantly Ž P- 0.05. the mineral content ŽTable 4.. Phosphorus was the most abundant in the weaning foods analysed, Žranging from 53.79 to 75.96 mgr100 g., followed by Ca with levels between 5.73 and 8.76 mgr100 g. Phosphorus and Ca content calculated as the average of the 25 samples were 62.66 mgr100 g and 7.59, respectively, which suppose an 56.96 and 7.02% of the RDI ŽCommittee on Dietary Reference Intakes, 1997. calculated from an intake of 250 g of weaning food per day. There was a positive correlation Ž r s 0.500, P- 0.01. between Ca and P concentrations, depending on the P content of pea puree Ž r s 0.418, P- 0.01., carrot Ž r s 0.382, P0.01. and chicken liver Ž r s 0.340, P- 0.05.; and Ca with percentages of pea puree Ž r s 0.340, P- 0.05., rice flour Ž r s 0.384, P- 0.01. and carrot Ž r s 0.544, P- 0.01.. We should point out that the ingredient added in the formulation is pea puree and not the whole seed, as fibre content and other antinutrients are reduced during industrial treatment ŽCantoral, Fernandez-Quintela, Alfredo Martınez & Macarulla, 1995; ´ Vidal, 2000.. Zinc concentrations ranged between 0.35 and 0.48
183
Table 2 Mineral content mgr100 g wrw Weaning food
P
Ca
Zn
Fe
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
53.79" 4.23 60.11" 1.71 56.69" 2.82 62.24" 0.67 61.29 " 0.38 60.36" 0.48 57.74" 0.33 55.97" 1.08 60.31" 2.64 64.17" 1.36 59.10" 2.08 62.50" 1.47 64.82" 9.29 65.62" 0.43 75.96" 4.92 61.42" 1.54 62.80" 0.12 64.89" 0.33 69.26" 0.70 66.62" 0.08 66.40" 0.35 60.56" 1.21 64.18" 0.66 67.12" 0.79 62.59" 7.21
5.73" 0.05 7.23" 0.28 6.72" 0.02 7.37" 0.09 8.17" 0.24 7.93" 0.50 7.10" 0.007 7.74" 0.19 7.30" 0.12 8.29" 0.056 6.62" 0.042 6.92" 0.30 6.94" 0.019 7.82" 0.59 7.92" 0.072 7.73" 0.028 8.19" 0.16 8.13" 0.37 8.39" 0.042 7.68" 0.37 7.28" 0.27 7.95" 0.47 7.89" 0.007 8.76" 0.28 7.98 " 0.11
0.45" 0.007 0.39" 0.02 0.36" 0.02 0.47" 0.0 0.48" 0.007 0.43" 0.0 0.42" 0.007 0.41" 0.007 0.42" 0.0 0.42" 0.07 0.35" 0.007 0.44" 0.0 0.41" 0.007 0.45" 0.012 0.47" 0.0 0.42" 0.0 0.44" 0.0 0.38 " 0.007 0.44" 0.03 0.43" 0.007 0.48" 0.02 0.44" 0.007 0.46" 0.007 0.47" 0.0 0.45" 0.0
0.37" 0.007 0.40" 0.98 0.34" 0.0 0.39" 0.007 0.34" 0.0 0.35" 0.007 0.32" 0.0 0.25" 0.0 0.38" 0.007 0.30" 0.007 0.20 " 0.0 0.37" 0.007 0.29" 0.0 0.24" 0.007 0.36" 0.007 0.29" 0.007 0.22" 0.012 0.31" 0.014 0.29" 0.0 0.40" 0.0 0.37" 0.0 0.28" 0.0 0.51" 0.0 0.43" 0.0 0.38" 0.007
mgr100 g, with an average value of 0.43" S.D. mgr100 g Žbased on the 25 different formulations. which will cover 14% of the RDA wNRC ŽNational Research Council., 1991x, calculated from an intake of 250 g of weaning food per day. This micromineral is especially important in children’s development because a lack of it will cause delay in growth. The type of meat has been reported to have a great influence over Zn content in weaning foods ŽSantaella et al., 1997., and for instance our research group revealed that Zn content is considerably higher than in chicken meat. For that reason, chicken liver was included into the formulation, and it was effective, increasing or getting a positive correlation between Zn content and chicken liver percentages Ž r s 0.298, P- 0.05.. Iron is one of the most studied trace elements in infant nutrition, since Fe deficiency is particularly prevalent in infants and is a major nutritional problem in the world today. In fact Fe food fortification is generally considered to be the best long-term strategy to combat Fe deficiency ŽHurrell, 1994; Martınez, Lopez, Ros, Vidal & Abellan, ´ ´ ´ 2000.. In our samples, Fe content ranged from 0.20 to 0.51 mgr100 g, the average content was 0.38 mgr100 g, therefore supposing 8.25% of the RDA wNRC ŽNational Research Council., 1991x calculated for an intake of 250 grday. The measured iron content of a food does not necessarily reflect the amount, which is absorbed when the food is eaten. The availability of iron depends on
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187
184
many factors, haem iron from meat being the most available form. Liver has been described as one of the main sources of Fe. In our study, Fe content and percentage of chicken liver were positively correlated Ž r s 0.510, P- 0.01.. Therefore a reasonable form of rising iron content in weaning foods would be increasing the percentage of this ingredient in the formulation of the product, which is, at the same time, a highly available form of this micronutrient. 3.2. In ¨ itro mineral a¨ ailability Percentage of mineral dialysability, PA and TDF contents and PA = CarZn molar ratio are given in Table 3. In vitro methods based on the determination of the amount of dialysable minerals under simulated physiological conditions have shown reasonably good correlation with in vivo availability and can be used for a relative prediction of the bioavailability of minerals ŽWolters, Schreuder, van den Heuvel, van Lonkhuijsen, Hermus & Voragen, 1993.. Modern nutrition programs have recommended increased intake of TDF. However, this fact can be especially controversial in children, since a high TDF content as well as PA have been demonstrated to bind Ca, Fe, Zn and other metals, resulting in low mineral availability. In this study, percentages of the main ingredients in the formulation of weaning foods resulted in a significant Ž P- 0.05. influence of Ca, Zn and Fe availability
ŽTable 4.. The values obtained for Ca availability ranged from 6.03 to 23.01%. The utilisation of this mineral is at a maximum from milk and milk products in children, since lactose appears to increase Ca absorption by infants. On the other hand, lactose, at levels normally present in milk, does not have a significant effect on Ca absorption by healthy adults consuming normal diets ŽMiller & Berner, 1989.. Calcium availability in other foods is considerably low, especially in plants, due to the fact that this mineral is linked to inhibitors such as oxalates, phosphates, TDF and PA ŽMiller, 1993.. However, the values obtained in vitro may be underestimated with respect to in vivo bioavailability because the Ca linked to uronic acids can be released by bacterial enzymes during digestion in the colon for absorption in the large intestine. In our study, a negative correlation was found between Ca availability and TDF Ž r s y0.330, P- 0.05., and although a negative correlation coefficient was also found between Ca availability and PA content it was not statistically significant. TDF content in the weaning foods could be reduced lowering carrot percentage as this ingredient seems to supply the main quantity of this antinutrient. The percentage of Zn dialyzable ranged from 1.75 to 7.10%. The bioavailability of zinc is influenced by other dietary components. Phytates form insoluble complexes with Zn and this is more pronounced if there is excess calcium in the diet ŽCOMA report, 1995.. That is the
Table 3 In vitro availability of Ca, Fe and Zn, phytate content ŽPA., total dietary fibre ŽTDF. and PA = CarZn molar ratio in weaning foods Weaning food
Ca Ž%.
Fe Ž%.
Zn Ž%.
PA Žmgrg.
TDF Ž%.
Ratio PA = CarZn
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
22.08" 8.79 23.01" 3.97 22.88" 0.90 11.99" 1.39 9.55" 0.04 8.12" 0.94 10.02" 3.27 13.19" 0.38 10.26" 2.02 13.02" 0.49 12.80" 2.40 12.87" 0.07 9.90 " 0.11 10.64" 0.26 9.59" 0.12 6.03" 1.27 11.95" 0.88 12.96" 0.07 13.14" 1.50 9.37" 0.78 17.53" 0.61 15.25" 0.94 12.49" 0.71 9.88" 1.24 16.37" 0.43
5.82" 3.92 2.11" 0.01 3.03 " 0.65 2.32" 0.09 3.03" 1.13 1.83" 0.25 1.84" 0.22 6.30" 0.07 2.53" 0.30 3.82" 0.30 5.14" 0.17 3.46" 0.18 2.87" 0.59 3.47" 0.49 3.57" 0.30 1.39" 0.15 5.12" 0.20 2.49" 0.33 3.95" 0.02 3.54" 0.11 4.06" 0.07 5.35" 0.23 3.10" 0.13 3.06" 0.09 4.53" 0.04
3.24" 1.59 3.36" 0.28 7.10" 0.70 3.62" 0.14 3.01" 0.09 2.45" 0.96 1.75" 0.64 5.41" 0.04 4.18" 0.90 4.46" 0.04 4.32" 0.55 5.06" 0.03 3.49" 0.24 3.68" 0.07 3.31" 0,08 2.78" 0.06 3.52" 0.09 3.60" 0.40 4.23" 0.18 3.83" 0.34 4.34" 0.52 5.28" 0.45 4.14" 0.18 3.66" 0.27 3.53" 0.47
1.42" 0.36 1.15" 0.32 0.97" 0.05 1.64" 0.53 1.78" 0.07 1.94" 0.12 0.98" 0.01 1.44" 0.08 1.70" 0.07 1.44" 0.08 1.22" 0.97 1.63" 0.21 1.58" 0.06 2.13" 0.03 1.03" 0.27 0.64" 0.25 1.77" 0.26 0.19" 0.08 1.50" 0.07 0.84" 0.02 1.09" 0.69 1.61" 0.41 0.95" 0.07 1.02" 0.29 1.90" 0.31
0.55" 0.01 0.44" 0.01 0.49" 0.02 0.48" 0.01 0.98" 0.02 0.25" 0.01 0.56" 0.04 0.72" 0.02 0.55" 0.03 0.73" 0.01 0.88" 0.01 0.96" 0.02 0.82" 0.02 0.75" 0.01 0.86" 0.02 0.91" 0.03 0.66" 0.02 0.59" 0.01 0.88" 0.02 0.89" 0.02 0.79" 0.01 0.68" 0.01 0.70" 0.01 0.66" 0.02 0.55" 0.01
0.26 0.26 0.24 0.35 0.39 0.46 0.25 0.44 0.44 0.39 0.34 0.38 0.36 0.48 0.24 0.16 0.45 0.05 0.36 0.21 0.24 0.41 0.19 0.26 0.45
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187 Table 4 One-way analysis of variance of mineral content and mineral availability Source of variance Mineral content Iron Zinc Calcium Phosphorus Mineral availability Iron Zinc Calcium
F
Significance
24 24 24 24
39.508 18.395 13.623 4.983
0.000 0.000 0.000 0.000
24 24 24
6.439 10.578 12.600
0.000 0.000 0.000
d.f.
reason why Davies et al. Ž1986. proposed the application of a PA = CarZn molar ratio as a predictor of the risk of Zn deficiency. According to this research the upper limit in humans must not exceed 0.5. All samples studied presented lower ratios, which means that Zn availability is not compromised in these weaning foods. Iron availability showed the lowest values among all
185
the minerals analysed Žfrom 1.39 to 6.30%.. Iron is most readily absorbed from foods rich in haem, particularly red meat but also other meats and meat products. Non-haem iron, present in plants, is less well absorbed. Phytic acid from cereals, legumes and other vegetables, tannin in tea and polyphenols in spinach, coffee, and other vegetables bind to iron and hinder iron absorption. It is a matter of concern that diets commonly used during weaning may provide inadequate absorbable iron ŽCOMA report, 1995.. Percentages of rice included in the formulation of the weaning foods analysed determined differences in Zn and Fe availability as significant negative Pearson correlation coefficients were found Ž r s y360, P- 0.05 and r s y281, P0.05, respectively.. In fact, it has been previously stated that rice flour is the main ingredient, which increases phytic acid content in weaning foods ŽRincon ´ et al., 1996.. However, we could not find a clear relationship between PA content and Fe and Zn availability. To determine the influence of antinutrients on avail-
Table 5 Cluster analysis, conglomerates final centres, significant levels and samples into each group Mineral availability
Conglomerates final centres 1
2
3
4
Significant level
Fe Ca Zn
4.65 16.38 4.38
3.61 11.49 3.90
3.65 22.66 4.57
1.69 8.06 1.86
0.026 0. 0.013
Samples
21, 22, 25
The rest
1, 2, 3
6, 7, 16
Fig. 1. Graphic representation of principal components analysis based on mineral availability.
186
A.B. Oli¨ ares et al. r Inno¨ ati¨ e Food Science & Emerging Technologies 2 (2001) 181᎐187
Fig. 2. Graphic representation of principal components analysis based in mineral availability and TDF and FA contents.
ability of minerals, regression analysis was performed. Negative regression coefficients were found between phytic acid and TDF and Ca dyalizable although only with the last one was statistically significant Ž bs y0.356, P- 0.05.. TDF also showed negative effects on Zn dialysability Ž bs ᎐0.003. although was not statistically significant. A Cluster analysis and factorial study were performed since, none of the 25 samples showed values higher than the others to Ca, Fe and Zn availability. The aim of two statistical analyses was the selection of a combination of different percentages with the optimal values of Fe, Ca and Zn availability. A Cluster analysis was used to obtain four homogeneous groups of samples determined by the distance between conglomeration final centres and means of Fe, Ca and Zn availability. Table 5 shows these distances, the rate of significance for three variables and the samples of each group. The four groups were significant at P- 0.05 to Fe and Zn availability and P- 0.01 to Ca availability. The groups 1 Žsamples 21, 22 and 25. and 3 Žsamples 1, 2 and 3. were the relative higher percentages to mineral availability. A principal components analysis of samples Žgrouped in previously describe four groups by mineral availability . and Fe, Zn, Ca availability, phytic acid and dietary fiber, calculated by means of alternative least squares was carried out and plotted in Figs. 1 and 2, respectively. These figures represented a bi-dimensional scaling defined by two factors where the association between samples or variables is determined by its position in the graph and their relative distances Žor dissimilarities . with the other elements. When both fig-
ures were overlapping, half of the samples were in the positive side of factor 1 with a great rate of proximity to the parameters of selection ŽFe, Ca and Zn availability. than the other half. This second analysis allows the selection of samples into each group by means of their behaviour Žproximity or distance. with respect to mineral bioavailability Ž P- 0.01.. Thus, we may select samples 3 and 22 since these represent the combination of ingredients Žpea puree, carrot, rice flour and chicken liver. which make infant weaning foods with the optimal Fe, Zn and Ca availability.
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