Properties of Calcium-fortified Potato Starch Prepared by Immersion in Natural Mineral Water and Its Food Application

Abstract

This work demonstrates the properties of calcium-fortified potato starch prepared by immersion in natural mineral water containing an extremely high level of calcium (468 ppm) and its food application. The calcium content of the fortified potato starch produced by use of the original mineral water was as high as 813 ppm, while calcium content of the control potato starch was 99 ppm. Rapid visco-analyzer data revealed that the calcium-fortified potato starch had a markedly lower peak viscosity and breakdown and a higher peak viscosity temperature than the control potato starch. Furthermore, calcium fortification caused a significant decrease in starch swelling power. Pound cakes made from the calcium-fortified potato starch and wheat flour blends tended to have a higher specific volume and sensory score of appearance than those made from the control potato starch and wheat flour blends. These findings suggest that the use of calcium-fortified potato starch is critical for making pound cakes with good quality in appearance.

Abbreviations

RVA, Rapid visco-analyzer.

TEXT

Compared to other starches, potato starch has a notably larger amount of covalently bound phosphates,¹⁾ which feature high viscosity and high swelling power.^{2) 3)} Furthermore, it is known that, in potato starch, metal cations are bound to the phosphate by ion forces.⁴⁾ Potato starch is now manufactured in local factories in Hokkaido, the northernmost island of Japan. Potassium is the primary cation in factory-made potato starch, while this starch has low concentrations of calcium and magnesium.^{5) 6) 7) 8)} A level of divalent cations, such as calcium and magnesium, seemed to affect the starch pasting properties, presumably by ionically cross-linking starch phosphate esters. For example, manifest reductions in peak viscosity and breakdown were observed due to the fortification of potato starch with calcium^{5) 6)} and magnesium,⁹⁾ implying that divalent cation-fortified potato starch exhibited good viscosity stability. The application of starch with good viscosity stability would be promising for making foods with desirable qualities. Factory-made potato starch does not exhibit good viscosity stability due to the deficiency of calcium and magnesium. Our previous study indicated an effective way to prepare calcium- and magnesium-fortified potato starches with good viscosity stability by immersion in CaCl₂ and MgCl₂ aqueous solutions, respectively, using factory-made potato starch as a material.¹⁰⁾ Some natural mineral water, what is called “extremely hard water,” contains high amounts of calcium and/or magnesium. It is important for manufacturing calcium- and/or magnesium-fortified potato starches to employ natural products that are safe for and appealing to consumers. Thus, the objective of this study was to prepare calcium-fortified potato starch by immersions in calcium-rich mineral water without using food additives such as CaCl₂ and to examine the effects of enrichment in calcium on starch properties. In addition, the suitability of calcium-fortified potato starch for making breads and pound cakes was also evaluated in wheat flour and potato starch blends.

The potato starch obtained from Toubu Tokachi Noukouren Starch Factory (Hokkaido, Japan) was used as the control starch in this study. Natural mineral water (Contrex), which was derived from Contrexéville, Lorraine, France, was purchased from Suntory Beverage & Food, Ltd. (Tokyo, Japan). It was extremely hard water, containing 468 ppm of calcium, 74.5 ppm of magnesium, 9.4 ppm of sodium, and 2.8 ppm of potassium on the basis of the chemical composition data on the bottle label. Commercial extra-strong wheat flour milled from a Japanese cultivar, Yumechikara, which was purchased from Yamamoto Tadanobu Shoten, K.K. (Hokkaido, Japan), was used in the preparation of bread. Commercial soft wheat flour, which was purchased from Nisshin Flour Milling Co., Ltd. (Tokyo, Japan), was used in the preparation of pound cake.

Five hundred grams of the control potato starch was treated with 1,500 mL of natural mineral water and thereafter held at room temperature for 3 h. The supernatant was discarded, and treatment of the starch with mineral water was repeated twice. Next, the residue was washed twice with distilled water and then dried at 20°C. For the test of diluted mineral water, the mineral water was normally diluted 2, 4, and 10 times with distilled water. Five hundred grams of potato starch was treated with 1,500 mL of each of the diluted solutions and thereafter held at room temperature for 3 h. Next, the residue was washed twice with distilled water and dried at 20°C. All of the starch samples obtained here were stored at 4°C until analysis.

For all potato starch samples examined, the Rapid visco-analyzer (RVA) pasting properties and the content of five minerals, namely, phosphorus, calcium, magnesium, sodium, and potassium, were determined. RVA pasting properties, namely, peak viscosity, breakdown, pasting temperature, and peak viscosity temperature, at 4% starch suspension (dry-weight basis, w/w) were evaluated using the RVA-4 (Newport Scientific Pvt., Ltd., Australia) as previously described.¹¹⁾ Phosphorus content was analyzed in accordance with Noda et al.,¹¹⁾ while the content of calcium, magnesium, sodium, and potassium was as previously reported.⁷⁾ For the control potato starch and that treated with non-diluted mineral water, the swelling power was determined according to the slightly modified method of Wickramasinghe et al.¹²⁾ Starch (20 mg, dry-weight basis) was directly weighted into a screw-cap test tube, and 5 mL of distilled water was added. The capped tubes were then placed on a Voltex mixer for 10 s and incubated at 70°C for 20 min with frequent mixing by inverting at 2-min intervals. The tubes were then cooled to 20°C for 5 min and centrifuged at 1,700 × G for 4 min, and the supernatant was removed with suction. The swelling power was calculated as the weight of swelled starch residue per 1 g of dry starch. The experiments were also conducted by changing the incubation temperature to 75, 80, and 85°C. Measurements of RVA pasting properties and swelling power were carried out in triplicate, whereas the estimations of minerals were performed only once.

The control potato starch and that treated with non-diluted mineral water were used for bread- and pound cake-making tests. The flours used for bread-making tests were 70% of the commercial strong wheat flour, Yumechikara, and 30% of one of the potato starches mentioned above, as well as the commercial strong wheat flour, Yumechikara, only. The bread-making tests were carried out using a no-time method according to the following white bread formulation: 200 g of flour, 10 g of sugar, 10 g of shortening, 4 g of salt, 4 g of yeast, 1 mL of 2% ascorbic acid solution, and 137 mL of water. Adequate water absorption in the bread-making tests was estimated using a Farinograph at 500 BU. The dough was mixed to just beyond peak development, as indicated by the current curve of the mixing motor, then divided into two 100 g pieces, rounded, and allowed to rest for 20 min in a fermentation cabinet at 30°C. Each dough piece was placed in an aluminum pan and proofed at 38°C and 85% humidity for 70 min and then baked at 200°C for 25 min. The specific loaf volume of the bread (the ratio of bread volume to bread weight) was determined after cooling the bread at room temperature for 1 h by the rapeseed replacement method. On sensory evaluation, nine panelists were asked to rate the appearance, inner phase, flavor, taste, and texture of samples on a 1‒4 scale (1 corresponding to bad, 2 to slightly bad, 3 to good, and 4 to very good). A potato starch-free sample was regarded as the control, and the panelists were required to rank it “3 (good).” The flours used for pound cake-making tests were 60% of the commercial soft wheat flour and 40% of one of the potato starches mentioned above, as well as the commercial soft wheat flour only. The pound cake-making tests were carried out according to the following cake batter formulation: 100 g of flour, 100 g of butter, 100 g of sugar, 3 g of baking powder, and two average-sized eggs. Butter and sugar were mixed thoroughly, and then the fresh, broken, whole eggs were poured into the mixture. Next, flour and baking powder were added to the mixture. The batters were placed in baking pans. The cakes were baked in an oven at 170°C for 35 min. The height and specific volume (the ratio of volume to weight) of the cake were determined after cooling the cake at room temperature for 2 h by the rapeseed replacement method. On sensory evaluation, seven panelists were asked to rate the appearance, color, flavor, and texture of samples on a 1‒4 scale (1 corresponding to bad, 2 to slightly bad, 3 to good, and 4 to very good). A potato starch-free sample was regarded as the control, and the panelists were required to rank it “3 (good).” Measurements of the specific loaf volume of the bread and the height and specific volume of the pound cake were carried out in duplicate.

Averages of the RVA pasting property parameters were computed, and Tukey’s range tests were conducted to measure variations in the RVA pasting property parameters among various concentrations of natural mineral water. Swelling-power averages were computed, and Tukey’s range tests were conducted to measure variations in swelling power among the calcium-fortified potato starch and the control potato starch at various temperatures. Additionally, averages of the sensory evaluation parameters of bread and pound cake were computed, and Tukey’s range tests were conducted to measure variations in the sensory evaluation parameters of bread and pound cake among the samples of bread and pound cake, respectively. Significance was defined at P < 0.05.

Figure 1 shows the content of phosphorus, calcium, magnesium, sodium, and potassium in potato starches prepared by immersion in the non-diluted (original) natural mineral water containing high calcium (468 ppm) and in the diluted mineral water. The control potato starch contained high phosphorus (821 ppm) and potassium (669 ppm), while it had a definitely lower content of calcium (99 ppm), magnesium (89 ppm), and sodium (113 ppm). Treatment of the potato starch with calcium-rich mineral water did not affect the phosphorus content. In contrast, the addition of different amount of calcium-rich mineral water had a large impact on the content of calcium, magnesium, sodium, and potassium. Treatment with a higher concentration of mineral water resulted in markedly higher calcium content and slightly higher magnesium content. The content of potassium and sodium decreased drastically with the increase in concentration of mineral water. Thus, we succeeded in preparing the potato starch containing as high as 8.2 times the calcium (813 ppm) of the control potato starch (99 ppm) by immersions in non-diluted mineral water. Even with the use of 10-fold-diluted mineral water, we could obtain a potato starch having 2.6 times the calcium (259 ppm) of the control potato starch. Potassium, which is the main cation in the control potato starch, was not detected in the potato starch treated with non-diluted mineral water, indicating that the potassium in the control potato starch was replaced by calcium during the immersions in non-diluted mineral water. The pasting properties of all the potato starches mentioned above were analyzed by the RVA, and their starch pasting property parameters are summarized in Table 1. The starch pasting properties altered profoundly due to treatment of the potato starch with calcium-rich mineral water. Severe reductions in peak viscosity and breakdown were found with an increase of the concentration of mineral water. This implied that the potato starch treated with a higher concentration of calcium-rich mineral water exhibited good viscosity stability. Treatment with a higher concentration of mineral water led to a manifestly higher peak viscosity temperature. Namely, the peak viscosity temperature of the potato starch produced by immersion in non-diluted mineral water was as high as 95.0°C, whereas that of the control potato starch was 79.0°C. In contrast, pasting temperature increased significantly but slightly with the addition of 4-fold-diluted to non-diluted mineral water. Thus, we established a novel way to manufacture calcium-fortified potato starch with good viscosity stability by the use of calcium-rich mineral water. We defined the potato starch obtained after the treatment of non-diluted mineral water as the calcium-fortified potato starch and used it for the following tests. The swelling power was determined at 70, 75, 80, and 8°C for the control potato starch and the calcium-fortified potato starch, and the results are shown in Fig. 2. The swelling power values of the control potato starch varied from 50.9 to 100.8, while those of the calcium-fortified potato starch ranged from 31.4 to 52.0. Both starches exhibited a sharp enhancement of the swelling power upon raising the temperatures from 70 to 85°C. The swelling power values of calcium-fortified potato starch were significantly lower than those of the control potato starch at all of the temperature conditions.

Fig. 1.

The content of phosphorus, calcium, magnesium, sodium, and potassium of potato starches prepared by immersion in natural mineral water containing high calcium.

(A) Control potato starch. (B) Potato starch treated with 10-fold-diluted mineral water. (C) Potato starch treated with 4-fold-diluted mineral water. (D) Potato starch treated with 2-fold-diluted mineral water. (E) Potato starch treated with non-diluted mineral water.

Table 1.

The RVA pasting property parameters of potato starches prepared by the immersion in natural mineral water containing high calcium.

The data are averages ± standard deviation of three determinations. ^a‒eNo significant difference among samples at P < 0.05.

Fig. 2.

The swelling power at 70, 75, 80, and 85°C for the control potato starch and the calcium-fortified potato starch.

The data are averages ± standard deviation of three determinations. ^a‒fNo significant difference at P < 0.05.

The characteristics of breads made from wheat flour supplemented with the control potato starch and with the calcium-fortified potato starch, as well as those made from wheat flour only, are given in Table 2. Potato starch-free breads showed the highest specific loaf volume (5.98 cm³/g). The specific loaf volume of breads made with the addition of calcium-fortified potato starch was slightly higher (5.40 cm³/g) than that of those made with the addition of the control potato starch (5.29 cm³/g). The results of sensory analysis of breads revealed that no significant differences were observed in all of the sensory attributes. The appearance score of breads made with the addition of calcium-fortified potato starch was slightly higher (2.6) than that of those made with the addition of the control potato starch (2.3). Thus, the substitution of wheat flour with the calcium-fortified potato starch slightly improved the specific loaf volume and appearance of the breads, as compared to the bread with the control potato starch. The characteristics of pound cakes made from wheat flour supplemented with each of the two potato starches and those made from wheat flour only are presented in Table 3. Decreases in the height and specific volume of cakes during baking result in undesirable characteristics. The height and specific volume of pound cakes were definitely reduced from 72.0 to 63.8 mm and from 2.27 to 2.01 cm³/g, respectively, by the substitution of wheat flour with the control potato starch. In contrast, the values of height and specific volume of pound cakes made from wheat flour supplemented with the calcium-fortified potato starch were as high as 76.0 mm and 2.25 cm³/g, respectively, which were similar to those made from wheat flour only. From the data for sensory analysis, all of the sensory attributes of pound cakes were not significantly different among the three samples examined. Pound cakes made from wheat flour substituted with the control potato starch showed a slightly lower score for appearance (2.4) than those made from wheat flour only (3.0) and those made from wheat flour substituted with the calcium-fortified potato starch (3.1).

Table 2.

Effect of substitution of wheat flour with the control potato starch and with the calcium-fortified potato starch on characteristics of breads.

In the data of sensory evaluation, the data are averages ± standard deviation of nine evaluations. ^aNo significant difference among samples at P < 0.05.

Table 3.

Effect of substitution of wheat flour with the control potato starch and with the calcium-fortified potato starch on characteristics of pound cakes.

In the data of sensory evaluation, the data are averages ± standard deviation of seven evaluations. ^aNo significant difference among samples at P < 0.05.

We previously established an effective way to prepare calcium-fortified potato starches with the addition of a high-concentration CaCl₂ solution using potassium-rich potato starch produced at a local factory in Hokkaido.¹⁰⁾ The use of natural water, instead of food additive-containing solution, is desirable for the preparation of calcium-fortified potato starch to appeal to consumers as being safe and comforting. Yagi and Yoshioka¹³⁾ and Wiesenborn et al.¹⁴⁾ noted that the potato starch extracted from tap water, presumably containing a high level of calcium, was slightly high in calcium (207‒282 ppm). Various brands of bottled mineral water differing in mineral composition are available in Japan. In this study, we selected the brand Contrex, which belongs to the “extremely hard water” category and contains a markedly high level of calcium (468 ppm), for preparation of the calcium-fortified potato starch. The calcium-fortified potato starch obtained in this study had 8.2 times the calcium (813 ppm) of the control potato starch, whereas that obtained with the addition of 1% CaCl₂ solution in our previous study¹⁰⁾ had 6.9 times the calcium of the control (686 ppm). We have determined the four parameters of RVA pasting properties, peak viscosity, breakdown, pasting temperature, and peak viscosity temperature, and the swelling power of the calcium-fortified potato starch prepared by immersion in natural mineral water. The RVA results of our previous study¹⁰⁾ confirmed manifest reductions in peak viscosity and breakdown due to the fortification of potato starch with calcium. Amylograph and swelling power tests performed by Kainuma et al.⁵⁾ and Yamamoto et al.⁶⁾ indicated that peak viscosity, breakdown, and swelling power became much lower, and peak viscosity temperature became much higher as a result of the calcium-fortification of potato starch. Kainuma et al.⁵⁾ also suggested that calcium ion bound two phosphate residues present in different glucosidic chains, forming cross-linkages, and that these cross-linkages led to the depressed dispersion of glucosidic chains and, as a result, inhibited increases in viscosity and swelling power. Inatsu et al.¹⁵⁾ reported that edible canna starch had almost the same amount of phosphates as potato starch, and it contained a relatively high amount of calcium (250 ppm). They also indicated that the substitution of calcium with potassium in canna starch increased peak viscosity, breakdown, and swelling power and decreased peak viscosity temperature. Supporting these results, this study confirmed that the calcium-fortified potato starch exhibited markedly lower peak viscosity, breakdown, and swelling power and higher peak viscosity temperature than the control potato starch. Thus, we succeeded in obtaining the potato starch altered largely in rheological characteristics by the use of calcium-rich mineral water, which is not a food additive-containing solution.

The rheological characteristics of the starch are of significance in using it for food processing. Calcium-fortified potato starch appears to be promising for food making because it shows good viscosity stability. In Japan, potato starch is generally cheaper (120-200 Yen/kg) than wheat flour (160-240 Yen/kg), and wheat flour-based foods are frequently produced with the addition of potato starch to improve their quality and/or to cut down on the cost of imported wheat flour. Using a Farinograph, dough characteristics of the mixtures of wheat flour and potato starches of three cultivars were studied to observe the feasibility of diversifying potato starches in wheat flour-based foods.¹⁶⁾ Moreover, the utilizations of potato starches of several cultivars were studied regarding the making of instant noodles¹⁷⁾ and Korean-style cold noodles¹⁸⁾ with wheat flour and potato starch blends. However, little research has been extended to the suitability of potato starch for other wheat flour-based foods. Therefore, we evaluated the applicability of calcium-fortified potato starch in making breads and pound cakes. First, breads were made from a blend of extra-strong wheat flour, Yumechikara, with a high protein content and extra-strong dough quality traits,¹⁹⁾ and each of the control potato starch and calcium-fortified potato starch and from wheat flour only. The substitution of wheat flour with purified starch generally led to decreased specific loaf volume due to a weakening of the gluten strength of composite dough. However, Nindjin et al.²⁰⁾ reported that up to a 30% substitution of yam starch and up to a 20% substitution of cassava starch did not change the loaf characteristics or the scores of sensory evaluation as compared to starch-free breads. The results of bread-making in this study revealed that a 30% substitution of each of the control potato starch and calcium-fortified potato starch lowered the specific dough volume but did not cause a significant reduction of sensory attributes. Furthermore, the addition of the calcium-fortified potato starch slightly raised the specific loaf volume and appearance of breads, as compared to those of the control potato starch. Second, pound cakes were made from a blend of soft wheat flour with the control potato starch and with calcium-fortified potato starch as well as from wheat flour only. Cakes are more complicated systems in terms of baking process as compared to bread, because the principal ingredients of cakes are sugar, fat, and eggs in addition to wheat flour (or starch). The final characteristics of cakes are governed by starch gelatinization and egg protein coagulation during baking. In general, cake making requires a good performance of volume development. The effects of different starches on cake quality have been studied.^{21) 22) 23)} According to Almeida et al.,²³⁾ the specific volume of the pound cakes supplemented with potato starch was significantly higher (2.18 cm³/g) than that of those supplemented with corn starch (1.77 cm³/g) or with rice starch (1.78 cm³/g). Similarly, Seyhun et al.²¹⁾ demonstrated that potato starch was more suitable in making cakes with higher volume than corn, waxy corn, and amylomaize starches. In this study, pound cakes made by the replacement of wheat flour with calcium-fortified potato starch tended to exhibit a higher specific volume and sensory score of appearance than those made with the control potato starch. It was suggested that the interaction of the calcium-fortified potato starch with sugar, fat, and egg protein had a positive effect on cake volume. However, the detailed reason for the improving effects of calcium-fortified potato starch for pound-cake making was unclear. Thus, we conclude that the use of calcium-fortified potato starch is of significance for making pound cakes with good quality in appearance. The present work demonstrates that the calcium-fortified potato starch prepared by immersion in natural mineral water can be regarded as practical and functional food ingredients.

Calcium-fortified potato starch was prepared successfully by immersion in calcium- rich mineral water. In addition to the properties of the calcium-fortified potato starch, its suitability for food making was also studied. RVA data confirmed that calcium fortification of the control potato starch significantly decreased peak viscosity and breakdown and increased peak viscosity temperature. A definite reduction in starch swelling power was observed as a result of calcium fortification. From the data on the roles of calcium-fortified potato starch in governing food qualities, pound cakes made from wheat flour supplemented with calcium-fortified potato starch tended to have a higher specific volume and sensory score of appearance than those made from wheat flour supplemented with the control potato starch. Thus, calcium-fortified potato starch can be used for making pound cakes to improve their overall quality.

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