EFFECT OF PASTA COOKING TIME ON THE CONTENT AND FRACTIONAL COMPOSITION OF DIETARY FIBER

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1 bs_bs_banner Journal of Food Quality ISSN EFFECT OF PASTA COOKING TIME ON THE CONTENT AND FRACTIONAL COMPOSITION OF DIETARY FIBER ALDONA SOBOTA 1 and PIOTR ZARZYCKI Engineering and Cereals Technology Department, University of Life Sciences in Lublin, Lublin ul, Skromna 8, Lublin , Poland 1 Corresponding author. TEL: ; FAX: ; aldona.sobota@up.lublin.pl Received for Publication March 16, 2012 Accepted for Publication December 9, /jfq ABSTRACT The objective of this study was to determine the effect of pasta cooking time on changes in the content of selected components in dry matter, including changes in the content of total dietary fiber (TDF) and of its insoluble (IDF) and soluble fractions. Longer time of cooking resulted in greater cooking loss. After 16-min, cooking loss was at 7% d.m. As a result of the application of extended cooking time, a significant increase was observed in the content of TDF, including the IDF fraction, in dry matter. There was slight change in the content of the soluble fiber fraction. PRACTICAL APPLICATIONS In the era of civilization diseases, such as obesity, type 2 diabetes, cardiovascular diseases and colorectal cancer, properly balanced diet is of very high importance. Cereal products rich in dietary fiber should be an inseparable element of such a diet. Numerous studies have been devoted to the content of dietary fiber in raw food. However, most food, for example pasta is not eaten raw but cooked. Many processes can cause changes in the content and fractional composition of dietary fiber. In this work, the effect of pasta cooking time on the content and fractional composition of dietary fiber was analyzed. The presented studies are important especially from the nutritional point of view. INTRODUCTION Next to bread, pasta is the most common processed cereal products. It is one of the convenient food it stores easily and is relatively quickly prepared for consumption. From the nutritional point of view, white pasta made from high extraction flour, is considered to be a high-energy product, characterized by relatively low levels of dietary fiber, vitamins and minerals. However, in spite of their relatively high glycemic load, the products, compared with other cereal products, are characterized by a low glycemic index (Foster-Powell et al. 2002; Atkinson et al. 2008). This valuable trait assumes a special importance in the era of a sudden increase of the incidence of diabetes and obesity (WHO 2003; Brennan 2005). Starch contained in pasta is digested slowly, and the released glucose is gradually absorbed in the small intestine (Granfeldt and Bjorck 1991). In consequence, this leads to low postprandial glycemia and weak insulin responses in humans.according to Fardet et al. (1998, 1999), slow digestion and gradual release of glucose from starch can be an effect of compact and dense structure of extruded pasta and gluten matrix closely adhering to starch which largely inhibits the access of a amylase. Numerous studies demonstrate that the susceptibility of starch to the effect of amylolytic enzymes depends also on the presence of nonstarch components, i.e., dietary fiber. Every increase in the content of dietary fiber in pasta, both the soluble and insoluble fractions, causes decrease in the digestibility dynamic of starch and, in consequence, also a lowering of the glycemic index of the products (Wolver 1990; Brennan 2005; Brennan and Tudorica 2008; Aravind et al. 2011). Many studies have shown that the cooking time affects the cooking quality of pasta (Grant et al. 1993; Dziki and Laskowski 2005; Sozer et al. 2007). It should be emphasized, that the pasta cooking time applied can also determine the chemical composition of the cooked products, and also their calorific and nutritional values. Journal of Food Quality 36 (2013) Wiley Periodicals, Inc. 127

2 DIETARY FIBER CONTENT IN COOKED PASTA A. SOBOTA and P. ZARZYCKI According to Bornet et al. (1990) and Foster-Powell et al. (2002), considerable extension of the cooking time leads to a lowering of the glycemic index of pasta. Such a tendency may result from an increase in the content of selected components of dietary fiber in dry matter of cooked pasta. Many papers have shown that pasta thermal treatment processes such as steaming, frying or cooking lead to an increase in resistant starch content (Sgrulletta et al. 2005; Fares et al. 2008; Dhital et al. 2010). According to Sgrulletta et al. (2005), as a result of cooking of white spaghetti, there is a significant increase in the content of resistant starch. Those authors report that the content of resistant starch in cooked pasta can be even 340% higher compared to uncooked pasta. Extension cooking time of pasta additionally increases that tendency. According to the authors, uncooked pasta contains 0.35% resistant starch (RS), cooked pasta 1.55%, while overcooked pasta -1.73%. However, not all studies show that heating increase in the RS content. A reverse tendency was noted by Garcia-Alonso et al. (1999) and Colonna et al. (1990). Those authors claim that the susceptibility of starch to a-amylase hydrolysis was always increased by cooking. Smaller pasta size and increased cooking time led to higher susceptibility. On the other hand, extended cooking time may lead to greater cooking losses and, at the same time, can cause changes in the percentage share of the particular components in the dry matter. In the course of cooking, components easily soluble in water can migrate to the solution to a notably greater extent, among those gelatinized starch and the products of its hydrolysis, oligosaccharides or simple sugars, and to a smaller extent insoluble components, among which we can include the insoluble fractions of dietary fiber. Grant et al. (1993) report that the extension of cooking time of spaghetti by 10 min with relation to the optimum cooking time leads to a notable reduction of the content of amylose in the cooked pasta, and to an increase in the level of that polymer in the water used for the cooking. A similar tendency was observed by Lintas (1988) in a study on the content of simple sugars and oligosaccharides in cooked pasta. That author found that the extension of the cooking time of spaghetti from 3 to 12 min caused a reduction in the content of such components as, e.g., fructose, glucose, saccharose and maltose in the cooked pasta, with simultaneous increase of those sugars in the water used for the cooking. Reduction of the content of rapidly and easily digestible carbohydrates and simultaneous increase in the content of dietary fiber in pasta dry matter may contribute to a reduction of the energy density and of the glycemic load and index of the products. Therefore, it appears to be worthwhile to conduct studies that will permit to determine whether modification of pasta cooking time may have an effect of its nutritional value, including the content and fractional composition of dietary fiber. MATERIALS AND METHODS Three assortments (designated as A, B and C) of spaghettitype pasta available on the Polish market, were used as the experimental material. The products were from three different manufacturers. They were produced with the use of various cereal materials flour of durum wheat, wheat pasta flour and semolina. Table 1 presents the material composition and characteristics of the pasta products studied. The content of total dietary fiber (TDF) and of the insoluble (IDF) and soluble (SDF) fiber fractions was determined both for the uncooked pasta and for the products after cooking. Uncooked pasta was fragmented to particle size of <0.1 mm. and then their moisture was determined with the oven-dry method (AACC 2000, Method 44-15A). Protein (N 5.7), ash and crude lipid contents of pasta samples were determined according to the Approved AACC (2000) Methods. The content of TDF and of the IDF and SDF fractions was determined with the use of enzymes produced by Megazyme, following the methods AACC 32-05, AACC and AACC (AACC 2000 Methods). The determinations of nutritional components in raw pastas were performed in three replications. One hundred grams of the spaghetti was cooked in 1,000 L of distilled water applying cooking times of 4, 6, 8, 10, 12, 14 and 16 min. After the cooking, the pasta was strained and cooled at room temperature for 20 min. Each time the cooking loss was determined. The level of cooking loss was determined by assaying the content of dry matter in the water after the cooking. The method applied was the oven-dry method AACC (2000), 44-15A. This method was TABLE 1. CHARACTERISTICS OF THE PASTA Samples Declared ingredients Declared cooking time (min) Diameter (mm) Nutritional components (% d.m.) Protein Fat Ash CHO A Durum wheat flour, water B Wheat flour, water C Semolina, water CHO, digestible carbohydrate and dietary fiber (by difference). 128 Journal of Food Quality 36 (2013) Wiley Periodicals, Inc.

3 A. SOBOTA and P. ZARZYCKI DIETARY FIBER CONTENT IN COOKED PASTA also used to determine dry matter content in the cooked products (AACC 2000, Method 44-15A). The levels of total dietary fiber and its particular fractions in the cooked pasta products were determined following the methods described above (AACC 2000 Methods). The cold pasta was fragmented thoroughly into fragments with dimensions of less than 0.5 mm. For the determination of dietary fiber content, portions of 2 g of the cooked product were taken. The assays were made for each sample of cooked pasta, in three replicates. Statistical Analysis Mean values and standard deviations were calculated. The significance of differences among the results was determined using the Duncan test (P 0.05). For selected continuous variables the trend lines, regression equations and coefficients of determination were determined. The statistical analysis of the results was performed with the use of the program SAS RESULTS AND DISCUSSION The uncooked spaghetti-type pasta products were characterized by moisture content at the level of % (Table 2). During cooking, the products absorbed water. The gradual extension of the pasta cooking time caused an increase in the content of water in the cooked products. Spaghetti cooked for 4 min was characterized by moisture content at the level of 53 57%, while cooked for 16 min had moisture in the range of 67 70% (Table 2). Therefore, longer time of cooking permitted the absorption of greater amounts of water with simultaneous reduction of the energy density of 100 g of cooked pasta. TABLE 2. MOISTURE CONTENT OF PASTA Moisture content (%) Samples Pasta A B C Uncooked ec hb ea Cooked for: 4 min db gc da 6 min cb fc da 8 min ba eb cb 10 min aa dc bb 12 min aa cb bab 14 min ab bb aa 16 min ac aa ab Mean values (n =9) standard deviation. Means in the same column with the same letters (a h) and in the same line with the same letter (A C) are not significantly different (Duncan test; P 0.05). TABLE 3. INFLUENCE OF THE COOKING TIME ON THE COOKING LOSS OF PASTA Cooking loss (% d.m.) Cooking time (min) Sample A B C ea db ea da ba da ca bb cb cba bb cbb cba bc bb bb aa bac ac aa ab Mean values (n =9) standard deviation. Means in the same column with the same letters (a e) and in the same line with the same letter (A C) are not significantly different (Duncan test; P 0.05). Longer time of pasta cooking corresponds to greater cooking loss. The lowest cooking loss was observed in the case of products cooked for 4 min. Extension of the cooking time to 16 min caused an increase in cooking loss more than twice (Table 3). This is connected with gradual hydration of deeper and deeper pasta s layers. Starch granules encased in the protein matrix swell and gelatinize. Protein structure becomes less compact. Water penetrates the product more intensively and leaches out mainly soluble components of dry matter. It should be emphasized that the level of dry matter losses in the tested samples of pasta was varied. This may have been due to the varied content of proteins in the products. In the case of pastas B and C, where protein content was 14.3 and 13.74%, respectively, lower dry matter losses were noted during cooking for 8, 10, 12 and 16 min. Greater dry matter losses were observed during the cooking of pasta A. That product, even though produced from durum wheat flour, was characterized by very low protein content of 11.48% (Table 1). Higher-protein pasta exhibits lower loss of solids to cooking water and better tolerance to overcooking because it maintains its integrity better during cooking (Malcolmson and Matsuo 1993; Oak and Dexter 2006; Samaan et al. 2006; Sobota and Dobosz 2010). Manthey and Schorno (2002) reported that pasta made with semolina had cooking loss values of around 6.5%. Malcolmson and Matsuo (1993) reported that good quality pasta should not lose more than 10% of dry matter during cooking. Brunori et al. (1994) and Oak and Dexter (2006) maintain that the level of dry matter losses depends not only on protein content but also on the fractional composition of gluten proteins. According to Yue et al. (1999) and Manthey and Schorno (2002), drying parameters of pasta are also very important. It is emphasized that high temperature drying strengthens the gluten matrix, which protects starch granules from rupturing during cooking. Journal of Food Quality 36 (2013) Wiley Periodicals, Inc. 129

4 DIETARY FIBER CONTENT IN COOKED PASTA A. SOBOTA and P. ZARZYCKI FIG. 1. TOTAL DIETARY FIBER (TDF) CONTENT IN UNCOOKED AND COOKED PASTA FIG. 2. INFLUENCE OF THE COOKING TIME ON THE TOTAL DIETARY FIBER (TDF) CONTENT IN PASTA So-called white pasta products are products characterized by relatively low levels of TDF. In the uncooked spaghetti-type pasta products under study, the level of that component varied in the range from 5.35 to 5.71% (Fig. 1). Among uncooked pastas, the highest content of TDF (5.71%) was found for the spaghetti produced from durum wheat flour type A. The content of the IDF in all the products studied was similar at the level of % (Fig. 5). Similar values ( %) were obtained in the case of the soluble fraction of dietary fiber (Fig. 3). Sobota and Skwira (2009) reported that in traditional extruded pasta the content of TDF is 4 4.5% d.m., soluble fraction is % d.m. and insoluble fraction is % d.m. Extension of the pasta cooking time caused an increase in moisture with simultaneous reduction of the share of dry matter in 100 g of cooked pasta. As a result of cooking, a decrease of dry matter content was observed a part of its components migrated to the solution. This caused changes in the percentage share of the particular components in dry matter. The changes related to, e.g., the content and fractional composition of dietary fiber. The content of the TDF in dry matter of the cooked pasta products was varied and depended both on the pasta type and on the cooking time. Short-time (4 min) process of cooking did not cause any significant changes in the content of TDF (Fig. 1). Its level in the cooked pasta was in the range of % and was similar to the TDF content in the uncooked pasta products. Gradual cooking time extension (from 4 to 16 min) caused an increase in TDF content by 22.1% (type A), 22.4% (type B) and 20.4% (type C), respectively (Fig. 2). The tendency in the changes of TDF content in the function of pasta cooking time is illustrated by the trend lines in Fig. 2. Increase in the content of TDF in the cooked pastas can be explained in 86 95% by the cooking time (0.86 < R 2 < 0.95). Among the cooked products, the highest content of dietary fiber was assayed for pasta type A produced from durum wheat flour. Similar trends were observed by Sgrulletta et al. (2005) Fares et al. (2008). Those authors demonstrate that the process of pasta cooking causes an increase in the content of TDF in dry matter. Sgrulletta et al. (2005) reported that in the case of traditional white pasta the increase in TDF content attains even 53%. The observed changes in the content of TDF resulted primarily from increases in the content of the insoluble fraction of dietary fiber (IDF). The level of the soluble fraction (SDF) in dry matter of overcooked pasta (cooking time 16 min) did not change significantly (type B and C) and even decreased (type A) (Fig. 3). The exact tendencies of changes in the content of SDF as a function of pasta cooking time are presented in Fig. 4. The coefficients of determination (R 2 ), describing the degree of fit of the trend FIG. 3. SOLUBLE DIETARY FIBER (SDF) CONTENT IN UNCOOKED AND COOKED PASTA 130 Journal of Food Quality 36 (2013) Wiley Periodicals, Inc.

5 A. SOBOTA and P. ZARZYCKI DIETARY FIBER CONTENT IN COOKED PASTA FIG. 4. INFLUENCE OF THE COOKING TIME ON THE SOLUBLE DIETARY FIBER (SDF) CONTENT IN PASTA FIG. 6. INFLUENCE OF THE COOKING TIME ON THE INSOLUBLE DIETARY FIBER (IDF) CONTENT IN PASTA line to the experimental results, fall within the range from 0.56 (type A) to 0.82 (type B and C). In the pasta products cooked for 16 min, the content of IDF was notably higher compared to the level of that fiber fraction in the dry matter of uncooked pasta or in that of pasta cooked for 4 min (Fig. 5). The cooking time extension from 4 to 16 min caused an increase in the content of IDF in dry matter of the products by 36.9% (type A), 25.2% (type B) and 26.6% (type C) (Fig. 6). Increase in the content of IDF in the cooked pastas can be explained in 93 96% by the cooking time (0.93 < R 2 < 0.96). Studies by Sgrulletta et al. (2005) and Fares et al. (2008) suggest that the observed changes may be related with an increase in the content of resistant starch in cooked pasta. Sajilata et al. (2006) maintain that the cooking process as such, under conditions of high moisture and temperature, can significantly lower the RS content by disrupting crystalline structure. Likewise, Colonna et al. (1990) reported that the susceptibility of starch to a-amylase hydrolysis was always increased by cooking. Extension of the pasta cooking time led to higher susceptibility of starch to digestion (Colonna et al. 1990). Increasing the levels of RS can be done in other conditions such as cooling after cooking (Sajilata et al. 2006; Dhital et al. 2010). The observed increase in the content of the insoluble fraction of dietary fiber in the pasta under study may also be caused by disproportional leaching of the particular components of dry matter in the course of pasta cooking. It is to be assumed that the insoluble components of dietary fiber (IDF) migrate to the water in the course of cooking to a lower degree than the soluble fractions of dietary fiber (SDF). Thus, their content in dry matter of cooked pasta increases. Cooking time extension intensifies that tendency. It should be emphasized that the spaghetti-type pasta products studied are relatively resistant to overcooking. Taking into account the relatively dry matter losses under the effect of extension of cooking time, the observed changes in the levels of TDF and IDF appear to be significant. CONCLUSIONS White pasta is a relatively poor source of dietary fiber. In the study presented here, an analysis was performed of the effect of pasta cooking time on changes in the content and fractional composition of dietary fiber. It was demonstrated that extension of pasta cooking time causes greater dry matter losses during the cooking. With an extension of the cooking time, there was an increase in the content of TDF and the IDF fraction in the cooked products. Extension of pasta cooking time did not cause any greater changes in the content of SDF fraction. REFERENCES FIG. 5. INSOLUBLE DIETARY FIBER (IDF) CONTENT IN UNCOOKED AND COOKED PASTA AACC Approved Methods of the American Association of Cereal Chemists, American Association of Cereal Chemists, St. Paul, MN. Journal of Food Quality 36 (2013) Wiley Periodicals, Inc. 131

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