Apple pomace as a source of dietary fiber and polyphenols and its effect on the rheological characteristics and cake making

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Abstract

Apple pomace, a by-product of apple juice industry, is a rich source of fibre and polyphenols. Also in view of the antioxidant property of pomace, it would play an important role in prevention of diseases. Apple pomace procured from fruit juice industry, contained 10.8% moisture, 0.5% ash and 51.1% of dietary fibre. Finely ground apple pomace was incorporated in wheat flour at 5%, 10% and 15% levels and studied for rheological characteristics. Water absorption increased significantly from 60.1% to 70.6% with increase in pomace from 0% to 15%. Dough stability decreased and mixing tolerance index increased, indicating weakening of the dough. Resistance to extension values significantly increased from 336 to 742 BU whereas extensibility values decreased from 127 to 51 mm. Amylograph studies showed decrease in peak viscosity and cold paste viscosity from 950 to 730 BU and 1760 to 970 BU respectively. Cakes were prepared from blends of wheat flour containing 0–30% apple pomace. The volume of cakes decreased from 850 to 620 cc with increase in pomace content from 0% to 30%. Cakes prepared from 25% of apple pomace had a dietary fibre content of 14.2% The total phenol content in wheat flour and apple pomace was 1.19 and 7.16 mg/g respectively where as cakes prepared from 0% and 25% apple pomace blends had 2.07 and 3.15 mg/g indicating that apple pomace can serve as a good source of both polyphenols and dietary fibre.

Introduction

Dietary fibre functions as a bulking agent and increases the intestinal mobility and moisture content of the feces (Forsythe, Chenoweth, & Bennink, 1976). Several authors have reviewed the importance of dietary fibre since 1970s (Eastwood, 1974, Leveille, 1975, Southgate, 1975). Dietary fibre consists of cellulose, hemicelluloses, lignins, pectins, gums etc. (Gallaher and Schneeman, 2001, Lamghari et al., 2000). Dietary fibres from different sources have been used to replace wheat flour in the preparation of bakery products. Pomeranz, Shogren, Finney, and Bechtel (1977) used cellulose, wheat bran and oat bran in bread making. Potato peel, a by-product from potato industry, rich in dietary fibre, was used as a source of dietary fibre in bread making (Toma, Orr, D’Appolonia, Dintzis, & Tabekhia, 1979). Apple pomace is the residue that remains after the extraction of juice from apple. Dried apple pomace, a fruit industry by-product, is considered as a potential food ingredient having dietary fibre content of about 36.8% and has been used in apple pie filling and in oatmeal cookies (Carson, Collins, & Penfield, 1994). Apple fibre wheat flour blends were shown to have poor bread baking quality (Chen, Rubenthaler, & Schanus, 1988a). Further, Chen, Rubenthaler, Leung, and Baranowski (1988b) having characterized by chemical and physical methods, found apple fibre to be superior to wheat and oat bran. They used apple pomace in cookie and muffin formulations at 4% level so that the quality of the end product was acceptable. In addition, citrus and apple fibres are known to consist of bioactive compounds such as flavonoids, polyphenols and carotenoids and also have been considered as a source of better quality dietary fibre (Fernández-Ginéz, Fernández-López, Sayas-Barberá, & Pérez-Alvarez, 2003). Fernando, Maria, Ana Maria, Chiffelle, and Fernando (2005) evaluated for some functional properties and reported that fibre concentrates from apple pomace and citrus peel can be considered as a potential source for fibre enrichment. Masoodi, Bhavana, and Chauhan (2002) studied cake making from apple pomace wheat flour blends at 5%, 10% and 15%, so as to enrich the cake with fibre content. Fresh apples seem to have antioxidant activity equivalent to 1500 mg of vitamin C and are suppose to inhibit the growth of colon and liver cancer cells (Eberhardt, Lee, & Liu, 2000). Lu and Foo (2000) indicated that the polyphenols, which are mainly responsible for the antioxidant activity, are present in apple pomace and hence could be a cheap and readily available source of dietary antioxidants. Several workers have also carried studies on the recovery of pectin and phenolic compounds from apple pomace by several workers (Schieber et al., 2003, Escarpa and González, 1988, Jham, 1996, Lu and Foo, 1997, Schieber et al., 2001). The objective of the present study was to characterize the apple fibre chemically, and to study its influence on dough properties and on cake making. Polyphenols present in the pomace as well as in cake prepared using apple pomace were also investigated.

Section snippets

Materials

Dried apple pomace was procured from a fruit juice industry (Southern Citrus Products Pvt. Ltd., Gudur, India). The dried apple pomace consisting of peel, stem and seed along with residue of juice extract was ground to powder to pass through 150 μm sieve. Commercial wheat flour procured from local market, having 11.4% moisture, 10.1% protein and 0.45% ash was used in the study.

Chemical analysis

Dried apple pomace was analysed for moisture, ash, protein and fat contents as per the standard AACC methods (2000).

Chemical characteristics of apple pomace

The results of chemical analysis of apple pomace is presented in Table 1. Apple pomace had moisture and protein contents of 10.8 % and 2.06 % respectively. The total dietary fibre content (TDF) was 51.1%, which is about 15–17% higher than the values reported by Carson et al. (1994). Chen et al. (1988b), in their studies have reported TDF of about 61.9% in apple fibre. The soluble fibre (SDF) was found to be 14.6% where as the insoluble fibre (IDF) was 36.5%. The bulk density of the apple pomace

Conclusion

Apple pomace like any other fibre source increases the water absorption capacity of the flour. In general apple pomace affected the elastic properties of the wheat flour dough as well as the pasting properties. Apple pomace having high amount of TDF can function as a valuable source of dietary fibre in cake making. Cakes prepared from 25% of apple pomace-wheat flour blend had 14.2% TDF with high acceptable quality. Addition of apple pomace in cake making can avoid the addition of other

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