Soluble Dietary Fiber generation from Apple Pomace

Transcription

1 Soluble Dietary Fiber generation from Apple Pomace Martha Dolores Bibbins-Martínez a, Blanca Enciso-Chávez, Soley Berenice Nava Galicia a, Dalia Castillo Hernández a a CIBA-IPN, Tlaxcala, México (marthadbm1104@yahoo.com.mx) ABSTRACT The action of four different commercial enzyme combinations on apple pomace soluble dietary fiber generation has been studied by using an alcohol- ethylic acetate insoluble substance prepared from frozen apple pomace. Fiber pomace composition included total dietary fiber (TDF) 64.5%, soluble dietary fiber (SDF) 8.0% and insoluble dietary fiber (IDF) 54.5%. The degree of decomposition of cell wall material and the increase of soluble oligomeric and/or polymeric dietary fiber components are caused by both the composition (pectinases, cellulases, and hemicellulases) and the activities of the enzyme preparations. The soluble fraction increased intensely during pomace treatment. The best enzymatic treatment for soluble dietary fiber generation was with Celluclast 1.5L at 45 C, ph de 4.0, which generated after 20 min 19% SDF. Furthermore, enzyme actions caused changes in the monosaccharide composition and in the molecular weight distribution of polysaccharides in filtrates. The molecular weight limit of water-soluble dietary fiber (SDF) determined by ultrafiltration was from 1000 to 5000 kda. Main monosaccharide determined by HPLC after SDF acid hydrolysis had the following composition (mol %): mannose, 10; arabinose, 22; galactose, 3; glucose, 24; xylose, 1; and galacturonic acid, 40. According with our results apple pomace showed high susceptibility to enzymatic hydrolysis and can be used as a source for soluble diertary fiber generation. Keywords: Apple pomace; soluble dietary fiber; Agro-industrial residues INTRODUCTION Dietary fiber is conventionally classified in two categories according to their water solubility, insoluble dietary fiber (IDF) such as cellulose, part of hemicellulose, and lignin; and soluble dietary fiber (SDF) such as pentosans, pectin, gums, and mucilage [1]. Apple pomace is the main byproduct produced in the apple fruit processing industry. It is a rich source of carbohydrate, pectin, crude fiber, and minerals. It has been reported that the dietary fiber content in apple pomace ranged between 33 to 35%, representing an important natural dietary fiber source. Its use for further product recovery is an appropriate measure for economic reasons as well as from an environmental point of view. Apple pomace is being used successfully for pectin production and recent work regards it as rich source of polyphenols [2]. In México this waste is destined to animal feeding or it is discharged without any other treatment causing environmental pollution, however it can be processed to generate valueadded products. Furthermore, insoluble dietary fraction from apple pomace can be converted into soluble dietary fiber by enzymatic treatment. This is accompanied with an increase in the free phenolic concentration, water-soluble antioxidant activity, and bioavailability of the phenol compounds as well as improving the sensory properties of pomace [2], [3]. A successful recovery process which can easily be integrated into existing production processes must be established and production of alternative products should be explored with the purpose of having an economically feasible apple pomace processing [4]. The objective of this work was to carry out pomace controlled enzymatic treatments to generate soluble dietary fiber with potential use in human food formulation.

2 MATERIALS & METHODS Frozen Apple pomace from a local cider industry was extracted with 80% ethanol and ethylic acetate to remove sugars and pigments. Ground dried samples were analyzed for total and insoluble fiber content according to AOAC method [5]. Enzyme treatments to optimize soluble dietary fiber production were done in beakers containing 5g pomace suspended in acetate buffer solution (ph 4.0) to bring a total volume to 100 ml at T 450 C. The enzyme complexes Cellubrix L, Celluclast 1.5L, Peelzyme IV and Viscozyme L (Novo Nordisk and Novozymes ) were added separately and as a mix at 0.02% each. The hydrolysis was carried out during 1 hour and samples were taken every 5 minutes to determine reducing sugars, total carbohydrates and soluble dietary fiber. Soluble dietary fiber was precipitated with 80% ethanol following drying and acid hydrolysis to identified their main mono and disaccharides components by high-performance liquid chromatography (HPLC) according to AOAC method Sugars were extracted into 50% ethanol; the extract was passed through C 18 Sep-Pak cartridge and then filtered through a 045μm nylon disc. Separation and quantitation were carried out on amino-bonded column Aminex HPX-87P with a mobile phase of water and sulfuric acid. The molecular weight limit of water-soluble dietary fiber (SDF) was determined by ultrafiltration (UF). The UF treatment was performed at a transmembrane pressure of 0.15 MPa and flow velocity of 0.6 ms 1 and membranes molecular weight cut off from 1 to 5 kda. RESULTS & DISCUSSION Table 1 shows the composition of the hydro-alcohol insoluble fraction of apple pomace. From the analysis of the physic-chemical composition it can be seen that the solid material had a moisture content of approximately 8%, a soluble protein content of 7% and an ash content of 1.4%. Fiber pomace composition included total dietary fiber (TDF) 64.5%, soluble dietary fiber (SDF) 8.0% and insoluble dietary fiber (IDF) 54.5%. The experimental data in table 1 are in agreement with reported data from [6]. According with [7], the insoluble fraction accounted for mass percent and contained mainly polysaccharides (cellulose, starch and hemicelluloses), pectin and lignin. The composition of apple total dietary fiber (TDF) reported includes insoluble fiber (IF) 47.7% which is composed mainly of 58.3% neutral polysaccharides (cellulose and hemicellulose), 8.3% pectin, and 4.2% tannins. The soluble fraction is make of 12.6% soluble fiber (SF) which includes 36.5% of hemicellulose and 63.5% of pectin,[6], [7], [8], [9]. Table 1. Dried apple pomace composition Component %(w/w) Moisture 8.0 Protein 7.0 Ash 1.4 TDF 64.5 IDF 54.5 SDF 8.0 In order to increase the apple pomace soluble dietary fiber concentration, controlled enzymatic hydrolysis assays were performed. The best enzymatic treatment for soluble dietary fiber generation was with Celluclast 1.5L at 45 C, ph de 4.0, which generated after 20 min 19% SDF (Figure 1). Figure 2 shows the time course of SDF, total carbohydrates and reducing sugars concentrations corresponding to enzymatic hydrolysis. During the reaction, the SDF ranged from 7 to 17%, the total carbohydrates (TC) range from 7 to 5% and direct reducing sugars (DRS) stayed constant at 2%. The Celluclast 1.5 complex has been used [7] for enzymatic hydrolysis of cellulose without accumulation of cellobiose. In [10] the action of three different commercial enzyme combinations on apple cell wall material has been examined in a model system under conditions of mash and pomace treatment by using an alcohol-insoluble substance prepared from apples. The model experiments allow an insight into

3 the reactions occurring during enzyme action on the plant cell wall, for example, during apple juice production using pectolytic and cellulolytic enzyme preparations. Figure 1. Fiber generation with Celluclast 1.5L. The enzymatic complexes Cellubrix L, Peelzyme IV and Viscozyme L produced 17%, 15% and 13% of SDF respectively after 60 min treatment. The composition of apple pomace and enzymatic digestibility were determined in order to evaluate its potential as a raw material for soluble dietary fiber generation. The extent of decomposition of cell wall material and the increase of soluble oligomeric and/or polymeric dietary fiber components are caused by both the composition of the apple pomace and the activities of the enzyme preparations. (pectinases, cellulases, and hemicellulases), as indicated by the results, with directed enzymatic treatment saccharification can be avoided and soluble fiber enhanced. However, to increase SDF yield, it is necessary to optimize the enzymatic method using different enzyme complex combinations. According with [4], incubated yellow hulls and ground pomace with Celluclast combined either pectinex for pomace or pectinex ultra SP-L for pea hulls, increased the soluble fiber content by 100% and the treatment also improve sensory proportiees of pomace. A newer treatment of a cereal product with a tailored preparation of a Trichoderma enzyme has been evaluated [3]. The authors have validated that the enzymatic treatment increases the SDF amount by 3 times its original amount without any marked decrease in TDF. The above treatment also causes the release of hydroxycinnamic acid, mainly ferulic acid that is linked to the polysaccharide chains. This is accompanied with an increase in the free phenolic concentration, water-soluble antioxidant activity, and bioavailability of the phenol compounds [3]. In order to determine monosaccharides that constitute the SDF, water soluble fraction was recovered by precipitation with 80% ethanol following drying and acid hydrolysis. The main monosaccharides determined by HPLC are demonstrated in table 2. There were significant differences of monosaccharides residues in molar percentages. As expected, galactouronic acid is one of the main components followed by glucose and arabinose. It has been demonstrated that apple fiber is rich in pectin which is structurally composed of chains of 300 to 1000 galacturonic acid moieties, plus neutral sugars such as L-rhamnose, D-galactose, and L- arabinose units [7]. The proportion of glucose coming from cellulose, starch or hemicellulosic polymers constituted 24% mol and the arabinose the 22% mol. Table 2. Monosaccharides composition of SDF Component % mol Mannose 10 Glucose 24 Galactose 3 Arabinose 22 galacturonic 40 acid Xilose 1

4 The SDF monsaccharides composition obtained in this work is consistent with the results reported by [7]. Mainly soluble dietary fiber colloids consisted of oligo- and polymeric arabinans, rhamnogalacturonans and arabinogalactans. Xylose, mannose and galactose moieties, making part of hemicellulosic polymers (e.g. arabinoxylan and arabinogalactan),varied in narrow range ( mass percent of oven-dry Alcohol Insoluble Fiber (AIF)), whereas arabinose and rhamnose units (this latter making part of rhamnogalacturonan) accounted jointly for mass percent of AIF. The same data corrected to express the corresponding contentss mass percent of oven-dry pomace led to average values of 8.5 for xylose, mannose and galactose moieties and 5.2 for arabinose and rhmanose moieties [7]. As part of the SDF characterization, the molecular weight limit of water-soluble dietary fiber (SDF) was determined by ultrafiltration (UF). Results shown that analysed SDF fraction is mainly retained in the 1 kda and 3 kda. The percentage of SDF passing through the 5kDa increased in comparition with the 1 and 3kDa ultrafilter membranes. Ultrafiltration and nanofiltration are the most promising methods for refining and concentrating oligosaccharides. The size-dependent selection mechanism of the membrane process results in the various concentrations of molecules with different molecular weights. Membrane separations have been used for the preparation of several oligosaccharides, such as pectic oligosaccharides [11].As the SDF is a mix of oligo- and polymeric colloids, it will be necessary to perform ultrafiltration experiments using a wider molecular weight cut off membranes allowing to define the SDF molecular weight range. CONCLUSION The composition of apple pomace and enzymatic digestibility were determined in order to evaluate its potential as a raw material for soluble dietary fiber generation. According with our results apple pomace showed high susceptibility to enzymatic hydrolysis. The yield of SDF increased from 7 to 19% after enzymatic treatment. Main SDF monosaccharides components are galactouronic acid, glucose and arabinose showing apple soluble dietary fiber is mainly make up pectin, cellulose and hemicellulose. The large quantity of pomace produced in the apple processing industries can be utilized for value-added biotechnological products generation avoiding environmental pollution when it is discharged without any treatment. ACKNOWLEDGEMENTS Authors wish to thank the National Council of Science and Technology (SIZA-CONACYT, México, Project ref ) for the financial support of this work. REFERENCES [1] Esposito F, Arlotti G, Bonifati AM, Napolitano A, Vitale D, Vincenzo F Antioxidant activity and dietary fiber in durum wheat bran by- products. Food Res Int 38: [2] Schieber, A. Hilta, P. Strekera, P. Ulrich, H. Rentschlerb C. & Carle R A new process for the combined recovery of pectin and phenolic compounds from apple pomace. Innovative Food Science & Emerging Technologies, 4(1), [3] Napolitano A, Lanzuise S, Ruocco M, Arlotti G, Ranieri R, Knutsen SH, Lorito M, Fogliano V Treatment of cereal products with a tailored preparation of Trichoderma enzyme increases the amount of soluble dietary fiber. Journal of Agriculture and Food Chemistry, 54: [4] Shalani, R. & Gupta, D.K Utilization of pomace from apple processing industries: a review. Journal of Food Science and Technology, 47(4), [5] AOAC, Official Methods of Analysis. 17 th ed. Gaithersburg, MD:AOAC ingernational [6] Goñi, I. Torre, M. & Saura-Calixto F Determination of dietary fibre in cider wastes comparison of methods. Food Chemistry, 33,

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