Sugarcane Bagasse as Dietary Fibre

Comparing past and present times the degenerative disorders are seen to be on an exponential increase rate and the solution to this problem is to increase fibre intake in our diets. Hence, alternative sources of fiber must be explored. Bagasse is a rich source of fiber which could be exploited for human consumption. Bagasse was subjected to different treatments namely: steam, acid, alkali at different concentrations (0.1N, 0.25N, 0.5N, 0.75N, 1N) for different time intervals (15min, 30min, 45min, 60min). Out of these treatments acid treatment did not give best results. Analysis of chemical, functional properties, and microbial assay was carried out. Cellulose, hemicellulose, lignin content of the sample ranged from 40-52percent, 07-25percent, 0927percent respectively. Functional properties namely: solubility index, swelling power, water absorption capacity, oil absorption capacity in the sample ranged from 1-3.25percent, 0.61.03percent, 6.8-9.7g/g, 2.47-9.10g/g respectively. Indigenous treated bagasse was also compared with the imported commercial product the results obtained were much better than commercial product. Thus the aim of the present study is to promote bagasse as a good source of dietary fibre which can be successfully incorporated in food products.


INTRODUCTION
Sugarcane is one of the most important crops in the tropics. As per statistics issued in 2016, Brazil is the largest sugarcane producer in the world at 38.99 MMT followed by India at 24.79 MMT 1 , however, the same has increased by around 25% over the last two years. About 30-32% of bagasse is produced from 1 ton of sugarcane. Since bagasse is a by-product of the cane sugar industry, the quantity of production is in line with the quantity of sugarcane produced. Bagasse is the fibrous residue of the cane stalk left after crushing and extraction of juice. It consists of fibre, water and relatively small quantities of soluble solids mostly sugar. A typical chemical analysis of bagasse (on dry weight basis) is as follows: Cellulose 45-55 percent, hemicelluloses 20-25 per cent, lignin 18-24 per cent, ash 1-4 per cent.
The term ""dietary fibre" which is receiving popularity as a functional ingredient is a complex mixture of indigestible polysaccharides (e.g., cellulose, hemicelluloses, oligosaccharides, pectins, gums), waxes and lignin found in plants, mainly as plant cell wall material. The most consistent definition that is now accepted is by (Trowell et al., 1985). "Dietary fibre consists of remnants of plant cells resistant to hydrolysis (digestion) by the alimentary enzymes of man", whose components are hemicellulose, cellulose, lignin, oligosaccharides, pectins, gums and waxes. Dietary fibre can be further classified into insoluble and soluble fibre fractions. Insoluble fibre primarily promotes the movement of material through the digestive system, thereby improving laxation. The majority of insoluble fibre is fermented in the large intestine, supporting the growth of intestinal microflora, including probiotic species. Soluble fibre can help to lower blood cholesterol and regulate blood glucose levels. The insoluble fibres include cellulose, hemicellulose, and lignin; the soluble fibres include the oligosaccharides, pectins, β-glucans, and galactomanan gums (Filho & Badr, 2000). Inadequate level of dietary fibre in the diet has been implicated in many human diseases like coronary heart disease, blood pressure, obesity, hypercholesterolemia, hyperlipidemia, gall stones, varicose veins, diabetes, constipation and diverticulitis.
Sugarcane bagasse can be a rich source of dietary fibre but its major limitation is its low digestibility which is due to association of lignin with cellulose and hemicellulose. Lignin reduces the digestibility of cellulose and hemicellulose by physically protecting them against enzyme degradation. To overcome this difficulty a number of chemical and biological treatments have to be done for delignification (Tosh & Yada, 2010).

MATERIALS AND METHODS
Bagasse sample for research purpose was procured from the Experimental Sugar Factory of National Sugar Institute (NSI).

A) Delignification of the bagasse
To study the quantity of delignification the bagasse was first washed thoroughly with water to remove dust and the remaining sugar. Washed bagasse was air dried and then kept in oven for overnight at 90°C. Dried bagasse was grounded and sieved through 80 meshscreen. Sieved samples were given different chemical treatments for different time intervals. 3g of bagasse was taken in conical flask and 30ml of alkaline solution was added to it. The pretreatments include 0.1N, 0.25N, 0.5N, 0.75N and 1N of NaOH. Pretreatment was given for different time intervals 15min, 30min, 45min and 60min. Left over solid fraction resulted from filtration washed to a neutral pH & dried in an oven for 24hour at 70°C. Before and after pretreatment, bagasse was analyzed for cellulose, hemicellulose and lignin content using standard methods. From sieved bagasse, 10g sample was taken in conical flask to isolate cellulose, hemicellulose and lignin. Separation of these three was done in stages. Samples were digested with different concentrations of NaOH and for steam they were autoclaved at 120°C for 1hour. Then the digested samples were washed thoroughly with distilled water. Alkaline extract were collected along with the washings. For each samples following was done. (a)Residue obtained for each sample in this step was used for estimation of cellulose after drying it at 60°C overnight. Filtrate along with the washings was acidified with 5N HCl to 2.0 pH which gave brown ppt. Brown ppt obtained was kept at 4°C in refrigerator for overnight. Settled ppt was removed from liquor by centrifugation at 4°C. After centrifugation obtained brown ppt was washed thoroughly with distilled water to neutral pH. (b) Brown ppt obtained was oven dried overnight at 60°C, which was used as lignin. (c) Liquid was used for hemicellulose determination. a, b, and c of untreated and alkali treated bagasse obtained from above method were used for analysis of cellulose, hemicellulose and lignin using Semi-Micro Method, Orcinol Reagent Methodand Denis Reagent Method respectively (Sadasivam & Manickam, 1991 (Rosario & Flores, 1981). Swelling Power and Solubility Index was done by Adebooye and Singh procedure (Adebooye & Singh, 2008).

RESULTS AND DISCUSSION
Bagasse is the fibrous residue of the cane stalk left after crushing and extraction of juice. It consists of total dietary fibre, mainly fibre fractions like cellulose, hemicelluloses, lignin and pectin. The determination of chemical composition of bagasse is therefore important, not only has to support clinical programme, but also to provide and validate data for legal requirements such as food labeling. Analysis of composition provides information on the basic chemical composition. These components are fundamental to the assessment of the nutritive quality of the food being analyzed.

A. Chemical composition of Untreated sugarcane bagasse
The chemical composition of untreated sugarcane bagasse shown in Table1 indicates that the moisture, ash, and crude fibre content was 23.5%, 1.2%, 57.553% respectively. However, the fat content of the bagasse was negligible. Cellulose, Hemicellulose, and Lignin of untreated sugarcane bagasse samples were 40.61%, 25.08%, and 27.22% respectively. The analysis performed and the reported values are expressed in relation to the dry weight of raw bagasse. It can be seen that the cellulose content (40.61%) obtained in the present study is at par than that reported by others from Brazil and China (Filho & Badr, 2004, Sun et al., 2004, Trindade et al., 2004, Mei et al., 2004, & Frollini et al., 2000.  Per cent swelling power, Per cent solubility index, water absorption capacity and oil absorption capacity of untreated sugarcane bagasse samples has been presented in Table  2. Despite the fact that humans cannot digest cellulose, it is nonetheless a very important part of the healthy human diet. This is because it forms a major part of the dietary fibre which is important for proper bowel movement. Since cellulose cannot be broken down and it passes through our systems basically unchanged, it increases fecal bulk and frequency of stool.As lignin reduces the digestibility of cellulose it was observed that the different treatments increased the cellulose content by breaking the ester bond between lignin and cellulose through hydrolysis reaction. Such a reaction damaged the ester bond linkage between lignin and carbohydrate and released cellulose from the encapsulation of lignin, making more cellulose exposed and available (Firdos et al., 1989).

B. Pretreatment of Sugarcane bagasse using acid + steam and alkali +steam of different concentrations
For this purpose fibres must be processed before utilizing for better absorption and assimilation. Hence, bagasse was subjected to the following treatments which include 0.1N, 0.25N, 0.5N, 0.75N and 1N of NaOH. Initially bagasse was also treated with acid of 0.1N and 1N HCL but acid did not give better results as compared to alkali. The particle size in the present study for both the untreated and the treated bagasse sample was 80 mesh.It can be observed (Table No. 3) that treated bagasse samples have better digestibility of cellulose than untreated or acid ones. Compared to untreated bagasse sample and acid treated, the alkali treated sample had lower lignin content because alkaline treatment reduces lignin and increases its solubility since lignin dissolves in alkali.  Solubility index (SI) measures the amount of product sediment after the application of low centrifugal process under specified condition. Finer the particle size higher will be the solubility index.It is important in the product development to improve the quality as well as consumer acceptability. Higher the solubility index better is the quality of the end product as it reduces the sedimentation especially in beverages because sedimentation is not an acceptable quality in any food product. Highersolubility index will also result in lower fat absorption capacity. Hencehigher solubility index is preferred.
Swelling power is the volume occupied by a known weight of the sample under controlled conditions. The sample is hydrated with water for a particular time with no external stress except gravity. Decrease in particle size increases the swelling capacity.
Water absorption (ml water/ g fibre) is the kinetics of water movement under controlled condition. Particle size of a dietary fibre has a role in colonic function by affecting transit time, fermentation and faecal bulking. The smaller the particle size the better is the water uptake. Better water absorption capacity (WAC) can be incorporation into food products would keep the products soft and moist for a longer period. Dietary fibre with high WAC can be used as functional ingredients to avoid synergies and modify the viscosity and texture of some formulated foods.The increased W.A.C. and Swelling Power (S.P.) of digest could slow down gastric emptying and concurrently increase stomach distention, which may trigger afferent vagal signals of fullness.

S.No. Treatment
Time ( Oil absorption is the ability of flours to retain oil and it is important in food applications because if oil absorption capacity of flours is high it makes the flours suitable in facilitating enhancement in flavor and mouth feel when used in food preparations. Higher oil absorption also keeps the texture of food products soft. Oil absorption capacity was observed to be higher in the treated samples than in the untreated one. Dietary fibre with high Oil Absorption Capacity (OAC) allow the stabilization of high fat food products and emulsions. Physical properties of untreated & treated sugarcane bagasse sample using alkali + steam of different concentrations are presented in Table 4.which reveals that solubility index,swelling power, water absorption capacity increased when treated with different concentration alkali & oil absorption capacity whereas oil absorption capacity showed decreasing trend except increased with 0.1 N NaOH concentration.  Table 5 which shows that the physico-chemical properties of bagasse samples pretreated with the lowest concentration ie. 0.1N NaOH was better that the commercial product available in the market. A. Microbial study of sugarcane bagasse sample Microbial load becomes an important issue from safety point of view as bagasse sample will be incorporated into food products. Hence, in the present study, microbial study was carried out both for untreated and Acid + steamed & Alkaline + steamed bagasse samples.
In all the three groups of microorganisms, i.e., bacteria, molds andyeasts the microbial load was found only in untreated samples once treated no micro flora was detected. Sangeetha et al. (2011) studied the influence of acidtreatment, alkali treatment and steaming on the microbial load of sugarcane bagasse fibre and observed that steaming was effective