5.3.1 Food and Animal Feed

Though OPWs have been considered as nonedible, the potential of producing highly nutritious foods (for both humans and animals) as well as vitamin supplements has been reported in recent studies. The fibres of the OPW (mostly EFB, OPT and OPF) comprise mainly cellulose (about 25-50%), hemicellulose (about 20-35%) and lig­nin (about 15-25%) which are readily convertible to carbohydrates and sugars such as glucose, sucrose and fructose for various applications in the food industries.

EFB is reported to compose of about 24% xylan (a sugar polymer made of pen­tose sugar called xylose) which can serve as a substrate for the production of sweet­ening agents such as xylitol, sorbitol, and lactitol by catalytic hydrogenation (Wyman 1994; Silva et al. 1995). Xylitol is used extensively in the food and phar­maceutical industries as sugar for diabetic patients, as supplements in energy drinks and as anticariogenic agent in toothpaste formulations for the prevention of cancer (Makinen 1992) . Aqueous sorbitol solutions are hygroscopic thus useful in the applications of humectants and softeners in the food and pharmaceutical industries (Gliemmo et al. 2008). Recent studies have reported the hydrolysis of xylose and glucose from sulphuric acid-pretreated EFB with concentrations of 31.1 and 4.1 g/l, respectively (Rahman et al. 2006) , steam-pretreated OPF with glucose yield of 92.78 wt% (Goh et al. 2010), steam-pretreated EFB with glucose yield of 209 g/kg EFB (Saleha et al. 2012), the juice from the OPF (Fazilah et al. 2009) with glucose concentration of 53.95 ± 2.86 g/l, thermally treated OPT (Ho et al. 2007), etc. OPT juice has been found by Chin et al. (2011) to have a higher glucose conversion yield compared to those for rubberwood sawdust and mixed hardwood sawdust. The highest yield of monomeric sugar (70% of total carbohydrate content) was found in EFB (41.82%, w/v) pretreated by enzyme and saccharified for 120 h (Rashid et al. 2011). Food flavouring such as vanilla essence can be extracted from EFB (Ibrahim et al. 2008).

PPF is used as fibre enrichment agent for the manufacture of bread which gives it a heavier consistency than normal white bread (Kamarun Zaman 2008). Fibre content of 6.1 g/100 g serving has been used in a formulation of the palm fibre bread which has the same fibre content as most whole meal breads. Pre-hydration of OPW fibres was reported to improve dough water absorption and high fibre bread loaf volume (Kamarun Zaman 2008). Again, OPT fibres, due to its high water absorp­tion rate (without congealing) coupled with its capability of withstanding high tem­peratures during food processing, have been successfully used as food fibre in yoghurt, pastries and bread in place of wheat. Currently, Malaysia produces special cereals from OPT fibres using patented process by the Sukhe International Sdn Bhd. Thus the transformation from wastes to wealth is highly feasible. PKC contains valuable dietary protein (14.5-19.5 g/100 g) (Alimon 2004) which can be commer­cially isolated (by enzyme-assisted extraction in alkaline medium with an optimum yield of 11.91 g/100 g) and concentrated for various applications in the food industry (Chee et al. 2012). PKC is also used as a substrate in solid-state fermentation (SSF) for the production of enzymes such as tannase (Sabu et al. 2005), phytase (Ramachandran et al. 2005), alpha amylase (Ramachandran et al. 2004), and P-mannanase (Ong et al. 2004). Ariffin et al. (2008) have also reported the feasibil­ity of producing an enzyme called bacterial endoglucanase from EFB for different applications in the food and nutraceutical industries.

Flour prepared from defatted PKC was used as a substitute for wheat bran for the preparation of dietary fibre-rich wheat cookies and bread. These cookies and bread from PKC showed better nutritive value (e. g. lower starch content) than those for normal wheat bread and cookies (Pacheco de Delahaye et al. 1994). The feasibility of monoacylglycerol production from PFAD as additives in bread and pastries has also been demonstrated by Junior et al. (2012) with a production yield of 73%.

The low protein and high fibre contents of OPF make it a good potential source of feed for many classes of herbivorous animals like cattle, buffaloes, sheep, etc. (Dahlan et al. 2000). The potential of using PPF for ruminant production has been examined by Abu Hassan et al. (1996) to be feasible especially when it is chemi­cally treated and well formulated to improve its nutritive value. Various pretreat­ment methods have been used to improve the quality of PPF to enhance its biodegradability and digestion in ruminants (Abu Hassan et al. 1996; Dahlan et al. 2000). Experimental goats were given OPF as a raw feed whose organic matter digestibility increased through ensiling, while pelleting increased the intake rate significantly (Dahlan et al. 2000; Kawamoto et al. 2001). PPF treated with sodium hydroxide has been reported by various studies (Kawamoto et al. 2001; Jelan et al. 1986) to increase its dry matter digestibility from 43.3% to 58.0% but detrimental to its palatability. Low-pressure steaming of OPF at 10 kg/cm2 for 20 min followed by oven drying at 60°C for 48 h have been reported by Bengaly et al. (2000) to sig­nificantly improve its nutrient degradability. Urea treatment (3% and 6%) had a negative effect on digestibility, but the addition of up to 3 g/kg of urea to steam — treated OPF increased its intake and digestibility in goats (Abu Hassan et al. 1996). However, in sheep, coupling urea treatment with heat treatment of OPF showed better intake and digestibility up to 16 g/kg (Bengaly et al. 2010).

Diets containing about 50% OPF which were ministered to cattle did not show any nutritional disorders as side effects (Abu Hassan et al. 1996). Goto et al. (2002) have reported low contamination risks in OPF as they are poor medium for aflatoxin (a food contaminant) production. Though much research have not been done on the use of EFB as feed for animals, Abu Hassan et al. (1996) have concluded that EFB processed into pellets may increase the nutritional value of the feed. The sustainable utilisation of fibres from the OPF, PPF and EFB is achieved when they are made into pellets. For instance, unpelleted or untreated OPF petioles are not palatable to goats (Dahlan et al. 2000). Cattle fed on OPF pellets measuring 9 mm in diameter and 3-5 cm in length with 33.3% total digestible nutrients gained 0.93 kg/day (Asada et al. 1991).

In order to maintain the availability of animal feed all year round, fibres from the OPW can be used in place of grass molasses and straw especially during the dry season when they get dried up. Also, the use of OPW fibre may save a lot of time used in grazing for ruminants (Abu Hassan et al. 1996). The integration of livestock rear­ing in oil palm plantation which result in internal food chain (i. e. OPFs, EFBs, OPLs, PKC etc. are used to feed the animals whilst the dung from the animals are also used to fertilize the plantation’s soil) may provide cost effective utilization of OPW.

Mixtures of OPW such as OPF (about 30%) and PKC (about 70%) which were administered to cows as feed increased their milk production more than the feed containing only grass (Abu Hassan et al. 1996). Rabbits fed on 50% pelleted OPF and 50% concentrate gained about 28.3 g/day (Dahlan et al. 2000). Abu Hassan et al. (1991) have shown that OPT fibre is a good source of roughage for ruminants compared to rice straw.