title: Physical modification of palm kernel meal improved available carbohydrate, physicochemical properties and in vitro digestibility in economic freshwater fish.
abstract: BACKGROUND
  Unavailable carbohydrates are an important limiting factor for utilization of palm kernel meal (PKM) as aquafeed ingredients. The aim of this study was to improve available carbohydrate from PKM. Different physical modifications including water soaking, microwave irradiation, gamma irradiation and electron beam, were investigated in relation to chemical composition, physicochemical properties and in vitro carbohydrate digestibility using digestive enzymes from economic freshwater fish.
  
  
  RESULTS
  Modified methods had significant (P < 0.05) effects on chemical composition by decreasing crude fiber and increasing available carbohydrates. Improvements in physicochemical properties of PKM, such as water solubility, microstructure, relative crystallinity and lignocellulosic spectra, were mainly achieved by soaking and microwave irradiation. Carbohydrate digestibility varied among the physical modifications tested (P < 0.05) and three fish species had different abilities to digest PKM. Soaking was the appropriate modification for increasing carbohydrate digestion specifically in Nile tilapia (Oreochromis niloticus), whereas either soaking or microwave irradiation was effective for striped snakehead (Channa striata). For walking catfish (Clarias batrachus), carbohydrate digestibility was similar among raw, soaked and microwave-irradiated PKM.
  
  
  CONCLUSIONS
  These findings suggest that soaking and microwave irradiation could be practical methods for altering appropriate physicochemical properties of PKM as well as increasing carbohydrate digestibility in select economic freshwater fish.
authors.affiliation: Department of Applied Science, Faculty of Science, Prince of Songkla University, Songkhla, 90112, Thailand; Biochemical Research Unit for Feed Utilization Assessment, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand.
authors.forename: Karun
authors.initials: K
authors.lastname: Thongprajukaew
authors.forename: Pinya
authors.initials: P
authors.lastname: Yawang
authors.forename: Lateepah
authors.initials: L
authors.lastname: Dudae
authors.forename: Husna
authors.initials: H
authors.lastname: Bilanglod
authors.forename: Terdtoon
authors.initials: T
authors.lastname: Dumrongrittamatt
authors.forename: Chutima
authors.initials: C
authors.lastname: Tantikitti
authors.forename: Uthaiwan
authors.initials: U
authors.lastname: Kovitvadhi
mesh_terms: D000821:Animal Feed; D000818:Animals; D028023:Arecaceae / Q000737:chemistry*; D001682:Biological Availability; D002241:Carbohydrates / Q000737:chemistry*; D023681:Cichlids; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004043:Dietary Fiber; D004063:Digestion; D005399:Fishes; D005511:Food Handling / Q000379:methods*; D006801:Humans; D008872:Microwaves; D012639:Seeds / Q000737:chemistry; D014867:Water
chemical_list: D002241:Carbohydrates; D004040:Dietary Carbohydrates; D004043:Dietary Fiber; D014867:Water
keywords: carbohydrate digestibility; economic fish; microwave irradiation; palm kernel meal; physicochemical properties; soaking