Effect of physical and physicochemical characteristics of chitosan on fat-binding capacities under in vitro gastrointestinal conditions

• Chitosan has been considered as dietary fiber that can inhibit fat absorption in human gastrointestinal tract.
• Fat-binding capacity of chitosan can be related to molecular weight, morphology and form of chitosan particulates.
• Increasing molecular weight and tap density of chitosan can significantly increase the fat-binding ability.
• Besides binding fat, chitosan can also effectively bind with cholesterol and bile acids.

The correlation of physical and physicochemical characteristics of five different chitosan on their fat-binding capacities was studied using in vitro model of gastrointestinal conditions. Increasing molecular weight (Mw) and tap density of chitosan could significantly increase their fat-binding ability. Higher Mw chitosan (2100 and 890 kDa) show significantly higher fat binding capacity than 30 kDa. When tested at chitosan to fat 1:40, the ratio often used as dietary supplement, higher tap density chitosan showed an improved fat-binding capacity at around 2-fold increase. Interestingly, 2100 kDa high density (HD1P) could maintain the highest oil entrapment, ranging between 0.77 and 27.50 g oil/g chitosan depending on the interaction ratios. In addition, HD1P already maximized its fat-binding capacity since 30 min under in vitro gastric condition. In vitro cholesterol- and bile acids-binding experiments were also performed with HD1P and found to bind cholesterol at 820.9 ± 21.43 mg/g chitosan, deoxycholic acid at 17.50 ± 0.18 mg/g chitosan, and cholic acid at 5.28 ± 0.57 mg/g chitosan. Therefore, this study shows that the ability of HD1P for binding high amount of fat at short dissolution time might be due to the combination characteristics of having high Mw and being in a high density form.