Value of a tomato byproduct as a source of dietary fiber in rats

A residue consisting of tomato peel and seeds is a byproduct of thetomato paste industry. This product had, after drying and grinding,101.4 g water, 175.6 g protein, 95.9 g lipids, 36.4 g ash and590.7 g total carbohydrates per kilogram of residue. The carbohydratesin the residue were mainly dietary fiber (495.3 g) from which 405.4 gwere insoluble fiber. Additionally, the residue had ascorbic acid 0.25 g, P 3 g, Ca 1.7 g, K 13.1 g, Mg 2.4 g, Cu 0.013 g, Fe0.248 g, Mn 0.018 g and Zn 0.174 g per kilogram of residue. Theresidue fed to rats at increasing concentrations in the diet (0, 134, 263and 387 g/kg diet) over 18 days had no effect on body weight gain;caused an increase in food intake and slightly reduced feed efficiency.Incorporation of the residue in the diet caused a substantialincrease in fecal mass, which was proportional to the dietary fiber providedby the residue (r = 0.89); apparent absorption of protein, energy,Ca, Mg, Fe, Zn and Cu present in the diets was reduced. These reductions were proportional to the amount of dietary fiber provided by the residueand became substantial when the residue was included at 263 or 387g/kg. However, when the residue was included at 134 g/kg, little effect onthe apparent absorption of the dietary nutrients was noted. Because thisconcentration provided the rats with approximately 10 times more fiberthan that recommended for humans, one can expect that if this tomatoresidue were consumed at concentrations recommended for humans, itshould have no effect on nutrient availability. These results indicate that thistomato residue represents an attractive source of fiber, which in rats had alow apparent absorption (52–56%). In addition, it was very effective inincreasing fecal mass with no negative effects on growth performance.