White grape pomace as a source of dietary fibre and polyphenols and its effect on physical and nutraceutical characteristics of wheat biscuits.
BACKGROUND
Grapes are one of the world's staple fruit crops, with about 80% of the yield being utilised for winemaking. Since grape by-products still contain large amounts of secondary metabolites, uses other than as fertilisers might be appropriate. In this study, white grape pomace (WGP) was incorporated in wheat flour at levels of 10, 20 and 30% (w/w) to investigate its influence on rheological, nutraceutical, physical and sensory properties.


RESULTS
Farinograph characteristics of dough with different levels of WGP showed a decrease in water absorption from 56.4% (0% WGP) to 45.9% (30% WGP). Addition of WGP reduced hardness and caused a deterioration in brightness and yellowness of all enriched samples. The smallest addition of WGP (10%) caused an approximately 88% increase in total dietary fibre content as compared with the control. The content of phenolic compounds increased from 0.11 mg g⁻¹ with 0% WGP to 1.07 mg g⁻¹ with 30% WGP. The most stable phenols were as follows: γ-resorcylic acid < gallic acid < tyrosol < catechin < isovanilic acid. An assay of radical-scavenging activity showed that WGP addition greatly enhanced the antioxidant properties of biscuits. Acceptable biscuits were obtained when incorporating 10% WGP.


CONCLUSIONS
WGP might be utilised for the novel formulation of biscuits as an alternative source of dietary fibre and phenols.
Department of Food Science and Nutrition, Poznań University of Life Sciences, Poznań, Poland. mildners@up.poznan.pl
Sylwia
S
Mildner-Szkudlarz
Joanna
J
Bajerska
Renata
R
Zawirska-Wojtasiak
Danuta
D
Górecka
D000975:Antioxidants / Q000032:analysis / Q000737:chemistry / Q000191:economics; D001939:Bread / Q000032:analysis* / Q000191:economics; D055598:Chemical Phenomena; D004043:Dietary Fiber / Q000032:analysis* / Q000191:economics; D005433:Flour / Q000032:analysis / Q000191:economics; D005527:Food, Fortified / Q000032:analysis* / Q000191:economics; D005525:Food-Processing Industry / Q000191:economics; D005638:Fruit / Q000737:chemistry*; D006801:Humans; D062385:Hydroxybenzoates / Q000032:analysis / Q000737:chemistry / Q000191:economics; D007220:Industrial Waste / Q000032:analysis* / Q000191:economics; D055595:Mechanical Phenomena; D009753:Nutritive Value; D010858:Pigmentation; D011044:Poland; D059808:Polyphenols / Q000032:analysis* / Q000737:chemistry / Q000191:economics; D025341:Principal Component Analysis; D012677:Sensation; D027843:Vitis / Q000737:chemistry*; D014867:Water / Q000032:analysis
D000975:Antioxidants; D004043:Dietary Fiber; D062385:Hydroxybenzoates; D007220:Industrial Waste; D059808:Polyphenols; D014867:Water; C412605:gamma-resorcylic acid