Composition Profiles and Functional Properties of Dietary Fiber Powder from Lime Residues: Effects of Pretreatment and Drying Methods

Abstract

Lime residues after juice extraction have proven to be a potential raw material for producing dietary fiber (DF) powder due to their good functional properties. Compositions and antioxidant activity of DF powder from lime residues as affected by selected pretreatment (hot-water blanching and ethanolic soaking) and drying methods, viz. hot air drying, vacuum drying, and low-pressure superheated steam drying (LPSSD) at 60–80°C, were investigated. Fresh lime residues contained significant amounts of vitamin C, phenolic compounds, and flavonoids. Hesperidin was a major flavonoid and only one polymethoxyflavone (i.e., tangeretin) was detected in small amounts. A decrease in the amount of interested bioactive compounds and their antioxidant activity was noted at almost all steps of processing. Higher retention of bioactive compounds was noted when the residues were subject either to vacuum drying or LPSSD; the total antioxidant activities were 61–62% and 81–82% when being assessed by the β-carotene bleaching and DPPH assays, respectively. Vacuum drying at 80°C was the most suitable condition for preparing DF powder from lime residues due to its short required drying time and its ability to retain bioactive compounds. The in vitro analyses imply that DF powder prepared by vacuum drying at 80°C has the potential to reduce blood glucose and cholesterol levels by exhibiting high glucose retardation index (GRI) and bile acid retardation index (BRI).

Keywords:

• Antioxidant
• Citrus by-products
• Drying
• Flavonoids
• Functional properties

Notes

Same letters in the same column indicate that values are not significantly different (p ≥ 0.05).

Numbers in parentheses indicate the ratio between IDF (insoluble dietary fiber) and SDF (soluble dietary fiber).

Carbohydrate was defined as the residues excluding protein, lipid, TDF (total dietary fiber), and ash and was calculated by difference (= 100 – lipid – protein – ash – TDF).

Numbers in parentheses indicate the retention (%) of compounds as compared with the amounts in fresh lime residues.

Same letters in the same row indicate that values are not significantly different (p ≥ 0.05).

ND = not detected.

Numbers in parentheses indicate the retention (%) of compounds as compared with the amounts in lime residues after blanching and soaking in ethanol.

Same letters in the same row indicate that values are not significantly different (p ≥ 0.05).

ND = not detected;

*mg/100 g dry basis;

**mg GAE/100 g dry basis.

Same letters in the same row indicate that values are not significantly different (p ≥ 0.05).

ND = not detected.

Same letters in the same row indicate that values are not significantly different (p ≥ 0.05).

Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/ldrt.