SOP: Extraction and Separation Scheme for Sweetening Agents and Preservatives

GIFSQ — Global Institute for Food Safety & Quality

Principle

Sweetening agents and ether-extractable organic preservatives (benzoic acid, esters of p-hydroxybenzoic acid, p- or o-chlorobenzoic acid, salicylic acid) are separated from the food matrix by rendering the sample alkaline and filtering; the schematic separation procedure (Fig. 12.3) then divides the extract into ether-extractable and non-extractable fractions for detection of saccharin, dulcin, cyclamates and the individual preservatives.

Apparatus required

• Mortar (for solid and semi-solid samples)
• Filter with a wad of cotton
• Separating funnel

Reagents

a. 10% NaOH solution.

b. Distilled water.

Procedure

Liquid samples — squashes, barley waters, cordials, syrups, ready-to-serve beverages: render 50 to 100 ml of the sample distinctly alkaline with 10% NaOH and filter through a wad of cotton; if the sugar concentration is high, dilute with sufficient distilled water to reduce the total soluble solids to 10–15%, make alkaline as before, and filter

↓

Solid or semi-solid samples — jams, jellies, marmalades, chutneys, pickles: grind 50 to 100 g of sample with 300–400 ml of water, render distinctly alkaline with 10% NaOH, allow to stand for 2 hr, and filter

↓

Tomato products: mix with water to a thin slurry, render distinctly alkaline with 10% NaOH, allow to stand for 30 min, and filter

↓

Apply the schematic procedure of Fig. 12.3 to the alkaline filtrate for the detection of the sweetening agents (saccharin, dulcin, cyclamates) and the preservatives (benzoic acid, salicylic acid, esters of p-hydroxybenzoic acid)

Note: Fig. 12.3 is a detailed flow figure whose text is partly illegible in the available extraction; the legible portions separate the ether-extractable fraction (acidified, extracted with ether, and examined for benzoic acid, salicylic acid and p-hydroxybenzoic esters) from the aqueous residue (examined for saccharin, dulcin and cyclamates). Consult the printed book for the full figure.

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.