🍎 Determination of the peroxide value of animal and vegetable fats and oils, fatty acids and their mixtures, margarines and fat spreads with potentiometric end-point determination — 5.0 g of sample (10.0 g for a value ≤ 1) is dissolved in 50 ml of glacial acetic acid–isooctane 60 : 40, 0.5 ml of saturated potassium iodide is added, stirred for exactly 60 s, 30–100 ml of water is added and the liberated iodine is titrated with 0.01 mol/l sodium thiosulfate using a combined platinum electrode; result in milliequivalents of active oxygen per kilogram, range 0–30 meq/kg, PN-EN ISO 27107

Food chemistry PN-EN ISO 27107

Overview

WHAT THE STANDARD COVERS. We read the text of the standard in the iTeh sample of ISO 27107:2008 in the corrected version of 15.05.2009 (English text): title page, foreword, introduction and Clauses 1–9 and the beginning of Clause 10 up to the peroxide value formula and the explanation of the symbols V, V0 and F — the sample ends on page 5, before the explanation of the symbol m and the rest of the standard (precision, test report, Annex A with titration curves). The second iTeh sample — SIST EN ISO 27107:2010 — we read in its European part: the EN foreword and the endorsement notice.

ACCORDING TO THE TEXT OF ISO 27107:2008. The first edition of 01.03.2008 was prepared by ISO/TC 34 “Food products”, Subcommittee SC 11 “Animal and vegetable fats and oils”. The corrected version of 15.05.2009 changes, among other things, the range of application in the introduction to “0 meq to 30 meq” (previously “0 mmol to 15 mmol”), the balance readability in 6.5 to 0.000 1 g (previously 0.001 g), the iodate mass in 9.2.2 to “0.001 g” (previously “0.001 mg”) and the formula for the factor F. Introduction: methods for determining peroxides are based on the liberation of iodine from potassium iodide in an acid medium (Wheeler method); the result depends on the test portion mass, so ISO/TC 34/SC 11 fixed the sample mass at 5 g for peroxide values greater than 1 and at 10 g for values not greater than 1, and limited application to 0–30 meq of active oxygen per kilogram; results may be slightly lower than with earlier standards. Scope (1): potentiometric end-point determination of the peroxide value, in milliequivalents of active oxygen per kilogram, of animal and vegetable fats and oils, fatty acids and their mixtures in the range 0–30 meq/kg, also of margarines and fat spreads with varying water content; the method does not apply to milk fats or lecithins (note: the iodometric method with a visual end point is given in ISO 3960, for milk fats — ISO 3976). Reference (2): ISO 661 (preparation of test sample). Definition (3.1): peroxide value — the quantity of substances in the sample, expressed as active oxygen, that oxidize potassium iodide under the conditions of the standard; the value in millimoles of active oxygen per kilogram is half the value in milliequivalents, and multiplying milliequivalents by 8 gives the active oxygen mass fraction in mg/kg. Principle (4): the sample is dissolved in isooctane and glacial acetic acid, potassium iodide is added, the iodine liberated by the peroxides is titrated with sodium thiosulfate, and the end point is determined electrochemically. Reagents (5): all free of dissolved oxygen; distilled water, boiled and cooled to 20 °C; glacial acetic acid and isooctane (2,2,4-trimethylpentane) degassed ultrasonically under vacuum or by purging with an inert gas (CO2 or N2); acetic acid–isooctane solution 60 ml + 40 ml, degassed; potassium iodide free from iodine and iodates; saturated KI solution 175 g/100 ml (about 14 g KI in about 8 g of freshly boiled water, with undissolved crystals), kept in the dark, prepared daily — check: 0.5 ml of the solution in 30 ml of the mixture with two drops of starch; if a blue colour forms and more than one drop of thiosulfate is needed to remove it, the solution is discarded; sodium thiosulfate 0.1 mol/l (on freshly boiled water, usable for 1 month, in a dark glass bottle); thiosulfate 0.01 mol/l (100 ml of the 0.1 mol/l solution to 1000 ml) — prepared just before use or with daily titre determination, because its stability depends on pH and free CO2; potassium iodate as a secondary standard traceable to NIST; hydrochloric acid 4 mol/l. Apparatus (6): automatic titrator with dosing device, stirrer and electrodes capable of dynamic titration (fast at the start, slow near the end point) — with other equipment the procedure has to be optimized; combined platinum electrode; pipettes 0.5, 1, 10 and 100 ml; cylinders 50 and 100 ml; balance readable to 0.000 1 g; magnetic stirrer with a 25 mm stirring rod and heating plate; 250 ml Erlenmeyer flasks; 250 ml tall beakers; volumetric flasks 250, 500 and 1000 ml; microwave oven; 1000 ml dark glass bottles. Sampling (7): not part of the method, recommended method in ISO 5555. Preparation (8): according to ISO 661; homogenization preferably without heating and aeration, without direct sunlight; solid fats are carefully heated in a microwave oven to 10 °C above the melting point; samples with visible impurities are filtered and this is noted in the test report; the test portion for the peroxide value is taken first, before portions for other tests, and determined immediately. Procedure (9): in diffuse daylight or artificial light, without direct sun, in vessels free from oxidizing and reducing compounds. Titre of 0.01 mol/l thiosulfate (9.2.2): 0.27–0.33 g of potassium iodate (to 0.001 g) in a 250 or 500 ml flask; 5 or 10 ml of this solution with 60 ml of boiled water, 5 ml of 4 mol/l HCl and 0.5 ml of saturated KI are titrated with thiosulfate; factor F = mKIO3 · V1 · 6 · 1000 · wKIO3 / (MKIO3 · V2 · V3 · cthio · 100), where 6 is the equivalent mass (1 mol KIO3 ⇔ 3 mol I2), MKIO3 = 214 g/mol, wKIO3 — iodate purity in g/100 g. Determination (9.3): the Erlenmeyer flask is purged with nitrogen or CO2 and 5.0 ± 0.1 g of sample is weighed to 0.1 mg for an expected value from > 1 to 30, or 10.0 ± 0.1 g for a value of 0–1; the peroxide value is a dynamic value depending on the history of the sample and on the test portion mass — with the prescribed mass, results may be slightly lower than with smaller test portions; when less than 5 g of extracted fat is available or the value exceeds 30 meq/kg, the user should choose a smaller test portion and report its mass together with the result. The sample is dissolved in 50 ml of acetic acid–isooctane solution; high-melting fats (hard and animal fats) — 20 ml of isooctane is added to the molten fat and then immediately 30 ml of acetic acid, with gentle warming if needed. After adding the stirring rod and 0.5 ml of saturated KI, the mixture is stirred on the titrator for exactly 60 s (timer ± 1 s) at medium speed to avoid spraying; immediately afterwards 30–100 ml of water is added depending on the apparatus — more water is needed because of phase inversion, the lower phase is titrated, and with more water the potential difference between start and end point is larger (about 100 mV) and the curve has a sharp inflection point. The electrode is immersed and titration with 0.01 mol/l thiosulfate is carried out with fast stirring; in a parallel blank test consumption must not exceed 0.1 ml; the equivalence point is evaluated by the titrator or graphically by the point of inflection method. Calculation (10): peroxide value in meq active oxygen/kg = (V − V0) · cthio · F · 1000 / m, where V is the thiosulfate volume in the determination, V0 in the blank, F the factor from 9.2 (the explanation of m lies outside the sample).

ACCORDING TO THE FOREWORD OF EN ISO 27107:2010. The text of ISO 27107:2008 in the corrected version of 15.05.2009 was taken over by CEN/TC 307 “Oilseeds, vegetable and animal fats and oils and their by-products — Methods of sampling and analysis”; EN ISO 27107:2010 supersedes EN ISO 27107:2008, and national standards had to implement it by October 2010 at the latest; the ISO text was approved without modification.

STATUS (as of 03.10.2026). In the PKN search (query “27107”, 03.10.2026) PN-EN ISO 27107:2012 (Polish version, “Wprowadza: EN ISO 27107:2010 [IDT], ISO 27107:2008 [IDT]”) carries no withdrawal note; PN-EN ISO 27107:2010 (English version) — “Wycofana i zastąpiona przez PN-EN ISO 27107:2012 – wersja polska”, and both PN-EN ISO 27107:2009 (Polish and English) — withdrawn and replaced by later editions. Card of PN-EN ISO 27107:2012: publication date 04.09.2012, 16 pages, KT 92 Nasion Roślin Oleistych, Tłuszczów Roślinnych i Zwierzęcych oraz ich Produktów Ubocznych, ICS 67.200.10, “Zastępuje PN-EN ISO 27107:2010 – wersja angielska”, no withdrawal note. In the iTeh catalogue (read 03.10.2026) ISO 27107:2008 has the status “Published”, stage 90.93 (International Standard confirmed).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 03.10.2026). The number 27107 appears in 4 records at 3 laboratories: AB 400 (2), AB 444, AB 1334. In the current PCA documents (read 03.10.2026; AB 1334 issue no. 31 of 04.05.2026, AB 444 issue no. 27 of 23.06.2026, AB 400 issue no. 37 of 07.08.2026) the number appears in 4 lines at the same 3 laboratories; in each document the number of page markers equals the number of PDF pages, without repetitions; a search of all PCA documents downloaded from the BIP on 03.10.2026 found no laboratories outside the database copy. Form “PN-EN ISO 27107:2012” (3 records) and “PN-EN ISO 27107” without year (AB 400, meals). None of these items is suspended. The “Laboratories” tab (query “PN-EN ISO 27107”) shows all 3 laboratories — checked by a tab query on the labcoda.pl production server on 03.10.2026.

WHAT THE LABORATORIES TEST (items in PCA). Object: vegetable and animal oils and fats (AB 444), oils, animal and vegetable fats (AB 1334), vegetable and animal oils and fats excluding milk fats (AB 400) and meals (AB 400). Characteristic: peroxide value. Ranges: (0.1–19.0) meq O2/kg (AB 1334), (0.3–20.0) meq/kg (AB 400, oils and fats), (0.25–30.0) meq O2/kg (AB 444); the AB 400 item for meals gives no range. Technique: potentiometric titration method (potentiometric titrimetric method for meals).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Test portion: the result depends on the sample mass — 5 g for a value > 1, 10 g for a value ≤ 1; a smaller portion is allowed only when there is less than 5 g of fat or the value exceeds 30, and then the mass is reported with the result (9.3.1) — for meals (AB 400) the amount of extracted fat determines the test portion. Matrix: milk fat and lecithins are outside the scope (1) — AB 400 excludes milk fats explicitly. Oxygen: all reagents free of dissolved oxygen, flask purged with inert gas, work without direct sunlight (5, 9.1, 9.3.1). Iodide: KI solution fresh daily and checked with starch (5.6), stirring for exactly 60 s (9.3.3). Thiosulfate: 0.01 mol/l solution prepared just before use or with daily titre (5.8, 9.2.2), blank ≤ 0.1 ml (9.3.6). Order: the test portion for the peroxide value is taken before portions for other determinations (8). Unit: meq/kg is twice mmol/kg (3.1) — the ranges of AB 444 and AB 1334 in “meq O2/kg” and of AB 400 in “meq/kg” are the same quantity. Comparison with the iodometric method with a visual end point (separate entry “Peroxide value of oils and fats — iodometry with visual end point”, PN-EN ISO 3960): according to the introduction, results according to ISO 27107 may be slightly lower than according to earlier standards.

WHAT WE DO NOT GIVE. Precision data (repeatability, reproducibility), test report requirements and Annex A with example titration curves are not quoted — they lie outside the sample. We do not give permissible peroxide values from regulations or from the Codex Alimentarius.

Method principle

A test portion of 5.0 g (10.0 g for an expected value ≤ 1) is dissolved in 50 ml of degassed glacial acetic acid–isooctane 60 : 40, 0.5 ml of saturated potassium iodide is added and stirred for exactly 60 s; peroxides liberate iodine. After adding 30–100 ml of water the iodine is titrated with 0.01 mol/l sodium thiosulfate (titre against potassium iodate), and the end point is determined with a combined platinum electrode. Peroxide value = (V − V0) · c · F · 1000 / m in meq active oxygen/kg.

Applications

• Animal and vegetable fats and oils, fatty acids and their mixtures, margarines and fat spreads — peroxide value 0–30 meq O2/kg (1)
• Not applicable to milk fat or lecithins (1)
• Vegetable and animal oils and fats and meals — items in the accreditation scopes of 3 laboratories in PCA

Key parameters

Standard

Standard number

PN-EN ISO 27107:2012

Title (PL)

Oleje i tłuszcze roślinne oraz zwierzęce — Oznaczanie liczby nadtlenkowej — Potencjometryczne oznaczanie punktu końcowego

Title (EN)

Animal and vegetable fats and oils — Determination of peroxide value — Potentiometric end-point determination

Step-by-step procedure

1. Sample

   According to ISO 661, without heating and aeration; solid fats to 10 °C above the melting point; the portion for the peroxide value is taken first (8). PN-EN ISO 27107:2012 with no withdrawal note in PKN (03.10.2026).

2. Thiosulfate titre

   0.27–0.33 g KIO3 in 250 or 500 ml; 5 or 10 ml with 60 ml water, 5 ml HCl and 0.5 ml KI, titration, factor F (9.2.2).

3. Dissolution

   Flask purged with N2 or CO2; 5.0 g (10.0 g for values ≤ 1) in 50 ml acetic acid with isooctane (9.3.1, 9.3.2).

4. Reaction with iodide

   0.5 ml saturated KI, stirring for exactly 60 s, then 30–100 ml water (9.3.3, 9.3.4).

5. Titration and result

   0.01 mol/l thiosulfate with platinum electrode, blank ≤ 0.1 ml; PV = (V − V0) · c · F · 1000 / m (9.3.5–9.3.7, 10).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Isooctane — flammable; work away from ignition sources, under a fume hood
• Glacial acetic acid and hydrochloric acid — corrosive, eye and hand protection

Frequently asked questions