過酸化物価

WordNet

fix or determine the value of; assign a value to; "value the jewelry and art work in the estate"
the amount (of money or goods or services) that is considered to be a fair equivalent for something else; "he tried to estimate the value of the produce at normal prices" (同)economic value
(music) the relative duration of a musical note (同)time value, note value
relative darkness or lightness of a color; "I establish the colors and principal values by organizing the painting into three values--dark, medium...and light"-Joe Hing Lowe
the quality (positive or negative) that renders something desirable or valuable; "the Shakespearean Shylock is of dubious value in the modern world"
a numerical quantity measured or assigned or computed; "the value assigned was 16 milliseconds"
an ideal accepted by some individual or group; "he has old-fashioned values"
(usually used in combination) having value of a specified kind; "triple-valued"
held in great esteem for admirable qualities especially of an intrinsic nature; "a valued friend"; "precious memories" (同)precious
an inorganic compound containing the divalent ion -O-O-
bleach with peroxide; "She must peroxide her hair-it looks unnaturally blond"
beliefs of a person or social group in which they have an emotional investment (either for or against something); "he has very conservatives values"

PrepTutorEJDIC

〈U〉(…の)『価値』,値打ち,有用性,重要性《+of+名》 / 〈U〉〈C〉(…の)『価格』,値段《+of+名》 / 〈U〉〈C〉《米》《修飾語句を伴って》(払った金銭に対する)正当な値打ち / 〈C〉(単語の)意味,意義 / 〈C〉値,数値 / 〈C〉音の長短 / 〈C〉色価,(色の)明暗の度 / 〈C〉《複数形で》(道義・倫理などの)価値基準,価値観 / (ある金額に)…‘を'『評価する』,見積もる《+名+at+名〈金額〉》 / …‘を'『高く評価する』,尊重する,重んじる
貴重な,高く評価される,大切な
過酸化物 / =hydrogen
〈髪〉‘を'過酸化水素で漂白する

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/10/16 15:09:37」(JST)

wiki en

Detection of peroxide gives the initial evidence of rancidity in unsaturated fats and oils. Other methods are available, but peroxide value is the most widely used. It gives a measure of the extent to which an oil sample has undergone primary oxidation, extent of secondary oxidation may be determined from p-anisidine test.^[1]

The double bonds found in fats and oils play a role in autoxidation. Oils with a high degree of unsaturation are most susceptible to autoxidation. The best test for autoxidation (oxidative rancidity) is determination of the peroxide value. Peroxides are intermediates in the autoxidation reaction.

Autoxidation is a free radical reaction involving oxygen that leads to deterioration of fats and oils which form off-flavours and off-odours. Peroxide value, concentration of peroxide in an oil or fat, is useful for assessing the extent to which spoilage has advanced.

Definition

The peroxide value is defined as the amount of peroxide oxygen per 1 kilogram of fat or oil. Traditionally this was expressed in units of milliequivalents, although if we are using SI units then the appropriate option would be in millimoles per kilogram (N.B. 1 milliequivalents = 0.5 millimole; because 1 mEq of O2 =1 mmol/2=0.5 mmol of O2, where 2 is valence). Note also that the unit of milliequivalent has been commonly abbreviated as mequiv or even as meq.

Method

The peroxide value is determined by measuring the amount of iodine which is formed by the reaction of peroxides (formed in fat or oil) with iodide ion.

2 I⁻ + H₂O + HOOH -> HOH + 2OH⁻ + I₂

Note that the base produced in this reaction is taken up by the excess of acetic acid present. The iodine liberated is titrated with sodium thiosulphate.

2S₂O₃²⁻ + I₂ -> S₄O₆²⁻ + 2 I⁻

The acidic conditions (excess acetic acid) prevents formation of hypoiodite (analogous to hypochlorite), which would interfere with the reaction.

The indicator used in this reaction is a starch solution where amylose forms a blue to black solution with iodine and is colourless where iodine is titrated.

A precaution that should be observed is to add the starch indicator solution only near the end point (the end point is near when fading of the yellowish iodine colour occurs) because at high iodine concentration starch is decomposed to products whose indicator properties are not entirely reversible.

AOCS methods are available from www.aocs.org. All versions are copyright and cannot be republished without permission.

Taste

Peroxide values of fresh oils are less than 10 milliequivalents/kg; when the peroxide value is between 30* and 40 milliequivalents/kg, a rancid taste is noticeable.

References

^ Chemistry And Technology Of Oils And Fats Chemistry And Technology Of Oils And Fats By Dr. M.M. Chakrabarty

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Near and mid infrared spectroscopy and multivariate data analysis in studies of oxidation of edible oils.

Wójcicki K1, Khmelinskii I2, Sikorski M3, Sikorska E4.
Food chemistry.Food Chem.2015 Nov 15;187:416-23. doi: 10.1016/j.foodchem.2015.04.046. Epub 2015 Apr 21.
Infrared spectroscopic techniques and chemometric methods were used to study oxidation of olive, sunflower and rapeseed oils. Accelerated oxidative degradation of oils at 60°C was monitored using peroxide values and FT-MIR ATR and FT-NIR transmittance spectroscopy. Principal component analysis (PCA
PMID 25977045

Effect of the refining process on Moringa oleifera seed oil quality.

Sánchez-Machado DI1, López-Cervantes J2, Núñez-Gastélum JA3, Servín de la Mora-López G4, López-Hernández J5, Paseiro-Losada P5.
Food chemistry.Food Chem.2015 Nov 15;187:53-7. doi: 10.1016/j.foodchem.2015.04.031. Epub 2015 Apr 18.
We evaluated the physicochemical properties and oxidative stability of the oil extracted from the seeds of Moringa oleifera during its refining process. Refining is accomplished in three stages: neutralization, degumming, and bleaching. Four samples were analyzed, corresponding to each step of the p
PMID 25976997

Comparison of five analytical methods for the determination of peroxide value in oxidized ghee.

Mehta BM1, Darji VB2, Aparnathi KD3.
Food chemistry.Food Chem.2015 Oct 15;185:449-53. doi: 10.1016/j.foodchem.2015.04.023. Epub 2015 Apr 14.
In the present study, a comparison of five peroxide analytical methods was performed using oxidized ghee. The methods included the three iodometric titration viz. Bureau of Indian Standard (BIS), Association of Analytical Communities (AOAC) and American Oil Chemists' Society (AOCS), and two colorime
PMID 25952892