Frying oils quality control: necessity for new approach of supervision

Purpose: The purpose of this paper is to investigate the quality of the frying oil used in restaurants, fast food establishments, and confectionary stores. The compliance of used frying oils with the quality standards as determined by the peroxide value (PV) and the total polar materials (TPMs) is investigated by analyzing 375 samples of oil. Design/methodology/approach: The PV was measured according to the national standard procedure number 4179, while the TPM was determined using a Testo 270 cooking oil tester. Frying oils with a PV>5 mEq/kg and a TPM>25 percent were considered to be non-edible. For a comparison of groups, the Mann-Whitney and Spearman correlation tests were used, and p<0.05 was considered significant. Findings: The maximum TPM and PV recorded for frying oils in fast food restaurants were 97.5 percent and 77.9 mEq/kg, respectively. The results also revealed that 60 percent of samples were non-edible according to the TPM, while 58.9 percent of the oil samples were non-edible because of the PV. TPM and PV correlated well with each other (r=0.99, p<0.001) and with oil replacement intervals (r=0.90, p<0.001). The relationship between the TPM and PV was stronger in the polynomial model than the linear model. The following equation was obtained: peroxide (mEq/kg oil)=0.0043 TPM2 (%)+0.1587 TPM (%)–0.6152. Originality/value: Considering the current limitations in official supervision by health authority, on-site self-monitoring of the TPM using the Testo 270 cooking oil tester by sellers as a solution seems a new approach. Food stores, restaurants, and confectionary stores should be equipped with TPM analyzers to determine the quality of the frying oil and the timely replacement of non-edible oils.