Detection of acid neutralizers in fraudulent milk: full validation of a classical qualitative method

Gondim, Carina de Souza; Palhares, Marina Penna e; Santos, Pedro Paulo Borges dos; Sousa, Roberto Cesar de; Junqueira, Roberto Gonçalves; Souza, Scheilla Vitorino Carvalho de

doi:10.21577/0100-4042.20170703

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Nota Técnica • Quím. Nova 44 (5) • May 2021 • https://doi.org/10.21577/0100-4042.20170703 copy

Detection of acid neutralizers in fraudulent milk: full validation of a classical qualitative method

Authorship SCIMAGO INSTITUTIONS RANKINGS

Neutralization with alkaline compounds is one of the most common adulterations in milk. The rosolic acid method is a classical test widely used in different countries for detection of neutralizers in milk. The official and a modified version were validated in a single laboratory validation process considering four adulterants: sodium bicarbonate(BI), sodium carbonate(CA), sodium hydroxide(HY) and sodium citrate(CI). The modified version, which presented better performance was selected for interlaboratory validation. In this process, samples of raw milk with acidities of 0.19% were neutralized with different concentrations of BI, CA, HY and C and tested for homogeneity and stability. Eight laboratories, which represented different sectors of the milk production chain, received and analysed these samples. The collaborative trial results confirmed the method performance, although sensitivity and precision were inferior to those obtained in the intralaboratory process, demonstrating its applications and limitations.

Keywords:
collaborative trial; milk adulteration; rosolic acid; single laboratory validation; screening method

Sodium bicarbonate (%, w/v)	Official method						Modified method
	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON
			1	2	3	CON			1	2	3	CON
0.0000	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0
0.0025	100.0	0.0	1.0	1.0	1.0	1.0	100.0	0.0	1.0	1.0	1.0	1.0
0.0050	90.0	10.0	0.8	0.8	0.6	0.8	100.0	0.0	1.0	1.0	1.0	1.0
0.0075	83.3	16.7	0.5	0.8	1.0	0.5	90.0	10.0	1.0	0.5	1.0	0.8
0.0100	83.3	16.7	0.6	0.5	1.0	0.6	70.0	30.0	0.5	0.5	0.8	0.6
0.0125	73.3	26.7	0.5	0.4	1.0	0.5	63.3	36.7	0.5	0.4	0.6	0.5
0.0150	60.0	40.0	0.4	0.4	0.6	0.4	43.3	56.7	0.5	0.6	0.5	0.5
0.0175	33.3	66.7	0.5	0.6	0.5	0.5	16.7	83.3	0.6	0.8	0.6	0.7
0.0200	16.7	83.3	1.0	0.8	0.5	1.0	3.3	96.7	1.0	1.0	0.8	0.9
0.0225	23.3	76.7	0.8	0.6	0.5	0.8	16.7	83.3	0.6	0.8	0.6	0.7
0.0250	20.0	80.0	1.0	0.8	0.4	1.0	3.3	96.7	1.0	1.0	0.8	0.9
0.0275	10.0	90.0	1.0	1.0	0.5	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0300	3.3	96.7	1.0	0.8	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0325	10.0	90.0	0.5	1.0	1.0	0.5	10.0	90.0	0.5	1.0	1.0	0.8
0.0350	10.0	90.0	0.6	0.8	1.0	0.6	6.7	93.3	0.6	1.0	1.0	0.9
0.0375	10.0	90.0	0.5	1.0	1.0	0.5	6.7	93.3	0.6	1.0	1.0	0.9
0.0400	3.3	96.7	1.0	0.8	1.0	1.0	3.3	96.7	1.0	0.8	1.0	0.9
0.0425	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0450	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0475	0.0	100.0	1.0	1.0	1.0	1.0	3.3	96.7	0.8	1.0	1.0	0.9
0.0500	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0

Sodium carbonate (%, w/v)	Official method						Modified method
	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON
			1	2	3	CON			1	2	3	CON
0.0000	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0
0.0025	100.0	0.0	1.0	1.0	1.0	1.0	100.0	0.0	1.0	1.0	1.0	1.0
0.0050	96.7	3.3	1.0	1.0	0.8	0.9	100.0	0.0	1.0	1.0	1.0	1.0
0.0075	83.3	16.7	1.0	1.0	0.4	0.7	76.7	23.3	0.5	0.8	0.5	0.6
0.0100	80.0	20.0	0.8	0.6	0.5	0.7	56.7	43.3	0.5	0.5	0.5	0.5
0.0125	73.3	26.7	0.5	0.6	0.5	0.6	40.0	60.0	0.8	0.4	0.5	0.5
0.0150	40.0	60.0	0.8	0.8	0.6	0.4	26.7	73.3	1.0	0.5	0.5	0.6
0.0175	16.7	83.3	0.8	0.8	0.5	0.7	6.7	93.3	1.0	1.0	0.6	0.9
0.0200	10.0	90.0	0.8	1.0	0.6	0.8	3.3	96.7	1.0	1.0	0.8	0.9
0.0225	6.7	93.3	0.8	0.8	1.0	0.9	3.3	96.7	0.8	1.0	1.0	0.9
0.0250	6.7	93.3	0.8	0.8	1.0	0.9	3.3	96.7	0.8	1.0	1.0	0.9
0.0275	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0300	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0325	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0350	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.0375	3.3	96.7	1.0	1.0	0.8	0.9	3.3	96.7	1.0	1.0	0.8	0.9
0.0400 to 0.0500	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0

Sodium hydroxide (%, w/v)	Official method						Modified method
	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON
			1	2	3	CON			1	2	3	CON
0.0000	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0
0.0025	100.0	0.0	1.0	1.0	1.0	1.0	96.7	3.3	1.0	0.8	1.0	0.9
0.0050	80.0	20.0	0.4	1.0	0.8	0.6	70.0	30.0	0.5	0.6	1.0	0.5
0.0075	63.3	36.7	0.4	0.8	0.4	0.5	20.0	80.0	0.6	0.5	1.0	0.7
0.0100	20.0	80.0	0.8	0.5	0.8	0.7	6.7	93.3	1.0	0.6	1.0	0.9
0.0125	10.0	90.0	1.0	0.6	0.8	0.8	3.3	96.7	1.0	0.8	1.0	0.9
0.0150	10.0	90.0	1.0	0.6	0.8	0.8	3.3	96.7	1.0	0.8	1.0	0.9
0.0175 to 0.0275	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0

Sodium citrate (%, w/v)	Official method						Modified method
	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON	FPR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or FNR	RLR or SLR^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR). or SNR	ACC (analytical batch)			CON
			1	2	3	CON			1	2	3	CON
0	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	100.0^* *FPR and SLR were estimated only for unadulterated samples, i.e., 0% acid neutralizer. ACC and CON values in bold correspond to levels outside to the unreliability region (UR).	1.0	1.0	1.0	1.0
0.03	80.0	20.0	1.0	0.5	0.6	0.7	70.0	30.0	0.8	0.4	0.5	0.6
0.04	60.0	40.0	0.8	0.5	0.4	0.5	40.0	60.0	0.8	0.6	0.8	0.4
0.05	66.7	33.3	0.5	0.5	0.8	0.5	33.3	66.7	0.5	0.8	0.4	0.5
0.06	26.7	73.3	0.5	0.8	0.8	0.6	6.7	93.3	0.8	0.8	1.0	0.9
0.07	13.3	86.7	0.5	1.0	0.8	0.8	6.7	93.3	0.8	1.0	0.8	0.9
0.08	13.3	86.7	0.5	1.0	1.0	0.7	0.0	100.0	1.0	1.0	1.0	1.0
0.09	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.10	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0
0.11	3.3	96.7	0.8	1.0	1.0	0.9	0.0	100.0	1.0	1.0	1.0	1.0
0.12	3.3	96.7	1.0	1.0	0.8	0.9	3.3	96.7	1.0	1.0	0.8	0.9
0.13 and 0.15	0.0	100.0	1.0	1.0	1.0	1.0	0.0	100.0	1.0	1.0	1.0	1.0

Laboratory	0.0		Sodium hydroxide (%, w/v)				Sodium bicarbonate (%, w/v)				Sodium carbonate (%, w/v)				Sodium citrate (%, w/v)
	0.0		0.0175		0.0625		0.0425		0.0625		0.0275		0.0625		0.10		0.15
	FPR	RLR	FNR	RLR	FNR	RLR	FNR	RLR	FNR	RLR	FNR	RLR	FNR	RLR	FNR	RLR	FNR	RLR
1	0.0	100.0	16.7	83.3	0.0	100.0	16.7	83.3	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0
2	0.0	100.0	50.0	50.0	0.0	100.0	100.0	0.0	33.3	66.7	50.0	50.0	0.0	100.0	66.7	33.3	0.0	100.0
3	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0
4	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0
5	16.7	83.3	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	100.0	0.0	0.0	100.0	0.0	100.0	16.7	83.3
6	0.0	100.0	100.0	0.0	16.7	83.3	100.0	0.0	66.7	33.3	83.3	16.7	83.3	16.7	83.3	83.3	83.3	16.7
7	33.3	66.7	0.0	100.0	0.0	100.0	0.0	100.0	16.7	83.3	0.0	100.0	0.0	100.0	0.0	83.3	0.0	100.0
8	0.0	100.0	0.0	100.0	0.0	100.0	16.7	83.3	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0	0.0	100.0
Total	6.3	93.8	20.8	79.2	2.1	97.9	29.2	70.8	14.6	85.4	29.2	70.8	10.4	89.6	18.8	81.3	12.5	87.5

Laboratory	0.0	Sodium hydroxide (%, w/v)		Sodium bicarbonate (%, w/v)		Sodium carbonate (%, w/v)		Sodium citrate (%, w/v)
Laboratory	0.0	0.0175	0.0625	0.0425	0.0625	0.0275	0.0625	0.10	0.15
1	1.00	0.67	1.00	0.67	1.00	1.00	1.00	1.00	1.00
2	1.00	0.40	1.00	1.00	0.47	0.40	1.00	0.47	1.00
3	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
4	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00	1.00
5	0.67	1.00	1.00	1.00	1.00	1.00	1.00	1.00	0.67
6	1.00	1.00	0.67	1.00	0.47	0.67	0.67	0.67	0.67
7	0.47	1.00	1.00	1.00	0.67	1.00	1.00	1.00	1.00
8	1.00	1.00	1.00	0.67	1.00	1.00	1.00	1.00	1.00
CON	0.88	0.64	0.96	0.54	0.74	0.54	0.79	0.66	0.76

Acid neutralizer	Concentration (%, w/v)	N	X	p	S _R	Lower limit	Upper limit
-	0	48	3	0.063	0.0155	0.0392	0.1398
Sodium hydroxide	0.0175	48	38	0.792	0.0456	0.6839	0.8742
Sodium hydroxide	0.0625	48	47	0.979	0.0074	0.9214	0.9963
Sodium bicarbonate	0.0425	48	34	0.708	0.0554	0.5932	0.8054
Sodium bicarbonate	0.0625	48	41	0.854	0.0304	0.7557	0.9220
Sodium carbonate	0.0275	48	34	0.708	0.0531	0.5932	0.8054
Sodium carbonate	0.0625	48	43	0.896	0.0368	0.8063	0.9512
Sodium citrate	0.1	48	39	0.813	0.0438	0.7074	0.8905
Sodium citrate	0.7	48	42	0.875	0.0365	0.7807	0.9396

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