Total alcoholic acidity and pH tests as quality parameters in stored soybean grains

Araujo, Maicon Marinho Vieira; Caneppele, Maria Aparecida Braga; Bianchini, Maria das Graças Assis

doi:10.1590/1983-40632016v4638707

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Scientific Articles • Pesqui. Agropecu. Trop. 46 (2) • Apr-Jun 2016 • https://doi.org/10.1590/1983-40632016v4638707 copy

Total alcoholic acidity and pH tests as quality parameters in stored soybean grains

Testes de acidez alcoólica total e pH como parâmetros de qualidade em grãos de soja armazenados

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Despite the technology available to agriculture, qualitative and quantitative losses occurring during post-harvest are still not controlled, and stored grains may undergo changes in their composition, due to storage conditions. This study aimed at determining the sensitivity of the alcoholic acidity and pH tests in soybean (GB 874RR cultivar) grains with different quality standards obtained during storage. A completely randomized design, in a 3 x 6 x 5 (3 storage conditions x 6 storage times x 5 methods) factorial scheme, was used. A correlation was observed among pH, total acidity content (r = 0.888) and grain quality parameters. Deterioration was identified based on the total acidity content, showing a high correlation with fungal incidence (r = 0.864), ether extract (r = -0.781) and electrical conductivity (r = 0.923). The use of phenolphthalein as indicator is more sensitive than pH 8.8. Among the pH determination methods, AOAC was the most suitable for assessing the quality loss during storage.

KEY-WORDS:
Glycine max L.; fatty acid; storage conditions

Variable	WC (%)	ASG	FI	FUS	ASP	PEN	PC	EE	CON¹ 1 Expressed as µS cm-1 g-1;	A² 2 expressed on a pH scale;	B² 2 expressed on a pH scale;	C² 2 expressed on a pH scale;	D³ 3 expressed as g 100 g-1 of dry matter.
ASG	0.271^* * Significant at 5 %;
FI	0.270^* * Significant at 5 %;	0.381^* * Significant at 5 %;
FUS	0.170^ns ns not significant at 5 %.	0.478^* * Significant at 5 %;	0.689^* * Significant at 5 %;
ASP	0.277^* * Significant at 5 %;	0.305^* * Significant at 5 %;	0.416^* * Significant at 5 %;	0.446^* * Significant at 5 %;
PEN	0.430^* * Significant at 5 %;	0.358^* * Significant at 5 %;	0.469^* * Significant at 5 %;	0.438^* * Significant at 5 %;	0.552^* * Significant at 5 %;
PC	0.342^* * Significant at 5 %;	-0.385^* * Significant at 5 %;	-0.173^ns ns not significant at 5 %.	-0.416^* * Significant at 5 %;	-0.120^ns ns not significant at 5 %.	0.017^ns ns not significant at 5 %.
EE	-0.475^* * Significant at 5 %;	-0.610^* * Significant at 5 %;	-0.458^* * Significant at 5 %;	-0.541^* * Significant at 5 %;	-0.432^* * Significant at 5 %;	-0.400^* * Significant at 5 %;	0.311^* * Significant at 5 %;
CON	0.505^* * Significant at 5 %;	0.557^* * Significant at 5 %;	0.724^* * Significant at 5 %;	0.865^* * Significant at 5 %;	0.702^* * Significant at 5 %;	0.605^* * Significant at 5 %;	-0.757^* * Significant at 5 %;	-0.850^* * Significant at 5 %;
A	-0.655^* * Significant at 5 %;	-0.728^* * Significant at 5 %;	-0.694^* * Significant at 5 %;	-0.836^* * Significant at 5 %;	-0.671^* * Significant at 5 %;	-0.575^* * Significant at 5 %;	0.759^* * Significant at 5 %;	0.754^* * Significant at 5 %;	-0.875^* * Significant at 5 %;
B	-0.556^* * Significant at 5 %;	-0.695^* * Significant at 5 %;	-0.637^* * Significant at 5 %;	-0.856^* * Significant at 5 %;	-0.555^* * Significant at 5 %;	-0.499^* * Significant at 5 %;	0.797^* * Significant at 5 %;	0.695^* * Significant at 5 %;	-0.854^* * Significant at 5 %;	0.851^* * Significant at 5 %;
C	-0.552^* * Significant at 5 %;	-0.507^* * Significant at 5 %;	-0.542^* * Significant at 5 %;	-0.836^* * Significant at 5 %;	-0.348^* * Significant at 5 %;	-0.441^* * Significant at 5 %;	0.271^* * Significant at 5 %;	0.617^* * Significant at 5 %;	-0.825^* * Significant at 5 %;	0.788^* * Significant at 5 %;	0.857^* * Significant at 5 %;
D	0.349^* * Significant at 5 %;	0.387^* * Significant at 5 %;	0.793^* * Significant at 5 %;	0.880^* * Significant at 5 %;	0.764^* * Significant at 5 %;	0.735^* * Significant at 5 %;	-0.215^* * Significant at 5 %;	-0.729^* * Significant at 5 %;	0.916^* * Significant at 5 %;	-0.851^* * Significant at 5 %;	-0.897^* * Significant at 5 %;	-0.837^* * Significant at 5 %;
E	0.482^* * Significant at 5 %;	0.430^* * Significant at 5 %;	0.864^* * Significant at 5 %;	0.858^* * Significant at 5 %;	0.858^* * Significant at 5 %;	0.875^* * Significant at 5 %;	-0.059^ns ns not significant at 5 %.	-0.781^* * Significant at 5 %;	0.923^* * Significant at 5 %;	-0.888^* * Significant at 5 %;	-0.875^* * Significant at 5 %;	-0.864^* * Significant at 5 %;	0.882^* * Significant at 5 %;

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[TFN1] The same lower case letter, in the columns, do not differ by the Tukey test at 5 %. A = AOAC method; B = method used for coffee; C = method used for soybeans; D = total acidity method using pH 8.8 as indicator; E = total acidity method using phenolphthalein as indicator.

pH
Condition	Method	Days
Condition	Method	0	60	120	180	240	300
Stress	A	6.79 a	6.66 a	6.53 a	6.31 b	6.16 b	5.99 c
	B	6.77 ab	6.68 a	6.50 ab	6.42 a	6.37 a	6.26 b
	C	6.73 b	6.52 b	6.46 b	6.42 a	6.35 a	6.33 a
Favorable	A	6.79 a	6.69 a	6.58 a	6.47 b	6.38 b	6.15 b
	B	6.78 a	6.68 a	6.63 a	6.58 a	6.49 a	6.31 a
	C	6.71 b	6.54 b	6.48 b	6.44 b	6.33 c	6.30 a
Natural environment	A	6.76 a	6.82 a	6.71 a	6.58 a	6.42 b	6.31 b
	B	6.75 a	6.62 c	6.64 b	6.51 b	6.56 a	6.48 a
	C	6.73 a	6.69 b	6.54 c	6.55 ab	6.53 a	6.47 a
CV = 11.51 %
Acidity (g 100 g^-1 of dry matter)
Condition	Method	Days
Condition	Method	0	60	120	180	240	300
Stress	D	0.296 b	0.340 b	0.392 b	0.447 b	0.523 b	0.560 a
Stress	E	0.429 a	0.523 a	0.678 a	0.766 a	0.890 a	1.192 a
Favorable	D	0.297 b	0.335 b	0.412 b	0.468 b	0.475 b	0.478 b
Favorable	E	0.499 a	0.577 a	0.598 a	0.641 a	0.665 a	0.841 a
Natural environment	D	0.353 a	0.467 b	0.556 a	0.585 b	0.602 b	0.644 b
Natural environment	E	0.389 a	0.471 a	0.634 a	0.733 a	0.822 a	0.938 a
CV = 12.77 %