52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
Stability Oxidative evaluation of Flaxseed Cake (Linum usitatissimum) by means of indices of acidity
and peróxidos1
Jessyca Caroline Rocha Ribas2, Marina Tolentino Marinho3, Adriana de Souza Martins4, Maria de Fátima dos
Santos Ribeiro5, Erica Machado6
1
Part of the final paper of Animal Science Course at the State University of Ponta Grossa - UEPG
Student of Animal Science, Graduate Program - UEM, Maringá-PR, Brazil. E-mail: [email protected]
3
Teacher, Department of Food Engineering, State University of Ponta Grossa - UEPG. Email: [email protected]
4
Teacher, Department of Animal Science at the State University of Ponta Grossa - UEPG. Email: [email protected]
5
Researcher of Plant Science and Agro-Energy Program Agronomic Institute of Paraná – IAPAR. Email: [email protected]
6
PhD Student, Animal Science Graduate Program – UEM, Maringá – PR, Brazil. E-mail: [email protected]
2
Resumo: Avaliou-se a estabilidade oxidativa do óleo da torta de linhaça em teste de oxidação acelerada, utilizando
métodos clássicos (acidez e peróxidos). A torta foi obtida por meio de prensagem a frio, com prensa experimental.
A estabilidade oxidativa foi determinada pelo método em estufa (oxidação acelerada), diariamente, durante nove
dias, em estufa a 65º C. Sob estas condições, cada dia na estufa equivale a um mês à temperatura ambiente. As
variáveis acidez e peróxido foram submetidas à análise de variância utilizando-se o teste de Fisher.O índice de
acidez aumentou com o tempo de armazenamento da torta, porém, manteve-se abaixo do limite máximo
estabelecido pela ANVISA. O índice de peróxidos apresentou oscilações durante o processo de oxidação acelerada.
O óleo da torta de linhaça submetido aos testes de acidez e peróxido manteve uma estabilidade oxidativa
satisfatória, podendo ser armazenada por um período de nove meses.
Palavras–chave: ácidos graxos, óleo, oxidação lipídica, palatabilidade
Abstract: Was evaluated the oxidative stability of oil of cake flaxseed in accelerated oxidation test, using classical
methods (acidity and peroxides). The cake was obtained by cold pressing, with experimental press. Oxidative
stability was determined by the method oven (accelerated oxidation) daily, for nine days in an incubator at 65ºC.
Under these conditions one day in the oven was equivalent a month at room temperature. The variables acidity and
peroxide were subjected to analysis of variance using the Fisher test. The acid value increased with storage time of
the pie, but remained below the ceiling set by ANVISA. The peroxide index showed variations during the
accelerated oxidation process. The oil of linseed cake subjected to acidity and peroxide tests maintained a
satisfactory oxidative stability and can be stored for a period of nine months.
Keywords: fat acids, oil, oxidative stability, palatability
Introduction
Flaxseed (Linum usitatissimum) is an oilseed plant produced on a large scale in Canada, where it is widely
used in dairy cows to produce milk enriched. In food, the increase in consumption of flaxseed has been associated
with decreased cardiovascular disease, prostate cancer and breast cancer, osteoporosis and menopausal symptoms.
The cake is a co-product of the oil extraction of oil plants through pressing, and has a higher oil content in
relation to meal. The oil contained in the cake increases the energy content of the diet and, when consumed by
animals, may amend this fatty acid profile in meat/milk products, making them healthier for human consumption.
Flaxseed contains polyunsaturated fatty acids, however, the disadvantage of working with oleaginous
materials is the possibility of oxidizing, reducing the nutritional quality of the food due to the degradation of fat
soluble vitamins and essential fatty acids, besides modifying the odor and taste food. The animals, in general, tend
to decrease the consumption of food with modified organoleptic properties. Therefore, the objective was to evaluate
the oxidative stability of oil linseed cake from the classical methods: acid values and peroxides.
Material e Methods
The experiment was conducted in Food Analysis Laboratory of the State University of Ponta Grossa
(UEPG). Flaxseed cake was obtained from a small-scale seed press Scott Tech model ERT-60. The flaxeed cake
used in this experiment presented 17% of ether extract.
The oxidative stability of linseed cake was evaluated by the method oven (accelerated oxidation), also
known as a Schaal method. According to the method, 9 trays of cake flaxseed crushed containing 100g of cake was
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
thermally stressed at 65 ° C in an oven and analyzed for acidity and peroxide over a period of nine days, one at a
time, including day 0 (zero), which comprises cake sample at room temperature. Thus, 10 samples were analyzed
during the evaluation period. Daily, at 9: 00min were collected 90 g sample of the cake for oil extraction for
determination of acidity and peroxide, the extraction was performed in triplicate, using 30 g cake per sample. The
oil extraction of cake was performed according to the Bligh-Dyer method (BLIGH and Dyer, 1959). Under
conditions of heat stress by storing in an oven, the every day in the oven equals one month at room temperature
(Almeida et al., 2011). When detecting the first signal or rancidity change in peroxide value, was determined the
induction period, measured in days.
The acid value was determined according to the methodology of the AOCS Ca 5A-40 (1990), expressed as
mg KOH per gram of sample and calculated according to the equation: IA = [V x f x 56,1]/m, where IA = index
acidity; V = volume of NaOH solution 0.01 mol L-1in the sample spent in the titration (ml); f= correction factor of
NaOH solution; 56.1 = equivalent weight basis of KOH; m = sample weight in grams.
The index of peroxides was obtained according to AOCS Cd 8-53 (1990), expressed in milliequivalents
peroxide per kg of the sample obtained by the following equation: IP = [(B-A) x N x f x 1000]/m; where PV =
peroxide value; B = volume of sodium 0.01 mol.L-1spent thiosulfate solution in the blank titration (ml); A = volume
of sodium 0.01 mol.L-1solution in spent thiosulfate titration of the sample (ml); C = concentration of sodium
thiosulphate solution; f = factor of the sodium thiosulfate solution; m = sample weight in grams.
The variables acidity and peroxide were subjected to analysis of variance (ANOVA) using Fisher's post hoc
test for difference between means, the 1% significance level.
Results and Discussion
The acid values and peroxide of samples subjected to the accelerated oxidative stability test are described in
Table 1.
Table 1: Index of Acid (AI) and peroxides (PI) from oil samples of flakseed cake, submitted to accelerated test
analysis in function of evaluation day
Day
0
1
2
3
4
5
6
7
8
9
AI (mg KOH/g )
1.80±0.02e
2.06±0.44de
2.38±0.01cd
2.38±0.01cd
2.47±0.21cd
2.78±0.16bc
3.01±0.19b
3.18±0.07b
3.69±0.18a
3.77±0.12a
PI (mEq peroxide/kg)
0.99±0.01c
1.96±0.03b
2.01±0.01b
2.97±0.03ª
2.97±0.09ª
2.97±0.03ª
3.51±0.70ª
2.00±0.01b
1.48±-0.71bc
1.47±0.65bc
Means followed by different letters at the same column, differ by the Fisher test (P<0.01).
The acid number indicates the condition of oils and fats. It is defined as the number of milligrams of
potassium hydroxide required to neutralize the free fatty acids of 1.0 g of the sample (ITB, 2008). Therefore, the
higher the acid value, the greater the deterioration of the product. This rate was increased (P <0.01) with the
progressive deterioration of thermal oil.
Ruminant rations containing oil may have stability issues due to factors such as ambient temperature,
humidity and storage because they favor the lipid oxidation process. The oxidative deterioration of lipids can cause
rancid flavor in food, reducing consumption by animals. According to ANVISA, cold pressed oils are unrefined and
having a maximum acid number of 4.0 mg KOH / g. Therefore, the results of flaxseed cake acid value are within
the standards recommended by ANVISA (BRAZIL, 2005). Thus, it appears that the linseed cake storage for nine
months (one day in a greenhouse was a month at room temperature) does not impair its properties, and therefore
will not interfere in the intake by the animals.
Peroxide Index (PI) is a way to detect rancidity of fat. According to Souza (2003) their use should be limited
only to the initial stage of oxidation, since the peroxides have poor stability, it decomposes into intermediate
products (aldehydes, alcohols, ketones and hydrocarbons). The oxidation of oils can form undesirable products in
foods such as peroxides and reactive intermediates, the so-called free radicals, which affect the quality of feed by
the reduced palatability and digestibility of food, harming animal performance.
The results showed oscillations in the peroxide value, where, at first moment (0 to 6 days of accelerated
oxidation), increase was observed in the peroxide level and then (7th to 9th day of oxidation), had progressive
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
decrease, reaching 1.47 meq peroxide / kg (9 days in accelerated oxidation process). For peroxide value, ANVISA
establishes the maximum limit of 15 mEq / kg, so the linseed cake also lie within the recommended levels for this
index. However, it is emphasized that the low level of peroxides in the sample does not represent good oxidative
stability guarantee and may mean pronounced change.
Conclusions
The oil of linseed cake subjected to acidity and peroxide tests maintained a satisfactory oxidative stability,
be within the standards recommended by ANVISA. Flaxseed cake can be stored for a period of nine months,
without compromising its oxidative stability.
References
Almeida, C. G.; Rodrigues, C.; Demiate, I. M.; Simões, D. R.; Tolentino, M. C.; 2011. Apoio técnico à implantação
de uma unidade processadora de derivados de tomate no município de reserva – processamento e análises. In:
9° CONEX: Conversando sobre extensão. UEPG, Paraná.
AOCS – American Oil Chemists’ Society. 1988.Official methods analysis: 3rd ed., Champaign, Illinois, USA.
Bligh, E. G.; Dyer, W. J. 1959. A rapid method of total lipid extraction and purification.p. 911-917. In: Canadian
Journal of Biochemistry and Physiology. v. 37, n. 8.
Brasil.
2005.
Resolução
nº270,
de
23
de
setembro
de
2005.
Disponível
em:
<http://elegis.anvisa.gov.br/leisref/public/showAct.php?id=18829&word>. Acesso em: outubro de 2013.
IAL - Instituto Adolfo Lutz (São Paulo). 2008.Métodos Físico-químicos para Análise deAlimentos. São
Paulo:Instituto Adolfo Lutz, p. 1020.
Souza, A. V. C. 2003. Avaliação da Qualidade e Valor Nutricional de Óleos e gorduras. .Net, São Paulo, Seção
Artigos do Mês. Disponível em: <http://www.polinutri.com.br/conteudo_artigos_anteriores_agosto0 3.htm>.
Acesso em: 2 maio de 2008.
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