Changes in the fatty acid profile and quality parameters produced during storage of organic cottage cheese supplemented with oregano essential oils Claudia M. Asensio1; Mariana Larrauri1; Patricia R. Quiroga1; M. Paula Martín1, Cecilia G. Riveros1, Nelson R Grosso1 1Facultad Ciencias Agropecuarias-Universidad Nacional de Córdoba, IMBIV CONICET, Cordoba, ARGENTINA;
[email protected]
Introduction The quality of food products changes during storage because exposure to heat, enzymes, transition metal ions, oxygen, and light, and this quality changes cause degradation or formation of flavor active compounds. Cheese is a milk concentrate that consists of proteins and fats, mainly. Processed cheese may be considered a stable product. However, its shelf life may be shortened for an extended period of storage. Dairy products as other water–oil emulsions can suffer hydrolytic and oxidative rancidity. The objective of this study was to evaluate the preserving effect of oregano essential oil (EO) on organic cottage cheese acting as a retarding agent of lipid oxidation. Materials and methods Organic cottage cheese (CC) was flavored with different Argentinean oregano EO (Compacto (COM), Cordobes (COR), Criollo (CRIO), and Mendocino (MEN)) and thymol (THY) at 0.05% w/w. Antioxidant activity (FRAP), chemical indicators of lipid oxidation (hydroperoxide value (HPV) and conjugate diene content (CD)), and changes in the fatty acid profile were determined every 10 days during 30 days under thermal storage (40 C). Statistical analysis was performed (ANOVA and Fisher- LSD test).. Results and discussion The oils evaluated had the ability to reduce the ferric diTPTZ complex. Criollo and Cordobes EOs presented higher AEAC (0.18474 mM/mg and 0.15486 mM/mg, respectively). These results could be attributed to the high content of thymol in both EOs and to the presence of ocymene and terpinene. The accumulation of hydroperoxides was affected by the storage time (p˂0.001) and antioxidant addition (p˂0.013).
The highest hydroperoxide value was observed in control sample (3.93 µeqO2/kg) and the lowest value was detected in the sample with thymol addition (2.46 µeqO2/kg), followed by the sample with Criollo EO (2.66 µeqO2/kg). It was also observed that CC-COR, CC-CRIO, CC-MEN, and CC-THY samples did no differ significantly between them at storage day 30. Spectrophotometrical detection of cheese samples showed that accumulation of conjugated dienes was significant (p < 0.001) from the first day to the end of the storage at 40 °C. At storage day 30, CC-COR and CC-THY presented lower conjugated dienes (15.94 and 15.53, respectively; p ˂ 0.001), whereas CC-C showed the highest value (17.54). In order to prevent or retard oxidative deterioration, essential oils were tested as free radical quenchers, singlet oxygen scavengers, and pro-oxidant metals suppressors. As thermal oxidation time increased, relative percentage of saturated fatty acids such as lauric, myristic, and stearic acids increased. The amounts of lauric and stearic acids increased up to 11 and 16 g/100 g in CC-C and CC-MEN samples, respectively. CC-COR showed lower increase in these two fatty acids (up to 8.02 and 15.57 g/100 g, respectively). The linolenic acid decreased to 0.57 g/100 g in CC-C and to 1.23 g/100 g in CC-COM. Control samples of organic cottage cheese presented higher negative slope than the other samples when the concentration of polyunsaturated fatty acids were compared. Cottage cheese with Mendocino EO and Control samples showed higher S/U ratio (1.94 and 1.88, respectively).. The ratio S/U increased with storage time, Compacto, Criollo and Cordobes EOs presented lower S/U ratio (1.67, 1.62, and 1.68, respectively). The fatty acids ratio changes differently during oxidation depending on the type of essential oil and fatty acid composition.
CONCLUSION Organic cottage cheese flavored with oregano essential oil shows lower degree of chemical deterioration during storage. Moreover, this product with Cordobes and Criollo EOs preserves longer polyunsaturated fatty acids against oxidation. The inclusion of natural compound as a food preserving agents would satisfy food manufacturers and consumers’ demands for healthier food. In addition, this natural GRAS compound, oregano essential oil, can be farmed and processed in organic condition and act as organic preserving agent useful for organic food products Figure 1. (A) Hydroperoxides and (B) conjugates dienes in organic cottage cheese samples flavored with oregano essential oils stored at 40 °C during 30 days.
B
Conjugated dienes (E1%;232nm)
A
4
Hydroperoxides (µeqO2/kg)
3,5 3
2,5 2
1,5 1
0,5 0 0
CC-C
10
CC-COM
CC-COR
CC-CRIO
20
CC-MEN
18 17 16 15 14 13 12 0
30
CC-THY
CC-C
10
CC-COM
CC-COR
20
CC-CRIO
30
CC-MEN
CC-THY
Footnote 1: CC-C (cottage cheese without any addition), CC-COM (cottage cheese with the addition of Compacto EO), CC-COR (cottage cheese with the addition of Cordobes EO), CCCRIO (cottage cheese with the addition of Criollo EO), CC-MEN (cottage cheese with the addition of Mendocino EO), CC-THY (cottage cheese with the addition of thymol). 1
Figure 2. Saturated/unsaturated ratio (A), and saturated (B) and unsaturated (C) fatty acid percentages in organic cottage cheese samples flavored with oregano essential oils stored at 40 °C during 30 days. b1
1,95
A 41
67
B 66
C1,9
40
65
1,85
39
64
38 37
1,8 1,75
63
S/U
g/100 g
g/100g
42
1,7
62
1,65
61
36
1,6
60
35
1,55
59
34 0
CC-C
10 CC-COM CC-COR
58
Days
20 CC-CRIO
CC-MEN
30 CC-THY
1,5 Days
0 10 20 30 CC-C CC-COM CC-COR CC-CRIO CC-MEN CC-THY
1,45
0
10
20
30
Days
CC-C CC-COM CC-COR CC-CRIO CC-MEN CC-THY
Footnote 1: CC-C (cottage cheese without any addition), CC-COM (cottage cheese with the addition of Compacto EO), CC-COR (cottage cheese with the addition of Cordobes EO), CC-CRIO (cottage cheese with the addition of Criollo EO), CC-MEN (cottage cheese with the addition of Mendocino EO), CC-THY (cottage cheese with the addition of thymol).
