Page 304 - Natural Antioxidants, Applications in Foods of Animal Origin

Application of Natural Antioxidants in Dairy Foods 283
VetBooks.ir polyphenols and the decrement of yoghurts’ antiradical and antioxidant

activities followed first order kinetics, with full-fat yoghurts exhibiting
higher deterioration rates and lower half-lives than the non-fat ones. In one
of the studies, stirred yoghurt was prepared from reconstituted skim milk
powder fortified with 5, 10, 15, 20, 25, 30, and 35% of the aqueous extract of
whole PPE, before and after inoculation with the traditional yoghurt starter
(El-Said et al., 2014). Addition of PPE before inoculation with the starter
resulted in stirred yoghurt of higher antioxidant activities than that with PPE
added after inoculation with the starter. Also, increasing the percentage of
the added PPE increased significantly the antioxidant activities of stirred
yoghurt up to 25% and further increase in the percentage of added PPE led
no significant effect.
Najgebauer-Lejko et al. (2014) evaluated the sensory quality and anti-
oxidant capacity of yoghurts with addition of selected vegetables (carrot,
pumpkin, broccoli, and red sweet pepper) (at 10% w/w) during two weeks
of refrigerated storage. The highest ability to scavenge DPPH radicals
was stated for yoghurts with broccoli and red sweet pepper. All vegetable
yoghurts were characterized by higher ferric reducing antioxidant power
(FRAP) values (measured directly after production) than the natural yoghurt.
However, the level of this parameter significantly decreased after storage.
Authors concluded that the red sweet pepper fortified yoghurt was the most
beneficial in terms of antioxidant properties and organoleptic acceptance of
the studied yoghurts.
Singh et al. (2013) carried out a study on the effect of strawberry poly-
phenol extract (0.5 mg/mL) addition on physicochemical and antioxidant
properties of stirred dahi preparation. This fortification resulted in a 7-fold
increase in the antioxidant activity of polyphenol-enriched stirred dahi, while
pH, acidity, water-holding capacity, and viscosity remained comparable with
the control. Sensory analysis indicated that the product was acceptable up to
two weeks when stored at 7–8 °C with no significant difference (p > 0.05) in
the antioxidant activity and total phenolic content (TPC).

7.9.4 CHEESE

The essential oils obtained from aromatic plants are natural products. Many
essential oils have demonstrated antioxidant properties; specifically, the
essential oils of oregano, rosemary, laurel, and other plants have been
studied as potential natural antioxidants (Kulisic et al., 2004; Olmedo et
al., 2008; Olmedo et al., 2009; Olmedo et al., 2012; Asensio et al., 2011).