Addition of tert-butylhydroquinone (TBHQ) to maize oil reduces lipid oxidation but does not prevent reductions in serum vitamin E in nursery pigs

Background

Maize oil is abundantly used in foods and feeds and is highly susceptible to oxidation. Consequently, commercially available antioxidants should be evaluated for effectiveness against lipid oxidation in swine diets. Our study was conducted to evaluate growth performance of nursery pigs fed oxidized maize oil and to determine effects of using antioxidants on oxidative status in a 2 × 2 factorial design. Two hundred eight weaned pigs were blocked by initial BW into 13 blocks, resulting in 4 pigs per pen and 13 pens per treatment. Dietary treatments included 6% unoxidized or oxidized maize oil, and 0 or 60 mg/kg of tert-butylhydroquinone (TBHQ), which was added after lipid oxidation. Data for growth performance were collected from 5 time periods of a two-phase feeding program (Phase 1 = d 0 to 12 and Phase 2 = d 13 to 34). Serum and liver samples were collected from one pig per pen, which had initial BW closest to average BW to determine oxidative status on d 34.

Results

Oxidized maize oil was heated for 12 h at 185 °C with 12 L/min of air, yielding a peroxide value (PV) of 5.98 mEq O₂/kg and TBARS of 0.11 mg MDA eq/g. Addition of TBHQ to diets containing oxidized maize oil decreased PV by 37% and increased the oil stability index by 69%. Final BW, ADG, ADFI, and G:F of pigs were not different among the four dietary treatments. However, pigs fed oxidized maize oil tended (P <  0.08) to increase hepatosomatic index by 5% compared with those fed unoxidized oil, and this was not affected by adding TBHQ. The serum vitamin E concentration of pigs fed oxidized maize oil was less (P < 0.03) than pigs fed unoxidized oil, but this reduction was not reversed by adding TBHQ. Finally, the serum and liver selenium concentration were not different among the treatments.

Conclusions

The addition of TBHQ did not affect growth performance and vitamin E status in pigs fed moderately oxidized maize oil, but TBHQ reduced lipid oxidation, enhanced the oil stability, and appeared to reduce oxidative stress.

The influence of cooking process on the microwave-assisted extraction of cottonseed oil

Cooking process is one of the most energy and time consuming steps in the edible oil extraction factories. The main goal of this study was cottonseed oil extraction by microwave radiation and elimination of any heat treatment of cottonseeds before extraction. The effect of cooking process on the physicochemical properties of extracted oil from two varieties of cottonseed (Pak and Sahel) was evaluated by free fatty acid content, melting point, smoke point and refractive index. Our results didn't show any significant differences between cooked and uncooked samples (P > 0.05) regarding physicochemical characteristics. From GC analysis of extracted oils, it was found there is no significant difference in fatty acid composition of cooked, uncooked and control (conventional extraction) samples. The thermal stability (Rancimat) analysis of oil samples showed the cooking process could cause a slight increase in the stability of oils for both varieties (about 40 min). The cooking process also increased total extracted phenolic compounds and considerably decreased total gossypol content of the cottonseed oil; but the extraction efficiency didn't change considerably after elimination of the cooking process. It can be concluded that microwave rays can destroy the structure of oil cells during process and facilitate the oil extraction without any heat treatment before extraction.