*****The last of these for a little while. Hopefully they’ve been of interest*****

Adding the preservatives butlyated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and tert-butylhydroquinone (TBHQ) to peanut oil increased its smoke point by 8-22C.

Wu and Yen (2004) Preventive effect of adding antioxidants on mutagenic compound formation in fumes of cooking oil. J. Sci. Food Agric. 84, 459–464.

Adding artificial preservatives BHT, BHA, TBHQ to vegetable oil increased its smoke point by around 10C.

Yen et al. (1997) Effects of Antioxidant and Cholesterol on Smoke Point of Oils. Lebensm.-Wiss. u.-Technol., 30, 648–652.

Comment: These fat soluble preservatives have to be added to all refined oils (canola, vegetable, grapeseed, flaxseed, ricebran etc etc) to give them a commercially acceptable shelf life. But it also improves the smoke point of the oil. So next time someone says – hey, I know that this refined oil has a higher smoke point than EVOO you might want to point out where some of that improvement came from! (and that the difference in smoke point between these oils and good EVOO i.e. with a low acidity, isn’t that different.)

_____________________________

Field grown olive trees watered with saline water produced smaller fruit and lower oil content than those irrigated with fresh water. Saline irrigation resulted in oils with 20% higher polyphenols and higher proportions of oleic and linoleic fatty acids.

Ahmed et al. (2009) Saline water irrigation effects on fruit development, quality, and phenolic composition of virgin olive oils, Cv. Chemlali. Journal of Agricultural and Food Chemistry 57, 2803-2811. Comment: An unreplicated study.

_____________________________

Nitrogen overfertilisation of mature Picual trees over three seasons resulted in reduced polyphenols and consequent bitterness and oxidative stability of the oil. Tocopherol level increased with fertilisation while the green and yellow olive pigments and fatty acid profiles remained unchanged.

Fernandez-Escobar et al. (2006) Olive oil quality decreases with nitrogen over-fertilization. Hortscience, 41, 215-219.

_____________________________

The availability of nitrogen (N), potassium (K) and phosphorus (P) positively influenced flowering intensity in potted Barnea while only N and P increased fruit set. Beyond a certain level, increases in N reduced fruit load.

Erel et al. (2009) Flowering and fruit set of olive trees in response to nitrogen, phosphorus and potassium. Journal of the American Society for Horticultural Science, 133, 639-647.

_____________________________

De-stoning three Spanish varieties (Picual, Hojiblanca, Manzanillo) prior to oil extraction resulted in polyphenol increases of up to 25%. The size of the increase was variety dependent, and was attributed to lower oxidation of polyphenols by the stone based peroxidase enzyme following its removal by de-stoning.

Luaces et al. (2007) Journal of the Science of Food and Agriculture, 87: 2721-2727.

Tweet This Post Facebook