Vegetable fats and oils
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Vegetable fats and oils are substances derived from plants that are composed of triglycerides. Nominally, oils are liquid at room temperature, and fats are solid; a dense brittle fat is called a wax. Although many different parts of plants may yield oil, in actual commercial practice oil is extracted primarily from the seeds of oilseed plants.
Many vegetable oils are consumed directly, or used directly as ingredients in food - a role that they share with some animal fats, including butter and ghee. The oils serve a number of purposes in this role:
- Texture - oils can serve to make other ingredients stick together less.
- Flavour - while having less flavour than other oils such as safflower oil command premium prices, oils such as olive oil or almond oil may be chosen specifically for the flavour they impart.
- Flavour base - oils can also "carry" flavours of other ingredients, since many flavours are present in chemicals that are soluble in oil.
Secondly, oils can be heated, and used to cook other foods. Oils that are suitable for this purpose must have a high flash point. Such oils include the major cooking oils - canola (rapeseed), sunflower, safflower, peanut etc. Some oils, including rice bran oil, are particularly valued in Asian cultures for high temperature cooking, because of their unusually high flash point.
Smoke Points of Oils
Basically, the higher the smoke point, the higher you can heat the oil. For seasoning equipment such as hard-anodised baking tins or terracotta cazuelas and tagines, it is advisable to choose an oil with a higher smoke point than the temperature required to effect the seasoning. The same applies when greasing tins.
- Avocado 270ºC / 520ºF
- Safflower 265°C / 510ºF
- Almond 257°C / 495ºF
- Soyabean 232°C / 450ºF
- Corn 232°C / 450ºF
- Sunflower 232°C / 450ºF
- Peanut 232°C / 450ºF
- Cottonseed 215°C / 420ºF
- Sesame (Light) 210°C / 410ºF
- Olive 210°C / 410ºF
- Grapeseed 204°C / 400ºF
- Rapeseed (Canola) 204°C / 400ºF
- Walnut 204°C / 400ºF
- Sesame 176°C / 350ºF
- Olive Oil (Extra Virgin or Virgin) 160°C / 320ºF
- Peanut 160°C / 320ºF
- Soyabean 160°C / 320ºF
- Corn 160°C / 320ºF
- Walnut 160°C / 320ºF
- Sunflower 107°C / 225ºF
- Rapeseed (Canola) 107°C / 225ºF
- Safflower 107°C / 225ºF
Flavoured Oils Safety
'Of the two preserving mediums, vinegars are more effective as the acidity kills of most bacteria and they have a longer shelf life than their oil equivalents. It is necessary to heat some oils, especially with chillies and garlic as they can be prone to botulism spores, to around 180ºC/350ºF before pouring into the jar/bottle. This also has the benefit of speeding up the infusion. Alternatively use dried chillies – it tends to be the moisture in fresh chillies (and garlic) that can cause botulism.
Once opened, to be on the safe side as oils also tend to go rancid relatively quickly once exposed to air, keep them in the fridge and monitor them closely for spoilage. They will need to be used up in about 2 weeks. Cold oils are the best ones to use with green herbs.