This article was originally published in December 2019.
Welcome to our Christmas dinner special. We’ll be talking about the food science of traditional Christmas dinner cuisine. Have you ever thought about the science behind your Christmas dinner? If the answer is yes, read our articles on dishes that are commonly served as part of traditional Christmas dinner. Our second article will be on none other than the Vegetarian Christmas bake: Nut Roast!
The humble Nut Roast is a vegetarian option for those who don’t want to eat meat, but at the same time would like to enjoy a rich, nutritious meal. This dish brings together nuts, mushrooms, a variety of vegetables, butter and eggs in a simple but flavoursome bake. A nut roast combines a hearty blend of walnuts, cashew, brazil, peanuts, pistachio and hazel nuts each carrying distinctive health benefits. They are full of fibre, unsaturated fatty acids vitamin E, folate and minerals (including but not restricted to zinc, potassium and magnesium).
Unroasted nuts: profile
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Walnuts |
Walnuts are rich in omega-3 and antioxidants and are a good source of mono-unsaturated fats, which helps to lower the cholesterol in the body. |
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Cashews |
A great source of protein and minerals (iron and zinc and magnesium). Magnesium is thought to improve recall of information and delay age-related memory loss. |
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Brazil |
Contain selenium (mineral) which helps to produce our active thyroid hormone and supports our immunity. |
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Peanuts are a great source of fibre and also contain a source of vitamin E, folates and antioxidants (in skin too). |
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Pistachios are high in vitamin B6 which helps balance our hormone levels. They also contain good levels of potassium and fibre. |
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Hazel |
A good source of folate and helps to regulate the levels of homocysteine in the blood stream. |
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Pecan |
Good for the heart. Pecans are antioxidant rich and can help prevent plaque formation in the arteries. They are also a good source of vitamin B3. |
Before baking a nut roast, the nuts are usually toasted in a pan to bring out their aroma and flavour. Roasting nuts may breakdown some bioactive compounds, but it can also form antioxidant compounds through the Maillard reaction. It can also help enhance the flavour of the nuts, because it increases the content of flavonoids (have antioxidant and anti-inflammatory properties) and phenols Depending on the temperature and the length of time of the roast, the heat can cause the reduction in B-group vitamins and vitamin E content in nuts, as they are not heat stable.
Heat-treated nuts will undergo a transformation and there will be some significant positive and/or negative changes in the properties of the nuts. Research on almonds and hazelnuts showed an increase in antioxidant activity as an effect of roasting. Other reactions such as thermal degradation, can affect the total antioxidant capacity of nuts, independent of the Maillard reaction products. Food researchers have suggested that roasting cashews at high temperature for a short time enhances its antioxidant activity. You can read more about the Maillard reaction in our first article on ‘The Food Science of Christmas Turkey’.
What brings the nut roast together?
In traditional recipes, eggs beaten in with the rest of the nut roast recipe act as a glue to bring together the dish. As it cooks in the oven, the proteins in the egg start to coagulate, like the process with meat, we explained in our first Christmas post. There are over forty different proteins which make up an egg and which gives eggs their interesting cooking properties. Proteins in the albumen denature at a different rate to the yolk; egg whites coagulate at 60°C, whereas egg yolks coagulate at 65°C and completely coagulate at 70°C. The egg binds together the nut roast, but what about people who want a fully vegan Christmas dinner, how do they replace the eggs?
To make vegan, eggs can easily be replaced with flaxseeds (linseed) and a couple of tablespoons of water or stock or broth. Flaxseed, when mixed with water creates a gelatinous texture which can also bind the ingredients of a nut roast. The epiderm, the outer-most layer of the flaxseed contains a mucilaginous material which makes up about 8% of the weight of the flaxseed. Flax gel is a hydrocolloid, this means that it is a substance that forms a gel when combined with water.
So now you’ve learned a lot about the Christmas Nut Roast, please come back next week for another Christmas Dinner dish. Can you guess which dish is we’re going to be explaining the food science for? It’s ?????? ??????????! Tweet us @IFSTNews with your guesses and don’t forget to share this article with your friends and family!