From Farm to Fork
The farmer plants and grows the wheat. After harvesting the grain is stored before being sent to the miller, who turns it into flour.The flour he makes can be used to make many different food products, including biscuits, cakes, bread and breakfast cereals or animal feed.From the farm to the fork there is a chain of events that need to take place. Here we will examine each step in more detail.
At the farm:
Most of the New Zealand milling wheat varieties are what is known as winter crops. This means that the farmer sows the seed in the autumn time, and the grain grows over the winter period and is ready for harvest in the summer.
The cycle begins after the harvest when the farmer ploughs over the field to prepare the soil and recycle the weeds and field debris. This turning of the soil allows for the debris of the previous crop to compost down and release nutrients the nutrients ready for the next crop.
When sowing the seed it is important to sow at the correct depth in the soil and then be covered immediately. The plants will grow slowly during the winter period and look just a field of grass.
In the spring time the wheat grows rapidly, taking advantage of the sunshine, warmth and water of New Zealand. Fertilisers are added during this time - Fertilisers are substances that are added to the soil to help increase the yield of the crop (Yield is a term which means how much wheat is produced per acre). These fertilisers work by providing essential nutrients that that the plants need to grow, and which may not be present in the soil in sufficient quantities to maximise the potential of the crop. These fertilisers include such things as Nitrogen, Potassium and Phosphates. Organic farmers can use other materials such as manure or waste crops to provide an alternative source of these minerals.
Each wheat plant will grow and produce a stem which can grow to between 40cm and 60 cm depending on the variety. The head of the plant or 'ear' grows late in the season and contains 30-40 grains.
All during the growing season the farmer must be vigilant to ensure that diseases do not attack the plant or its leaves, weeds do not strangle the growth or insects and pests do not eat the crop! Herbicides are commonly used to control the weeds and fungicides to control diseases. The farmer must be careful not to overdo the addition of such things, and to strike a balance between the cost of such treatment and the yield improvements it can create, but also be conscious of the environment and potential for leeching of nutrients into local waterways or the effects of herbicides on local flora and fauna.
When the wheat ripens, all the nutrients from the plant are channeled into the grain. In the wild, these grains would form new wheat plants. In some cases farmers will retain a portion of their crop to become the seed for the next season. This is known as farmer saved seed.
When the crop is ready sometime from December through January, the farmer will harvest the crop. This is usually done by a combine harvester which cuts down the wheat plant and separates the grain from the stalks. At his stage the combine harvester will also remove large impurities that may have been picked up by the harvester - this is done by passing the grains over a series of large sieves.
The straw lwft over from the harvest is either chopped and returned to the ground to provide nutrients for the next crop, baled as straw to use as winter bedding for livestock or can be used as a low value animal feed.
Following the harvest the farmer must store the grain before he can sell it. Before he does this he must ensure that the moisture content is low enough to safely store the wheat. If wheat is stored at too high a moisture there is a risk the grain will go mouldy or generate heat and begin to germinate - if this happens the crop is worthless and cannot be used for bread making. To ensure the correct moisture a farmer may have to dry the crop to bring it down to a safe level - less than 15% moisture content is considered OK.
Many farms are now required to keep full records of every stage of the growing process. This is known as traceability and records will be passed from the farmer to the miller who in turn may be asked to provide this information to the end user. This is part of a process called Quality Assurance and is widely used throughout the food industry.
At the mill:
Generally millers will have wheat grown for them by farmers on contract. That is to say the miller has promised to buy from the farmer a specified quantity of wheat at a guaranteed quality for a certain price. The specifications and price is usually agreed before the crop is sown. The miller will usually call down on these contracts during the year and the farmer will be required to deliver the grain to the mill. If the grain arriving at the mill is not of the contracted quality the miller has the option to claim a reduction in price to compensate for the lower quality or even reject the delivery completely. If a delivery is rejected, the grain will have to be sold elsewhere to be used for animal feed manufacture, and will lose the premium price paid for bread wheat. If a load is rejected, the farmer can still be held liable to fulfill the contracted quantity specified in the contract.
Assuming that wheat is accepted at the mill, the miller will test the delivery for various quality parameters such as protein, moisture and enzyme activity, and segregate and store the wheat accordingly in large storage vessels called silos. When transferring the grain from the delivery vehicle to the silo a basic cleaning of the grain takes place - this will involve the removal of large impurities and rubble, as well as as much dust as possible. The large items are removed primarily to protect machinery at the plant and the dust is removed to minimise the risk of dust explosion both here, and later on in the process.
During storage at the mill, the miller must monitor and control things such as moisture and temperature of the grain. If either of these get out of control the wheat will be spoilt and cannot be used for flour - this can be disastrous financially considering the price premium paid for the grain.
The miller will draw on wheat from the silos for his daily production requirements. He can either draw from a single silo using the quaity segregation parameters used on intake, or can blend from a number of silos to produce a blend or "grist" of wheat. The miller will have carefully calculated which of these options to use by balancing the cost of the grain with the quality of flour he trying to produce. Generally speaking flour is produced on a protein basis but many other characteristics of the grain can also be considered when blending.
When the wheat is transferred to the mill for milling, it must first be processed to maximise the quality and extraction of the finished flour (extraction is the term used to describe the amount of flour that is derived from the grain on a percentage basis - most grains contain upto 85% endosperm, but maximum extraction ranges from around 76%-82% due to constraints on finished product quality)
The first process undertaken is to thoroughly clean the grain. This is done using a variety of machines which remove all the impurities from the grain such as straw, stones, seeds, dust, other grains and tramp metal. After this process the grain is conditioned for milling by the addition of water (a process also known as tempering). Unlike storage moisture, during the conditioning process moisture is raised to between 16% and 17% and allowed to stand for between 6 and 24 hours. As this is only a short term process, none of the adverse effects high moisture content seen in long term storage occur. During this standing time the water permeates the skin of the grain and loosens the layers of bran wrapped around the grain and also makes the bran more flexible which helps reduce the potential contamination of the flour by bran particles that would otherwise be created during the grinding process.
Once conditioned correctly the wheat passes into the milling process. Using a continuous process of grinding, grading and sieving the grain is separated into its constituent parts of bran, flour and germ. The germ is the part of the grain that is the beginning of the new grain were it to be used as seed - this needs to be removed as it has a high fat content and can go rancid and spoil the flour. Fortunately it only represent around 2% of the grain.
During the milling process there are still a few quality parameters that can be adjusted that were not dictated by the composition of the grist. These are colour and water absorption; During the milling process, when the endosperm is ground by the rollermills, there is a chance that bran can be reduced to powder - if this happens, there is no chance to remove the bran as it is the same particle size as the flour, and imparts a darker hue on the flour. The water absorption (the amount of water that be sustained in the dough making process without causing problems) is adjustable by the amount of grind imparted by the rollermills. By squeezing the endosperm between two fast moving rollers, the starch granules within the endosperm are damaged and this increases the flours' ability to absorb water. The careful selection of wheats during gristing plays a part in dictating the range of damage possible. The baker likes starch damage because he can get more dough from less flour ($$$), but too much starch damage has disastrous effects on the enzymic activity of fementation leading to very poor quality bread. So it is clear that it is a delicate balancing act for everyone.
When the flour is made off the mill it is then stored in silos before packing out in bags, or bulk loading into a tanker, for delivery to the customer. It is preferable to hold flour for at least a few days in these silos to allow the flour to "age". This ageing process improves the quality of the flour and removes the yellowish tinge of freshly milled flour.
At the bakery:
The bakery will receive the flour either in small bags ranging in size from 10kg to 25kg, or for plant bakeries in a tanker holding as much as 27 tonnes. Bulk flour will be blown into a silo at the bakery. Most deliveries will come with some form of quality declaration for the customer and traceability information completing the chain from the field to the bakery.
At the bakery there are a complex series of event that take place to make your daily loaf:
The main ingredients for bread making are flour, yeast, water and salt. Most modern plant bakeries use a method of mixing known as “High Speed” mixing (also called the Chorleywood Process), which takes three to four minutes minutes.
Once the dough has been mixed it goes through a dividing machine which cuts it into smaller pieces, each of which will eventually become a loaf of bread. These pieces are then shaped into balls and left to rest – this allows the yeast time to begin it's work, and rests the dough after the stress of the mixing process. This resting stage is known as the first proof.
The dough pieces are then moulded by a machine that flattens the dough between two rollers. The dough is then rolled up like a swiss roll. This moulding produces an even texture in the finished loaf. Some loaves are made using a four piece process which cuts the roll into four pieces that are then dropped into one tin. Other moulding techniques use a single piece of dough.
The dough pieces then pass into a proover where in a warm moist atmosphere the yeast produces gas through fermentation to make the dough rise. This is known as the final proof stage. After about 45-50 minutes in the proover, the dough is ready for baking.
The risen dough passes into a pre-heated oven at about 270-280°C for approximately 20-25 minutes. The bread must reach a temperature greater than 92°C at its core to ensure that it is fully baked. This results in a rounded high topped loaf, To make a square loaf a lid is placed on the tin before baking.
After baking the bread travels into a cooler which takes at least 2 hours to bring the temperature of the baked loaf back down to the ambient temperature. The atmosphere is controlled to keep the bread soft.
The bread is sliced and wrapped as soon as it leaves the cooler to maintain softness. The tag on the bag will indicate the traceability data such as the day of production and best before date printed on the tag
The bread is then packed on to trays or baskets and delivered to your local store.
So now you have followed the chain of events from the grain in the field to the bread in your shop. But don't forget, there are many uses for flour other than for bread and cakes - How many uses can you name? (clue: see Made with Flour article)