tynabelle » how stuff works

how stuff works: bread + bread machine

tyna — Fri, 06 Feb 2009 03:47:20 +0000

Bread Basics

If you pick up a slice of bread and examine it closely, you can see that it is full of air holes. This makes it spongy and soft. You will also see that bread is moist. If you let a slice of bread sit out on the counter for a day, you will realize just how moist fresh bread is!

Bakers use two simple facts of life to create soft, spongy, moist bread:

First, they use the fact that yeast (a single-cell fungi) will eat sugar, and from the sugar create alcohol and carbon dioxide gas as waste products. The carbon dioxide gas created by yeast is what gives bread its airy texture, and the alcohol, which burns off during baking, leaves behind an important component of bread’s flavor.
Second, wheat flour, if mixed with water and kneaded, becomes very elastic. The flour-and-water mixture in bread becomes stretchy like a balloon because of a protein in wheat known as gluten. Gluten gives bread dough the ability to capture the carbon dioxide produced by yeast in tiny flour balloons.

How does a bread machine work?

[the basics]

Bread machines are essential motors connected to a drive shaft, which moves a kneading blade inside a bread pan. A thermostat regulates the temperature inside the machine for rising and baking while a microchip contains programs for the various cycles that the individual bread machine performs.

How Does a Bread Maker Work?

Introduction of the Ingredients

A bread maker, overall, does the exact same thing that someone making bread by hand would do. The obvious advantage is that it is all done for you without much effort or thought. The most important (and virtually only) step in how a bread maker works is the introduction of the ingredients into the bread maker. Bread making is more like a science experiment than cooking because if you don’t put the exact right amount of a certain ingredient into the recipe, the whole thing won’t work. Make sure you measure out the exact amount of flour, water, yeast, salt and any other ingredient before you put it into the bread maker to ensure it produces a satisfactory end product.

Mixing and Kneading

Once the ingredients are in, a program is selected for the bread maker to follow. Most bread makers come with a certain number of set programs that are available at the touch of a button. The timing may be slightly different, but they all follow the same basic series of commands, the first being mixing and kneading. The bread maker will start by mixing the ingredients with its dough hook for a short amount of time, probably around two minutes. It will then let the dough rest for ten to fifteen minutes to develop it’s gluten, then the dough hook will begin turning again, this time kneading the dough. This will last for five or six minutes.

Rising

The thermostat in your bread machine will raise the temperature slightly around the dough in your machine, allowing the bread to rise for the appropriate amount of time. Once it is done rising, the machine will immediately go into baking mode.

Baking

After rising, the microchip that controls the thermostat in your bread maker will, once again, raise the temperature. This time, though, it will be baking your bread. Your bread will bake for the predetermined amount of time programmed by you, and when it is done baking, the machine will shut itself off. Your bread will be cooled and ready to eat in thirty minutes to an hour.

how stuff works: the food processor

tyna — Fri, 06 Feb 2009 03:20:38 +0000

[closest thing I could find to a juicer]

The Basic Components
Modern food processors come in three basic sizes: full, compact, and mini. No matter what size they are, however, the basic components are the same: a motor, a bowl with a lid and feed tube, and a set of attachments.

The motor is housed in the base of the appliance, and it is the heaviest part of the device. Full-size machines generally have larger, more powerful motors, and can weigh more than 20 lbs (9 kg). This weight has a utilitarian value: The heaviness of the base gives the appliance stability and ensures that it doesn’t move around while the motor is running. Though the first food processor bases were clad only in white, hard plastic, today they are available in a range of stylish colors and with metal and plastic finishes, ensuring that your appliance will fit in with your kitchen decor.

From the motor, a shaft extends upward to power the attachments. The bowl, which is usually made of durable, transparent plastic, fits onto this shaft and locks into position. The lid, usually made of the same material, locks onto the top of the bowl; in many older models, engaging the locking mechanism turns on the motor, but newer models generally have an on/off switch or button.

The lid has a feed tube fitted with a plunger. You can insert food into the device through this feed tube, pushing it down with the plunger. Some models have wider and narrower feed tubes for use with larger and smaller food items. The size of the bowl varies according to the size of the machine:

Full-size bowls generally have a capacity of 9 to 13 cups.
Compact-size bowls can accommodate 5 to 7 cups.
Mini-size bowls can fit 2 to 5 cups.

Some models come with large and small bowls for use with the same base.

In the next section, we’ll look at the attachments that do a food processor’s slicing and dicing.

Common attachemnt:

A citrus juicer – This is a dome-shaped attachment that fits on top of the shaft and turns to squeeze the juice from oranges, grapefruits, lemons, limes, etc.

how stuff works: the toaster

tyna — Fri, 06 Feb 2009 02:55:49 +0000

link: sophisticated design

video: how toasters work

Toaster Basics

The basic idea behind any toaster is simple. A toaster uses infrared radiation to heat a piece of bread (see How Thermoses Work for information on infrared radiation). When you put your bread in and see the coils glow red, the coils are producing infrared radiation. The radiation gently dries and chars the surface of the bread.

The most common way for a toaster to create the infrared radiation is to use nichrome wire wrapped back and forth across a mica sheet, like this:

[Toaster heating element, nichrome wire on mica sheet]

Nichrome wire is an alloy of nickel and chromium. It has two features that make it a good producer of heat:

Nichrome wire has a fairly high electrical resistance compared to something like copper wire, so even a short length of it has enough resistance to get quite hot.
The nichrome alloy does not oxidize when heated. Iron wire would rust very quickly at the temperatures seen in a toaster.

The very simplest toaster would have two mica sheets wrapped in nichrome wire, and they would be spaced to form a slot about an inch (2.5 cm) wide. The nichrome wires would connect directly to a plug. To make toast:

You would drop a piece of bread into the slot.
You would then plug in the toaster and watch the bread.
When the bread became dark enough, you would unplug the toaster.
Then you would tip the toaster upside down to get the toast out!

Most people don’t have this sort of patience, nor do they like crumbs all over the counter. So a toaster normally has two other features:

A spring-loaded tray pops the toast out. This keeps you from having to turn the toaster upside down.
A timer turns the toaster off automatically and at the same time releases the tray so the toast pops up.

The Spring-Loaded Tray

The photo below shows you the view down one of the slots of a typical toaster. Two mica/nichrome sheets line either side of the slot. A metal holder rides up and down in the slot to raise and lower the bread.

Many toasters include a pair of grates on either side of the slot. The grates press against the bread and center it. Two metal springs get pushed when the holder nears the bottom of the slot, and they pull the grates inward.

The holders in each slot are connected to the handle that you depress to lower the bread into the toaster, as shown below:

[Toaster lowering mechanism]

Popping the Toast Up

When you push the handle down, three things have to happen:

Some sort of mechanism needs to hold the handle down to keep the toast inside the toaster for a period of time.
Power needs to be applied to the nichrome wires.
Some sort of timer needs to release the holder at the proper time so the toast pops up.

In this particular toaster, both the hold-down mechanism and the power switch are part of the handle:

[Plastic plate attached to toast-lowering lever, plastic wedge (on left) that switches on the power]

[When the bar is lowered, the metal tab contacts the electromagnet.]

Above you can see a plastic bar and a piece of metal attached to the handle. The plastic bar presses into a pair of contacts on the circuit board to apply power to the nichrome wires, and the piece of metal gets attracted to an electromagnet to hold the toast down. You can see both the contacts (copper strips on the right) and the electromagnet (green block on the left) below:

[Toaster circuit board]

Circuit Board

The following two photos show how the plastic bar applies power to the toaster. In the first photo, the plastic bar is being simulated by a pencil, and you can see how it pushes the contacts apart:

[Toaster circuit card showing electrical contacts]

[Toaster circuit board with contacts engaged]

In this particular toaster, here is how the whole mechanism works:

When you push down on the handle, the plastic bar presses against the contacts and applies power to the circuit board.
120-volt power runs directly through the contacts to the nichrome wires to start toasting the bread.
A simple circuit made up of transistors, resistors and capacitors turns on and supplies power to the electromagnet.
The electromagnet attracts the piece of metal on the handle, holding the bread in the toaster.
The simple circuit acts as a timer. A capacitor charges through a resistor, and when it reaches a certain voltage it cuts off the power to the electromagnet. The spring immediately pulls the two slices of bread up.
In the process, the plastic bar rises and cuts off power to the toaster.

In this toaster, the darkness control is simply a variable resistor. Changing the resistance changes the rate at which the capacitor charges, and this controls how long the timer waits before releasing the electromagnet.

Less sophisticated toasters use a bi-metallic strip (see How Thermometers Work for details on bi-metallic strips) to turn off the electromagnet. As the strip heats up (due to rising temperatures inside the toaster), the strip bends and eventually trips a switch that kills the power to the electromagnet. The bi-metallic strip approach has two problems:

If the kitchen is cold, the first piece of toast will be darker than usual.
If you try to make a second batch of toast, it will be too light because the toaster is already hot.

The electronic circuit in this toaster provides much more consistent toast!