The production of applesauce starts with growing apples, a succulent fruit, also known as pomes, in orchards. The science of apples is call pomology.
Agricultural engineers know that apple trees can be grown in temperate climates where the weather in the summer is sunny with at least 100 days of no frost and adequate rain. Apple trees require cold enough winters for their leaves to fall, so that they may rest in dormancy. The temperature in the winter can be anywhere from 45 degrees Fahrenheit, and -30 degrees Fahrenheit.
In January and February, when the apples trees are bare and dormant, they are pruned with a tool to remove dead or diseased branches which helps the growth of new, healthy branches. So that the upper branches won't shade the lower ones during growing season, the apple trees are pruned into a triangular shape so that more leaves get sunlight to promote growth. To trim high treetops, growers use a sharp saw on the ends of long poles, and they use sharp handsaws or clippers for trimming the low ends. Dwarf trees are preferred in orchards for ease of access.
Although apple trees can live over 100 years it is usual to replace them in 20-30 years. In the spring or autumn new trees are planted to replace old trees, or to have more varieties in the orchard. In orchards in the south, new trees can be planted in the winter because of warmer weather in the south.
The grower replants the older trees with young trees, rather than seeds to know exactly what variety of apple will be produced. Agricultural engineers discovered grafting and budding to create the variety of tree that will produce the desired type of apple. These processes are the only ways to grow trees that will bear exactly the variety of apple wanted. Cross pollination produces apples with seeds that are a cross of two varieties or a cross of crabapple which maybe inedible or have poor taste. Seeds from fruit of dwarf trees may produce full-sized trees.
To graft, a scion, or green twig with a bud, is cut form the variety of apple tree to be grown. This scion is inserted into a slit of a one year old tree called a whip. The scion and whip are tied and grow together, forming a new young tree. To bud, the growers peel a bud from the green bark of a tree. Then, the bud section is slipped into a whip of a tree where the green bark was split and peeled back. Eventually, the bud section will grow onto the whip, creating a new tree that produces the same variety of apple that grew on the tree from which the bud was taken. In this way, new trees of desired varieties are determined from young trees that otherwise would produce an unknown variety and quality of apple.
Chemical engineers develop fertilizers that provide nutrients for optimal tree growth and fruit production. New trees are fertilized annually for 2-3 years, until they produce apples. The growers test the pH of the soil for balance for optimum apple tree health. Fertilizers for apple trees provide nitrogen, phosphorous and potassium and other nutrients. Yellow leaves and poor apple growth are signs that the trees need fertilizer.
Chemical engineers developed pesticides and fungicides to trees help control diseases, such as apple scab and powdery mildew. Apple scab causes black spots on the bottoms of the apples, but if it is controlled, the apple doesn't gain more scab spots later. Powdery mildew makes the leaves look as though powder has been sprinkled on, and it destroys new growth. Fungicides kill the disease and allow the health of the tree to return. An oil pesticide is sprayed on trees by helicopter when the leaf buds open to kills spider mite eggs. Spider mites eat the apples causing yellow-specked leaves, and small, deformed apples.
Agricultural engineers work with bee keeper because although most apple blossoms have both male and female parts, but need pollen from another tree to produce fruit. A few varieties of apple trees selfpollinate. The honey bees while collecting nectar also provide cross pollination to the apple blossoms. Boxes of bees are placed throughout orchards during blossoming of the trees.
In the autumn, apples are heavy and ripe and ready to be picked. Mechanical engineers developed a tool called a refractometer that the farmer uses to test for ripeness by measuring on a brix scale, which indicates the sugar content of the apples. The refractometer measures the amount of light that is refracted in the apple’s juice. More light indicates a higher degree of brix, and thus the higher the dissolvable solids, including sugars, packed with nutrients. Higher brix variety of apples, like Fuji with brix levels >18, have more natural flavor and sugars and the applesauce made from them will require less artificial sweeteners than apples with brix levels of 10 or 11 like Red Delicious varieties.
Apples are picked by hand. After harvesting, bins full of apples are sent to a storage and packing plant. A bushel of apples weigh about 42 pounds and will yield 20-24 quarts of applesauce. Refrigeration, developed by mechanical engineers, allows apples to be stored longer and safer. Temperatures under 41 degrees slow bacteria growth and it slows ripening by 6-10 times than room temperature. These apples can be used to produce applesauce throughout the year.
Mechanical and electrical engineers contributed to the invention of equipment used to process applesauce. The entire line of mechanical equipment used to turn apples into applesauce consists of a washer, pre-boilers, a beater, refiners, a concentrated boiler or evaporator, a mixing tank, and filler. The filler puts a precise amount of applesauce into each jar.
Canning applesauce gives the food a longer shelf life, lasting safely up to five years. To keep the food from going bad before and during canning, the applesauce may go through pasteurization which slows spoilage by slowing microbial growth; refrigeration; and vacuum treatment, to remove excess air which removes the oxygen. Without the presence of oxygen the growth of bacteria and the breakdown of enzymes are greatly reduced resulting in a longer shelf life for applesauce.
The plastics engineers of today are developing lightweight plastics for use in future canning with less weight. Shipping charges are calculated by weight. Heavier items cost more to ship. Lighter plastic applesauce jars will reduce shipping costs, and increase company profits or reduce the cost of the product to the consumer. Also, the product will be easier for consumers to carry home in grocery bags. The plastics engineers are trying to develop a sturdy, lighter plastic jar to keep the food fresh, economical, and transportable.
Carnegie Mellon University and the Robotics Institute are developing automated systems to enable precision apple farming. Using robotics engineering, robot vehicles with sensors gather data about the health of apple trees in orchards. Computer tracking will allow farmers to monitor orchards. The robot vehicles will administer precise amounts of water and agricultural chemicals like fertilizer, pesticide, and fungicides where needed. The Robot vehicles will also mow between rows of trees. Apple farmers can use data collected to monitor pest management and irrigation, and to make pruning and fertilization decisions about the apple trees. This engineering research may lead to automated farming in the future apple orchards.
Mechanical harvesting is also on the future of agricultural engineering. Some ideas for designs include vacuum-assisted devices that aid in harvesting apples without replacing human harvesting.
Bringing applesauce to the table involves much more engineering than the average consumer would ever know. Engineers improve life by contributing to the quality of food production, including applesauce, in many ways. Fortunately, all the engineering and hard-work ends with a delicious and healthy snack: applesauce.