Effects of Food Density, Shape and Size and Amount of Food

image of person using tablet How does density affect food's size, shape and amount?

The energy density of food refers to the amount of energy or calories per gram of food. A calorie is the amount of heat required to raise one gram of water one degree Celsius. Lower energy density foods provide fewer calories per gram of food. This means that you can have a satisfying portion of food with a relatively low calorie content. Low energy density foods include soups, stews, pasta and rice that absorb water during cooking and foods that are naturally high in water such as fruits and vegetables.

Nutrient density refers to how much nutrition a food provides per calorie. If a food is high in nutrients but low in calories, we say it is nutrient dense. This is the most useful way to compare two foods. If a food provides more nutrition for the same amount of calories (or the same nutrition for fewer calories), it is more nutrient dense than the other food. For example, a glass of orange juice has about the same number of calories as a glass of soda, but the juice contains more nutrients. Therefore, the juice is more nutrient dense than the soda.

Specific Gravity (SG), which is an expression of density, is the most widely accepted measurement of potato quality. There is a very high correlation between the specific gravity of the tuber and the starch content and also the percentage of dry matter or total solids. These are very important to the potato processor because they affect the quality and yield of the processed product. They also affect processing costs because the oil absorption rates during frying are related to dry matter levels. Higher specific gravity contributes to higher recovery rate and better quality of the processed product.

Factors Affecting Specific Gravity

Factors Affecting Specific Gravity
Varieties	Discuss choice of variety with the processor, including planting and delivery times and any other agronomic management specific to that variety. Make sure you are aware of the financial incentives offered by the company for delivery of high quality tubers.
Planting Time	Specific gravity will be higher in tubers grown during a period of increasing day length and temperature. As specific gravity is related to maturity, the longer a crop grows the more likely it is to produce tubers with high specific gravity.
Seed Quality and Seed Piece Size	Planting good, healthy seed will generally give higher yields of high specific gravity potatoes. Use healthy seed to produce vigorous crops that have less disease and have the potential to grow for a longer period.
Planting Density	Low plant density caused by incorrect seed spacing, skips or early decay of the seed-pieces can result in lower specific gravities.
Nutrition	Nitrogen and potassium nutrition can affect specific gravity.
Irrigation	Applying water in excess of crop requirements can reduce the final specific gravity. Periods of water stress during the growing season will reduce yield and specific gravity.
Weeds, Insects and Diseases	Excessive weed growth within a crop can reduce yield and specific gravity through competition for applied nutrients. Use herbicides where necessary to control weeds. Insect damage to crops can reduce their growth period and so reduce yields and specific gravity.
Soil Type	Potatoes produced in sandy soils often have lower specific gravity than those grown on heavier textured soils. However, with proper irrigation and nutrient management, high specific gravity potatoes can be harvested from sandy soils.

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