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1. Abstract of the experiment
2. Introduction/Theory
Water is an important part of a large number of foods. The deterioration of foods, both microbiological and chemical, is affected by the presence of water in the food.
Indirect distillation (or drying) methods involve the measurement of the weight lost due to the evaporation of water. The open dish method is applicable to a wide range of foods. The vacuum oven method is particularly recommended for food when decomposition is likely to occur. The infrared balance method is used for rapid routine work.
The influence of water activity on food quality and spoilage is increasingl being recognized as an important factor. Water activity has a profound effect on the rate of many chemical reactions in foods and on the rate of microbial growth. Moulds and yeasts start to grow at aw between 0.7 and 0.8. Bacterial growth takes place when aw reached 0.8. Enzyme activity increases gradually between aw of 0.3 and 0.8 then increases rapidly from 0.8 to 1.0. Lipid oxidation rates are high in the range of aw 0 to 0.25; passing from a minimum at aw 0.3 to 0.4 and to a maximum at aw 0.8.
3. Objectives
a. To observe the keeping quality of some food products
b. To study the various simple methods of moisture determinations using different drying methods
c. To determine the water activity of some food samples
4. Procedure
a. Observation of the keeping quality of some food products ( with respect to the moisture content)
a.1. Some food products were given.
a.2. The different types of spoilage that may occur during storage to the products given were recorded on a data sheet.
a.3. Suggestions on how to improve shelf life of these products were then recorded on the data sheet.
b. Determination of moisture in an open dish
b.1. A clean metal dish with cover and a short piece of glass rod were placed in the oven, at 130°C, for 10 minutes.
b.2. The clean metal dish with cover and glass rod were then
2. Introduction/Theory
Water is an important part of a large number of foods. The deterioration of foods, both microbiological and chemical, is affected by the presence of water in the food.
Indirect distillation (or drying) methods involve the measurement of the weight lost due to the evaporation of water. The open dish method is applicable to a wide range of foods. The vacuum oven method is particularly recommended for food when decomposition is likely to occur. The infrared balance method is used for rapid routine work.
The influence of water activity on food quality and spoilage is increasingl being recognized as an important factor. Water activity has a profound effect on the rate of many chemical reactions in foods and on the rate of microbial growth. Moulds and yeasts start to grow at aw between 0.7 and 0.8. Bacterial growth takes place when aw reached 0.8. Enzyme activity increases gradually between aw of 0.3 and 0.8 then increases rapidly from 0.8 to 1.0. Lipid oxidation rates are high in the range of aw 0 to 0.25; passing from a minimum at aw 0.3 to 0.4 and to a maximum at aw 0.8.
3. Objectives
a. To observe the keeping quality of some food products
b. To study the various simple methods of moisture determinations using different drying methods
c. To determine the water activity of some food samples
4. Procedure
a. Observation of the keeping quality of some food products ( with respect to the moisture content)
a.1. Some food products were given.
a.2. The different types of spoilage that may occur during storage to the products given were recorded on a data sheet.
a.3. Suggestions on how to improve shelf life of these products were then recorded on the data sheet.
b. Determination of moisture in an open dish
b.1. A clean metal dish with cover and a short piece of glass rod were placed in the oven, at 130°C, for 10 minutes.
b.2. The clean metal dish with cover and glass rod were then
Bibliography: or references