2/6/ Moisture Relationships

– Amount of moisture affects the following: Density: particle density decreases with increasing moisture content Force-deformation characteristics Thermal conductivity Heat capacity Electrical resistance: lower resistance with higher moisture content 2/6/20162 Moisture Relationships

– Amount of moisture affects: Fruits and veggies: 70-95% mc Grains, seeds, dry food products: < 14% Meats: 60-80% MC influences market value 2/6/20163 Moisture Relationships

– Three concepts: Equilibrium mc Water activity Water potential 2/6/20164 Moisture Relationships

– Equilibrium mc Moisture transfers from product to air during drying. EMC describes the final moisture reached during drying of lower moisture food products, grains, seeds Affects rate of drying Explains mold growth in grain 2/6/20165 Moisture Relationships

– Water Activity Describes rate of deterioration – Water Potential Describes the effect of moisture loss or gain on volume change and force deformation behavior of fruits and veggies 2/6/20166 Moisture Relationships

– Determining Moisture Content (VERY IMPORTANT) Wet Basis – % of total weight with water Dry Basis – Ratio of water weight to dry matter weight One can be calculated using the other 2/6/20167 Moisture Relationships

– Equations: Wet basis Dry basis 2/6/20168 Moisture Relationships

– Equations: Conversion – Wet to dry – Dry to wet 2/6/20169 Moisture Relationships

– Wet basis example 700 kg of wheat contains 84 kg of water. What is the MC w ? 2/6/ Moisture Relationships

– Dry basis example 950 kg of oats contains 105 kg of water. What is the MC d ? 2/6/ Moisture Relationships

– Conversion example Convert the wheat and oat examples above 2/6/ Moisture Relationships

– “How much water did we lose” example 750 kg of canola is dried from 17% MC w to 12% MC w How much water is removed during the drying process? 2/6/ Moisture Relationships

– Another example A bin holds 2000 kg of wet grain containing 500 kg of water. This grain is to be dried to a final MC of 14% (wb). What are the initial and final moisture contents of the grain (wb and db)? How much water is removed during drying? 2/6/ Moisture Relationships

– Another example An elevator has 14,000 kg of wheat at 12% MC w and 25,000 kg of wheat at 17% MC w. The manager has a rule that all stored wheat must be below 15% MC w. If the wheat is mixed together, will it meet the storage criteria? 2/6/ Moisture Relationships

– Another example A bag containing 1.5 kg of popcorn has been stored in the cabinet for a long time. When heated appropriately, only a few kernels popped. Testing showed that the MC w was 9%. Popcorn pops best at 13%. How much water should be added to bring it to this moisture? 2/6/ Moisture Relationships