《食品化学 Food Chemistry》课程教学课件（讲稿，英文版）Water activity and toxins

Water activity and toxins

Water activity and toxins

Water activity calculations l http://www.users.bigpond.com/webbtech/wad load.html

Water activity calculations l http://www.users.bigpond.com/webbtech/wad load.html

Example 1 l Your company just completed development of a new super water binding agent. You are asked to collect some data to be used in a technical brochure as to its water binding properties. It will be promoted for baked cereal products such as cookies and crackers as a major competitor for oat bran. You have the following data from the standard static desiccator method

Example 1 l Your company just completed development of a new super water binding agent. You are asked to collect some data to be used in a technical brochure as to its water binding properties. It will be promoted for baked cereal products such as cookies and crackers as a major competitor for oat bran. You have the following data from the standard static desiccator method

Example 1 cont. Salt Aw pan weight wt initial wt final g g g LiCl 0.116 3.84168 4.85064 4.90759 MgCl2 0.331 3.90058 4.90004 5.04579 K2CO3 0.445 3.78457 5.0753 5.32094 Mg(NO3)2 0.54 3.74701 5.03955 5.3639 NaNO2 0.665 3.84532 5.19294 5.62567 NaCl 0.75 3.77085 5.24571 5.82968 BaCl2 0.88 3.6421 5.2753 6.47804 K2SO4 0.978 3.73253 4.80209 6.40414 Initial moisture4.44% water (wb)

Example 1 cont. Salt Aw pan weight wt initial wt final g g g LiCl 0.116 3.84168 4.85064 4.90759 MgCl2 0.331 3.90058 4.90004 5.04579 K2CO3 0.445 3.78457 5.0753 5.32094 Mg(NO3)2 0.54 3.74701 5.03955 5.3639 NaNO2 0.665 3.84532 5.19294 5.62567 NaCl 0.75 3.77085 5.24571 5.82968 BaCl2 0.88 3.6421 5.2753 6.47804 K2SO4 0.978 3.73253 4.80209 6.40414 Initial moisture4.44% water (wb)

Example 2 l The following data for the wet basis moisture content of corn flakes and raisins at 23°C were obtained. It is proposed to make a cereal mix with a blend of 20% fruit. water activity Raisin Corn Flakes % water (wb) % water (wb) 0.113 7.59 1.32 0.22 8.91 2.21 0.33 9.62 3.81 0.45 12.22 6.01 0.54 15.61 7.45 0.77 28.37 17.1 0.89 45.18 24.2 Initial moisture (%) 17.3 1.5

Example 2 l The following data for the wet basis moisture content of corn flakes and raisins at 23°C were obtained. It is proposed to make a cereal mix with a blend of 20% fruit. water activity Raisin Corn Flakes % water (wb) % water (wb) 0.113 7.59 1.32 0.22 8.91 2.21 0.33 9.62 3.81 0.45 12.22 6.01 0.54 15.61 7.45 0.77 28.37 17.1 0.89 45.18 24.2 Initial moisture (%) 17.3 1.5

Example 2 cont. l Create an isotherm for: corn flakes, raisins and mix l What water activity would they reach if equilibrium occurred in the package? l Raisins get hard below 0.44 aw and bran loses crunchiness above an aw of 0.4. Is there a problem with this mixture and how would you solve it?

Example 2 cont. l Create an isotherm for: corn flakes, raisins and mix l What water activity would they reach if equilibrium occurred in the package? l Raisins get hard below 0.44 aw and bran loses crunchiness above an aw of 0.4. Is there a problem with this mixture and how would you solve it?