Captions for figures
Figure 1. Reaction scheme and molecular structures of amino acids used in the current study
Figure 2. Retention of tocopherols in soybean oil at 180 °C: a) α-, b) γ-, and c) δ- tocopherols in soybean oil containing 5.5 mM alanine (Ala) and alanine potassium salt (Ala K), and d) α-, e) γ-, and f) δ- tocopherols in soybean oil containing 5.5 mM phenylalanine (Phe) and phenylalanine potassium salt (Phe K). Error bars indicate standard deviation (n=4). Means not sharing a common letter are significantly different (P < 0.05).
Figure 3. Synergism of amino acid potassium salts with mixed tocopherols in comparison with the corresponding amino acids in stripped soybean oil during heating at 180 °C for 2 h: a) %loss of olefinic protons and b) %PTAG with L-alanine (Ala) K salt, c) %loss of olefinic protons and d) %PTAG with L-phenylalanine (Phe) K salt, and e) %loss of olefinic protons and f) %PTAG with L-proline (Pro) K salt. Error bars indicate standard deviations. Means not sharing a common letter are significantly different (P < 0.05).
Figure 4. Antioxidant activity of amino acids or amino acid salts (5.5 mM) during micro-frying of potato cubes at 180 °C for 8 h: a) % loss of olefinic protons, b) % loss of bisallylic protons, and c) % polymerized triacylglycerols (PTAG). Error bars indicate standard deviations (n = 3). Means not sharing a common letter are significantly different (P < 0.05).
Table 1. Antioxidant activity of 5.5 mM amino acid, amino acid sodium salt, or amino acid potassium salt in soybean oil during 8-h heating at 180 °C.