| Fried Potato Foods (French Fries and potato chips), the annual trade volume of which is nearly 40 billion US dollar, and the consumers of which are mainly children and adolescents, are typical foods with high acrylamide level. It’s revealed lately that fried potato foods not only contain acrylamide (AM), but also some other Maillard reaction-derived contaminants like advanced glycation end products (AGEs) and heterocyclic amines (HAAs), which haven’t attracted much attention in fried potato foods.This thesis discussed the mechanism of high exposure of AM in fried potato foods from the two perspectives of uniqueness of the potato matrix as a member of the family Solanaceae, and the uniqueness of being fried. Potato glycoalkaloids were confirmed to promote AM formation in a model system, and the mechanism was discussed; Polyunsaturated fatty acids (PUFA) were proven to strongly influence the content of AM in both fried potato chips and model systems, and the mechanism of how oil-soluble antioxidants can inhibit AM was studied. Finally, real potato matrix was used again to evaluate the effectiveness of five oil-soluble antioxidants inhibiting four kinds of Maillard reaction-derived contaminants---AM, Nε-(carboxymethyl)-lysine (CML, a typical AGEs), Norharman and Harman (two kinds of β-carboline HAAs). The main research contents and results were summarized as follows:1. Current UPLC-MS/MS method to determine AM in food matrix was optimized, focusing on simplification of the pretreatment process. A method to simultaneously detect 14 kinds of HAAs in food was also developed based on UPLC-MS/MS. The two methods were validated to be sensitive, stable and reliable.2. An asparagine-potato glycoalkaloids (Asn-SGA) model system was established to reveal that TGA had relatively significant influence on high AM exposure in potato-based foods, which might make the food contain at least 5% more of AM. The mechanism was proposed as: the saccharide groups in α-solanine and α-chaconine can be dropped off under high temperature and participate in the carbonyl-amine reaction; when α-solanine and glucose (Glc) were put together, a significant synergetic effect was found, whose mechanism was proven to be that the apparent activation energy of the reaction where Asn and Glc reacted to produce AM was decreased, which enhanced AM formation.3. As for the role of frying in AM formation, eight kinds of frying oil with different fatty acids composition were chosen and continuously heated under 180℃. The change in quality assays and contents of Maillard reaction-derived contaminants were determined and analyzed. It was found that the proportion of PUFA significantly affected the amount of AM and β-carboline HAAs formed in the potato chips, and that as the heating time prolonged, the formation was strongly enhanced. It could be inferred that the oxidation of PUFA might be the key factors influencing AM formation in fried potato foods.4. Three kinds of most common and most important PUFAs (linoleic acid, a-linolenic acid and y-linolenic acid) were chosen to build up a model system. The law of PUFA affecting AM formation was studied, and a response surface model was established. The most suitable conditions for AM formation was calculated and optimized.5. Six kinds of commonly-used oil-soluble antioxidants:oil-soluble tea polyphenols (OTP), oil-soluble antioxidant of bamboo leaves (AOB-o), oil-soluble rosemary extract (RE-o), vitamin E (VE), tert-butylhydroquinone (TBHQ) and p-carotene were tested for their effect towards AM formation in the Asn-linoleic acid model system. It was demonstrated that OTP, AOB-o, RE-o, Ve and TBHQ showed potent mitigation effect while β-carotene promoted AM formation. Two kinetics models (Logistic-Fermi & Logistic-exponential) were used to fit the experiment data and the kinetics process. Results showed that the action site of oil-soluble antioxidants was the formation process rather than the elimination process of AM.6. A so-called "Effectiveness Value" system was established to evaluate the effectiveness of oil-soluble antioxidants in the inhibition of various Maillard reaction-derived contaminants. For the fabricated potato chips, the AM content, CML content, and HAAs contents can be reduced by 97%,78% and 85%, also, the stability of oil can be strengthened by 58% when 0.02% of AOB-AA (combinition of AOB-w and amino acid) was added to the dough and golden palm oil with 0.01% AOB-o was used for frying. It could be calculated that the Effectiveness Value can reach 85.64, and the safety for eating can be greatly enhanced.The research results showed that, except for the generally accepted pathway, namely the asparagine pathway, the mechanism of high AM level in fried potato foods may also include interaction between oxidation product of fatty acids in the frying oil and asparagine, and the existence of glycoalkaloids in the potato matrix. So, in the design and construction procedure of whole-process-controlled fried potato foods, the goal of simultaneous control of Maillard reaction-derived contaminants as well as a prolonged shelf-life can be achieved by utilization of antioxidants in both water and oil phase, and selection of proper frying oil. |
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