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Zhang F, Zhang R, He S, Guan J, Feng Z, Wu Z. Formation of free radicals in Chi-aroma Baijiu during aging process with fat pork. Free Radic Res 2023; 57:271-281. [PMID: 37401820 DOI: 10.1080/10715762.2023.2232095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 06/26/2023] [Accepted: 06/27/2023] [Indexed: 07/05/2023]
Abstract
Soaking aged fat pork is a special aging process in the production of Chi-aroma Baijiu considered to involve the formation of free radicals. This study aimed to investigate the free radicals' formation pathway in Chi-aroma Baijiu during aged fat pork soaking by using electron paramagnetic resonance (EPR) and spin trapping with 5,5-dimethyl-1-pyrrolin-n-oxide (DMPO). The alkyl radical adducts (DMPO-R) and hydroxyl radical adducts (DMPO-OH) were detected in Baijiu after soaking the fat pork for aging. During the preparation process of aged fat pork, alkoxy radicals adduct (DMPO-RO) were mainly detected since lipid oxidation. Oleic acid and linoleic acid, the two main unsaturated fatty acids in fat pork, produced alkoxy radicals in the oxidation process. The total amounts of spins in linoleic acid and oleic acid after 4-month oxidation treatment increased by 248.07 ± 26.65% and 34.17 ± 0.72% than 0-month. It indicated that the free radicals in aged Chi-aroma Baijiu were mainly derived from the two main unsaturated fatty acids in aged fat pork and linoleic acid had a stronger ability to produce free radicals than oleic acid. Alkoxy radicals (RO·) from fat pork reacted with ethanol in Baijiu to form alkyl radicals (R·). The peroxide bond of hydroperoxides from the oxidation of unsaturated fatty acid was cleaved to form hydroxyl radicals (·OH) that were transferred to Baijiu. The results provide theoretical guidance for the subsequent work of free radicals scavenging.
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Affiliation(s)
- Fengjiao Zhang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
| | - Renjie Zhang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
- Pan Asia (Jiangmen) Institute of Biological Engineering and Health, Jiangmen, P.R. China
| | - Songgui He
- Guangdong Jiujiang Distillery Co., Ltd, Foshan, P.R. China
| | - Jingyi Guan
- Guangdong Jiujiang Distillery Co., Ltd, Foshan, P.R. China
| | - Zhaoxing Feng
- Guangdong Jiujiang Distillery Co., Ltd, Foshan, P.R. China
| | - Zhenqiang Wu
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China
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2
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Buck SP, Pegg RB, Tyl C. Oxidative Stability of Oil Obtained From a Low‐erucic Acid Pennycress (
Thlaspi arvense
L.) Mutant with Potential for Food Use. EUR J LIPID SCI TECH 2022. [DOI: 10.1002/ejlt.202200053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sabrina P. Buck
- Department of Food Science and Technology, College of Agricultural and Environmental Sciences The University of Georgia Athens GA USA
| | - Ronald B. Pegg
- Department of Food Science and Technology, College of Agricultural and Environmental Sciences The University of Georgia Athens GA USA
| | - Catrin Tyl
- Faculty of Chemistry, Biotechnology and Food Science Norwegian University of Life Science 1432 Ås Norway
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3
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Wei D, Deng P, Tian X, He S, Li W, Wu Z. Accelerating the oxidation of pork fat by illumination and fat oil for the production of Baijiu beverage. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2021; 101:918-926. [PMID: 32737878 DOI: 10.1002/jsfa.10699] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 07/05/2020] [Accepted: 07/31/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Aged pork fat, deeply oxidized pork fat soaked in basic liquor for more than half a year, is an important material in producing Chi-aroma Baijiu (CAB). With the expansion of production scale of CAB, innovative strategies for efficient production of aged pork fat are in great demand. The purpose of this study is to accelerate the lipid oxidation of pork fat and improve the productivity of aged pork fat. RESULTS Results showed that polyunsaturated fatty acids (PUFAs) were the main reactant; generation reactions of lipid peroxides and free fatty acids (FFAs) were two limiting steps during the preparation of aged pork fat. Processing under illumination could alleviate the first limiting step by increasing the peroxide value and p-anisidine value of pork fat to 16.22- and 28.48-fold higher than control samples and simultaneously the PUFAs were increased to 190.60 ± 0.19 g kg-1 . Soaking in basic liquor with deeply oxidized fat oil could alleviate the second limiting step by transferring FFAs from fat oil into pork fat. With more oxidized PUFAs, the acid value of the pork fat was 7.91-fold higher than that of the control. CONCLUSION Illumination and deeply oxidized fat oil could alleviate the two rate-limiting steps of lipid oxidation and improve the productivity of aged pork fat significantly. The results are highly applicable in the CAB industry. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Daiyue Wei
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, P. R. China
| | - Penghua Deng
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, P. R. China
- Pan Asia (Jiangmen) Institute of Biological Engineering and Health, Jiangmen, P. R. China
| | - Xiaofei Tian
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, P. R. China
| | - Songgui He
- Guangdong Jiujiang Distillery Co., Ltd, Foshan, P. R. China
| | - Weigang Li
- Guangdong Jiujiang Distillery Co., Ltd, Foshan, P. R. China
| | - Zhenqiang Wu
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou, P. R. China
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4
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Chen X, Lv M, Gan H, Zeng D, Yang C, Ma H. Impact of chitosan-based coatings on myofibrillar protein denaturation, muscle microstructure and lipid oxidation of oyster (Crassostrea hongkongensis) during 0 °C storage. JOURNAL OF AQUATIC FOOD PRODUCT TECHNOLOGY 2020. [DOI: 10.1080/10498850.2020.1828525] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Xiuli Chen
- Guangxi Key Laboratory of Aquatic Preservation and Processing Technology, Guangxi Academy of Fishery Science, Nanning, Guangxi, China
| | - Min Lv
- Guangxi Key Laboratory of Aquatic Preservation and Processing Technology, Guangxi Academy of Fishery Science, Nanning, Guangxi, China
| | - Hui Gan
- Aquaculture Processing, Guangxi Aquatic Animal and Husbandry College, Nanning, Guangxi, China
| | - Digang Zeng
- Guangxi Key Laboratory of Aquatic Preservation and Processing Technology, Guangxi Academy of Fishery Science, Nanning, Guangxi, China
| | - Chunling Yang
- Guangxi Key Laboratory of Aquatic Preservation and Processing Technology, Guangxi Academy of Fishery Science, Nanning, Guangxi, China
| | - Huawei Ma
- Guangxi Key Laboratory of Aquatic Preservation and Processing Technology, Guangxi Academy of Fishery Science, Nanning, Guangxi, China
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5
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Li D, Xie H, Liu Z, Li A, Li J, Liu B, Liu X, Zhou D. Shelf life prediction and changes in lipid profiles of dried shrimp (Penaeus vannamei) during accelerated storage. Food Chem 2019; 297:124951. [DOI: 10.1016/j.foodchem.2019.124951] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 04/26/2019] [Accepted: 06/05/2019] [Indexed: 02/02/2023]
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6
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Xie H, Zhou D, Hu X, Liu Z, Song L, Zhu B. Changes in Lipid Profiles of Dried Clams ( Mactra chinensis Philippi and Ruditapes philippinarum) during Accelerated Storage and Prediction of Shelf Life. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:7764-7774. [PMID: 29965751 DOI: 10.1021/acs.jafc.8b03047] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
To predict the shelf life through an Arrhenius model and evaluate the changes in lipid profiles, two types of dried clams were stored at 50 and 65 °C and collected periodically for analysis. The predicted shelf life values of the two dried clam samples were 530 ± 14 and 487 ± 24 h (24 °C), and the relative errors between the actual and predicted values were 5.7 and 6.8%, respectively. During accelerated storage, the peroxide value, p-anisidine value, thiobarbituric acid-reactive substances value, total oxidation value, acid value, and free fatty acid content all increased, while the levels of triacylglycerol, phosphatidylcholine, phosphatidylethanolamine, major glycerophospholipid molecular species, and polyunsaturated fatty acid (PUFA) decreased. Moreover, content of phospholipid containing PUFA decreased significantly than that of triacylglycerol containing PUFA. Results indicated that the Arrhenius model was suitable for the shelf life prediction of dried clams and accelerated storage caused loss in quality of dried clams in terms of lipids.
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Affiliation(s)
- Hongkai Xie
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering , China Agricultural University , Beijing 100083 , People's Republic of China
- National Engineering Research Center of Seafood , Dalian 116034 , People's Republic of China
| | - Dayong Zhou
- National Engineering Research Center of Seafood , Dalian 116034 , People's Republic of China
- School of Food Science and Technology , Dalian Polytechnic University , Dalian 116034 , People's Republic of China
| | - Xiaopei Hu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering , China Agricultural University , Beijing 100083 , People's Republic of China
- National Engineering Research Center of Seafood , Dalian 116034 , People's Republic of China
| | - Zhongyuan Liu
- National Engineering Research Center of Seafood , Dalian 116034 , People's Republic of China
- School of Food Science and Technology , Dalian Polytechnic University , Dalian 116034 , People's Republic of China
| | - Liang Song
- National Engineering Research Center of Seafood , Dalian 116034 , People's Republic of China
- School of Food Science and Technology , Dalian Polytechnic University , Dalian 116034 , People's Republic of China
| | - Beiwei Zhu
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering , China Agricultural University , Beijing 100083 , People's Republic of China
- National Engineering Research Center of Seafood , Dalian 116034 , People's Republic of China
- School of Food Science and Technology , Dalian Polytechnic University , Dalian 116034 , People's Republic of China
- Tianjin Food Safety & Low Carbon Manufacturing Collaborative Innovation Center , Tianjin 300457 , People's Republic of China
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7
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Calligaris S, Manzocco L, Anese M, Nicoli MC. Shelf-life Assessment of Food Undergoing Oxidation-A Review. Crit Rev Food Sci Nutr 2017; 56:1903-12. [PMID: 25746427 DOI: 10.1080/10408398.2013.807222] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Oxidation is the most common event leading to the end of shelf life of microbiologically stable foods. Thus, a reliable shelf-life assessment is crucial to verify how long the product will last before it becomes oxidized to an unacceptable level to the consumers. Shelf-life assessment strategies of foods and beverages suffering oxidation are critically discussed focusing on definition of the acceptability limit, as well as the choice of the proper oxidative indicators, and methodologies for shelf-life testing. Testing methodologies for shelf-life determination under actual and accelerated storage conditions are considered, highlighting possible uncertainties, pitfalls, and future research needs.
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Affiliation(s)
- Sonia Calligaris
- a Dipartimento di Scienze degli Alimenti , Università di Udine , Udine , Italy
| | - Lara Manzocco
- a Dipartimento di Scienze degli Alimenti , Università di Udine , Udine , Italy
| | - Monica Anese
- a Dipartimento di Scienze degli Alimenti , Università di Udine , Udine , Italy
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8
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Reineccius GA, Yan C. Factors controlling the deterioration of spray dried flavourings and unsaturated lipids. FLAVOUR FRAG J 2015. [DOI: 10.1002/ffj.3270] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- G. A. Reineccius
- Department of Food Science and Nutrition; University of Minnesota
| | - C. Yan
- Beverage Application; PepsiCo Global R&D
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9
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Dynamics in Polysaccharide Glasses and Their Impact on the Stability of Encapsulated Flavors. FOOD BIOPHYS 2015. [DOI: 10.1007/s11483-015-9405-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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10
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Toikkanen O, Lähteenmäki M, Moisio T, Forssell P, Partanen R, Murtomäki L. Study of oxygen transfer across milk proteins at an air-water interface with scanning electrochemical microscopy. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2014; 62:2284-2288. [PMID: 24559153 DOI: 10.1021/jf5008715] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Scanning electrochemical microscopy (SECM) combined with a Langmuir trough was used for studying oxygen transfer across protein films at an air-water interface. The method allows the comparison of the oxygen permeability of different emulsifiers without any concerns of interference of atmospheric oxygen. Two milk proteins, β-lactoglobulin and β-casein, were compared, and the permeabilities obtained were for β-casein PD ≈ 2.2 × 10(-7) cm(2)/s and for β-lactoglobulin PD ≈ 0.6 × 10(-7) cm(2)/s, which correspond to the lowest limit of the diffusion coefficients and are 2 orders of magnitude lower than the diffusion coefficient of oxygen in water, yet several orders of magnitude higher than previously reported for milk protein films. The method allows characterization of the oxygen barrier properties of liquid interfacial films, which is of crucial importance for understanding the role of the interface in the inhibition of oxygen transport and developing modified interfaces with higher oxygen blocking efficacy.
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Affiliation(s)
- Outi Toikkanen
- VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
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11
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Moisio T, Damerau A, Lampi AM, Piironen V, Forssell P, Partanen R. Interfacial protein engineering for spray–dried emulsions – Part I: Effects on protein distribution and physical properties. Food Chem 2014; 144:50-6. [DOI: 10.1016/j.foodchem.2013.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 03/25/2013] [Accepted: 04/02/2013] [Indexed: 11/28/2022]
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12
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Formation, rheology and susceptibility to lipid oxidation of multiple emulsions (O/W/O) in table spreads containing omega-3 rich oils. Lebensm Wiss Technol 2013. [DOI: 10.1016/j.lwt.2012.12.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Serfert Y, Schröder J, Mescher A, Laackmann J, Shaikh MQ, Rätzke K, Gaukel V, Schuchmann HP, Walzel P, Moritz HU, Drusch S, Schwarz K. Characterization of the spray drying behaviour of emulsions containing oil droplets with a structured interface. J Microencapsul 2012; 30:325-34. [DOI: 10.3109/02652048.2012.726282] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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14
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Characterization and authentication of a novel vegetable source of omega-3 fatty acids, sacha inchi (Plukenetia volubilis L.) oil. Food Chem 2012; 134:1173-80. [DOI: 10.1016/j.foodchem.2012.02.143] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 01/10/2012] [Accepted: 02/22/2012] [Indexed: 11/19/2022]
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15
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Calligaris S, Manzocco L, Lagazio C. Modeling Shelf Life Using Chemical, Physical, and Sensory Indicators. FOOD PRESERVATION TECHNOLOGY 2012. [DOI: 10.1201/b11871-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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16
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Jin G, He L, Zhang J, Yu X, Wang J, Huang F. Effects of temperature and NaCl percentage on lipid oxidation in pork muscle and exploration of the controlling method using response surface methodology (RSM). Food Chem 2012. [DOI: 10.1016/j.foodchem.2011.09.050] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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17
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Branco GF, Castro IA. Optimization of Oil Oxidation by Response Surface Methodology and the Application of this Model to Evaluate Antioxidants. J AM OIL CHEM SOC 2011. [DOI: 10.1007/s11746-011-1842-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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18
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Sullivan JC, Budge SM, St-Onge M. Modeling the primary oxidation in commercial fish oil preparations. Lipids 2010; 46:87-93. [PMID: 21104333 DOI: 10.1007/s11745-010-3500-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 11/04/2010] [Indexed: 11/26/2022]
Abstract
The quality of commercial fish oil products can be difficult to maintain because of the rapid lipid oxidation attributable to the high number of polyunsaturated fatty acids (PUFA), specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). While it is known that oxidation in fish oil is generally the result of a direct interaction with oxygen and fatty acid radicals, there are very few studies that investigate the oxidation kinetics of fish oil supplements. This study uses hydroperoxides, a primary oxidation product, to model the oxidation kinetics of two commercially available fish oil supplements with different EPA and DHA contents. Pseudo first order kinetics were assumed, and rate constants were determined for temperatures between 4 and 60 °C. This data was fit to the Arrhenius model, and activation energies (E(a)) were determined for each sample. Both E(a) agreed with values found in the literature, with the lower PUFA sample having a lower E(a). The oil with a lower PUFA content fit the first-order kinetics model at temperatures ≥20 °C and ≤40 °C, while the higher PUFA oil demonstrated first-order kinetics at temperatures ≥4 °C and ≤40 °C. When the temperature was raised to 60 °C, the model no longer applied. This indicates that accelerated testing of fish oil should be conducted at temperatures ≤40 °C.
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Affiliation(s)
- Jenna C Sullivan
- Department of Process Engineering and Applied Science, Dalhousie University, Halifax, NS, Canada.
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19
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LIU TAITI, YANG TSUNGSHI. OPTIMIZATION OF EMULSIFICATION AND MICROENCAPSULATION OF EVENING PRIMROSE OIL AND ITS OXIDATIVE STABILITY DURING STORAGE BY RESPONSE SURFACE METHODOLOGY. J FOOD QUALITY 2010. [DOI: 10.1111/j.1745-4557.2010.00358.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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20
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Tazi S, Plantevin F, Falco CD, Puigserver A, Ajandouz EH. Effects of light, temperature and water activity on the kinetics of lipoxidation in almond-based products. Food Chem 2009. [DOI: 10.1016/j.foodchem.2009.01.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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21
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Drusch S, Rätzke K, Shaikh MQ, Serfert Y, Steckel H, Scampicchio M, Voigt I, Schwarz K, Mannino S. Differences in Free Volume Elements of the Carrier Matrix Affect the Stability of Microencapsulated Lipophilic Food Ingredients. FOOD BIOPHYS 2009. [DOI: 10.1007/s11483-008-9100-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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22
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Aragao GMF, Corradini MG, Peleg M. A Phenomenological Model of the Peroxide Value’s Rise and Fall During Lipid Oxidation. J AM OIL CHEM SOC 2008. [DOI: 10.1007/s11746-008-1305-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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23
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Partanen R, Raula J, Seppänen R, Buchert J, Kauppinen E, Forssell P. Effect of relative humidity on oxidation of flaxseed oil in spray dried whey protein emulsions. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2008; 56:5717-5722. [PMID: 18572915 DOI: 10.1021/jf8005849] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Flaxseed oil was emulsified in whey protein isolate (WPI) and spray-dried. Powder characteristics and oxidative stability of oil at relative humidities (RH) from RH approximately 0% to RH 91% at 37 degrees C were analyzed. Oil droplets retained their forms in drying and reconstitution, but the original droplet size of the emulsion was not restored when the powder was dispersed in water. The particles seemed to be covered by a protein-rich surface layer as analyzed by electron spectroscopy for chemical analysis (ESCA). Oxidation of flaxseed oil dispersed in the WPI matrix was retarded from that of bulk oil but followed the same pattern as bulk oil with respect to humidity. A high rate of oxidation was found for both low and high humidity conditions. The lowest rate of oxidation as followed by peroxide values was found at RH 75%, a condition that is likely to diverge significantly from the monolayer moisture value. A weak baseline transition observed for the WPI matrix in a differential scanning calorimetry (DSC) thermogram suggested a glassy state of the matrix at all storage conditions. This was not consistent with the observed caking of the powder at RH 91%. Scanning electron microscopy (SEM) images revealed a considerable structural change in the WPI matrix in these conditions, which was suggested to be linked with a higher rate of oxygen transport. Possible mechanisms for oxygen transport in the whey protein matrix under variable RHs are discussed.
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