Z Xu

Louisiana State University, Baton Rouge, Louisiana, United States

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Publications (7)11.87 Total impact

  • X Yue · Z Xu ·
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    ABSTRACT: Thermal stability of 10 anthocyanins found in a bilberry extract was studied at different heating temperatures and times. Degradation of the 10 anthocyanins, delphinidin, cyanidin, petunidin, peonidin, and malvidin derivat with different conjugated sugars, followed 1st-order reaction kinetics at heating temperatures 80, 100, and 125 degrees C. Though the degradation rate constants of anthocyanins were not significantly different from each other at the same heating temperature, they increased drastically when heating temperature was increased to 125 degrees C. At that temperature, the half-lives for all anthocyanins were less than 8 min. The degradation rate constants followed the Arrhenius equation. The trend of lower activation energy of the anthocyanins with arabinoside than with galactoside or glucoside was observed. These conjugated sugars were cleaved from the anthocyanins to produce their corresponding anthocyanidins or aglycones during heating. The production of anthocyanidins increased con stantly and was converted from approximately 30% of the degraded anthocyanins when heated at 100 degrees C for up to 30 min. At 125 degrees C, the increase of anthocyanidins lasted for 10 min, after which the degradation rate of anthocyanidins exceeded the production rate. Antioxidant activities of the heated extracts were estimated by measuring DPPH (2, 2'-diphenyl-1-picrylhydrazyl) free radical scavenging activity. The extracts heated at 80 degrees C for 30 min, 100 degrees C for 10 and 20 min, and 125 degrees C for 10 min had higher free radical scavenging capability than unheated extract.
    Journal of Food Science 09/2008; 73(6):C494-9. DOI:10.1111/j.1750-3841.2008.00845.x · 1.70 Impact Factor
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    ABSTRACT: Capabilities of crude soy oil, degummed oil, gum, and defatted soy flour extract in preventing the oxidation of menhaden oil and its omega-3 fatty acids, DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), during heating were evaluated. The menhaden oil mixed with defatted soy flour extract demonstrated the greatest stability by producing the lowest TBA reactive oxidation products and retaining the highest concentrations of DHA and EPA after heating at 150 °C for 30 min. A range of 62.8% to 71.5% of DHA and 67.7% to 75.9% of EPA remained in the fish oil with defatted soy flour extract, while only 29.9% of DHA and 37.2% of EPA were retained in the fish oil with no addition. Stabilizing capability from highest to lowest was defatted flour extract > gum > degummed oil = crude oil. The defatted flour extract had the highest level of total phenolic content (11.3 μg catechin equivalent/g), while crude oil, degummed oil, and gum contained 7.1, 6.1, and 6.0 μg catechin equivalent/g, respectively. The level of isoflavones in the defatted soy flour extract was 55 mg/g, which was over 100 times higher than in the crude oil or gum. Although isoflavones were not detected in the degummed oil, it contained the highest level of tocopherols (414 μg/g), whereas the lowest level (215 μg/g) was found in the defatted flour extract. The order of free radical scavenging capability measured from high to low was the defatted soy flour extract, crude oil, degummed oil, and gum.
    Journal of Food Science 12/2007; 73(1):C19 - C23. DOI:10.1111/j.1750-3841.2008.00586.x · 1.70 Impact Factor
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    ABSTRACT: Capabilities of methanol extracts from oregano and rosemary in retarding oxidation of long-chain polyunsaturated fatty acids, docosahexaenoic acid C22:6 (DHA) and eicosapentaenoic acid C20:5 (EPA), in menhaden oil were investigated. The fish oils after mixing with the extracts at different concentrations were oxidized in an accelerated study by heating at 150 degrees C for 30 min or incubating at 60 degrees C for 5 d. After heating at 150 degrees C, only 15.9% of DHA and 18.5% of EPA remained in the fish oil without extract, while 38.8% to 65.9% of DHA and 44.7% to 69.0% of EPA were retained in the fish oil mixed with 1% to 5% of oregano extract. The highest retained DHA (56.9%) and EPA (58.0%) in the fish oils mixed with rosemary extract were observed at 2.5% addition. Increasing rosemary extract to 5% lowered its capability of inhibiting DHA and EPA oxidation. After incubation at 60 degrees C for 5 d, the highest inhibition capability was also found at 2.5% of added rosemary extract, and the oil retained 88.2% DHA and 88.3% EPA. However, only 18.8% DHA and 23.6% EPA were retained in the fish oil mixed with 5% of oregano extract and no DHA and EPA were detected in the fish oil without extract after 5-d incubation at 60 degrees C. Thus, antioxidant activity of the rosemary extract was greater than that of oregano extract, but was sensitive to heat. The rosemary extract also demonstrated higher DPPH (2,2'-diphenyl-1-picrylhydrazyl) free radical scavenging capability, which was approximately 3 times higher than oregano extract, although there was no significant difference in the total phenolic contents between both extracts.
    Journal of Food Science 12/2007; 72(9):C504-8. DOI:10.1111/j.1750-3841.2007.00569.x · 1.70 Impact Factor
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    ABSTRACT: Chitosan is a modified, natural biopolymer derived by deacetylation of chitin, a major component of the shells of crustacean. Recently, chitosan has received increased attention for its commercial applications in the biomedical, food, and chemical industries. Use of chitosan in food industry is readily seen due to its several distinctive biological activities and functional properties. The antimicrobial activity and film-forming property of chitosan make it a potential source of food preservative or coating material of natural origin. This review focuses on the applications of chitosan for improvement of quality and shelf life of various foods from agriculture, poultry, and seafood origin.
    Journal of Food Science 07/2007; 72(5):R87-100. DOI:10.1111/j.1750-3841.2007.00383.x · 1.70 Impact Factor
  • T Sun · Z Xu · C-T Wu · M Janes · W Prinyawiwatkul · H K No ·
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    ABSTRACT: Antioxidant compounds and their antioxidant activity in 4 different colored (green, yellow, orange, and red) sweet bell peppers (Capsicum annuum L.) were investigated. The total phenolics content of green, yellow, orange, and red peppers determined by the Folin-Ciocalteau method were 2.4, 3.3, 3.4, and 4.2 micromol catechin equivalent/g fresh weight, respectively. The red pepper had significantly higher total phenolics content than the green pepper. Among the 4 different colored peppers, red pepper contained a higher level of beta-carotene (5.4 microg/g), capsanthin (8.0 microg/g), quercetin (34.0 microg/g), and luteolin (11.0 microg/g). The yellow pepper had the lowest beta-carotene content (0.2 microg/g), while the green one had undetectable capsanthin and the lowest content of luteolin (2.0 microg/g). The free radical scavenging abilities of peppers determined by the 2,2'-diphenyl-1-picrylhydrazyl (DPPH) method were lowest for the green pepper (2.1 micromol Trolox equivalent/g) but not significantly different from the other 3 peppers. All 4 colored peppers exhibited significant abilities in preventing the oxidation of cholesterol or docosahexaenoic acid (DHA) (C22:6) during heating. However, these 4 peppers did not show significant differences in their abilities in preventing cholesterol oxidation. The green pepper showed slightly higher capability in preventing the oxidation of DHA compared to the other 3 peppers.
    Journal of Food Science 04/2007; 72(2):S98-102. DOI:10.1111/j.1750-3841.2006.00245.x · 1.70 Impact Factor
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    ABSTRACT: This study evaluated consumer acceptance and purchase intent of nonwheat butter cake formulations prepared with Thai jasmine rice flour. Three nonwheat rice butter cakes were prepared with varying amounts of powdered emulsifier (propylene glycol ester:diacetyl tartaric acid ester of monoglyceride, 8:2) at 0% (product A), 7.5% (product B), and 15% (product C) of the margarine content (15%) in the cake formulation. A commercial wheat-based butter cake served as the control. Consumers (n= 400) evaluated acceptability of 9 sensory attributes using a 9-point hedonic scale. Overall acceptance and purchase intent were determined with a binomial (yes/no) scale. At least 81% of consumers accepted products B and C, of which 42.1% and 47%, respectively, would purchase the products if commercially available. Product A was neither liked nor disliked with an overall liking score of 5.39. The butter cake products were differentiated by textural acceptability (overall texture, softness, and moistness) with a canonical correlation of 0.71 to 0.79. Overall liking and taste influenced overall acceptance and purchase intent. Odor influenced purchase intent (P= 0.0014), but not overall acceptance. The odds ratio of overall liking was 3.462 for purchase intent, indicating the probability of the product being purchased is 3.462 times higher (than not being purchased, P < 0.0001) with every 1-unit increase of the overall liking score. Based on the logit model, overall acceptance and purchase intent could be predicted with 89.3% and 83.3% accuracy, respectively. The study demonstrated feasibility of completely substituting wheat flour with Thai jasmine rice flour for production of butter cake products acceptable to American consumers.
    Journal of Food Science 03/2007; 72(2):S92-7. DOI:10.1111/j.1750-3841.2006.00256.x · 1.70 Impact Factor
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    ABSTRACT: Raw tomato contains a high level of lycopene, which has been reported to have many important health benefits. However, information on the changes of the lycopene content in tomato during cooking is limited. In this study, the lycopene content in raw and thermally processed (baked, microwaved, and fried) tomato slurries was investigated and analyzed using a high-performance liquid chromatography (HPLC) method. In the thermal stability study using a pure lycopene standard, 50% of lycopene was degraded at 100 °C after 60 min, 125 °C after 20 min, and 150 °C after less than 10 min. Only 64.1% and 51.5% lycopene was retained when the tomato slurry was baked at 177 °C and 218 °C for 15 min, respectively. At these temperatures, only 37.3% and 25.1% of lycopene was retained after baking for 45 min. In 1 min of the high power of microwave heating, 64.4% of lycopene still remained. However, more degradation of lycopene in the slurry was found in the frying study. Only 36.6% and 35.5% of lycopene was retained after frying at 145 and 165 °C for 1 min, respectively.
    Journal of Food Science 09/2006; 71(8):C461 - C464. DOI:10.1111/j.1750-3841.2006.00163.x · 1.70 Impact Factor

Publication Stats

464 Citations
11.87 Total Impact Points


  • 2008
    • Louisiana State University
      • Department of Food Science
      Baton Rouge, Louisiana, United States
  • 2007
    • Kasetsart University
      • Department of Product Development
      Krung Thep, Bangkok, Thailand
    • Catholic University of Daegu
      • Department of Food Science and Technology
      Kayō, North Gyeongsang, South Korea
  • 2006-2007
    • Louisiana State University Agricultural Center
      Baton Rouge, Louisiana, United States