Glycerolysis of Chinese vegetable tallow (CVT) fraction was investigated using a 1,3-specific lipase from Rhizopus arrhizus as catalyst. Based upon a binary gradient HPLC with an evaporative light-scattering detector ...Glycerolysis of Chinese vegetable tallow (CVT) fraction was investigated using a 1,3-specific lipase from Rhizopus arrhizus as catalyst. Based upon a binary gradient HPLC with an evaporative light-scattering detector (ELSD), the contents of free fatty acids (FFA), monoglycerides (MG), diglycerides(DG) and triglycerides (TG)with their positional isomers during the glycerolysis were determined. The effects of water content and the ratio of glycerol to oil on the product distribution of glycerolysis were studied. Under the optimum reactant conditions:250 units lipase per gram oil at 37 ℃ with 1:2 molar ratio of oil to glycerol in a solvent-free system, after 24 h reaction, the product consisted of 7.2% TG, 25.6% MG, 56.1% DG and 4.9% FFA (all by mass). Furthermore, the mechanism of glycerolysis was discussed in detail.展开更多
The purpose of this work was to study the thermal characterization of oils extracted from native seeds and fruits of the Argentina, Uruguayan region. This is important because it＇s necessary to find new applications ...The purpose of this work was to study the thermal characterization of oils extracted from native seeds and fruits of the Argentina, Uruguayan region. This is important because it＇s necessary to find new applications for food industry. Uruguayan wild cardoon seed, Argentinian wild papaya seeds, Argentinian avocado pulp, Argentinian cherimoya seeds, Argentinian grapeseeds and four commercial brands of chia oils were studied. The thermal behaviors of the oils were analyzed on a differential scanning calorimetry （DSC）, TA Instrument, Q20 model equipped with an intercooler. These oils＇ thermal profiles presented differences, which are related to the compositions of fatty acids and triacylglycerols. The thermogram for the chia oil, with a high content of linolenic acid, presented a very important peak at about -40 ℃; whereas, the papaya oil with an oleic acid content of 74%, showed a peak at about -3 ℃. When comparing the thermal behaviors of these oils to commercial brand oils, it was found that the chia oil is similar to the flaxseed oil, the papaya similar to the olive oil and the avocado similar to the rice bran oil. The avocado oil, in particular, presents high solid content at cold store or winter temperatures, which would make its use in those conditions difficult （for example, a cosmetic cream or gourmet oil）. In conclusion, the thermal behavior of one oil sample as determined by DSC provides valuable information with regards to the possible use of new oils of American origin as replacement of usual commercial others.展开更多
Adverse health consequences are associated with consumption of so-called trans fatty acids （FAs） generated during chemical hydrogenation processes. Naturally-occurring trans fats, including trans vaccenic acid （TVA...Adverse health consequences are associated with consumption of so-called trans fatty acids （FAs） generated during chemical hydrogenation processes. Naturally-occurring trans fats, including trans vaccenic acid （TVA） derived from a conjugated isomer of linoleic acid （18：2 cis-9, trans-11）, （CLA） in contrast, are recognized as having potentially beneficial effects on human health. These natural trans FAs are found in fat from dairy products and meat of ruminants, and have distinct effects compared with trans FAs industrially produced. The lipid composition of cheeses depends on the milk used. In this work was determined CLA and TVA content in milk fat of sheep and cow to be 1.4% and 3.2%, respectively, and from goat, 0.7% and 1.8%. Also, differences in CLA and TVA content were found in fat extracted from samples of the same cheese type made from cow＇s milk from the same company but with different production dates during a year. The levels of CLA and TVA found in Uruguayan cheeses were generally higher than levels reported in previous studies with comparable cheeses produced in other countries. Milk fat is well-known to confer specific properties to foods. This in turn will affect the rheology and sensory attributes as food. For this reason, it is of interest to determine the triglyceride （TAG） composition in milk-derived foods. Results show that there are characteristic differences in the TAG composition of the different cheeses. We found minimal differences between cheeses from goat and sheep but found distinct characteristics for TAGs from cow milk-derived cheese.展开更多
基金国家重点基础研究发展计划(973计划)，国家自然科学基金，the National Key Technology Program，国家高技术研究发展计划(863计划)
文摘Glycerolysis of Chinese vegetable tallow (CVT) fraction was investigated using a 1,3-specific lipase from Rhizopus arrhizus as catalyst. Based upon a binary gradient HPLC with an evaporative light-scattering detector (ELSD), the contents of free fatty acids (FFA), monoglycerides (MG), diglycerides(DG) and triglycerides (TG)with their positional isomers during the glycerolysis were determined. The effects of water content and the ratio of glycerol to oil on the product distribution of glycerolysis were studied. Under the optimum reactant conditions:250 units lipase per gram oil at 37 ℃ with 1:2 molar ratio of oil to glycerol in a solvent-free system, after 24 h reaction, the product consisted of 7.2% TG, 25.6% MG, 56.1% DG and 4.9% FFA (all by mass). Furthermore, the mechanism of glycerolysis was discussed in detail.
文摘The purpose of this work was to study the thermal characterization of oils extracted from native seeds and fruits of the Argentina, Uruguayan region. This is important because it＇s necessary to find new applications for food industry. Uruguayan wild cardoon seed, Argentinian wild papaya seeds, Argentinian avocado pulp, Argentinian cherimoya seeds, Argentinian grapeseeds and four commercial brands of chia oils were studied. The thermal behaviors of the oils were analyzed on a differential scanning calorimetry （DSC）, TA Instrument, Q20 model equipped with an intercooler. These oils＇ thermal profiles presented differences, which are related to the compositions of fatty acids and triacylglycerols. The thermogram for the chia oil, with a high content of linolenic acid, presented a very important peak at about -40 ℃; whereas, the papaya oil with an oleic acid content of 74%, showed a peak at about -3 ℃. When comparing the thermal behaviors of these oils to commercial brand oils, it was found that the chia oil is similar to the flaxseed oil, the papaya similar to the olive oil and the avocado similar to the rice bran oil. The avocado oil, in particular, presents high solid content at cold store or winter temperatures, which would make its use in those conditions difficult （for example, a cosmetic cream or gourmet oil）. In conclusion, the thermal behavior of one oil sample as determined by DSC provides valuable information with regards to the possible use of new oils of American origin as replacement of usual commercial others.
文摘Adverse health consequences are associated with consumption of so-called trans fatty acids （FAs） generated during chemical hydrogenation processes. Naturally-occurring trans fats, including trans vaccenic acid （TVA） derived from a conjugated isomer of linoleic acid （18：2 cis-9, trans-11）, （CLA） in contrast, are recognized as having potentially beneficial effects on human health. These natural trans FAs are found in fat from dairy products and meat of ruminants, and have distinct effects compared with trans FAs industrially produced. The lipid composition of cheeses depends on the milk used. In this work was determined CLA and TVA content in milk fat of sheep and cow to be 1.4% and 3.2%, respectively, and from goat, 0.7% and 1.8%. Also, differences in CLA and TVA content were found in fat extracted from samples of the same cheese type made from cow＇s milk from the same company but with different production dates during a year. The levels of CLA and TVA found in Uruguayan cheeses were generally higher than levels reported in previous studies with comparable cheeses produced in other countries. Milk fat is well-known to confer specific properties to foods. This in turn will affect the rheology and sensory attributes as food. For this reason, it is of interest to determine the triglyceride （TAG） composition in milk-derived foods. Results show that there are characteristic differences in the TAG composition of the different cheeses. We found minimal differences between cheeses from goat and sheep but found distinct characteristics for TAGs from cow milk-derived cheese.
