不同加热方式对植物油质量的影响

以大豆油、花生油作植物油的代表,比较电磁炉、微波炉、常规加热3种加热方式对植物油中酸价和过氧化值的影响,结果表明,电磁炉加热对油脂品质的影响最大,其次为微波炉加热,再次为常规加热;含不饱和脂肪酸越多的油对热效应越敏感;间歇加热、加新油加热有利于油脂品质的保护。     

微波对植物油品质的影响

通过对菜籽油、芝麻油、粟米油三种特种植物油进行微波加热和常规加热处理，与不加热时的样品进行比较，并分别检测其酸价和过氧化值，研究了微波加热对其品质的影响；同时也探讨了油脂中添加VE对其加热品质的影响。     

三种加热方式对油脂品质影响的比较

采用电磁炉、微波炉、常规加热对大豆油、花生油进行处理，测定其酸价和过氧化值，以比较三种加热方式对油脂品质的影响。结果表明，电磁炉加热对油脂品质的影响最大，微波炉加热对油脂品质的影响次之，常规加热的影响最小；花生油、豆油依次对热效应的敏感程度增加；间歇加热、加新油加热有利于油脂品质的保护。     

微波对特种植物油品质的影响

对菜籽油、芝麻油、粟米油3种特种植物油进行微波加热和常规加热处理,并与不加热时的样品进行比较,分别检测其酸价和过氧化值;研究了微波加热对植物油品质的影响,同时也探讨了油脂中添加VE对其加热品质的影响.     

微波对特种植物油品质的影响

对菜籽油、芝麻油、玉米油 3种特种植物油进行微波加热和常规加热处理 ,与不加热时的样品进行比较 ,并通过检测其酸价和过氧化值 ,研究了微波加热对其品质的影响 ,同时也探讨了油脂中添加VE 对其加热品质的影响     

电磁加热对植物油品质的影响

系统研究了电磁加热对油脂品质的影响。结果表明：随加热温度的升高和时间的延长，油脂的酸值和过氧化值都在升高；含不饱和脂肪酸越多的油脂对热越不稳定；电磁加热与常规加热相比，电磁加热条件下油脂的酸值和过氧化值均高于常规加热；三种方式相比，油脂的酸值和过氧化值的大小顺序为连续加热〉间歇加热〉连续加新油加热。     

微波环境中植物油品质变化的研究

通过实验探讨了不同微波辐射功率和时间下植物油的过氧化物（ＰＶ）和硫代巴比妥酸值（ＴＢＡ）等理化指标的变化情况。研究结果发现，微波的辐射功率和时间均将使所实验的植物油ＰＶ值和ＴＢＡ值升高，因此，当利用微波处理植物油时，应该合理地控制微波施加的功率和时间，以确保其品质。     

常规加热和微波加热对两种植物油维生素E含量的影响

目的 研究常规加热和微波加热两种加热方式对植物油中维生素E的8种异构体的影响。方法 大豆油、棕榈油进行常规加热和微波加热后, 用异辛烷进行超声提取, 最后用正相高压液相色谱法测定。结果 两种加热方式都会使植物油中维生素E的含量降低, 其中微波加热对维生素E的影响更大。结论 加热时间过长会影响植物油的品质, 同时也能通过对植物油中维生素E的检测推论该植物油是否经过加热处理。     

三种加热方式对大豆油品质影响的比较

采用电磁炉、微波炉、常规加热对大豆油进行处理,以酸价和过氧化值为指标,比较了三种加热方式对大豆油品质的影响。结果表明,电磁炉加热对大豆油品质的影响最大,微波炉加热对大豆油品质的影响次之,常规加热的影响最小;大豆油的酸价、过氧化值与加热的温度及时间有良好的线性关系。间歇加热、加新油加热有利于油脂品质的保护。     

微波辐射与常规加热方式作用下植物油品质变化的对比试验

系统地研究了一定输出功率下 ,微波辐射法和常规外加热法对植物油品质影响的差异。发现在微波辐射下 ,植物油的PV值及TBA值随处理时间而增大的幅度均略高于常规外加热方法 ,但对植物油中α—VE 含量的减少幅度则略低于常规外加热方法。     

微波加热对食用油品质及脂肪酸成分的影响

研究微波加热对食用油品质及脂肪酸成分影响,为家庭健康烹调提供理论依据。用家用微波炉的不同加热档位,对菜籽油、大豆油等8种常用食用油加热不同时间,用滴定法测定加热后油脂的酸价和过氧化值,GC-MS测定油脂的脂肪酸成分,并以这些指标评价微波加热对食用油品质的影响。在实验所用加热条件下,8种食用油的酸价和脂肪酸成分均未发生明显改变。不同食用油的过氧化值变化曲线有所不同,菜籽油、大豆油、花生油、芝麻油、调和油的过氧化值随着微波功率和时间增加而上升,玉米油、橄榄油和葵花籽油的过氧化值随着微波功率和时间增加先上升后下降。微波加热虽然改变了食用油的过氧化值,但酸价尚未发生改变,认为油脂尚未发生酸败,微波加热也没有破坏食用油原有的脂肪酸组成。从微波加热对食用油的品质和脂肪酸成分影响的结果看,可以认为微波加热是日常生活中安全和健康的加热方式。     

Oxidative changes in hazelnut,olive, soybean,and sunflower oils during microwave heating

The effects of microwave heating for 3, 6, and 9 min at a frequency of 2450 MHz on fatty acid composition, tocopherols, iodine value, free fatty acids (%), peroxide value, conjugated dienes and trienes, and hexanal contents of refined hazelnut, soybean, sunflower, and virgin olive oils were investigated. A significant (p < 0.05) decrease was observed in linoleic and linolenic acids contents of soybean oil during exposure to microwave heating. Tocopherol contents of oil samples significantly decreased (p < 0.05) during microwave heating. Free fatty acids of the samples slightly increased and iodine value showed reduction throughout the process. Conjugated dienes contents of samples showed an increasing trend up to the 6 min, followed by a reduction at 9 min. Conjugated triene fatty acids of all the samples significantly increased (p < 0.05) throughout the application. While peroxide value showed increasing trend up to the 3 min and sharply decreased at 9 min, hexanal contents of refined hazelnut, virgin olive, soybean, and sunflower oils increased 63, 28, 55, and 389 fold, respectively, after 9 min exposure to microwave heating. Kinetic analysis of data showed that the reaction orders for peroxide and hexanal formation were zero and first order, respectively, and in the tested oils the reaction rate followed the order: soybean oil ? sunflower oil ? hazelnut oil ? virgin olive oil for peroxide, and sunflower oil ? soybean oil ? hazelnut oil ? virgin olive oil for hexanal formation. It was concluded that hexanal could be considered as a parameter for evaluation of the quality of oils exposed to microwave heating.     

Comparison of microwave irradiation and conventional thermal heating on volatile profiles and degree of oxidation in corn oil

Volatile profiles and degree of oxidation in corn oils after microwave treatment for 50 min were compared to oils with conventional heating at 180°C for 4 h. Oil microwaved for 10 and 50 min showed a similar degree of oxidation compared to the oil heated at 180°C for 1 and 3 h, respectively, based on the primary and secondary oxidation products. However, the total volatile contents of 50 min-microwaved oil were significantly lower than that of corn oil heated for 1 h at 180°C (P < 0.05). Microwave treatment accelerated the rates of lipid oxidation by 4.6 times compared to 180°C thermal oxidation. Relatively short treatment with microwave irradiation may not provide sufficient time to generate volatiles from oil. Microwaved corn oil for 50 min had higher contents of hexanal and t-2-heptenal and lower contents of 2,4-decadienal and nonanal than the oils heated at 180°C for 3 h. Reactive oxygen species may be involved in volatile formation in microwave-irradiated oils.     

An implementation of central composite design: Effect of microwave and conventional heating techniques on the triglyceride composition and trans isomer formation in corn oil

Triglyceride composition and trans fatty acid content of corn oil subjected to microwave and conventional heating were evaluated with the aid of central composite design methodology. Oil samples with and without α-tocopherol were prepared on the basis of central composite design and, the effects of the main three factors (temperature, contact time, and the amount of α-tocopherol) were tired to investigate 10 at different five levels. Linoleic acid-linoleic acid-linoleic acid content in triglyceride structure of corn oil and the amount of trans fatty acids in the same oils were taken as response values for evaluation of central composite design assays. Based on the response surface, the optimum conditions (at which trans fatty acid formation and the change in the triglyceride composition are minimum) were determined for both heating procedures. The results showed that the increasing of the temperature and contact time increased the trans fatty acid formation and changed triglyceride structure of the oil in both heating techniques, although, the addition of α-tocopherol at high concentration caused pro-oxidant effect on triglyceride composition (bad effect), while reducing the formation of trans fatty acid (good effect). The results revealed that the heating 20 treatments caused significant changes in the triglyceride composition and trans fatty acid isomers of unsaturated fatty acids of the oil, while the saturated fatty acid contents did not change substantially. These alterations were much greater in microwave-heated samples (trans fatty acid ≤ 7.26%) than in Q3 corresponding samples heated in a conventional stove (trans fatty acid ≤ 0.56%).     

不同加热方式对槟榔油品质的影响

用GC-MS方法鉴定出槟榔油中各成分含量,其中主要成分为亚油酸和油酸,相对含量分别为26.84%、26.91%,占总脂肪酸含量的一半以上。并对槟榔油、椰子油、猪油分别进行常规和微波加热处理,探讨不同加热温度和时间及微波对油脂的酸值和过氧化值的影响,结果表明油脂的酸值随着加热时间的延长不断升高,而过氧化值随加热时间呈曲折升高趋势,槟榔油、椰子油在加热条件下与猪油相比其酸值、过氧化值变化趋势相对较小,可能是本身含有的抗氧化物质,阻止了脂质过氧化物的链式反应。     

Microwave roasting of peanuts: Effects on oil characteristics and composition

Roasting of peanuts by microwave heating (MWH) for different periods was studied in comparison with conventional heating method (CHM). The oils extracted from microwave roasted peanuts (MWRP) showed gradual darkening by time of heating. Colour indices of the oil samples were calculated to show the effect of heating on the oil colour. Chemical characteristics and fatty acid composition of the extracted oils were determined. In addition, peroxide value, conjugated dienes and trienes were determined. It was found that very low amounts of epoxy and conjugated fatty acids as well as fatty acid peroxides were formed as detected by GLC, UV spectrophotometry and peroxide value determinations. Freshly extracted peanut oils subjected directly to MWH showed increase of formation of conjugated trienes. In addition, the MW treatment causes oil darkening and higher colour indices were obtained. It was generally concluded that even short period MWH accelerates the formation of some undesirable and harmful compounds (e.g. oxidation products, transformed pigments ... etc.) during peanut roasting.     

Microwave heating of different vegetable oils: Relation between chemical and thermal parameters

Changes of DSC profiles and thermal properties (upon cooling and heating) were evaluated at different times of microwave heating on refined peanut (Pto), high oleic sunflower (HOSo) and canola (Co) oils and compared to the results obtained for standard chemical indices (free fatty acids, peroxide, p-anisidine, OSI time) and antioxidant capacity (Trolox equivalent antioxidant capacity). Co was more extensively oxidised by microwave heating than the other two oils probably as a consequence of the higher degree of unsaturation, even though it showed a higher antioxidant capacity. Microwave heating also induced alterations in both cooling and heating profiles of the oils, mainly in Pto and Co, shifting phase transitions towards lower temperature and enlarging temperature range. High statistical correlation coefficients were obtained among thermal properties both upon cooling and heating and chemical indices (i.e. free fatty acids and p-anisidine values). The analysis of both cooling and heating profiles and related thermal properties appears to be a valuable tool to assess different degrees of lipid thermoxidation induced by microwave in vegetable oils being also very useful for the ready-to-eat food sector and the vegetable oil industry.     

Comparative studies of different heat treatments on quality of fried shallots and their frying oils

The objectives of this study were to compare the quality of shallot-flavoured frying oil from microwave heat treatment with that from gas heat treatment. Frying of shallot pieces by the microwave treatment required shorter heating time to obtain the same colour quality as through gas treatment. The amount of total volatile compounds of shallot-flavoured frying oil obtained from microwave treatment was greater than that from gas treatment. Oil-frying of shallots by microwave heating showed better oil quality, with lower acid and peroxide values than after frying by gas heating. In storage tests these two differently treated oils at 25°C, the acid value (AV) showed no significant increase during storage for 80 days. However, the peroxide value (PV) of these two oils increased in parallel as storage time increased. The effect of moisture content, of the shallots, on the quality of resultant shallot-flavoured frying oil was studied. Slight moisture reduction of shallot pieces from 72 to 63%, by a toasting pretreatment gave the highest amount of total volatile compounds of the shallot-flavoured frying oil. However, this total volatile compounds decreased if the moisture content of shallot pieces was less than 63%.