Quality And Its Changes On Oil-tea Camellia Seed Oil

Camellia is one of the four main oil-bearing trees (palm, coconut, olive and tea) in the world. The oil from camellia seeds has long been important in China and Japan, to a lesser extent. Camellia oil with its low saturated fatty acid and high monunsatuarted oleic acid content is a natural competitor for olive and grape seed oils. Since it has regional property, the attributes and their changes during processing and cooking of camellia oil, particularly, sensory and nutritional properties have not been surely understood. In this study, the quality changes during roasting, bleaching and frying were investigated. Actually, the quantitative analyses and changes of polyphenols and volatiles as minor compounds in camellia oil were the highlights in the study.Solid Phase Microextraction (SPME) has been widely used for extraction of volatile in gas, liquid and solid matrices. Four fibers, i.e.100μmPDMS,85μmPA,65μmPDMS/DVB and50/30μmDVB/CAR/PDMS, were selected for extraction in camellia oil volatile analysis. The results showed that:1) benzaldehyde, octanal, octonol, nonanal, and nonanol which have relatively higher boiling points were sensitive in65μm PDMS/DVB fiber, while the relative lower boiling point compounds were sensitive in50/30μm DVB/CAR/PDMS fiber;2) the total peak areas in gas chromatography ranked as following sequence:DVB/CAR/PDMS>PDMS/DVB>PA>PDMS;3) linear regressive relationship between total peak area and volatile amount (0-120μg/g) in DVB/CAR/PDMS, PDMS/DVB, PA, PDMS was existed with R2of0.9939,0.9888,0.9176and0.9917, respectively; These factors indicate that65μm PDMS/DVB and50/30μmDVB/CAR/PDMS are suitable for extraction of volatile of camellia oil.A method for volatile analysis of hydraulic pressed camellia oil(Camellia oleifera Abel) by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) using50/30μm DVB/CAR/PDMS fiber is presented. Calibration curves were constructed for13compounds commonly reported in camellia oil headspace with coefficients of determination (R2) ranging from0.9840to0.9999and limits of detection (LOD) from0.04μg/g to0.43μg/g. The recoveries and coefficient of standard deviation in repetitive determination ranged from90.88%to105.03%and from3.66%to7.42%, respectively.37volatile compounds in hydraulic pressed camellia oil were identified by mass spectrum and standard retention time that included aldehydes, alcohols, ketons, esters and acids etc. The total concentration of the top ten compounds, namely, hexanal, a-pinene, ethyl acetate, pentanol, benzaldehyde, octanol, a-Muurolene, nonanol, decanol, and octanal, reached21.26μg/g and accounted for68.40%of total. These factors indicate that this method is rapid, sensitive and convenient for volatile analysis of camellia oil.Combined with the results of sensory evaluation and GC/MS analysis for camellia oil, odour active values (OAV) for interested compounds were calculated through the thresholds in references. About10compounds were selected as main aromatic volatiles according to OAVs to form about20formula by diffenrent concentrations and adding potential compounds for contributing aroma.2formula were confirmed through triangle test compared to hydraulic pressed oil(p>0.05).Results of optimization of roasting and aqueous extraction conditions showed that:1) the optimum extracted rate and oil yield could be got when camellia seed kernel was roasted at175℃for15min followed by separation using water (water/meal,4.5/1) for150min.2) the moisture and volatile content, PV decreased but IV and SV increased with the enhancement of time and temperature of roasting.3) the volatiles in camellia oil extracted by the above method were classified into aldehyde, alcohol and ester. Among them, ethyl acetate ranked first. Majority of these compound accumulated up to the highest level at170℃and decreased when temperature further increased. But the concentrations of most of compounds increased with the increase of roasting time.In order to understand the quality change and oxidative state of camellia oil(Camellia oleifera Abel) in the bleaching step, measurements of various quality parameters, i.e. peroxide value (POV), free fatty acid (FFA) and UV absorbance, and volatile profile of crude and bleached oils were carried out. The results showed that FFA, K270and K232increased, whereas POV decreased, with increase of the activated earth dosage of0-4%and of bleaching time from0to40min at110℃. As the amount of activated earth was increased from0%to4%with bleaching at110℃for30min, various classes of volatile compounds increased in concentration:aldehydes (23.7μg/g), alcohols (13.2μg/g), esters (8.0μg/g), alkenes (2.0μg/g) and ketones (1.9μg/g). Likewise when bleaching was carried out at110℃with3%activated earth, and the bleaching time varied between0and40min, concentrations of volatile compounds also increased:aldehydes (27.7μg/g), alcohols (18.2μg/g), esters (7.3μg/g), ketones (3.2μg/g) and alkenes (0.6μg/g). These findings indicate that hydroperoxides in oil were decomposed into lower molecular weight products in the process of bleaching and that the extent of this decomposition can be controlled by time and amount of activated earth.Refined camellia (GB11765, pressed oil, Grand1) was used for deep frying for French fryer with comparison of palm oil. During30h (120batches) frying procedure, acid, peroxide, carbonyl, iodine, saponification, and K values and polar compounds of frying oil and oil extracted from French fryer were analysed. Volatile of frying oil and sensory attributes of French fryer were also evaluated. The results were showed that acid, peroxide, carbonyl, and K values and polar compounds of camellia and palm oils increased gradually, while iodine and saponification values decreased; Total volatile accumulated with a trend of "up-down" of lower molecular weight volatiles; Total score of French fryers fried with fresh oil and with camellia oil were higher than those from the latter bathches and fried with palm oil; Except of peroxide value, other values assessed in the oil extracted from French fryer were lower than those in the relative batch frying oil. According the regulation of GB7102, except that carbonyl value at24h exceeded the limit, other indices were still within the required limit. The factors as given above indicate that the frying life of camellia oil should be24hours and the French fryer fried with camellia oil could be more acceptable by consumers.A claim of a camellia oil healthcare benefit as a result of the high amount of'tea polyphenol'arises a widely discussion in China currently, A laboratory solvent extracted crude oil (SECO) and a commercial cold pressed oil (CPO) were used for evaluation of oil attributes, particularly, total phenol content (TP). Effects of different solvents on phenol extraction for phenol profile were also investigated. According to GB11765(a Chinese standard for camellia oil quality), acid value (AV), peroxide value (POV), sensory attributes, i.e. transparency, odour and flavour of CPO met the requirements, while SECO showed turbid. TP in SECO had no significant difference compared with that in CPO, thus, the phenol profile of SECO seemed to be more complicated in comparison to that of CPO. Different solvents showed different effects on phenol profiles: low molecular alcohol aqueous solution could extract more phenolic compounds, while gallic acid as a solely coumpound was extracted by acetone. These factors indicate that SECO should be refined and solvent effect on phenolic compound extraction would be helpful on further research for the interested phenol fraction in camellia oil.