焙烤时间对椰子油品质及氧化稳定性的影响

本研究以椰子片为原料,探究焙烤对椰子中油脂的理化性质、脂肪酸组成、结构及氧化动力学的影响。结果表明,在200℃下椰子片经过200～220 s的焙烤,所提取椰子油的品质未发生明显改变,脂肪酸组成和含量无显著变化,仅有少量氧化产物生成。氧化动力学研究结果表明,焙烤后椰子油的氧化诱导期(IP)增加,氧化反应表观活化能(E_a)、活化焓(ΔH)和活化熵(ΔS)都明显增大,说明焙烤处理增加了椰子油的氧化稳定性,这可能与焙烤过程中产生的美拉德产物有关。     

Physicochemical and bioactive compounds at edible ripeness of eleven varieties of avocado (Persea americana) cultivated in the Andean Region of Peru

This work aimed evaluating some physicochemical compounds, hydrophilic (H-AC) and lipophilic (L-AC) antioxidant capacity of eleven avocado genotypes grown in the Andes. The results show great variability in physical and chemical properties, dry matter (DM) and lipid contents with ranges of 18.4–39.3% and 10.1–23.2%, respectively. All genotypes had high oleic acid content (50.4–69.9%) and a high unsaturated fatty acid/saturated fatty acid ratio (UFA/SFA, from 3.05 to 6.05), while the unsaponifiable fraction contained mainly β-sitosterol (140.83–235.51 mg/100 g DM) and α-tocopherol (17.44–71.29 µg/g DM). Total phenolic compounds (TPC), H-AC and L-AC ranged from 0.48 to 0.88 mg EAG/g DM, 5.37 to 14.00 and 1.87 to 6.71 μmol ET/g DM, respectively. Although the genotype influences avocado characteristics, climatic conditions in the Andean region seem to be important for the biosynthesis of metabolites of interest and should be considered in future studies.     

牛油果椰油的湿法制备及其品质特性分析

针对食用椰子油椰香味浓郁,但必需脂肪酸和油脂伴随物缺乏的问题,研究了采用超声波辅助水酶法从牛油果浆与椰浆中制备牛油果椰油的方法。通过单因素实验优化了制备工艺,并分析了所得油脂的品质指标。结果表明,牛油果椰油的适宜制备工艺条件为:在椰浆中添加30%的牛油果浆(以椰浆质量计)、0. 25%的木瓜蛋白酶和0. 05%果胶酶(以总物料质量计),于60℃酶解1h,然后超声处理2 h,将物料冷冻(-20℃)、解冻(60℃,1 h) 2次后离心提油。在适宜条件下,油得率为26. 4%,牛油果椰油呈现淡绿色,兼具椰子及牛油果特有的芳香味,酸价(KOH)为0. 36 mg/g,所得牛油果椰油强化了椰子油的营养价值,其不饱和脂肪酸含量为10. 55%,总酚酸、类胡萝卜素和黄酮含量分别为(0. 24±0. 15) mg/g、(0. 61±0. 03) mg/kg、(0. 013±0. 002) mg/m L。     

Rheological behaviour of emulsions of avocado and watermelon oils during storage

Rheological properties of emulsions made out of avocado pulp and watermelon seed oils with whey protein concentrate were determined during different storage periods. The oils, as well as the emulsions behaved like non-Newtonian liquids, having shear-thinning characteristics. Both oils showed moderate shear-thinning characteristics as the flow behaviour indices were between 0.86 and 0.88. The shear-rate/shear-stress data could be adequately fitted (r = 0.997–0.999) to a common rheological equation, e.g. the power-law model. Avocado pulp oil was markedly more viscous than was watermelon seed oil which was also evident from the higher apparent viscosity and consistency index values.     

Antioxidant properties of garden strawberry leaf extract and its effect on fish oil oxidation

The present study characterises garden strawberry leaf extract and reports its effect on shelf life and quality characteristics of fish oil. Radical scavenging capacity of the extract in DPPH^? and ABTS^?+ assays was equivalent to 1207 and 1579 μmol g^?1 of trolox equivalents, respectively, total phenolic content was 257 mg g^?1 of gallic acid equivalents. Phenolic and volatile constituents were analysed by liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS). The extract was added to fish oil and its oxidation was followed during 42 days: peroxide, p‐anisidine values and hexanal concentration were lower in the samples with extract, particularly at the end of storage. The effect of extract on fatty acid composition was not significant, however the changes in the percentages of some individual acids were observed. Fish oil containing 5% of extract had lower levels of lipid oxidation in comparison to other samples. The results indicate that strawberry leaves could be a potential source of natural antioxidants.     

Hypolipidemic effect of blends of coconut oil with soybean oil or sunflower oil in experimental rats

Blended oils, consisting of coconut oil with sunflower oil or soybean oil, were prepared (22–24% linoleic acid) to provide higher amounts of PUFA to coconut oil consumers. Animal experiments were carried out to find the effects of coconut oil blends, using weanling rats, by feeding native and blends of oils at 10% level in the diet for 60 days. Serum cholesterol levels were reduced by 5% and 21%, respectively, in rats given blended oils containing CNO/SFO and CNO/SBO while liver cholesterol did not show a significant change when rats were given blends in comparison with rats given CNO. Serum and liver lipid analyses also showed significant change in TG concentration in rats fed blended oils compared with rats given CNO. These studies indicated that the atherogenic potentials of a saturated fatty acid-rich CNO can be significantly decreased by blending with an oil rich in unsaturated lipids in appropriate amounts.     

椰子油粉末油脂制备工艺研究

以低温压榨椰子油为芯材,采用乳化与喷雾干燥相结合方法制备椰子油粉末油脂。通过单因素试验并经正交试验确定最佳制备工艺参数:乳化剂单甘油酯与蔗糖酯质量比为1∶4、乳化剂与芯材比为3.0%、壁材明胶与多孔淀粉比为1∶6、乳化温度为60℃、固形物浓度为20%,均质压力为40 MPa、进风口温度为195℃、进料速度为20 ml/min,在该条件下,制备产品含油率为48%、表面含油率为1.81%、包埋率为96%。     

贮藏条件对南瓜籽及其油脂品质的影响

目的 研究不同包装方式与贮藏温度下对裸仁南瓜籽及其油脂品质的影响。方法 将新鲜裸仁南瓜籽分别贮藏于不同温度[低温(4±1) ℃、常温(15±1) ℃和高温(35±2) ℃]和不同包装(空气包装、真空包装与气调包装)中, 通过测定南瓜籽含油率、酸价、过氧化值、霉菌总数以及南瓜籽油感官品质和脂肪酸组成, 分析不同贮藏条件对南瓜籽及其油脂品质的影响。结果 低温气调包装的南瓜籽在贮藏期内, 南瓜籽的酸价、过氧化值均呈现上升趋势, 贮藏210 d后分别为(2.15±0.04) mg/g、(0.15±0.01) g/100 g, 南瓜籽霉菌总数受温度影响较大; 低温贮藏、真空或气调包装贮藏条件下的南瓜籽含油率下降速率最慢; 低温气调包装贮藏的南瓜籽油的感官评定最佳, 南瓜籽油不饱和脂肪酸均呈现下降的趋势(P<0.05), 饱和脂肪酸含量呈上升趋势。结论 低温气调包装的贮藏方式有利于南瓜子仁及其油脂品质, 该研究可为南瓜籽籽储藏及后续加工提供技术支持。     

Volatile compounds and oxidative stability of Pinus halepensis Mill. seed oil under heating conditions

Heating conditions of Pinus halepensis seed oil were monitored to evaluate the effect of thermo‐oxidation processes on the bioactive compounds contained in the samples. The following parameters were monitored: ultra violet absorption at 232 and 270 nm, fatty acid composition, oxidative stability, antiradical activity and aromatic profiles. Under thermo‐oxidation process, trans fatty acids (TFA) increased and conjugated linoleic acid isomers appeared. The antiradical activity significantly decreased from 73.3% to 52.5% after 120 min of heating. Oxidative stability decreased (r = ?0.70). The volatile profile was heavily influenced by heating with the formation of new volatile compounds, such as the two isomers (E,Z)‐2,4‐decadienal and (E,E)‐2,4‐decadienal. α‐pinene, and the main terpene compound was very vulnerable to heating conditions. Despite its peculiar pleasant aroma and nutritional value, the P. halepensis seed oil should not be used for cooking. Indeed, under frying conditions, its antioxidant properties and oxidative stability are lost and potential toxic compounds, such as TFA and unsaturated aldehydes, are formed.     

Use of ATR-FTIR spectroscopy coupled with chemometrics for the authentication of avocado oil in ternary mixtures with sunflower and soybean oils

Avocado oil is a high-value and nutraceutical oil whose authentication is very important since the addition of low-cost oils could lower its beneficial properties. Mid-FTIR spectroscopy combined with chemometrics was used to detect and quantify adulteration of avocado oil with sunflower and soybean oils in a ternary mixture. Thirty-seven laboratory-prepared adulterated samples and 20 pure avocado oil samples were evaluated. The adulterated oil amount ranged from 2% to 50% (w/w) in avocado oil. A soft independent modelling class analogy (SIMCA) model was developed to discriminate between pure and adulterated samples. The model showed recognition and rejection rate of 100% and proper classification in external validation. A partial least square (PLS) algorithm was used to estimate the percentage of adulteration. The PLS model showed values of R² > 0.9961, standard errors of calibration (SEC) in the range of 0.3963–0.7881, standard errors of prediction (SEP estimated) between 0.6483 and 0.9707, and good prediction performances in external validation. The results showed that mid-FTIR spectroscopy could be an accurate and reliable technique for qualitative and quantitative analysis of avocado oil in ternary mixtures.     

鼠尾草酸对椰子油热加工过程中主要理化性质、脂肪酸组成与自由基的影响研究

以叔丁基对苯二酚(TBHQ)为对照,对比分析鼠尾草酸(CA)对椰子油热加工过程(180℃)中主要理化指标(酸价、游离脂肪酸含量、过氧化值、总氧化值、茴香胺值)、脂肪酸组成及自由基含量的影响。结果表明:加入抗氧化剂能够显著降低椰子油的主要理化指标, CA与TBHQ效果基本相当;加入CA和TBHQ可以抑制和延缓反式油酸、反式亚油酸的产生;CA和TBHQ对椰子油热加工过程中自由基含量的增加具有明显的抑制作用,且CA的抑制效果与TBHQ相差不大。因此,可以考虑将CA作为TBHQ在油脂热加工过程中的替代抗氧化剂使用。     

Effect of harvest date on the nutritional quality and antioxidant capacity in 'Hass' avocado during storage

The effect of harvest date on nutritional compounds and antioxidant activity (AOC) in avocado (Persea americana Mill. cv Hass) fruit during storage was determined. The fruits were harvested at seven different dates and ripened at 25 °C following 21 or 35 days of cold storage. The results indicated that the phenolic and glutathione contents were increased and the ascorbic acid content was not significantly different in early harvested fruit (January to March), and the phenolic, ascorbic acid and glutathione contents were increased slightly and then decreased on late harvested fruit (April to June). Similar trends were observed in the changes of AOC. Furthermore, AOC in early harvested fruit after storage for 35 days was much higher than that in late harvested fruit after storage for 21 days. Therefore, avocado can be harvested earlier for economic benefits according to the market and can keep high nutritional value for human health benefits.     

Stability of avocado oil during heating: Comparative study to olive oil

The stability of the saponifiable and unsaponifiable fractions of avocado oil, under a drastic heating treatment, was studied and compared to that of olive oil. Avocado and olive oil were characterised and compared at time 0 h and after different times of heating process (180 °C). PUFA/SFA (0.61 at t = 0) and ω-6/ω-3 (14.05 at t = 0) were higher in avocado oil than in olive oil during the whole experiment. Avocado oil was richer than olive oil in total phytosterols at time 0 h (339.64; 228.27 mg/100 g) and at 9 h (270.44; 210.30 mg/100 g) of heating. TBARs was higher in olive oil after 3 h, reaching the maximum values in both oils at 6 h of heating treatment. Vitamin E was higher in olive oil (35.52 vs. 24.5 mg/100 g) and it disappeared earlier in avocado oil (at 4 vs. 5 h). The stability of avocado oil was similar to that of olive oil.     

椰子汁饮料的稳定性研究

系统地研究了椰子汁饮料的生产工艺及影响其稳定性的主要因素，得到最佳的工艺条件：椰子肉和水的质量比为1：10，pH控制在6．5左右，加糖量为4．0％，均质条件是在70℃左右保持压力为20～25MPa，杀菌条件是121℃、20min，同时探讨了不同HLB值的混合乳化剂和增稠剂对椰子汁饮料稳定性的影响，结果表明：HLB值在11．27时乳化剂具有良好的效果，Tween60的效果优于其他乳化剂，黄原胶的效果比海藻酸钠要好。通过b9（3^4)正交试验得出稳定剂配方为；0．02％单甘酯、0．08％Span20、0．10％Tween60，0．02％黄原胶、0．02％海藻酸钠。     

氧化羊骨油脂肪酸组成及挥发性风味物质分析

采用气相色谱与气相色谱-质谱联用技术,分析氧化及未氧化羊骨油中脂肪酸组成与挥发性风味物质成分。通过"相对气味活度值(ROAV)"评价各挥发性风味物质对羊骨油总体风味的贡献,并结合聚类分析方法,确定氧化后羊骨油的关键挥发性风味物质。结果表明:羊骨油中检测出7种脂肪酸,其中包括3种饱和脂肪酸和4种不饱和脂肪酸,氧化使得羊骨油中亚油酸含量显著降低(P0.05);羊骨油中反-2-烯醛和反,反-2,4-二烯醛等醛类化合物为主要挥发性物质,氧化后羊骨油挥发性风味物质种类增加了22种,总峰面积是未氧化羊骨油风味物质总面积的4倍以上;亚油酸的氧化产物反-2-壬烯醛是羊骨油氧化后生成的最关键挥发性风味物质。总之,氧化羊骨油可以产生大量挥发性风味物质,并对脂肪香气起到强化作用。     

Effects of virgin coconut oil on the physicochemical,morphological and antibacterial properties of potato starch-based biodegradable films

This study investigated the effects of adding different concentrations of virgin coconut oil (VCO) on the optical, mechanical, thermodynamic and antimicrobial properties, as well as water vapour permeability and morphology of potato starch-based biodegradable films. Increasing VCO concentrations caused a rise in the light transmittance of the films from 2.13 to 4.79 mm⁻¹ and a decrease in water vapour transmittance from 6.77 to 2.12 (10⁻⁵ GPa⁻¹ h⁻¹ m⁻¹). At a VCO concentration of 14 wt% (based on potato starch), the tensile strength reached its highest value (19.98 MPa). Scanning electron microscopy showed that the surface of the film became smoother as VCO concentration increased. The addition of VCO inhibited the growth of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli. In conclusion, VCO supplementation improved the mechanical, antibacterial and water barrier properties of starch-based films. These results could expand the scope of the application of starch-based films in food packaging.     

精炼工艺对椰子油品质的影响

研究了精炼工艺对椰子油品质的影响。分析了毛椰油、碱炼油、脱色油、脱臭油的理化指标、脂肪酸、甘油酯组成和脂肪伴随物(甾醇、生育酚、多酚)的变化情况。结果表明:精炼工艺使椰子油的酸值、过氧化值显著降低,脂肪酸和甘油酯组成无显著变化;总甾醇、总生育酚和多酚含量显著降低,损失率分别为63.77%、68.03%、71.20%。综上表明,精炼能够显著影响油脂品质,需注重油脂适度加工技术的应用。