储藏条件对炒制原香味葵花籽酸败的影响

本实验以炒制原香味葵花籽为研究对象,考察温度、避光、充氮等不同储藏条件对葵花籽贮存中酸价、过氧化值和TBA值的影响。结果表明:葵花籽的酸败速度随温度升高而加快;采用充氮和避光包装均可明显延缓葵花籽的酸败;采用充氮包装的葵花籽,在30℃避光储藏时可以延长30d的货架期。     

Kinetics of the Kreis test through response surface methodology

The Kreis test is one of the procedures for early detection of oxidative products of fats and oils. The reaction is complicated, sensitive and continuous. The kinetics of the Kreis test have been studied as a function of reagent, phloroglucinol, oil quantity and incubation period for three oils with different fatty acid profiles, storage life and presence of compounds other than triglycerides. A central composite rotatable design with each factor at five levels required 20 experiments for each oil. The results of experiments carried out in duplicate have been examined by analysis of variance, and polynomials of appropriate degree were fitted to the data. The polyhedron search method was used to compute optimum conditions for carrying out the test for each oil. Three-dimensional graphs were generated to bring out the differences in the oils and the kinetics for each oil. Though “compromised” optimized conditions have been reported, the results indicate the necessity of more detailed investigation into the reaction.     

Oxidation kinetics in olive oil triacylglycerols under accelerated shelf‐life testing (25–75 °C)

A kinetic study of the autoxidation reaction in olive oil triacylglycerols stored in darkness at different temperatures (25, 40, 50, 60 and 75 °C), in absence of pro‐ and antioxidant compounds to avoid confounding effects, is described. After the induction period (IP) the decrease in the oxidizing substrate and the formation of primary oxidation products followed a pseudo‐zero‐order kinetic, and the calculated E_a from the Arrhenius equation for the formation of hydroperoxides was 32.1 kJ·mol^?1. The formation of secondary oxidation products followed a pseudo‐first‐order kinetic whose rate reaction constant also increased exponentially with temperature. The first oxidation index to exceed the upper limit in the EU regulations was PV, followed by K₂₃₂ and K₂₇₀. The time required reaching these limits and the rancidity threshold showed a potential dependence on temperature, and therefore with accelerated storage at 75 °C, POO shelf‐life in ambient conditions (25 °C) can be predicted. Finally, there was a good linear relationship between the time required to reach the rancidity threshold and the IP of the formation of the 2,4‐decadienal, and hence this instrumental determination could be useful to measure sensory recognition of the rancid defect in POO.     

An evaluation of the efficacy of antioxidants in soap by differential scanning calorimetry (DSC)

A simple, rapid method for the evaluation of the efficacy of commercial antioxidants in soap products has been developed. The procedure involves forced oxidation of a sample in an oxygen-pressurized differential scanning calorimetry (DSC) cell. The analysis is complete in 30 min and requires 5-10 mg of sample. The forced oxidation DSC methodology described in this work may be a useful tool in the development and optimization of an antioxidant system for bar soap products and for fatty materials in general.     

Oil stability index correlated with sensory determination of oxidative stability in canola oil

The usefulness of the Oil Stability Index (OSI) as an accelerated oxidative stability test for canola oil was studied by correlating the OSI with the induction period as determined by sensory analysis. Canola oil was treated by holding it for differing times (0, 1, 2, 3, 4, and 6 d) at elevated temperature (60°C) in the dark with agitation. The sensory induction period (SIP) was determined by storing the five treatments of oil and the control at 60°C in the dark with agitation and removing aliquots of oil for a nine-member sensory panel to evaluate over a 9-d period. The time it took for a treatment to reach an average sensory score of 5 (10-point scoring scale) was defined as the treatment’s SIP. OSI values were obtained on day 0 using a heating block temperature of 110°C and an air pressure of 6 psi. The relationship between SIP and OSI had a 0.89 coefficient of determination (r ²). This relationship may be sufficiently strong to warrant use of the OSI in industry applications but may not be ideal for more precise experimental studies of canola oil shelf life.     

酸败油脂再生法研究

通过对油脂酸败过程的理论分析，找出了油脂产生酸败的原因及酸败过程中可能生成的产物，通过实验研究探索出一种酸败油脂再生方法。     

2-thiobarbituric acid test for lipid oxidation in food: Synthesis and spectroscopic study of 2-thiobarbituric acid-malonaldehyde adduct

Synthesis, purification, elemental analysis, and spectroscopic studies were undertaken to characterize the structure of the red adduct 2:1 thiobarbituric acid (TBA)-malonaldehyde involved in the evaluation of oxidative rancidity in fats and oils. Thin-layer chromatography, infrared and ultravioletvisible absorption, ¹H (¹H NMR) and ¹³C nuclear magnetic resonance (NMR) spectra were used. A yield of 93% was obtained in the synthesis. The results of elemental analysis agree with the formula for the chloro-monohydrated form, C₁₁H₁₁N₄O₅S₂Cl. Three characteristic absorption maxima at 532, 310, and 245 nm, respectively, were shown in acid aqueous medium (pH 2.9). The characteristic vibrations assigned to the -NH, -OH, C^αH (exocyclic) and -C=S groups were confirmed in the infrared spectra. There was no evidence of thioenolization. ¹H NMR data at δ 5.10 (-CONH- group, H₂O and HCl molecules); δ 11.54 (-OH group of keto-enol tautomer, -NH group); and δ 176.4 (-CONH- group) also were observed. The experimental results obtained were consistent with the existence of two spectral equivalent tautomeric structures. The colored adduct was compared with other TBA-aldehyde compounds.     

仙谷米花糖哈败成因及防止措施

野苋菜是我国重要的野生蔬菜资源,由其种子加工而成的仙谷米花糖口感酥脆、天然健康,深受消费者青睐,市场开发潜力大。但仙谷米花糖在贮藏和销售过程中易产生氧化哈败、风味劣变,保质期较短。本实验研究了仙谷米花糖在不同条件下的储藏效果、仙谷油脂的脂肪酸组成及其理化特点。并用气相色谱-质谱联用（gas chromatograph-mass spectrometer,GC-MS）分析仙谷油脂加速氧化前后的成分差异。结果表明：仙谷含油率为6.26%、油脂酸价为2.79 mg/g、皂化值为144.79 mg/g、碘值为87.48 g/100 g;其中亚油酸含量为33.91%、油酸36.05%、棕榈酸15.39%、硬脂酸4.01%、角鲨烯7.03%;仙谷油脂加速氧化后角鲨烯消失,脂肪酸种类增加,醛类、酯、吡嗪、烯烃、苯胺、酚、酮类物质产生,说明角鲨烯是导致仙谷米花糖氧化哈败的主要原因,铝箔真空包装加脱氧剂能有效减缓仙谷米花糖哈败。     

米糠及其脂肪酶的研究进展

米糠是稻米加工的重要副产物,过去常被人们所忽视导致利用率不高。随着近些年来对米糠研究的深入,研究人员逐渐意识到了米糠的营养价值,米糠富含维生素E、谷维素等营养物质,可以用于进一步生产米糠油。米糠中脂肪酶的存在导致米糠快速酸败是限制其进一步加工利用的主要原因,近些年国内外学者提出了多种稳定化米糠的方法,但是许多方法会破坏米糠中的营养成分或者稳定化的效果不佳,故对米糠中脂肪酶的性质及作用机制的研究是一个新思路。本文对米糠及其产物的营养价值、米糠稳定化及脂肪酶的研究进展进行概述,旨在为米糠研究和抑制米糠的酸败提供参考,为米糠的综合利用提供借鉴。     

相对湿度对大豆调和油氧化酸败的影响

研究相对湿度(RH)对大豆调和油(BSO)氧化酸败的影响。采用自组装氧化装置,在温度50℃、大气氧分压21 kPa、初始顶空率50%和室内光照强度(840 lx)的条件下,通过磷酸氢二钾溶液分别控制RH为50%、60%、70%、80%和90%,氧化BSO试样,测定不同氧化时间(t)时BSO的过氧化值(POV)和酸价(AV),由POV-t和AV-t回归曲线分析RH对BSO氧化酸败的影响。结果表明:BSO氧化酸败符合零级反应动力学特征,POV与AV随RH的增大和t的延长而升高;反应速率常数(k)随RH增大而增大。RH越大,氧化酸败速率越快,二者遵循二项式关系k_(POV)=-1E-05 RH~2+0. 002 4 RH-0. 049 6和k_(AV)=2E-07 RH~2-2E-05 RH+0. 000 5。因此,在生产、贮存、运输和消费过程中,应尽量降低BSO的贮存环境湿度,以减缓BSO的氧化酸败速率。