胡萝卜干燥加工过程中维生素含量的变化规律

以胡萝卜为研究对象,研究胡萝卜在干燥加工过程中的维生素含量变化规律。对胡萝卜分别采用真空冷冻干燥、热泵干燥、热风干燥等进行干燥加工,对干燥过程中胡萝卜中的不同维生素的含量进行测定,采用SPSS 12.0对所得实验数据进行统计学处理。结果表明:较干燥前,干燥后的胡萝卜中的维生素总量损失较大。其中,冷冻干燥过程中,维生素A的总损失率为62.23%,维生素B1为54.95%,维生素B2为48.32%,维生素C为66.52%;热风干燥过程中,在干燥温度为100℃时,四种维生素的损失率达到最高,其中维生素A的损失率为80.75%,维生素B1为77.45%,维生素B2为79.63%,维生素C为80.47%。在热泵干燥过程中,当出风温度为100℃时,四种维生素的损失率达到最高,其中维生素A的损失率为80.23%,维生素B1为69.54%,维生素B2为64.35%,维生素C为89.27%。在胡萝卜干燥加工过程中维生素A与维生素C的损失率最高,因此为减少胡萝卜干燥加工过程中的维生素损失,应该不断改进胡萝卜干燥加工工艺。     

Sensory and chemical changes in five varieties of carrot (Daucus carota L) in response to mechanical stress at harvest and post‐harvest

Carrots harvested by hand or machine and given additional mechanical stress by shaking in a transport simulator were analysed for taste, flavour and content of sugars, terpenes, 6‐methoxymellein and ethanol as well as for ethylene production and respiration. Carrots stressed by shaking had higher ethylene production and respiration, higher content of ethanol and 6‐methoxymellein and lower levels of total terpenes, several individual terpenes and sugars. This corresponded to a higher sensory score for ethanol flavour and odour, bitter taste, earthy flavour, terpene flavour, aftertaste and sickeningly sweet taste and a lower score for acidic taste and sweet taste as measured by an expert taste panel. Ethanol content was highly correlated with ethanol flavour and odour and sickeningly sweet taste. Of five varieties tested, ‘Bolero’ ‘Panter’ and ‘Yukon’ were most sensitive to mechanical stress, whereas ‘Napa’ and ‘Newburg’ were most resistant. Hand‐harvested carrots were not significantly different from machine‐harvested carrots as regards chemical or sensory variables. Principal component analysis showed only slightly different placing of these samples in the score plot. A digital carrot could monitor the degree of mechanical stress to which the carrots were subjected. © 2001 Society of Chemical Industry     

Drought Effects on the Marketable and Nutritional Quality of Carrots

In two cultivars of carrots (Daucus carota L) drought stress was imposed at different developmental stages in order to examine how the marketable and nutritional quality was influenced. Experiments were conducted on both a sandy loam soil and a coarse sandy soil. Although drought stress during a 3-week period at any growth stage reduced total tap-root production, the yield of marketable tap roots increased on the sandy loam soil when drought stress occurred just prior to harvest. This was the result of a decrease in the proportion of split roots when drought stress was imposed during this period. An increased risk of infection by common scab (Streptomyces scabies) was seen when drought stress occurred during early growth. Cultivar differences in susceptibility to split roots and common scab were observed. Significant differences in chemical composition between cultivars were seen. However, drought stress imposed at a specific growth stage did not influence the chemical composition of tap roots in any consistent manner. When drought stress occurred during early growth on the coarse sandy soil the concentration of dry matter was low and that of potassium and nitrate high. However, the opposite was found on the same soil when drought stress occurred just prior to harvest. Averaging the effect of drought periods and cultivars, drought stress was observed to increase the concentration of sucrose in tap roots from the sandy loam soil and decrease that of phosphorus in tap roots from the coarse sandy soil. Various effects on magnesium, β-carotene and vitamin C were detected. Severe drought stress increased the storage losses due to the development of diseases. © 1997 SCI     

Validation of a mathematical model for predicting high pressure carbon dioxide inactivation kinetics of Escherichia coli spiked on fresh cut carrot

Inactivation kinetics of Escherichia coli spiked on fresh cut carrot and exposed to high pressure carbon dioxide (HPCD) treatment at several conditions of pressure (6, 8, 10, and 12 MPa) and two conditions of temperature (26 and 35 °C) were obtained as a function of the treatment time (up to 30 min).The Weibull model was applied to fit the inactivation kinetics and calculate δ and n model parameters for each pressure and temperature. The results demonstrated that the model was able to fit with good agreement the inactivation curves (high R² and low RMSE values). In a second attempt, the model parameters were correlated with CO₂ density resulting in a linear relationship. Validation of the proposed model was also performed at 6.6 and 10 MPa, 26 °C and at 8 MPa, 35 °C providing log reduction residual values (observed value–predicted value) lower than 0.50 and showing a good agreement between the experimental and the predicted inactivation data.The model proved to be a powerful tool to fit and predict, in the proposed operative range, the inactivation kinetics of E. coli spiked on fresh cut carrot treated by HPCD. The results demonstrated the potential of a relative simple correlative model for the interpretation of the inactivation data and for HPCD process design and optimization.     

恒温实时荧光法快速检测婴幼儿辅助食品中胡萝卜成分的研究

为建立婴幼儿辅助食品中胡萝卜成分的恒温实时荧光快速检测方法，根据胡萝卜ITS1-5.8SRNA-ITS2基因序列设计合成恒温实时荧光法（LAMP）的特异性引物，以常见农产品及不同胡萝卜质量分数的白萝卜DNA分别验证方法的特异性和灵敏度，选取不同品系胡萝卜种子验证方法的适用范围，并通过预包装食品检测其实用性。结果表明：所建方法与其他物种无交叉反应，特异性强，能在1 h内检测低至质量分数为0.01%的胡萝卜成分，灵敏度高，适用于不同品系胡萝卜的检测。适用范围广，通过实际样本的检测验证，结果快速、准确。该方法操作简单、成本较低、数据智能判读实时同步、结果准确快速，可用于婴幼儿辅助食品中胡萝卜成分的快速检测，为婴幼儿食品标签管理及食品安全监管提供技术依据。     

芹菜、番茄、胡萝卜复合蔬菜汁的研制

研究了芹菜汁、番茄汁、胡萝卜汁的提取方法。通过正交试验确定生产复合蔬菜汁的最佳配方,并较好地解决了蔬菜汁的沉淀及特有风味的保留等问题。