食品液体(南瓜汁)蒸发浓缩过程动力学研究

本文对蒸发浓缩过程营养损失动力学进行了研究,建立了汽一液一固三相循环流化床蒸发器蒸发浓缩南瓜汁时胡萝卜素损失的动力学模型。实验结果表明:模型预测值与实验值吻合良好,该模型对工业生产有一定的应用价值。     

红甜菜萃取液蒸发浓缩过程研究(Ⅰ)红甜菜萃取液蒸发浓缩动力学

对红甜菜萃取液的蒸发浓缩动力学作了研究,表明甜菜红色素损失速率为表观二级反应,温度的影响遵循Arrhenius 方程,建立了甜菜红色素降解速率与料液温度、料液相对密度、抗坏血酸浓度相关联的蒸发浓缩动力学模型。新型异形竖板降膜蒸发器中蒸发浓缩过程中甜菜红色素吸光度实测值与动力学理论模型的吸光度预测值吻合良好,表明动力学模型对预测工业蒸发器浓缩过程中甜菜红色素损失程度具有良好的准确性,可用于指导工业生产。     

红甜菜萃取液蒸发浓缩过程研究(I)红甜菜萃取液蒸发浓缩动力学

对红甜菜萃取液的蒸发浓缩动力学作了研究。表明甜菜红色素损失速率为表观二级反应,温度的影响遵循Arrhenius方程,建立了甜菜红色素降解速率与料液温度、料液相对密度、抗坏血酸浓度相关联的蒸发浓缩动力学模型。新型异形竖板降膜蒸发器中蒸发浓缩过程中甜菜红色素吸光度实测值与动力学理论模型的吸光度预测值吻合良好,表明动力学模型对预测工业蒸发器浓缩过程中甜菜红色素损失程度具有良好的准确性;可用于指导工业生产。     

胡萝卜汁蒸发浓缩过程质量评估与优化

在胡萝卜汁蒸发浓缩过程动力学研究的基础上,提出了胡萝卜素保留率为评估蒸发浓缩过程质量的准则,并在评估准则的指导下对髯萝卜汁浓缩过程进行了优化,同了最优浓缩工艺,讨论了最优工艺的实现方法．本文的研究方法和研究结果可用于指导工业生产。     

果蔬汁(菠萝汁)蒸发浓缩过程中营养损失动力学

为研究异形竖板降膜蒸发器浓缩蔬菜汁时蒸发温度对品质的影响,对蒸发浓缩过程中营养损失动力学进行分析研究,结合Arrhenius模型、Z值模型、H-E模型,建立蒸发浓缩果蔬汁时营养损失的新的动力学模型;同时给出反应级数的精确计算方法。     

绿茶汁蒸发浓缩过程品质损失动力学

运用均匀设计和逐步回归议程,建立了绿茶汁在蒸发浓缩过程中的品质损失动力学,并在异形竖板降膜蒸发器中验证了所得的动力学模型,结果表明动力学模型的准确性较高。     

采用微波辅助法提高胡萝卜汁中的β-胡萝卜素含量

通过对微波辅助法提高胡萝卜汁中β-胡萝卜素含量影响的研究,确定了微波辅助法处理的最佳工艺参数:微波输出功率600 W,料液比(g∶mL)1∶3,处理时间58 s,处理次数3次,β-胡萝卜素(与对照相比)平均增长率为117.25%。     

胡萝卜制汁过程中β-胡萝卜素保存率的研究

通过对胡萝卜制汁生产过程中的去皮、软化、榨汁、均质、浓缩等各单元操作工艺的优化研究,探讨了加工方式对β-胡萝卜素保存率的影响,确定了浓缩胡萝卜汁生产的最佳工艺条件为:质量分数5%复合磷酸盐95℃3min去皮;在0.5%柠檬酸+0.3%Vc混合液中95℃条件下热烫3min;趁热打浆[m(胡萝卜)∶m(混合液)=1∶2.5],先粗碎、再粗磨、最后细磨;在超声波输出功率400W、超声时间4s、间歇时间3s、总工作时间6min、料液比(g∶mL)1∶3、超声温度40℃条件下进行细胞破壁;二次均质压力分别为19、25MPa;脱气条件为60℃,0.065MPa;微波灭菌2min。在该条件下,整个制汁过程中β-胡萝卜素的保存率为83.03%。     

采用超声波法提高胡萝卜汁中的β-胡萝卜素含量

探讨了超声波作用对胡萝卜汁中 β 胡萝卜素含量的影响。结果表明 ,超声波输出功率40 0W、超声时间 4s、间歇时间 3s、总工作时间 6min、料液比 (g∶mL) 1∶3、超声温度 40℃的条件下 ,其影响效果显著     

新型常压低温热泵蒸发浓缩装置

给出了一种常压低温热泵蒸发浓缩装置.该装置可为热敏性料液的高效、高质量和低成本蒸发浓缩提供一条新的途径.对该装置的工作原理进行了简要介绍,计算了典型工作参数下的性能指标(吨水能耗比),分析了吨水能耗比随料液温度的变化规律,并对围绕该装置进一步需研究的课题进行了探讨.     

A review of the changes in carotenes during ensiling of forages

The dietary availability of carotenes to the animal depends in part on the relative proportions of different isomers and these may alter during ensiling. The proportions of the more available β-carotenes are higher in well preserved silages than in clostridial silages. Under anaerobic conditions only small losses of carotenes occur with acidtreated silages but the provitamins are degraded rapidly in some fodder plants in the presence of both acids and oxygen. The presence of nitrites in silages is considered to increase destruction of carotenes.     

ADSORPTION ISOTHERM STUDIES OF PALM CAROTENE EXTRACTION BY SYNTHETIC POLYMER ADSORBENT

The use of different synthetic polymer resin adsorbents, including HP 20, Exa 31, Exa 32 and Exa 50 for the removal of carotenes from crude palm oil was investigated. The adsorption of carotene was determined using several adsorption isotherm models such as Langmuir and Scatchard plots. The Langmuir adsorption model was found to be sufficient to describe the adsorption of carotenes by using these four types of resins, suggesting that the process was favorable, saturable and an equilibrated mechanism. A curve of Scatchard transformation plot showed that the adsorption involves multiple binding sites. The maximum uptake capacity of all resins used in isopropanol (IPA) was about 5 fold higher than the maximum uptake capacity obtained in n-hexane. The adsorbent found to be most efficient for carotene was HP 20 for experiment carried out in IPA. The carotenes concentration obtained by HP 20 in IPA was 31.44 mg/L compared to 7.12 mg/L obtained in n-hexane.     

Degradation of Lycopene, α-Carotene, and β-Carotene During Lipid Peroxidation

The stability and antioxidant effectiveness of lycopene, a-carotene, and b-carotene were compared during oxidation of methyl linoleate at 37 and 60 °C. Two carotene concentrations, 80 or 160 mg/g of methyl linoleate, were used to determine a concentration effect. At 37 °C, the degradation rates were: lycopene > β-carotene > α-carotene. Lycopene and α-carotene inhibited hydroperoxide formation, lycopene being the more effective antioxidant. β-Carotene inhibited hydroperoxide formation at the lower concentration but did not show an antioxidant effect at the higher concentration. At 60 °C, the carotenes degraded 6 to 8 times faster than at 37 °C and did not show an antioxidant effect. BHT or α-tocopherol effectively suppressed the hydroperoxide formation and degradation of the carotenes.     

Effect of Sodium Chloride, Acetic Acid, and Enzymes on Carotene Extraction in Carrots (Daucus carota L.)

ABSTRACT: Carrot root cores were cut off longitudinally and treated with NaCl (0.6 and 1.2 M ) and/or acetic acid (1.33%, 2.67%, and 4%) solutions. The extractability of the carotenes was estimated. Similarly, carrot cores were also treated with some degrading enzymes (carbohydrases, lipases, and proteases) alone or in combination to study the effect of the tissue rupture or the hydrolysis of possible complexes or interactions between carotenes and other components on the carotene extractability. The results showed that acetic acid increased the extractability of α- and β carotenes up to 99.8% and 94.6%, respectively, at a 4% acid concentration compared with the samples without any treatment. This increase was directly proportional to the acid concentration. An increase in extractability was also observed for NaCl, although the increases were not as high as in the previous case with values of 49% and 41.4% for α- and β-carotenes respectively at a 0.6 M concentration. The study of microstructural changes and extractability revealed that the enzymatic treatments could have broken some carotene complexes and interactions and altered the carbohydrate matrix structure, increasing to a certain extent the extractability of carotenes. It can be concluded then that pickling with 4% acetic acid is a good method to increase the extractability of α- and β-carotenes.     

Quality Maintenance of "Ready-to-eat" Shredded Carrots by Gamma Irradiation

Shredded carrots were either chlorinated, rinsed, and spin-dried as in industrial processes, or irradiated (2 kGy), replacing the three steps. Several factors defining the quality of minimally processed vegetables were monitored during storage at 10°. Atmospheres inside micro-porous plastic bags stabilized at 7–15% O₂ and 10–15% CO₂. Sugar levels in tissues were twice as high in irradiated samples as in chlorinated ones. Irradiation also prevented losses of orange color and carotenes. Growth of aerobic mesophilic and lactic microflora was strongly inhibited by irradiation. Sensory analysis demonstrated preferences for irradiated vegetables. Irradiation, avoiding three potential denaturing steps preserved “ready-to-eat” shredded carrots with better quality than those prepared by conventional industrial processes.     

Bioaccessibility of carotenes from carrots: Effect of cooking and addition of oil

Food processing and occurrence of dietary lipids are believed to be important and limiting factors for carotenoid bioavailability in humans. In the present study the isolated and combined effects of household cooking and addition of olive oil on the bioaccessibility of carotenes from carrots have been investigated. Although thermal treatment during cooking showed to have a negative impact on the carotenoid content, a positive effect on the micellarisation of carotenes and therefore on their bioaccessibility was found. Carotenes transferred to the digests were micellarised to a higher extent from cooked carrots (52%) than from crude carrots (29%). Addition of olive oil to carrot samples during cooking and before application of the in vitro digestion model had a marked positive effect on the release of carotenes, although the design of the model did not allow the correct estimation of this effect. The higher amounts of micellarised carotenes (80%) were found in the digest prepared from cooked carrots containing 10% olive oil. In general, the inclusion of olive oil during cooking increased the carotenoid extraction and micellarisation in a dose-dependent fashion. Although β-carotene and α-carotene were affected in a similar way by the cooking process, α-carotene appeared to be more efficiently incorporated into the micelles when olive oil was added to the samples. In conclusion, both processing and mainly lipid content (cooking oil in this case) significantly improve carotenoid bioaccessibility from carrots, and therefore may increase bioavailability in humans.Industrial relevanceThe consumption of carotenoid-rich foods such as fruits and vegetables has been associated with a decrease of the risk of developing certain types of degenerative and chronic diseases. Processing of food and the interaction of carotenoids with lipophilic food components or ingredients may modify the amount of the released pigment from the food matrix, and therefore potentially increase or decrease their bioavailability. For this purpose, in the present study we have investigated the effects of cooking and presence of olive oil on the release of carotenes from carrots (as a model food) and their incorporation into absorbable micelles, the bioaccessibility. From the industrial point of view, a better understanding of the factors governing the release of carotenoids and other active components from vegetable foods is of great importance with the aim of optimising the manufacturing processes.     

Application of Response Surface Methodology to Improve Carotene Production from Synthetic Medium by <Emphasis Type="Italic">Blakeslea trispora</Emphasis> in Submerged Fermentation

Optimization of the medium components which enhance carotene production by Blakeslea trispora was achieved with the aid of response surface methodology. In the first step, a central composite design was employed to achieve the highest carotene concentration at optimum values of the process variables, i.e., linoleic acid, Span 20, and butylated hydroxytoluene (BHT), added in the basal medium. The fit of the model was found to be significant. The production medium to achieve the highest carotene concentration (139.0 ± 4.5 mg/g dry biomass) was composed of the basal medium supplemented with linoleic acid (21.3 g/l), Span 20 (16.0 g/l), and BHT (4.7 g/l). The results show that the optimization strategy led to an increase in carotene production by 35-fold. The carotenes content in Β. trispora were β-carotene (45%), γ-carotene (31%), and lycopene (24%). In the second optimization step, the production medium was supplemented with different trace elements which significantly affect carotene production (i.e., CuSO₄^.5H₂O, FeCl₃^.6H₂O, and Co(NO₃)₂.6H₂O). The experimental validation showed that the model was effective. The optimized medium for enhanced carotene concentration consists of the production medium supplemented with 395.64 mg/l CuSO₄^.5H₂O, 10.0 mg/l FeCl₃^.6H₂O, and 1.12 mg/l Co(NO₃)₂^.6H₂O. Practical validation of the above optimum medium gave carotene production 154.0 ± 5.0 mg/g dry biomass, which is 10% higher than the concentration of carotenes in the production medium. In this case, the carotenes consisted of β-carotene (37%), γ-carotene (47%), and lycopene (16%). Thus, the addition of trace elements to the production medium increased slightly the concentration of carotenes, but changed mainly the composition of the carotenes to a drastic increase of γ-carotene concentration.     

Carotenoid Photostability in Raw Spinach and Carrots During Cold Storage

A reverse-phase gradient HPLC method was developed for separating xanthophylls, chlorophylls, carotenes and cisβ-carotene isomers from raw spinach and carrots. The effect of dark and lighted cold storage on pigment stability was studied. Light promoted pigment losses in raw spinach. Degradative losses at 8 days ranged from 60% for violaxanthin to 22% for lutein. Dark, cold storage did not affect carotenoid levels except for all-transβ-carotene which showed an 18% loss at 8 days. In raw carrots, neither lighted nor dark cold storage affected major carotenoids. In spinach, the isomeric distribution of β-carotene showed strong linear correlations between trans and cis forms.     

Changes in carotenoids during processing and storage of pumpkin puree

Changes in the contents of carotenoids and their true retentions (% TR) during the production of puree of Cucurbita moschata ‘Menina Brasileira’ and of Cucurbita maxima ‘Exposição’ pumpkins and the stability of such compounds during 180 days of storage were monitored by liquid chromatography coupled with a photodiode array detector. Cooking caused higher losses than commercial sterilisation. High losses of xanthophylls such as lutein and violaxanthin were noted during processing and storage of pumpkin puree. Such losses show the low stability of these compounds. The major carotenoids, pro-vitamin A carotenes, namely, α-carotene and all-trans-β-carotene for C. moschata ‘Menina Brasileira’ and all-trans-β-carotene for C. maxima ‘Exposição’ obtained high retentions (>75%) after processing. A slight degree of isomerisation of β-carotene was noted in the puree samples, but with low concentrations of cis-isomers. Storage for 180 days did not significantly affect (P ? 0.05) the concentrations of these carotenoids.     

Optimisation of minimal processing variables to preserve the functional quality and colour of carrot juice by means of the response surface methodology

Combined processes based on acidification (pH: 4.5, 5.0, 5.5) and mild thermal treatments (T: 56, 58, 60°C) at different exposure times (t: 2, 4, 6 min) were optimised using the response surface methodology to improve the functional quality of carrot juice. The effects on α‐ and β‐carotenes, total antioxidant activity (TAA) and colour parameters were assessed. All combinations exhibited higher α‐ and β‐carotenes than untreated juice due to an increase on the extractability during processing. T was the most influential factor increasing carotenes as T increased. Conversely, TAA was more affected by pH. The maximum TAA was observed at pH 4.5 at 56°C. Moreover, samples with the lowest pH were the most luminous with highest a* and b*. The combination of pH 4.5 at 60°C, 4 min simultaneously showed high carotenes and TAA, resulting a good alternative to improve the functional quality and colour of carrot juice.