Effects of microwave and hot‐air drying methods on colour, β‐carotene and radical scavenging activity of apricots

The effects of drying by microwave and convective heating at 60 and 70 °C on colour change, degradation of β‐carotene and the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH) scavenging activity of apricots were evaluated. Microwave heating reduced significantly the drying time (up to 25%), if compared with convective one, also owing to the higher temperature reached during the last phase of the process, as monitored by infrared thermography. Colour changes of apricot surface, described with lightness and hue angle, in both drying methods followed a first‐order reaction (0.927 ≤ R² ≤ 0.996). The apricots dried by microwave were less affected by the darkening phenomena. The evolution of β‐carotene in fresh apricots (61.2 ± 5.6 mg kg^?1 d.w.) during the drying highlighted a wider decrease (about 50%) when microwave heating was employed for both the temperatures used. Radical scavenging activity increased (P < 0.05) in all dried samples except for hot‐air dried apricots at 60 °C.     

Effects of maltodextrin level,frying temperature and time on the moisture,oil and beta‐carotene contents of vacuum‐fried apricot slices

Response surface methodology was used to investigate the effects of frying temperature, time and maltodextrin (MD) levels on the moisture, oil and beta‐carotene contents of the vacuum‐fried apricot slices. Based on the results, the moisture content of vacuum‐fried apricot slices decreases with increasing frying temperature and frying time. Generally, the oil content of vacuum‐fried apricot slices decreases with decreasing frying temperature and frying time. The beta‐carotene content of vacuum‐fried apricot slices increases with increasing frying temperature. But the trend of increase in the beta‐carotene content of the product with frying temperature was higher at lower MD level. When processing vacuum‐fried apricot slices, a frying temperature of 100 °C, frying time of 72.5 min and an MD level of 70% must be used to achieve a product of acceptable moisture, oil and beta‐carotene contents.     

Liposomes encapsulating beta‐carotene produced by the proliposomes method: characterisation and shelf life of powders and phospholipid vesicles

The objective of this study was to investigate the feasibility of producing proliposomes incorporating beta‐carotene by spray drying and to assess the capacity of the liposomes produced by the hydration of the dry phospholipid particles to preserve the encapsulated carotenoid. Powders containing beta‐carotene, hydrogenated phosphatidylcholine and sucrose were obtained and characterised in terms of crystallinity, morphology, thermal behaviour, density, solubility and hygroscopicity. The preservation of beta‐carotene in the powder was evaluated for two storage conditions under normal atmosphere and vacuum. The proliposome was highly soluble, with all components embedded in the matrix and capable of preserving more than 90% of the incorporated beta‐carotene for 60 days of refrigerated storage under vacuum. The liposome dispersions maintained their average size, polydispersity index and zeta potential for 100 days of storage. After 60 days, the degradation of encapsulated beta‐carotene was minimal, and the colour of the dispersions was preserved.     

Effect of different drying methods on drying characteristics,colour, total phenolic content and antioxidant capacity of Goldenberry (Physalis peruviana L.)

In this study, the effects of convective, microwave and microwave–convective drying methods on the drying characteristics, colour, total phenolic content and antioxidant capacity of goldenberry fruits were investigated. To select the most appropriate thin‐layer drying model for drying treatments, nine mathematical drying models were fitted to the experimental data. Based on the statistical tests used for evaluation, the Midilli et al. and Wang and Singh models were considered the best models to describe the drying behaviours of goldenberry fruits in all drying methods. The colour values (L*, a* and b*) of fresh fruit were decreased by drying. Compared with the fresh sample, the dried samples exhibited a 64–75% and 65–75% decrease in total phenolic content and antioxidant capacity, respectively. Among the different drying treatments, the values closest to those of fresh samples with respect to colour values, total phenolic content and antioxidant capacity were achieved with the 160 W microwave drying method.     

干燥方法对杏肉全粉品质及抗氧化活性的影响

采用微波干燥(MD)、热风干燥(HAD)、微波真空干燥(MVD)、微波对流干燥(MCD)4种干燥方法制备纯天然杏肉全粉,比较了干燥方法对杏肉全粉营养成分、物理特性、感官品质和抗氧化能力的影响。结果表明,干燥方法对杏肉全粉品质的影响显著(P0.05),MVD和MCD 2种方法干燥的杏肉全粉总糖和还原糖保留较好,并且MCD法干燥的产品总酚和VC损失最少,而HAD法对总酸的保留最好;MD法制备的产品吸湿性和结块度最低,MCD法制备的产品堆积密度和休止角最小,且获得的感官评价分值最高(95.2分);制备的杏肉全粉还原力及清除DPPH、超氧阴离子和羟自由基的能力呈显著的量效依赖性且存在显著差异,MVD法制备的产品对DPPH自由基清除能力最强,而MCD对羟自由基、超氧阴离子自由基的清除能力最强,还原力也最大,分别为88.5%,85.1%,1.98。     

热泵干燥温度对柿子片干燥特性及品质的影响

目的:探明热泵干燥温度对柿子片干燥特性和品质的影响。方法:以柿子为原料,研究干燥温度对柿子片干燥时间、干燥速率,以及干制品色泽、硬度、复水率、单宁、总糖、维生素C和总酸的影响。结果:当热泵干燥温度为65℃时,柿子片干燥速度快,干燥时间短,此时干燥产品色泽鲜艳,与鲜果色泽相近,复水性能好,硬度最低,口感最好,总酸和维生素C含量最高,总糖等营养成分含量适中。结论:柿子片的最适热泵干燥温度为65℃。     

Microencapsulation of β‐carotene using native pinhão starch,modified pinhão starch and gelatin by freeze‐drying

Beta‐carotene was microencapsulated by freeze‐drying using native pinhão starch, hydrolysed pinhão starch 6 dextrose equivalent (DE), hydrolysed pinhão starch 12 DE and the mixture of these materials with gelatin as coating material. The purpose of this research was to produce and characterize these microcapsules. The capsules’ efficiency, surface content, moisture, morphology, solubility, particle size and glass transition temperature were analysed. The hydrolysed pinhão starch 12 DE showed the highest total β‐carotene content and the lowest surface β‐carotene content, unlike the native starch. Using scanning electron microscopy, it was observed that all microcapsules presented undefined shapes. The samples with gelatin had wider particle size distribution, higher diameters, lower solubility and higher glass transition temperature when compared with other the samples. Results obtained suggest that the modified pinhão starch can be considered as potential wall material for encapsulation of β‐carotene.     

Single-layer drying characteristics and colour kinetics of red chilli

Single‐layer drying experiments were conducted under controlled conditions of temperature, relative humidity (RH) and air velocity to find out the effects of drying conditions and blanching on the drying rate and colour of Thai red chilli. Drying rate increased with an increase of drying air temperature and a decrease of RH. Air temperatures above 65 °C affected the colour of red chilli. Red chilli should be dried at an air velocity equal to or just above 0.50 m s^?1. Above this value, the drying rate becomes independent of air velocity. RH and air velocity have no effect on the colour of red chilli. Faster drying rate and higher colour value was found for the blanched sample rather than the unblanched sample. The Newton and the Page equations were fitted to the experimental data. The Newton equation was found to describe the single‐layer drying of red chilli better than the Page equation.     

Compositional variation in β‐carotene content,carbohydrate and antioxidant enzymes in selected banana cultivars

Banana is one of the most important tropical fruits, and India ranks first in its world production. Banana cultivars rich in provitamin A carotenoids may offer a potential food source for alleviating vitamin A deficiency, particularly in developing countries. With a view to exploit banana peels as a source of valuable components, in the present study, proximate composition, carotenoids, beta‐carotene and some anti‐oxidative enzymes as well as carbohydrate content of selected Indian banana varieties were determined. Karpooravalli cultivar of banana showed the maximum accumulation of carotenoid content in the non‐edible (68 μg g^?1 d.w.) portion of banana, while being the second highest in beta‐carotene content (143.12 μg per 100 g). However, Red Banana ranked highest in total carotenoid contents for pulp (4 μg g^?1 d.w.) and beta‐carotene was estimated to be the highest in the case of peels (241.91 μg per 100 g) and in pulp (117.2 μg per 100 g). Karpooravalli cultivar of banana is also rich in carbohydrate content in terms of total starch (1786.0 μg g^?1 d.w. in peels and 544.85 μg g^?1 d.w. in pulp) and sugars (53.53 μg g^?1 d.w. in peels and 39.05 μg g^?1 d.w. in pulp). The catalase enzyme activity in these peels ranged from 5.66 to 35.57 nmol min^?1 mg^?1 proteins and was found at a higher level in cultivar Poovan, while the ascorbate peroxidase showed the range of 2.25 to 6.22 μmol min^?1 mg^?1 proteins. The peels of cultivars Red Banana and Karpooravalli are rich source of bioactive compounds, such as carotenoids (beta‐carotene), anti‐oxidative enzymes and carbohydrate contents.     

热风干燥条件对中式腊肠微生物及质构特性的影响

采用4种不同的工艺干燥中式腊肠,通过测定干燥过程中腊肠水分含量与活度、微生物菌群数量,并采用TPA法测定不同干燥工艺加工过程中腊肠的硬度、弹性、咀嚼性等质构特性的变化趋势,分析干燥条件对腊肠质量的影响。结果表明:干燥工艺对微生物的影响差异显著(P<0.05),对产品质构特性也有很大的影响。升温干燥模式制作的腊肠微生物数量最低,但质构偏硬;先高温后低温干燥模式制作的腊肠微生物数量较高,但质构最软;五段变温干燥模式和恒温干燥模式差异不显著(P>0.05),与文献[5]的传统工艺生产的腊肠微生物特性与质构特性差异不显著(P>0.05)。三段式升温烘烤模式相对于其他干燥工艺能更好的抑制微生物生长,更适用于中式腊肠的生产。     

Drying characteristics and thermal degradation kinetics of hardness,anthocyanin content and colour in purple‐ and red‐fleshed potato (Solanum tuberosum L.) during hot air drying

Purple‐fleshed potatoes (PFP) and red‐fleshed potatoes (RFP) were dried using hot air. The hardness, anthocyanin content and colour in PFP and RFP during drying were evaluated at 60, 70 and 80 °C. The hardness was characterised by a softening stage in the early drying period, followed by a hardening stage. The times to reach at the transition were 420, 300 and 240 min at 60, 70 and 80 °C, respectively, for PFP, and 480, 360 and 240 min for RFP. However, the moisture content of both PFP and RFP at the transition time was identical at 0.3 (d.b.). The two stages of hardness changes were well described by combining two modified first‐order kinetics models. The activation energy (E_a) for the degradation of anthocyanin in PFP and RFP was 25.12 and 28.43 kJ mol^?1, respectively. The E_a values demonstrated that the thermal sensitivity of PFP was higher than that of RFP.     

基于温度控制的猕猴桃片微波真空干燥特性研究

目的：研究温度控制下猕猴桃片微波真空干燥特性,并确定其最佳数学干燥模型。方法：以猕猴桃片为原料,利用自制的温度自适应微波真空干燥机干燥猕猴桃片,研究不同控制温度、真空度和微波功率密度对其干燥特性和水分有效扩散系数的影响,利用SPSS 19.0软件将试验数据与6个常用的薄层干燥模型进行非线性拟合,以确定系数R²,均方根误差R_MSE及卡方χ²作为评价指标,筛选出最佳干燥模型。结果：温度控制条件下的猕猴桃片的微波真空干燥为降速干燥过程,无明显恒速阶段。在试验范围内,控制温度与真空度对猕猴桃片的干燥特性影响显著,控制温度越高、真空度越大,物料的干燥速率越大;根据费克第二定律计算出猕猴桃于温度控制下微波真空干燥过程中的水分有效扩散系数,且随着控制温度与真空度的增大而增大,其最大值为6.814 97×10^-6 m²/s,平均活化能为70.77 kJ/mol。所选用的6个模型中,Two-term exponential模型具有最大的确定系数R²（0.999 9）,最低的R_MSE（0.002 02）和最小的χ²（0.000 30）,是猕猴桃片温度控制下微波真空干燥的最佳模型。结论：控制温度、真空度对猕猴桃片微波真空干燥特性、干燥速率和水分有效扩散系数具有显著影响。在试验范围内,Two-term exponential模型的拟合度最高,可有效描述猕猴桃片温度自适应下微波真空干燥过程中的水分随时间的变化规律。     

干燥方式和温度对草莓果粉性质及多酚含量的影响

本文主要研究了冷冻干燥、热风干燥、真空干燥方式及干燥温度对草莓果粉性质及多酚含量的影响。用50%甲醇和70%丙酮两步法提取可萃取多酚（EPP）;甲醇/H2SO4水解残渣获得不可萃取多酚（NEPP）。Folin-phenol试剂法测定多酚的含量;用色差计测定草莓果粉的L*、a*、b*值;在665 nm处测定其上清液的透光率。结果表明冷冻干燥草莓果粉的EPP和原花青素含量最高,随着干燥温度的升高,草莓果粉中EPP的含量降低,而干燥温度对NEPP的含量影响与EPP相反,各处理中TPP的含量变化不显著。干燥方式和温度对草莓果粉的溶解指数影响不明显。干燥温度升高,果粉上清液的透光率以及草莓果粉的L*、a*和b*值明显降低。总之,冷冻干燥方式可很好地保留草莓中EPP和原花青素含量以及原料本身的色泽。      

Influence of particle characteristics and E/Z‐isomer ratio on the colour of concentrated β‐carotene dispersions

The influence of particle concentrations (0.02–0.40%), mean particle sizes (0.45–1.5 μm) and all‐E‐isomer ratios (95–30%) on the CIELAB colour coordinates (L*, a*, b*) of concentrated β‐carotene dispersions was investigated. Particle concentration between 0.06% and 0.40% had a slight impact on the colour parameters. However, with decreasing the mean particle size from 1.50 to 0.45 μm, there were increases in ΔL* = 8.0, in Δa* = 2.26 and in Δb* = 13.1. And with decreasing the all‐E‐isomers ratio from 95% to 30%, there were increases in ΔL* = 8.66, in Δb* = 17.51 but decrease in Δa* = 7.42. The experimental results were explained in terms of the scattering and absorption of light by dispersions. These findings have important implications for food industry as they offer a means to control and optimise the colour of food dispersions.     

干燥方式对牛肝菌干燥特性、品质及抗氧化能力的影响

以武陵山区新鲜牛肝菌为原料,采用真空冷冻干燥、热风干燥(60,70,80℃)、微波+60℃热风干燥以及超声波+60℃热风干燥6种不同方式对牛肝菌进行干燥处理,考察干燥方式对牛肝菌色泽、干燥速率、多酚、黄酮及多糖含量的影响,并进一步分析了6种干燥产品的抗氧化活性。研究结果表明,真空冷冻干燥产品颜色变化较小,微波预处理及超声波预处理加深了牛肝菌的颜色;微波+热风干燥法的干燥速率最快,干燥时间为5.5h,干燥用时最短,而真空冷冻干燥能最大程度地保留牛肝菌的活性物质,其多糖、黄酮、多酚的含量分别为147.24,3.70,6.69mg/g,且显示出最强的抗氧化活性,其次是60℃热风干燥。考虑到生产成本,60℃热风干燥是牛肝菌干燥最为合理的方式。     

烘干温度对铁皮石斛茎多糖抗氧化活性影响的研究

本实验主要研究了不同烘干温度对铁皮石斛茎多糖得率和抗氧化活性的影响.结果表明:不同温度条件下,40 ℃热风烘干后铁皮石斛茎多糖得率最高,达到45.93％且抗氧化能力最强,当溶液浓度为2.5 mg/mL时,对DPPH自由基、羟基自由基、超氧阴离子自由基的消除率分别为46.88％、56.44％、49.02％.说明烘干温度会...     

Encapsulation of Beta‐carotene in Lipid Microparticles Stabilized with Hydrolyzed Soy Protein Isolate: Production Parameters,Alpha‐tocopherol Coencapsulation and Stability Under Stress Conditions

The objectives of this research were to study the encapsulation of beta‐carotene (BC) in solid lipid microparticles (SLM) of palm stearin (PS) and stabilized with hydrolyzed soy protein isolate (HSPI), and also to investigate the effect of alpha‐tocopherol (TOC) addition to the systems. Through the characterizations of SLM produced with different formulations, it was verified that systems with 5% (w/v) PS, 1.0% (w/v) HSPI, and 0.3% (w/v) xanthan gum (XG) presented the highest stability, with average diameters of approximately 1.2 μm. This formulation was applied for the production of BC‐loaded SLM, with different concentrations of TOC. In SLM containing TOC, nearly 75% of encapsulated BC was preserved after 45 d of storage. The kinetic profiles for degradation of encapsulated BC were fitted to a pseudo‐1st‐order model, and the results showed that the main difference among the systems with different BC:TOC ratios was the residual concentration of BC. The stability of the BC‐loaded SLMs was also studied after stress conditions, and the results showed that the SLMs were able to support thermal treatments over 60 °C but presented low stability after different ionic strength stresses.