冻干方便米饭复水品质的研究

本文采用三种不同冷冻工艺制作冻干方便米饭,通过分析其在不同温度下的复水速度和质地变化,研究影响复水品质的因素.通过研究发现冻干饭粒的孔隙越大,内部结构越松散,米淀粉的回生越小,复水就越快,质地也越好.由此提出了结构吸水和米淀粉吸水溶胀是冻干方便米饭的复水机制,通过分析这两种机制可以为改进工艺提供理论依据.     

冻干方便米饭前处理工艺参数的确定

以米与水的比例、一次浸泡温度和时间、二次浸泡温度和时间、蒸煮时间为试验因素,安排设计6因素5水平25个处理,进行正交试验,运用最新统计软件SPSS,对干燥后米饭的复水率、α-度及其感官特性,进行了综合评价,得出冻干压缩全营养方便米饭前处理的最优工艺参数。结果表明,冻干压缩全营养方便米饭前处理的最优工艺参数为:原料米与水的比例为1∶1.5;一次浸泡温度为60℃,时间为45min;二次浸泡温度为40℃,时间为45min;蒸煮时间为20min(二次)。     

基于分形理论的预冻温度对冻干猕猴桃片干燥特性及品质的影响

研究预冻温度(-20、-30、-40、-50℃)对冻干猕猴桃片干燥特性及品质的影响,运用扫描电镜和图像分析技术测试不同预冻温度下冻干猕猴桃片的微观结构,分析预冻温度对冻干猕猴桃片孔隙和分形的影响。结果表明,对于干燥特性,预冻温度越低,猕猴桃片的干燥速率越小。在品质上,预冻温度越低,猕猴桃片的硬度和脆性越大,复水比越小。从感官结果来看,-40℃和-50℃预冻下的冻干猕猴桃片的感官评分显著高于-20℃和-30℃。扫描电镜和分形分析结果表明,预冻温度越低,冻干猕猴桃片形成的孔隙越小且多,平均孔隙面积、孔隙率、平均孔隙周长和平均孔隙直径越小,结构更规则,分布更均匀。综合以上各种指标,降低预冻温度使得冻干猕猴桃片的孔隙结构更小更均匀,一定程度上能够提高冻干猕猴桃片的感官品质,但降低了干燥速率,延长干燥时间,会使得能耗增加,生产成本增加。     

冻干草莓内部孔隙率的分布及其影响的实验研究

冻干食品内部是多孔的疏松结构，针对不同预冻结速率和厚度的草莓，进行了冻干实验，采用微型CT扫描仪对冻干样品进行扫描和图像重构，计算得到了孔隙率。测量了冻干过程失水率，冻干后复水比，并且用二甲苯-二氯靛酚比色法测定了冻干前后抗坏血酸的值。结果表明：预冻结速率越快，孔隙率越小，且超速冻（速率大于10em／h）的孔隙率基本维持在一恒值10％。物料厚度越大，升华干燥速率越慢，孔隙率越大，复水比越大。8mm切片抗坏血酸保持得最好，并且孔隙率越大，抗坏血酸保持率越低。     

龙眼真空冻干与热风干燥品质比较研究

以龙眼为原料,通过实验确定预处理参数：漂烫温度和时间,护色液浓度和浸泡时间。采用热风干燥、真空冻干两种方法,对龙眼肉进行加工干制。在60℃、22h热风干燥,绝压300Pa、冷阱温度-60℃、22h真空冻干下,通过测定干制品的品质评价参数,对获得的两种产品进行比较。结果表明：真空冻干制品的色泽、外观与鲜果肉相比变化不大;维生素C含量、总糖含量损失均比热风干燥少;复水率比热风干燥好。     

浸泡温度对米饭回生特性及食用品质的影响

目的:研究浸泡温度对米饭短期回生特性的影响。方法:将粳米分别于20,35,50,65,80℃浸泡15 min,利用低场核磁共振技术、差式热量扫描仪、质构仪、色差仪等研究其蒸煮特性、热学特性、质构特性以及色差来反映其回生特性。结果:当浸泡温度为50℃,即低于淀粉糊化温度时浸泡,短期回生后,有利于米粒内水分的保持,食感最好,亮度最高,回生程度低。结论:浸泡温度低于淀粉糊化温度有利于改善其短期回生。     

切片形式对杏鲍菇真空冻结冷冻干燥特性与品质的影响

为了研究斜切、横切、纵切3种切片形态对杏鲍菇真空冻结冷冻干燥特性的影响,以新鲜的杏鲍菇为原料,比较分析不同切片形态在冻结失水率、温度、冻干耗时、冻干样品复水比、硬度、微观结构等方面的差异。结果表明:40 min真空冻结后,斜切、横切、纵切杏鲍菇片失水率分别为21.21%、20.19%、19.93%,冻结温度分别为-26.85、-26.04、-25.30℃。斜切、横切、纵切杏鲍菇片冷冻干燥耗时分别为9.5、10.4、11.6 h,冻干样品复水比分别为6.71、6.37、6.06,产品硬度分别为16.19、14.93、11.99 N,均呈现出显著差异(p0.05)。斜切、横切杏鲍菇片冻干样品微观组织孔隙较大、多孔结构蓬松,保持了鲜品原有外观形态,纵切杏鲍菇冻干片微观组织孔隙小、多孔结构致密,皱缩塌陷严重。综合研究表明,斜切是杏鲍菇真空冻结冷冻干燥工艺中切分处理的最适宜形式。研究结论可为杏鲍菇冷冻干燥加工技术优化和生产实践提供参考。     

冻干技术对米饭品质特性影响的研究

以辽粳28号作为试验对象,分别对新鲜米饭和冻干米饭复水后的感官特性、营养成分和内部结构进行了研究.比较了不同冷冻温度下进行冻干处理得到的米饭与新鲜米饭感官特性之间的区别,并对冻千米饭内部微观结构进行分析.得出结论:采用-25℃冷冻温度得到的冻千米饭感官特性与新鲜米饭最接近,且随着冷冻温度的降低米饭内部微观结构孔隙渐小且趋向均匀,复水性与冷冻温度呈负相关.     

真空冷冻干燥对牡蛎品质的影响

我国牡蛎产量丰富,除部分鲜销外很多加工为干制品,然而传统牡蛎干制品复水性差、产品附加值低。为了得到高品质的牡蛎干制品,本研究对牡蛎进行真空冷冻干燥加工,并对冻干加工牡蛎的复水性、质构和蛋白、脂肪及部分滋味成分含量的变化情况进行探讨。研究结果表明:牡蛎的共晶点和共熔点温度分别为-25℃和-17.5℃,牡蛎在-30℃~-35℃条件下预冻2 h,在冷阱温度达到-40℃后在真空度20 Pa条件下干燥15 h得到干品;与对照产品(市售蚝干)相比,冻干牡蛎复水性较好,其在20 min即可复水完全,复水比为3.68;冻干牡蛎的质构也优于对照,除脂肪含量较低外,蛋白质和几种滋味成分含量也均高于对照。由此可见,真空冻干燥不仅可以减少牡蛎干制时的蛋白损失,且能够较好保持质构和原有风味,可以用于高品质牡蛎干制品的加工。     

提高冻干山药片品质的工艺优化

为改善冻干山药片的复原率、质构、色泽以及口感,对加工过程中的烫漂、浸泡液处理方案和冻干工艺进行研究。结果表明：山药片在95℃条件下烫漂60s可防褐变,并有利于后续的浸泡和冻干;用含有5% NaCl、10%葡萄糖和10%麦芽糊精的浸泡液,在30℃条件下浸泡30min,可提高复原率;较优的冻干工艺为使用带有强对流鼓风的速冻生产线在－30℃条件下对山药片冻结,采用5℃保持7h,35℃保持2h程序冻干。该工艺生产出的山药片具有较好的复原率和感官品质。     

Effect of starch and non-starch components on water migration,microstructure, starch retrogradation and texture of flat rice noodles made from different rice varieties

Effects of starch and non-starch components on rice noodle quality, water migration during rehydration, texture, microstructure and starch retrogradation of dried rice flour and rice starch noodles made from five rice varieties with similar high amylose contents were examined. Rice noodle qualities depended mainly on starch properties and to a lesser extent on the presence of non-starch components. Elongation of rice flour noodles was lower than rice starch noodles due to the presence of non-starch components that interrupted the starch network. Non-starch components reduced cooking loss of flour noodles in some varieties. Water migration in rice flour noodles with a looser microstructure was faster than in rice starch noodles. Nuclear magnetic resonance imaging revealed different water migration speeds in rice flour noodles among varieties, related to noodle microstructure and retrogradation properties. For production of good quality rice noodles, manufacturers should consider not only amylose content but also non-starch components.     

干燥方法对方便米粉老化特性的影响

以Rapid Visco Analyser(RVA)、X-衍射和FTIR为检测手段,研究了不同干燥方法(冷冻干燥、热风干燥、微波干燥)对方便米粉老化特性的影响。结果表明,热风干燥后得到的方便米粉,其红外1 047/1 022 cm-1处吸光度比值、结晶度、糊化温度、回生值最大,表明其老化程度最大,而冷冻干燥制得的方便米粉老化程度最小,微波干燥其次。对不同干燥方法下得到的方便米粉的复水率和复水时间进行研究,冷冻干燥的复水性最好,热风干燥的复水性最差。方便米粉的复水性能,可能与其在干燥过程中的老化程度有关。     

Effects of cooking, drying and pretreatment methods on texture and starch digestibility of instant rice

Instant rice produced from a conventional process consisting of the cooking, washing and drying steps possesses poorer eating quality compared with that of freshly cooked rice. The objective of this work was therefore to study the effects of cooking, pretreatment and drying methods on microstructure, textural properties and starch digestability of instant rice after rehydration; jasmine white rice was chosen as a test material. Conventional boiling method and electric rice cooking were selected as the methods to prepare cooked rice. In the case of boiling, cooked rice was frozen at −20 °C or cooled at 4 °C for 24 h prior to drying, while the cooked rice from an electric rice cooker was washed with ambient or cool water for 30 s prior to drying. After pretreatment the cooked rice was dried either by freeze drying or hot air drying at 80 °C. Based on the scanning electron microscopic results it was found that the cooking, pretreatment and drying methods all affected the rice morphology. The hardness and stickiness of instant rice after rehydration were lower for samples prepared from the rice cooker than those of freshly cooked rice, while both textural properties appeared to be improved significantly for the samples from boiling. The texture of the freeze-dried products was not different from that of the air-dried one. The freezing pretreatment provided the texture and glycemic index of instant rice after rehydration similar to those of the freshly cooked rice. On the other hand, the cooling pretreatment resulted in the harder texture and higher glycemic index of the samples.     

Mild steam treatment: Enhancing the rehydration performance of instant rice noodles by changing the physicochemical properties and gel structure of rice starch

The “instant” quality of instant rice noodles is significantly affected by slow rehydration during cooking. This happens as a result of the native rice starch's low ability to gelatinize as well as the high shear and pressure utilized in industries during the widely used extrusion molding process. In order to address this issue, the rice flour was pretreated with mild steam (MS) technology. The results revealed that the rehydration qualities of the rice noodles that were extruded from the steam-treated flour significantly improved. There was a reduction of 25.5% in the rehydration time, from 443 to 330 s. The MS-treated rice starch's peak viscosity increased to 4503 from 4044 mPa/s. Decreases in gelatinization enthalpy (ΔH) and short-range ordering also suggest a reduction in difficulty in accomplishing starch gelatinization. Scanning electron microscopy studies showed particle aggregation increased as the treatment duration lasted longer. In conclusion, our findings indicate that we successfully addressed the issue of slow rehydration in instant rice noodles while presenting a novel approach for their manufacturing in the manufacturing sector.     

Effect of freezing temperature on rehydration and water vapor adsorption characteristics of freeze-dried rice porridge

Effect of freezing temperature of rice porridge on quality properties of freeze-dried rice porridge was investigated at various temperatures. Slow freezing produced porous freeze-dried rice porridges with large pores and more brittle structure than rapid freezing. All the quality properties tested were greatly influenced by both freezing temperature and temperature for the property evaluation. Both the initial rehydration ratio and the dissolution time of the freeze-dried rice porridge decreased with increase in water temperature. Results on the effect of freezing temperature on rehydration ratio and dissolution time indicated slow freezing is more preferable for the freeze-dried rice porridge. The Peleg model was fitted better than the Singh and Kulshrestha model to explain the water vapor adsorption kinetics. The activation energy for the water vapor adsorption of the freeze-dried rice porridge determined by using the Peleg model ranged 16.2-23.1 kJ/mol depending on the freezing temperature.     

保鲜方式对鲜湿米粉品质的影响

通过分析鲜湿米粉的菌落总数、糊化特性、水分含量、色泽、提取液吸光度、质构特性及感官评分的变化,并观察鲜湿米粉凝胶微观结构,研究酸浸、水浴及酸浸+水浴处理对鲜湿米粉品质的影响。结果表明,与空白组相比,水浴组、酸浸组及酸浸+水浴组鲜湿米粉的淀粉糊黏度、衰减值和回生值显著（P<0.05）降低。水浴处理使鲜湿米粉的质构特性及感官评分得到提升,保质期延长。酸浸处理使鲜湿米粉的水分含量、色泽、提取液吸光度及黏性显著（P<0.05）增大,咀嚼硬度及弹性显著（P<0.05）减小,随着贮藏时间的延长菌落总数增加较慢,但综合品质劣变迅速,到后期凝胶结构破坏严重,感官评分显著（P<0.05）降低。酸浸+水浴处理使鲜湿米粉的初始品质得到提升,但弹性略小于水浴处理组,随着贮藏时间的延长菌落总数增加最慢,并且能始终保持较好的色泽、质构特性及感官评分。综合鲜湿米粉质构特性及感官评分,酸浸+水浴组的鲜湿米粉品质最好。     

Innovative hybrid strategy for efficient production of high-quality freeze-dried instant noodles: Combination of laser with leavening agent

The present study was carried out to improve the drying efficiency and quality of freeze-dried instant noodles by a novel hybrid pretreatment method that combines laser puncturing along with use of a leavening agent mixture. The influence of several variants of this combined treatment on drying time, energy consumption, rehydration behavior and pasting properties of dried noodles as well as the quality parameters of soaked noodles were examined. Results demonstrate that the intervention of laser puncturing treatment and the addition of leavening agent mixture are all positive on reducing drying time and energy consumption of noodles, but the drying enhancement effect of puncturing treatment is better. Combining laser puncturing treatment with leavening agent mixture can further reduce drying time of noodles by up to 34.15% and energy consumption by up to 33.17%. Although all single treatment methods can improve the quality of products including soaking time, rehydration rate and hardness, the effect is unsatisfactory. Hybrid strategies are found to have a synergistic effect on the production of high-quality freeze-dried instant noodles and according to the sensory evaluation results, the optimum conditions are as follows: 0.1  mm perforation diameter, 10 mm spacing between perforations, 2 mm depth and 3% leavening agent mixture (on flour basis).Industrial relevanceDifficult rehydration of products and high energy consumption of the production process are the key issues that limit the industrial production of freeze-dried instant noodles. Laser puncturing treatment and adding a leavening agent mixture can increase the contact area between freeze-dried noodles and water and enrich the internal porous structure of freeze-dried noodles, respectively, which promotes the mass production of high-quality freeze-dried instant noodles.     

以短生育期籼稻为原料的鲜湿米粉食用品质与消化特性研究

以早、晚季种植的短生育期籼米品种(CPPC16、CPPC18、CPPC38、CPPC52)为对象,对大米淀粉物化特性进行比较;并对8种短生育期大米加工的鲜湿米粉的食用品质和消化特性进行探究。结果表明：早季稻与晚季稻相比较,早季稻的直链淀粉含量、回生值与糊化温度高于同品种的晚季稻。大米淀粉特性与鲜湿米粉质构特性相关性分析中,直链淀粉含量、回生值与最终黏度、水溶性与质构指标呈显著(P<0.05)或极显著正相关(P<0.01),膨胀力与质构指标呈显著负相关(P<0.05)。对比两种鲜湿米粉加工专用米种,短生育期品种中以早季18号的综合评分最高(0.93),略低于桂朝米的1.07,高于阳春米的0.87。     

方便米饭老化特性研究

研究了方便米饭存放过程中的老化特性,结果表明：方便米饭在存放过程中晶体结构有所变化,但结晶度变化不大;起始玻璃化温度上升,玻璃化温度范围缩小,晶体熔解温度稍有上升;复水扩散系数下降,起始玻璃化温度的升高对扩散系数的影响较大,存放10天后,起始玻璃化温度是影响方便米饭速食性能和老化的主要因素。