硬脂酰乳酸钙的制备工艺研究

硬脂酰乳酸钙是一种阴离子乳化剂,在食品加工中有广泛用途。以L-乳酸和硬脂酸为原料,用一步法制备了硬脂酰乳酸钙,以酯值为指标,研究了L-乳酸与硬脂酸的摩尔比、反应时间、反应温度、催化剂用量等因素对反应的影响,并用红外光谱法鉴定了产品。结果表明,制备硬脂酰乳酸钙的最佳工艺条件为:L-乳酸与硬脂酸的摩尔比为1.8∶1,反应温度为110℃,催化剂用量为1.0%,反应时间为4h。实验结果将对硬脂酰乳酸钙的进一步应用提供基础数据。      

硬脂酰乳酸钙的制备工艺研究

硬脂酰乳酸钙是一种阴离子乳化剂,在食品加工中有广泛用途。以L-乳酸和硬脂酸为原料,用一步法制备了硬脂酰乳酸钙,以酯值为指标,研究了L-乳酸与硬脂酸的摩尔比、反应时间、反应温度、催化剂用量等因素对反应的影响,并用红外光谱法鉴定了产品。结果表明,制备硬脂酰乳酸钙的最佳工艺条件为:L-乳酸与硬脂酸的摩尔比为1.8∶1,反应温度为110℃,催化剂用量为1.0%,反应时间为4h。实验结果将对硬脂酰乳酸钙的进一步应用提供基础数据。     

利用L-阿拉伯糖结晶母液回收L-阿拉伯糖的研究

L-阿拉伯糖母液是生产L-阿拉伯糖之后残余的糖液,其L-阿拉伯糖含量54%~57%,直接进行二次结晶十分困难,作为废料处理又造成极大的浪费。采用脱色、离子交换脱盐与真空结晶相结合的方法能够提高从L-阿拉伯糖母液回收L-阿拉伯糖的回收率。本工艺中L-阿拉伯糖母液,经过脱色后,透光度由20.6%提高至83.5%;经过离子交换脱盐后电导率降低90%;浓缩、真空结晶得到L-阿拉伯晶体含量84.1%;重结晶后,L-阿拉伯糖含量98.5%。采用本工艺可以将L-阿拉伯糖的收率提高30%以上,回收得到的晶体经过重结晶后可以得到高品质产品。     

乳酸钙的功能和应用

介绍了钙的生理作用,补钙的重要性,由于乳酸钙的溶解性质,作为补钙的钙源较其他化合物处于优势地位,并参照原始文献选载了一些对比资料．     

牡蛎壳合成L-乳酸钙的工艺研究

对牡蛎壳制备L-乳酸钙的工艺进行了详细研究.试验结果表明,最佳条件为牡蛎壳在900℃下灰化120 min,2.00 g灰分加水40.0 mL制成石灰乳,石灰乳中加入12.00 mL 80%的L-乳酸,在60℃发生中和反应,经过滤、结晶、洗涤后在55℃下干燥制得白色粉末产品.在此工艺条件下产率为92.45%,L-乳酸钙含量为89.41%.     

L-鸟氨酸盐酸盐结晶新工艺研究

探索通过电导率仪在线调控结晶过程的可行性,考察添加晶种、消晶水对晶体晶形及晶体平均粒径的影响。实验发现:可以根据电导率的变化趋势比较直观地了解结晶速率的变化情况,进而可以对结晶过程进行调控。5min时加2%的晶种,晶种平均粒径为134·59μm,结晶时间4h,最终得到晶体产品纯度99%,收率86·3%,粒径270·6μm。      

L-鸟氨酸-阿司匹林复合盐结晶工艺研究

以纯度和晶体平均粒径为关键指标,研究了L-鸟氨酸-阿司匹林复合盐(L-ornithine-aspirin compound salt,以下简称"LOA")溶析结晶操作策略,如晶种加入策略、溶析剂加入量及流加速率等。根据LOA在乙醇/水二元溶剂体系中的溶解度曲线,将其结晶过程分成了5个阶段。结果表明,乙醇和LOA溶液的体积比为0.8时加入4%的晶种以及第III阶段适当降低乙醇流加速率有利于晶体生长。得到的产品纯度为97.9%,平均粒径为270.6μm。     

旋光法测定L—乳酸钙中L—型的含量

采用旋光法对L-乳酸钙中具有生物活性的L-型含量进行了定量测定,结果表明,对纯度较高的乳酸钙的L-型鉴定有较高的准确度。     

分离米渣后发酵乳酸钙提取工艺的研究

以大米为原料，将米渣分离后进行发酵乳酸钙提取工艺的研究。针对成熟发酵液中影响蛋白质沉淀因素进行试验，从而确定了一个比较适宜的乳酸钙提取工艺，使乳酸钙提取收率达８０％以上，通过与未离米渣的发酵相比其乳钙结晶收得率提高９．９４％，提取收得率提高９．３１％。     

Chemical changes that predispose smoked Cheddar cheese to calcium lactate crystallization

We have observed a high incidence of calcium lactate surface crystals on naturally smoked Cheddar cheese in the retail marketplace. The objective of this study was to identify chemical changes that may occur during natural smoking that render Cheddar cheese more susceptible to calcium lactate crystal formation. Nine random-weight (approximately 300 g) retail-packaged samples of smoked Cheddar cheese were obtained from a commercial manufacturer immediately after the samples were smoked for about 6 h at 20°C in a commercial smokehouse. Three similarly sized samples that originated from the same 19.1-kg block of cheese and that were not smoked were also obtained. Within 2 d after smoking, 3 smoked and 3 control (not smoked) samples were sectioned into 5 subsamples at different depths representing 0 to 2, 2 to 4, 4 to 6, 6 to 8, and 8 to 10 mm from the cheese surface. Six additional smoked cheese samples were similarly sectioned at 4 wk and again at 10 wk of storage at 5°C. Sample sections were analyzed for moisture, l(+) and d(−) lactate, pH, and water-soluble calcium. The effects of treatment (smoked, control), depth from cheese surface, and their interactions were analyzed by ANOVA according to a repeated measures design with 2 within-subject variables. Smoked samples contained signficantly lower moisture and lower pH, and higher total lactate-in-moisture (TLIM) and water-soluble calcium-in-moisture (WSCIM) than control cheeses. Smoked samples also contained significant gradients of moisture, pH, TLIM, and WSCIM, with lower moisture and pH, and higher TLIM and WSCIM, occurring at the cheese surface. Gradients of moisture were still present in smoked samples at 4 and 10 wk of storage. In contrast, the pH, TLIM, and WSCIM equilibrated and showed no gradients at 4 and 10 wk. The results indicate that calcium and lactate in the serum phase of the cheese were elevated because of smoking, especially at the cheese surface immediately after smoking treatment, which presumably predisposes the smoked cheeses to increased susceptibility to calcium lactate surface crystallization.     

Compositional factors associated with calcium lactate crystallization in smoked Cheddar cheese

Previous researchers have observed that surface crystals of calcium lactate sometimes develop on some Cheddar cheese samples but not on other samples produced from the same vat of milk. The causes of within-vat variation in crystallization behavior have not been identified. This study compared the compositions of naturally smoked Cheddar cheese samples that contained surface crystals with those of samples originating from the same vat that were crystal-free. Six pairs of retail samples (crystallized and noncrystallized) produced at the same cheese plant on different days were obtained from a commercial source. Cheese samples were 5 to 6 mo old at the time of collection. They were then stored for an additional 5 to 13 mo at 4°C to ensure that the noncrystallized samples remained crystal-free. Then, the crystalline material was removed and collected from the surfaces of crystallized samples, weighed, and analyzed for total lactic acid, l(+) and d(−) lactic acid, Ca, P, NaCl, moisture, and crude protein. Crystallized and noncrystallized samples were then sectioned into 3 concentric subsamples (0 to 5 mm, 6 to 10 mm, and greater than 10 mm depth from the surface) and analyzed for moisture, NaCl, titratable acidity, l(+) and d(−) lactic acid, pH, and total and water-soluble calcium. The data were analyzed by ANOVA according to a repeated measures design with 2 within-subjects variables. The crystalline material contained 52.1% lactate, 8.1% Ca, 0.17% P, 28.5% water, and 8.9% crude protein on average. Both crystallized and noncrystallized cheese samples contained significant gradients of decreasing moisture from center to surface. Compared with noncrystallized samples, crystallized samples possessed significantly higher moisture, titratable acidity, l(+) lactate, and water soluble calcium, and significantly lower pH and NaCl content. The data suggest that formation of calcium lactate crystals may have been influenced by within-vat variation in salting efficacy in the following manner. Lower salt uptake by some of the cheese curd during salting may have created pockets of higher moisture and thus higher lactose within the final cheese. When cut into retail-sized chunks, the lower salt, higher moisture samples contained more lactic acid and thus lower cheese pH, which shifted calcium from the insoluble to the soluble state. Lactate and soluble calcium contents in these samples became further elevated at the cheese surface because of dehydration during smoking, possibly triggering the formation of calcium lactate crystals.     

Surface roughness and packaging tightness affect calcium lactate crystallization on Cheddar cheese

Calcium lactate crystals that sometimes form on Cheddar cheese surfaces are a significant expense to manufacturers. Researchers have identified several postmanufacture conditions such as storage temperature and packaging tightness that contribute to crystal formation. Anecdotal reports suggest that physical characteristics at the cheese surface, such as roughness, cracks, and irregularities, may also affect crystallization. The aim of this study was to evaluate the combined effects of surface roughness and packaging tightness on crystal formation in smoked Cheddar cheese. Four 20-mm-thick cross-section slices were cut perpendicular to the long axis of a retail block (~300 g) of smoked Cheddar cheese using a wire cutting device. One cut surface of each slice was lightly etched with a cheese grater to create a rough, grooved surface; the opposite cut surface was left undisturbed (smooth). The 4 slices were vacuum packaged at 1, 10, 50, and 90 kPa (very tight, moderately tight, loose, very loose, respectively) and stored at 1°C. Digital images were taken at 1, 4, and 8 wk following the first appearance of crystals. The area occupied by crystals and number of discrete crystal regions (DCR) were quantified by image analysis. The experiment was conducted in triplicate. Effects of storage time, packaging tightness, surface roughness, and their interactions were evaluated by repeated-measures ANOVA. Surface roughness, packaging tightness, storage time, and their 2-way interactions significantly affected crystal area and DCR number. Extremely heavy crystallization occurred on both rough and smooth surfaces when slices were packaged loosely or very loosely and on rough surfaces with moderately tight packaging. In contrast, the combination of rough surface plus very tight packaging resulted in dramatic decreases in crystal area and DCR number. The combination of smooth surface plus very tight packaging virtually eliminated crystal formation, presumably by eliminating available sites for nucleation. Cut-and-wrap operations may significantly influence the crystallization behavior of Cheddar cheeses that are saturated with respect to calcium lactate and thus predisposed to form crystals.     

An improved model of the seeded batch crystallization of glucose monohydrate from aqueous solutions

The current research has produced an accurate model of the non-nucleating seeded batch crystallization of glucose monohydrate which includes complex phenomena including crystal growth rate dispersion and the effect of the mutarotation reaction. The model is able to predict the population density of crystals in the batch as a function of particle size and batch time, n=n(L,t) as well as total glucose concentration in the mother liquor and the fraction of glucose in the α-d-glucopyranose form. A previous model of similar systems was limited by considering only systems with monosize seed crystals, and where growth rate dispersion had a negligible effect on the particle size distribution. Because of the nature of the ‘common history’ crystals that are produced by the growth of glucose monohydrate, the modifications required to the model to account for these additions to the model are remarkably simple. By predicting the full population density the model produces an accurate mass balance for the crystallization process, since the second moment of the crystal size distribution (CSD) may be calculated analytically at every point in the simulation. This enables the competitive kinetics between the rate of crystal mass deposition of α-glucose and the rate of production of α-glucose via the mutarotation reaction to be more accurately accounted for, and hence the significance of the mutarotation reaction on the crystal growth to be more accurately predicted.     

Nonstarter lactic acid bacteria and aging temperature affect calcium lactate crystallization in cheddar cheese

The occurrence of unappetizing calcium lactate crystals in Cheddar cheese is a challenge and expense to manufacturers, and this research was designed to understand their origin. It was hypothesized that nonstarter lactic acid bacteria (NSLAB) affect calcium lactate crystallization (CLC) by producing D(-)-lactate. This study was designed to understand the effect of NSLAB growth and aging temperature on CLC. Cheeses were made from milk inoculated with Lactococcus lactis starter culture, with or without Lactobacillus curvatus or L. helveticus WSU19 adjunct cultures. Cheeses were aged at 4 or 13 degrees C for 28 d, then half of the cheeses from 4 and 13 degrees C were transferred to 13 and 4 degrees C, respectively, for the remainder of aging. The form of lactate in cheeses without adjunct culture or with L. helveticus WSU19 was predominantly L(+)-lactate (> 95%, wt/wt), and crystals were not observed within 70 d. While initial lactate in cheeses containingL. curvatus was only L(+)-lactate, the concentration of D(-)-lactate increased during aging. After 28 d, a racemic mixture of D/L-lactate was measured in cheeses containing L. curvatus; at the same time, CLC was observed. The earliest and most extensive CLC occurred on cheeses aged at 13 degrees C for 28 d then transferred to 4 degrees C. These results showed that production of D(-)-lactate by NSLAB, and aging temperature affect CLC in maturing Cheddar cheese.     

Isothermal batch crystallization of alpha-lactose: A kinetic model combining mutarotation,nucleation and growth steps

A kinetic model combining first-order differential equations of the three consecutive steps of lactose crystallization, i.e., mutarotation, nucleation and crystal growth rate, was developed. Numerical solutions successfully fitted the variations of crystal mass growth rate as a function of lactose concentration during unseeded isothermal batch crystallization, at different initial lactose concentrations and temperatures. The model allowed the induction phase and the influence of seeding to be simulated by taking into account the dependency of crystal growth rate on total crystal surface area and, consequently, on nucleation rate. The proposed model highlights the large influence of the mutarotation step, even in unseeded crystallization kinetics. The effects of high lactose supersaturations that prevail at industrial scale during whey powder manufacturing and the effects of alkaline pH (9.5) on lactose crystallization kinetic were successfully predicted.     

Automating batch processes

Batch processes are a suitable means of describing milk and dairy processes and therefore suitable applications for the emerging batch control systems standards. These involve powerful recipe handling, scheduling and information management concepts. Recipes are regarded in these standards as transportable objects incorporating formulae, equipment requirements, process procedures and instructions for data acquisition of data for batch histories. The main impact of these recipes will be to permit increased production flexibility as control systems become more functionally oriented and subject to the instructions within recipes. Production scheduling will enable the order of recipes and production to be established according to customer demands. Any supported schedules will have to be dynamic, to allow for severe disruptions. The final concept of information management enables the creation and use of batch reports for quality, internal and external, financial and maintenance functions and analysis within a company. Although these concepts and their interrelationships are reasonably new, control systems are being created that will support software implementing these concepts.     

浆液组分与配比对浆液和浆膜性能的影响

表面活性剂虽能改善浆液的某些性能，但给浆膜性能带来不利影响；增塑剂能显著改善淀粉浆膜的弹性、韧性、但浆液粘附力和浆膜强度、模量降低。变性淀粉，部分醇解ＰＶＡ等浆料的内增塑作用能显著改善浆液和浆膜性能；共聚浆料通过改变各共聚单体的种类和配经能调节其浆液和浆膜性能；浆料的物理共混能够综合各共混浆料的性能，但浆料的共混性能受浆料相容性的影响。     

水溶性聚酯浆料的浆液性能

为探讨水溶性聚酯浆料浆液性能,以对苯二甲酸二甲酯、1,2-丙二醇、一缩二乙二醇和间苯二甲酸二甲酯-5-磺酸钠为聚合单体,通过酯交换-缩合聚合反应方法,合成制备了水溶性聚酯浆料,并对溶液性能进行了分析.结果表明:水溶性聚酯浆料热粘稳定性优良,具有相对较低的表观粘度、适宜的吸湿性、良好的水溶性和成膜性;水溶性聚酯浆料溶液属于非牛顿流体,温度升高,浆液假塑性行为降低,粘度稳定性提高,有利于浆液对纱线渗透和均匀上浆;水溶性聚酯浆料溶液的表面张力为55 dyne/cm,更适合表面张力较大的亲水性纤维纱线的上浆.