Crystallization behavior of lactose/sucrose mixtures during water-induced crystallization

The crystallization behavior of lactose/sucrose mixtures during water-induced crystallization was studied to gain more insight about their crystallization during storage. Solutions with different ratios of lactose and sucrose, 75:25 and 50:50, were spray dried to produce amorphous powders. The powders were kept at a controlled temperature and humidity to study their sorption–desorption behavior. X-ray diffraction and light microscopy analysis were performed to study their crystallization behavior. Two-step desorption was observed after sieving the powders as sample preparation. Sieving decreased the crystallization time for lactose/sucrose mixture 75:25 from 22 days to 2.5 days. Based on the X-ray diffraction analysis during this two-step process of water desorption, it was concluded that lactose crystallizes first and more quickly than sucrose. The degree of crystallization for the lactose crystals increases by 89% (relative to their final level of crystallinity), whereas sucrose crystals increase their level of crystallinity by only 28% during the first step of crystallization in the lactose/sucrose (75:25) mixtures. The light microscopy images also suggested that the crystallization of amorphous lactose/sucrose powders during water-induced crystallization may occur as a solution rather than in the solid phase.     

The effects of operating conditions on lactose crystallization in a pilot-scale spray dryer

The effects of operating conditions on the rate of drying and degree of crystallinity of lactose have been explored in a pilot-scale spray dryer. Temperature, moisture content, feed flow rate, atomizing air-flow rate, main air-flow rate and particle size have been varied to estimate the range of crystallinity of lactose obtainable in a pilot-scale spray dryer. Modulated differential scanning calorimetry (MDSC) and sorption tests (water-induced crystallization) have been used to assess the degree of crystallinity for freshly spray-dried samples. The degree of crystallinity could be varied from 18% to 72% by varying the operating conditions while allowing reasonable drying of the material. The study suggested that the use of a lower inlet temperature increased the crystallinity of the product from 25% (at 230 °C) to 60% (at 170 °C). A decrease in product crystallinity was also noted when using a lower atomizing air-flow rate. Statistical analysis with t-tests confirmed these differences to be significant with 95% confidence. The results suggest differences between small and pilot-scale spray dryers due to differences in particle sizes and drying rates.     

Water sorption and glass transition properties of spray dried lactose hydrolysed skim milk powder

The moisture sorption behaviour and glass transition temperature of spray dried skim milk powder with hydrolysed lactose (SMPHL) were determined. Spray drying of skim milk with hydrolysed lactose resulted in very low cyclone recovery of 25% and a large amount of powder remained stuck inside the spray dryer. The equilibrium moisture content of SMPHL was lower than that of lactose for each range of water activity when humidified for 21 days at 23 °C using saturated salt solutions. Unlike lactose, SMPHL did not lose water when the water activity exceeded 0.432 and no crystallization was noticed at water activity ?0.753. The sorption isotherm data for SMPHL fitted well with the BET and GAB models with monolayer moisture contents of 7.55 and 8.27 g/100 g, respectively. The glass transition temperature of anhydrous SMPHL was 49 °C. The critical water activity and moisture content for SMPHL were 0.15 and 2.4 g/100 g dry solid, respectively. The low critical values indicated hydrolysis of lactose necessities maintenance of very low moisture of powder for its long-term stability.     

The effects of probiotics in lactose intolerance: A systematic review

Over 60 percent of the human population has a reduced ability to digest lactose due to low levels of lactase enzyme activity. Probiotics are live bacteria or yeast that supplements the gastrointestinal flora. Studies have shown that probiotics exhibit various health beneficial properties such as improvement of intestinal health, enhancement of the immune responses, and reduction of serum cholesterol. Accumulating evidence has shown that probiotic bacteria in fermented and unfermented milk products can be used to alleviate the clinical symptoms of lactose intolerance (LI). In this systematic review, the effectiveness of probiotics in the treatment of LI was evaluated using 15 randomized double-blind studies. Eight probiotic strains with the greatest number of proven benefits were studied. Results showed varying degrees of efficacy but an overall positive relationship between probiotics and lactose intolerance.     

Prediction of moisture transfer parameters for microwave drying of lactose powder using Bi–G drying correlation

The mass transport properties characterising the drying of lactose powder were determined using a correlation proposed by Dincer and Hussain [Dincer, I. & Hussain, M. M. (2004). Development of a new Bi–Di correlation for solids drying. International Journal of Heat and Mass Transfer, 47, 653–658]. Experimental moisture content data for lactose samples dried under convective, microwave, combined convective-microwave and combined vacuum-microwave conditions were collected. The drying coefficients and lag factors were calculated from the experimental data and incorporated into the model. The Bi numbers were in the range 0.185–439, and moisture diffusivities and diffusion coefficients in the range from 0.135 × 10⁻⁹ to 102 × 10⁻⁹ and from 0.194 × 10⁻⁶ to 118 × 10⁻⁶ m/s, respectively. The predicted moisture profiles showed adequate agreement with the experimental observations, with the average error between experimental and predicted results being ±13.7%.     

壳聚糖对菠萝汁澄清效果的研究

研究了壳聚糖对菠萝汁的澄清效果，确定了最佳的工艺参数，并在单因素试验的基础上，通过多因素正交试验，获得澄清菠萝汁的最适工艺条件为：壳聚糖用量0．05％、果汁pH为3、温度35℃，此时菠萝汁的透光率能达到了96％以上。     

Multivariate near-infrared and Raman spectroscopic quantifications of the crystallinity of lactose in whey permeate powder

The use of near-infrared (NIR) and Fourier transform Raman spectroscopy for quantification of crystalline lactose content in whey permeate powder was investigated using chemometric methods. Sample sets consisting of binary mixtures of crystalline (50.0–98.0%) and amorphous lactose and process whey permeate samples with different amounts of crystalline lactose (75.0–95.5%) added were analyzed. The best results for quantification of crystallinity were obtained by partial least squares (PLS) regression on NIR data in five selected intervals in the range 1100–2498 nm. Data analysis on the total sample set of 35 samples yielded a prediction error (root mean square error of cross validation) of 0.627%. The corresponding result for Raman spectroscopy in the range 3500–100 cm⁻¹ was 1.62%. Interval-PLS regression was used for the selection of relevant spectral intervals as well as for improving the spectral interpretation. Alternating regression was used to show that the amorphous lactose preparation contained only a negligible amount of crystalline lactose.     

The influence of powder morphology on the effect of rosemary aroma microencapsulation during spray drying

The influence of particle morphology of spray dried powders obtained by using different carriers on the efficiency of microencapsulation of rosemary aroma is shown in the present research. It was found that the type of the carrier influenced the size but not the shape of rosemary aroma capsules and all the capsules were spherical with cracks. The biggest particles, d₅₀ = 55 μm, were obtained with 25% maltodextrin (MD) as a carrier, and the smallest, d₅₀ = 29 μm with 30% gum arabic (GA). The efficiency of encapsulating aroma inside of the capsules depended on the particles size and apparent density. An increase in the quantity of microencapsulated aroma from 10% for 25% MD to about 60% for 30% GA as the carrier was seen, which co‐related with a decrease in the average diameter of the powder particles. Similarly, an increase in the efficiency of aroma retention was followed by an increase of apparent density of powders from 796 (25% MD) to 1156 kg m^?3 (30% GA).     

含茶多酚的壳聚糖涂膜对鸡蛋保鲜效果的影响

用茶多酚和壳聚糖制成的复合涂膜液对鸡蛋进行涂膜处理,以感官指标、失重率、蛋黄指数、蛋清pH值、哈夫单位为质量指标定期取样分析测定,研究所制成的涂膜液在室温条件下对鸡蛋的保鲜效果。结果表明,和对照相比,含茶多酚的壳聚糖涂膜液能较好地保持鸡蛋的新鲜度和品质,尤其以1.5%的壳聚糖溶液联合200mg/kg茶多酚制得的涂膜液保鲜效果最好,经此涂膜液处理后的鸡蛋室温下贮存35d,失重率为1.89%,蛋黄指数为0.26,哈夫单位为60.109,蛋清pH值为8.20。     

牛乳中乳糖低温水解的研究

主要探讨了鲜牛乳中乳糖的低温水解?试验表明生奶中加入0．15U／kg的乳糖酶，在5℃、水解18h，可使生鲜牛乳中的乳糖降解55％左右，从而可以克服乳糖不耐症的问题。     

An activated-state model for the prediction of solid-phase crystallization growth kinetics in dried lactose particles

Molecular-level understanding of solid-phase crystallization growth kinetics has the potential to improve the fundamental basis for understanding this process. This understanding has been developed here as part of an activated-state model, which accounts for the effects of the moisture content and the temperature on the crystallization rate. Water-induced crystallization (WIC) at different temperatures (15 °C, 25 °C, 40 °C) and a constant relative humidity (75%) environment has been used to analyze the changes in enthalpy, entropy and Gibbs free energy of activation for the solid-phase crystallization of lactose. WIC showed that, at higher temperatures, crystallization commences at lower moisture contents. The enthalpy and Gibbs free energy of activation increased during the crystallization process, which suggested that the binding energy needed for the formation of an activated complex increased as the moisture content decreased, making the formation of the activated complex more difficult. The entropy of activation, on the other hand, decreased with the decrease in the moisture content. From the activated rate equation, the energy of activation has been estimated to be 39 ± 2 kJ mol⁻¹, which is similar to the literature value (40 kJ mol⁻¹) for the solid-phase crystallization of lactose. The reaction rate constant at 25 °C is 1.4 × 10⁻⁴ s⁻¹, which is similar to the literature value of 1.3 × 10⁻⁴ s⁻¹. The WLF equation is inconsistent and hence unreliable in predicting the rates of crystallization at the glass-transition temperature from the analysis of experimental data at different temperatures.     

Short communication: Effect of lactose on the spray drying of Lactococcus lactis in dairy matrices

The effects of unfavorable conditions responsible for the viability loss of Lactococcus cells during spray drying can be minimized by the application of dairy matrices as encapsulating materials. This study aimed to evaluate the use of dairy matrices with different lactose contents on the survival of Lactococcus lactis during drying and storage. The use of hydrolyzed-lactose milk resulted in notable loss of cell viability (3.90 log cycles). However, milk enriched with lactose or without fat showed better protection (viability loss between 0.26 and 1.41 log cfu/g) and greater cell survival during storage at room temperature. The enrichment of milk with lactose seems to be ideal for the drying of heat-sensitive bacteria.     

The effect of chitosan on the properties of emulsions stabilized by whey proteins

The influence of the cationic amino polysaccharide chitosan content (0–0.5%) on particle size distribution, creaming stability, apparent viscosity, and microstructure of oil-in-water emulsions (40% of rapeseed oil) containing whey protein isolate (WPI) (4%) at pH 3 was investigated. The emulsifying properties, apparent viscosity and phase separation behaviour of aqueous WPI/chitosan mixture at pH 3 were also studied. The interface tension data showed that WPI/chitosan mixture had a slightly higher emulsifying activity than had whey protein alone. An increase in chitosan content resulted in a decreased average particle size, higher viscosity and increased creaming stability of emulsions. The microstructure analysis indicated that increasing concentration of chitosan resulted in the formation of a flocculated droplet network. This behaviour of acidic model emulsions containing WPI and chitosan was explained by a flocculation phenomenon.     

Hydrostatic pressure effects on the structural properties of condensed whey protein/lactose systems

Hydrostatic pressure effects on whey protein/lactose mixtures were recorded with subsequent analysis of their structural, molecular and glass transition properties in comparison to thermal effects at atmospheric pressure. Experimental techniques used were small deformation dynamic oscillation in shear, modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, and theoretical modelling of glass transition phenomena. Levels of solids ranged from 30 to 80% (w/w) in formulations with a protein/co-solute ratio of four-to-one. Addition of lactose protects the secondary conformation of the protein under application of high hydrostatic pressure. Nevertheless, pressurized protein systems are able to form three-dimensional structures due to the reduction in polymeric free volume and the development of an efficient friction coefficient amongst tightly packed particles. Systems can be seen as developing a “molten globular state”, where the structural knots of pressure-treated networks remain in the native conformation but achieve intermolecular cross-linking owing to frictional contact. Furthermore, pressure treated assemblies of condensed whey protein preparations could match the viscoelasticity of the thermally treated counterparts upon cooling below ambient temperatures. That allowed examination of the physical state and morphology of a condensed preparation at 80% solids by the combined framework of reduced variables and free volume theory thus affording derivation of glass transition temperatures for pressurized and atmospheric samples.     

纳米壳聚糖的制备及其对真丝纤维性能的影响

采用离子凝胶法制备了平均粒径100nm以下的纳米壳聚糖,对比研究了纳米壳聚糖分散液和壳聚糖溶液对真丝纤维的填埋特征、微观形态和强伸力作用。结果表明,纳米壳聚糖分散液对真丝纤维处理后,填埋效果比普通壳聚糖溶液更为理想,真丝纤维经纳米壳聚糖处理后断裂强度和伸长率增大。     

Effectiveness of gelatine and chitosan spray coating for extending shelf life of vacuum-packaged beef

The effects of applying gelatine (10%) and chitosan (1%) as spray coatings to extend the shelf life of vacuum-packaged beef was studied and compared against uncoated vacuum-packaged beef for up to 21 days. The impact of edible coatings on the water-holding properties of vacuum-packaged beef was investigated by LF-NMR together with physicochemical, microbiological and sensorial assessments. Chitosan coating significantly reduced lipid oxidation by ~30% to 36% and inhibited the growth of lactic acid bacteriaby ~ 1–2 log cfu compared to purge collected from uncoated and gelatine coated samples. It did not negatively affect the meat pH, tenderness and colour, and exhibited significantly higher sensorial acceptance compared to beef coated with gelatine. Both coatings were not effective in reducing purge loss in vacuum-packaged meat as the storage time increased. This study suggests that chitosan spray coating could be easily adapted to industrial plant settings as an antioxidant and antimicrobial application before carrying out meat vacuum packaging operation.     

中式灌肠生产中壳聚糖的抑菌效果研究

目的：研究壳聚糖在中式灌肠生产中的抑菌效果；方法：采用中性蛋白酶水解方法制备出不同黏均分子量的壳聚糖，添加到灌肠中，测定不同保存天数时的细菌总数和感观变化；结果：添加0．2％壳聚糖的灌肠在室温条件下的保质期提高2d以上，风味比其他添加量要好，且在同样添加量的条件下，黏均分子量低的壳聚糖比黏均分子量高的壳聚糖抑菌效果更好。