Ultrasonic characterization of lactose crystallization in gelatin gels

Ultrasonic velocity and attenuation measurements (2.25 MHz center frequency) were used to follow bulk crystallization of lactose (43% and 46%) from gelatin (1.5% and 3%) gels at 25 °C, and compared to turbidity (500 nm) and isothermal calorimetric measurements. Ultrasonic velocity decreased slightly (approximately 0.5%) during crystallization while ultrasonic attenuation was low in the absence of lactose crystals and increased progressively during crystallization. The lag time before the onset of crystallization decreased and the maximum rate of increase in attenuation during crystallization increased with increasing lactose supersaturation but was not affected by gelatin concentration (P < 0.05). Similar results were seen in turbidity and isothermal calorimetric measurements. Ultrasonic attenuation measurements have the potential to measure crystallization kinetics in complex food matrices and to be applied on-line. Practical Application: Many foods contain crystals that affect their taste and texture (for example, lactose crystals can give a grainy defect in ice cream). The formation of crystals is often hard to predict so methods to measure the development of crystals inside real foods are useful. In this study, we show that as lactose crystallizes in a gelatin gel the ultrasonic attenuation--capacity to absorb sound--increases and can be related to the amount of crystals present. Ultrasound is easier to apply in real food processing than the existing methodologies.     

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.     

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。     

Caking of lactose: A critical review

BackgroundCaking is a recurrent problem in various industries, whether it occurs during the production, storage or transport of powders. Caked powder results in longer processing times and decreased product quality, leading to significant economic loss. Several caking mechanisms have been described in the literature. However, they are often difficult to take into account in an industrial context, given the many parameters which influence the overall caking phenomenon.Scope and approachThis review describes the three relevant caking mechanisms for food powders in general. Focussing on predominantly crystalline lactose powder, we discuss how each of these mechanisms can explain caking and be prevented in the industrial context. The second part of this paper presents a critical review of the methods used to characterise caking to date.Key findings and conclusionsThe presence of amorphous material and other impurities must be assessed in crystalline lactose powders, as they can trigger amorphous and humidity caking. Particle size distribution is another key parameter requiring control as it can encourage caking through enhancement of particle interactions. In general, preventing caking in food powders can only be achieved by a thorough understanding of the production process and storage conditions. Moreover, the characterisation of caking remains a challenge as most methods published in the literature do not fit the needs of the food industry. The real demand is for a reliable method to predict caking which would be rapid and easy enough to be applied to each batch for quality control.     

Egg shell as catalyst of lactose isomerisation to lactulose

A feasible way to produce lactulose, employing milk ultrafiltrate as source of lactose and egg shell as catalyst, is proposed as an alternative means for utilising these industrial wastes. Influences of catalyst loadings, lactose concentration and pH on lactose isomerisation were studied. Optimal production of lactulose was reached at 98 °C, employing 6 mg/ml of catalyst loading within 60 min of reaction. Quantities of lactulose of 1.18 g/100 ml and low levels of secondary products (epi-lactose, galactose and organic acids) were produced under these conditions of reaction. Methodology to remove coloured by-products from lactulose syrup in a range of 65–92% was established.     

Development of a method for water determination in lactose

The determination of water content of lactose and the water activity, which is related to it, are important to assess its microbiological stability as well as its technical and commercial quality. Lactose is a very important product in the dairy sector, but also in the pharmaceutical domain.     

On quantifying the dissolution behaviour of milk protein concentrate

Milk protein concentrate (MPC) is a newly developed dairy powder with wide range of applications as ingredients in the food industry, such as cheese, yogurt, and beverage. MPC has relatively poor solubility as a result of their high protein content (40–90 wt%), with distinct dissolution behaviour in comparison to skim milk or whole milk powders. Here, a focused beam reflectance measurement (FBRM) was used to monitor the dissolution process of an MPC powder, with the data used to develop a kinetic dissolution model based on the Noyes–Whitney equation. The model was used to estimate the dissolution rate constant k and the final particle size in suspension d_∞, describing dynamic dissolution behaviours and final solubility respectively of a particular powder. In this work, the effects of dissolution temperature, storage duration and storage temperature on dissolution properties of an MPC powder were also investigated. A quantitative understanding of relationship between process and storage conditions with powder functionality could be achieved from k and d_∞ profiles. This approach can potentially be applied to predict the dissolution behaviour of specific dairy powders in a more robust manner than conventional solubility tests.     

The effect of chitosan hydrogen bonding on lactose crystallinity during spray drying

The effect of chitosan on the crystallization behavior of lactose has been studied during the spray drying of lactose/chitosan solutions. Solutions with different ratios of lactose and chitosan have been spray dried at an inlet temperature of 160 °C using a laboratory-scale spray dryer. Water-induced crystallization, X-ray diffraction analysis and differential scanning calorimetry have been used to study the crystallinity of the spray-dried lactose/chitosan powders. Results show that, despite the ability of chitosan to retain moisture for a longer time during spray drying, the spray-dried powders were in the amorphous form. Moisture-induced crystallization and differential scanning calorimetry results suggest that the presence of chitosan delays lactose crystallization. This finding may be due to the high glass-transition temperature of chitosan, despite its ability to hydrogen bond with water, which was suggested previously by other researchers to be a reason for crystallizing lactose during spray drying in the presence of polyethylene glycol.     

Influence of temperature on accelerated lactose crystallization in dulce de leche

The aims of the present work were to study the crystallization of lactose in dulce de leche and to evaluate the influence of temperature on this process. Samples of approximately 1 g were placed in plastic containers and stored at –5, 5, 20 and 35°C for 25 days. Lactose crystal and lactose crystal agglomerate numbers and size were measured by using an optical microscope. Results suggested that stirring and placing a small sample of dulce de leche in a small container induced lactose crystallization. Lower storage temperatures resulted in an increase of crystal and agglomerate number but in a decrease of crystal and agglomerate size. The effect of temperature on crystal and agglomerate growth rates could be attributed to the effect of temperature on viscosity, as lower temperatures resulted in decreased crystal mobility in dulce de leche and therefore reduced crystal and agglomerate growth rate.     

Development of ESR method for gamma-irradiated lactose powders

In this study, ESR was used to characterize the differences between irradiated lactose and non-irradiated lactose. A multi-component ESR spectrum was observed from most of the non-irradiated commercial lactose powder as well as the gamma-irradiated lactose powder. However, the signal pattern of non-irradiated lactose powder was different from that of irradiated lactose powder. Moreover, the multi-component ESR spectrum intensity of radicals generated by milling was weaker than that by gamma-irradiation. Among the several possible causes of generating radicals such as irradiation, lipid oxidation, protein oxidation, influence of ash or mineral and mechanical radical by grinding, the multi-component ESR spectrum from the non-irradiated lactose powder was shown to have resulted from the generation of mechanical radicals during milling in the manufacturing processes.     

A novel enzymatic method for the measurement of lactose in lactose-free products

The cover image is based on the Research Article A novel enzymatic method for the measurement of lactose in lactose-free products by David Mangan et al., DOI: 10.1002/jsfa.9317 . This cover was supported by Megazyme.

     

Effects of melamine on the Maillard reaction between lactose and phenylalanine

The effects of melamine on Maillard reaction were investigated in chemical model systems. The reaction products in the model systems with/without melamine were analysed by GC–MS and LC–MS/MS. Impact of melamine on Maillard browning in the above models was also examined by colourimetric methods. It was found that melamine can react directly with lactose and Strecker aldehydes formed in Maillard reactions to produce new adducts. In addition, the presence of melamine in chemical model systems also affects the formation of Maillard flavours and browning.     

Crystallization kinetics of lactose in sytems co-lyofilized with trehalose. Analysis by differential scanning calorimetry

The objective of the present work was to study by differential scanning calorimetry phase/state transitions in model systems of amorphous lactose and lactose co-lyophilized with trehalose. The obtained parameters, such as glass transition temperatures (T_g) and enthalpies of crystallization were employed to test the applicability of different proposed models to predict the behavior of these systems. Thermograms of low moisture lactose–trehalose mixtures showed only one glass transition temperature indicating that compatibility exists between both sugars. The increase of trehalose concentration in the mixture promoted a delay of lactose crystallization in isothermal runs, and of the crystallization temperature (T_cr) in dynamic experiments. The presence of trehalose delayed lactose crystallization, without affecting the T_g value. Several factors (thermodynamic, geometric, kinetics) may modify the molecular environment in the combined systems, affecting nucleation and/or crystal growth. Three models [Arrhenius, Williams–Landel–Ferry (WLF) and Vogel–Tamman–Fulcher (VTF)] were used to study the temperature dependence of the crystallization time. Although experimental points were fitted fairly well by all these models in the range of temperature from 14 to 59 °C above T_g value, the VTF equation appears to apply better for sugars.     

Elucidation of mechanism of aminoreductone formation in the Maillard reaction of lactose

The aim of this study was to elucidate the formation mechanism of aminoreductone, an important indicator for estimating the extent of Maillard reaction of lactose and amino compounds. Using the model system of lactose and butylamine, the model solution of lactose and milk proteins, and milks, it was concluded that d ‐galactose was liberated at the same time as the generation of aminoreductone. It was shown that the extent of the Maillard reaction and the lactose degradation during heating depended closely on the concentration ratio of amino group/lactose in the sample solution.     

Developments in whey protein and lactose permeate production processes and their relationship to specific product attributes

This paper reviews recent developments in whey processing and the production of whey protein concentrate and lactose permeate powders with particular reference to a new whey processing facility in the Netherlands. The processes have been designed to optimise product quality with the whey protein concentrate targeted for use in nutritional applications and the permeate powder for use in lactose replacement.     

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.     

Available lysine and fluorescence in heated milk proteins/dextrinomaltose or lactose solutions

In order to predict and compare the effects of dextrinomaltose and lactose on available lysine loss by the Maillard reaction, six model systems were prepared by mixing casein, laboratory whey protein or commercial whey protein with dextrinomaltose or lactose. The solutions were prepared at concentrations similar to those used in enteral and infant formula processing and were heated at 100, 120 or 140 °C for 0–30 min. The progress of the Maillard reaction in these model systems was followed by monitoring free fluorescence intermediary compounds. Model systems with lactose showed higher available lysine less than the model systems with dextrinomaltose; linear lysine losses were obtained between 0 and 20 min at 100 and 120 °C. At sterilization temperature and time (120 °C/10 min), lysine losses of milk proteins with dextrinomaltose as reducing sugar were 6.1% for casein, 4.1% for laboratory whey protein and 13.4% for commercial whey protein. Available lysine showed correlation with furosine in model systems prepared with lactose and casein or laboratory but not commercial whey protein at 100 and 120 °C. The initial fluorescence value obtained by mixing casein or laboratory whey protein with lactose or dextrinomaltose was low (between 3.8 and 5.7), whereas the value obtained when commercial whey proteins were used was close to 9. At 120 °C/10 min, there was only a small increase of fluorescence in casein and laboratory whey protein but a large increase in commercial whey protein (threefold the initial value). Fluorescence measurement is useful for finding the extent of the Maillard reaction in commercial whey protein (thermally damaged protein). An absolute value greater than 10 may indicate that products were prepared with thermally damaged proteins.     

Recent advances refining galactooligosaccharide production from lactose

The production of prebiotic galactooligosaccharides (GOS) by the β-galactosidase catalysed conversion of lactose has become commercially important. Yet it remains a challenge to sufficiently understand the structure and activity of β-galactosidase, to increase the efficiency of transgalactosylation and GOS production and to improve the quality of GOS products in a rational way. This review covers the broad but related aspects of GOS synthesis including: the structure and reaction mechanism of β-galactosidase, factors effecting yield and productivity of GOS synthesis systems, the structure of GOS products, models for the kinetics of GOS synthesis and reactor configurations for GOS synthesis. It aims to couple recent discoveries with established knowledge to enhance understanding of the complex biochemistry of GOS synthesis.     

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.