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Lactose/Galactose Assay Kit (Rapid)

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00:03  Introduction
00:59   Principle
02:00   Reagent Preparation
03:36    Sample Treatment
05:50    Procedure
10:50     Calculations

Lactose-Galactose Assay Kit Rapid K-LACGAR Scheme
Product code: K-LACGAR

115 assays per kit

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Content: 115 assays per kit
Shipping Temperature: Ambient
Storage Temperature: Short term stability: 2-8oC,
Long term stability: See individual component labels
Stability: > 2 years under recommended storage conditions
Analyte: D-Galactose, Lactose
Assay Format: Spectrophotometer
Detection Method: Absorbance
Wavelength (nm): 340
Signal Response: Increase
Linear Range: 4 to 80 µg of D-galactose (or 8 to 160 µg of lactose) per assay
Limit of Detection: 2.96 mg/L
Reaction Time (min): ~ 15 min
Application examples: Milk, dairy products (e.g. cream, milk / whey powder, cheese, condensed milk and yogurt), foods containing milk (e.g. dietetic foods, bakery products, baby food, chocolate, sweets and ice-cream), food additives, feed, cosmetics, pharmaceuticals and other materials (e.g. biological cultures, samples, etc.).
Method recognition: Methods based on this principle have been accepted by AOAC Method 2006.06, NBN, DIN, GOST and IDF

The Lactose/Galactose (Rapid) test kit is used for the rapid test of lactose, D-galactose and L-arabinose in food and plant products. Galactose dehydrogenase can be used the measurement and analysis of both D-galactose and L-arabinose. Suitable for the analysis of lactose in “low-lactose” or “lactose-free” samples which contain high levels of monosaccharides. The reagents provided in this kit are also suitable for use with AOAC method 2006.06 – Lactose in milk.

Note for Content: The number of manual tests per kit can be doubled if all volumes are halved.  This can be readily accommodated using the MegaQuantTM  Wave Spectrophotometer (D-MQWAVE).

View our full range of mono/disaccharide test kits.

Scheme-K-LACGAR LACGAR Megazyme

  • Very rapid reaction due to inclusion of galactose mutarotase (patented technology PCT / IE2004 / 00170) 
  • Very competitive price (cost per test) 
  • All reagents stable for > 2 years after preparation 
  • Mega-Calc™ software tool is available from our website for hassle-free raw data processing 
  • Standard included
Validation of Methods

Traditional Grain-Based vs. Commercial Milk Kefirs, How Different Are They?. 

Nejati, F., Capitain, C. C., Krause, J. L., Kang, G. U., Riedel, R., Chang, H. D., Kurreck, J., Junne, S., Weller, P. & Neubauer, P. (2022). Applied Sciences, 12(8), 3838.

Traditional kefir, which is claimed for health-promoting properties, is made from natural grain-based kefir, while commercial kefirs are made of defined mixtures of microorganisms. Here, approaches are described how to discriminate commercial and traditional kefirs. These two groups of kefirs were characterized by in-depth analysis on the taxonomic and functional level. Cultivation-independent targeted qPCR as well as next-generation sequencing (NGS) proved a completely different microbial composition in traditional and commercial kefirs. While in the traditional kefirs, Lactobacillus kefiranofaciens was the dominant bacterial species, commercial kefirs were dominated by Lactococcus lactis. Volatile organic compounds (VOCs) analysis using headspace-gas chromatography-ion mobility spectrometry also revealed drastic differences between commercial and traditional kefirs; the former built a separate cluster together with yogurt samples. Lactose and galactose concentrations in commercial kefirs were considerably higher than in traditional kefirs, which is important regarding their health properties for people who have specific intolerances. In summary, the analyzed commercial kefirs do not resemble the microbial community and metabolite characteristics of traditional grain-based kefir. Thus, they may deliver different functional effects to the consumers, which remain to be examined in future studies.

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Gas production by Paucilactobacillus wasatchensis WDCO4 is increased in Cheddar cheese containing sodium gluconate.

McMahon, D. J., Sorensen, K. M., Domek, M. J., Dai, X., Sharma, P., Oberg, T. S. & Oberg, C. J. (2022). Journal of Dairy Science, 105(5), 3896-3910.

Paucilactobacillus wasatchensis can use gluconate (GLCN) as well as galactose as an energy source and because sodium GLCN can be added during salting of Cheddar cheese to reduce calcium lactate crystal formation, our primary objective was to determine if the presence of GLCN in cheese is another risk factor for unwanted gas production leading to slits in cheese. A secondary objective was to calculate the amount of CO2 produced during storage and to relate this to the amount of gas-forming substrate that was utilized. Ribose was added to promote growth of Pa. wasatchensis WDC04 (P.waWDC04) to high numbers during storage. Cheddar cheese was made with lactococcal starter culture with addition of P.waWDC04 on 3 separate occasions. After milling, the curd was divided into six 10-kg portions. To the curd was added (A) salt, or salt plus (B) 0.5% galactose + 0.5% ribose (similar to previous studies), (C) 1% sodium GLCN, (D) 1% sodium GLCN + 0.5% ribose, (E) 2% sodium GLCN, (F) 2% sodium GLCN + 0.5% ribose. A vat of cheese without added P.waWDC04 was made using the same milk and a block of cheese used as an additional control. Cheeses were cut into 900-g pieces, vacuum packaged and stored at 12°C for 16 wk. Each month the bags were examined for gas production and cheese sampled and tested for lactose, galactose and GLCN content, and microbial numbers. In the control cheese, P.waWDC04 remained undetected (i.e., <104 cfu/g), whereas in cheeses A, C, and E it increased to 107 cfu/g, and when ribose was included with salting (cheeses B, D, and F) increased to 108 cfu/g. The amount of gas (measured as headspace height or calculated as mmoles of CO2) during 16 wk storage was increased by adding P.waWDC04 into the milk, and by adding galactose or GLCN to the curd. Galactose levels in cheese B were depleted by 12 wk while no other cheeses had residual galactose. Except for cheese D, the other cheeses with GLCN added (C, E and F) showed little decline in GLCN levels until wk 12, even though gas was being produced starting at wk 4. Based on calculations of CO2 in headspace plus CO2 dissolved in cheese, galactose and GLCN added to cheese curd only accounted for about half of total gas production. It is proposed that CO2 was also produced by decarboxylation of amino acids. Although P.waWDC04 does not have all the genes for complete conversion and decarboxylation of the amino acids in cheese, this can be achieved in conjunction with starter culture lactococcal. Adding GLCN to curd can now be considered another confirmed risk factor for unwanted gas production during storage of Cheddar cheese that can lead to slits and cracks in cheese. Putative risk factors now include having a community of bacteria in cheese leading to decarboxylation of amino acids and release of CO2 as well autolysis of the starter culture that would provide a supply of ribose that can promote growth of Pa. wasatchensis.

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Traditional analytical approaches for lactose residues determination in lactose hydrolysed milks: A review.

Rao, P. S., Singh, P., Sharma, V. & Arora, S. (2021). LWT, 151, 112069.

Lactose, a major carbohydrate of mammalian milk is being digested by the intestinal enzyme lactase. Lactase activity decreases in later childhood and throughout life in the majority of the world's population leading towards lactose intolerance. To overcome this challenge, lactose-free milk and milk products have emerged as a boon to lactose-intolerant people all over the world. The wide availability of lactose-free products is encouraging consumers to select them as a preferred choice for dairy foods, driven by the increasingly wide product range. Lactose content should be less than 100 mg/L in order to comply with the legal standards of lactose-free milk products. During the preparation of lactose-free products, lactose hydrolysis increases the level of glucose and galactose in milk along with galactooligosaccharides (GOS) due to transgalactosylation activity of the lactase enzyme. These carbohydrate moieties interfere in the accurate estimation of lactose in lactose-free milk. This review summarizes various techniques such as chromatographic, enzymatic, or sensor-based developed to estimate residual lactose in low lactose milk system along with their advantages and limitations. Among all the detection methods, high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) showed the highest accuracy and specificity without any interference from other disaccharides. However, it is quite expensive and therefore not used widely. Thus, there is a need to develop a rapid and cost-effective method for the detection of residual lactose in a low-lactose milk system.

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Fortified blended foods prepared from fermented milk and cereal: Effect of storage conditions on composition, color, and pasting behavior.

Shevade, A. V., O’Callaghan, Y. C., O’Brien, N. M., O’Connor, T. P. & Guinee, T. P. (2021). Journal of Food Processing and Preservation, 45(5), e15419.

Fortified blended food powders (FBF) were prepared by blending fermented milk with parboiled wheat (FBFw), barley (FBFb), or oats (FBFo), incubating the blend, drying, milling, and fortifying the powder with vitamins, minerals, and refined soya oil. FBFs were stored at 15°C, 30°C, or 37°C for 0-18 months, and evaluated for compositional and functional properties. FBFo had lower contents of lactose and galactose, and higher contents of starch and fat, water-holding capacity (WHC) and pasting viscosity than FBFw or FBFb. Storage time and temperature affected composition (lactose, galactose, and lysine), color, WHC, pasting viscosity, and flow to a degree dependent on cereal type. FBFs stored at 15°C were generally stable over the 18 months, while those stored at 37°C underwent a rapid deterioration in color, WHC, and viscosity after storage times of ≤4 months. Storage of FBF at 15°C is recommended, whereas storage at 37°C should be avoided.

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Predictive modeling of the early stages of semi-solid food ripening: Spatio-temporal dynamics in semi-solid casein matrices.

Kern, C., Stefan, T., Sacharow, J., Kügler, P. & Hinrichs, J. (2021). International Journal of Food Microbiology, 349, 109230.

A mechanistic, spatio-temporal model to predict early stage semi-solid food ripening, exemplary for semi-solid casein matrices, was created using software based on the finite element method (FEM). The model was refined and validated by experimental data obtained during 8 wk of ripening of a casein matrix that was inoculated by one single central injection of starter culture. The resulting spatio-temporal distributions of lactococci strains, lactose, lactic acid/lactate and pH allowed us to optimize a number of parameters of the predictive model. Using the optimized model, the agreement between simulation and experiment was found to be satisfactory, with the pH matching best. The predictive model unveiled that effective diffusion of substrate and metabolites were crucial for an eventual homogeneous distribution of the measured substances. Hence, while using the optimized parameters from the single injection model, an injection technology for starter culture to inoculate and ferment casein matrices homogeneously was developed by means of solving another optimization problem with respect to injection positions. The casein matrix inoculated by the proposed injection pattern (21 injections, distance = 19 mm) showed sufficient homogeneity (bacterial activity and pH distribution) after the early stages of ripening, demonstrating the potential of application of the injection technology for fermentation of casein-based foods e.g. cheese.

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Ligustilide inhibits the proliferation of non-small cell lung cancer via glycolytic metabolism.

Jiang, X., Zhao, W., Zhu, F., Wu, H., Ding, X., Bai, J., Zhang, X. & Qian, M. (2020). Toxicology and Applied Pharmacology, 410, 115336.

Non-small cell lung cancer (NSCLC) is one of the leading causes of cancer-related death worldwide. The abnormal activation of glycolytic metabolism and PTEN/AKT signaling in NSCLC cells are highly correlated with their proliferation abilities and viability. Ligustilide is one of the major bioactive components of multiple Chinese traditional medicine including Angelica sinensis and Ligusticum. Ligustilide exposure inhibits the proliferation and viability of multiple cancer cell lines in vitro. However, the impact of ligustilide to the progression of NSCLC and its detailed pharmacological mechanisms remain unclear. In this research, CCK-8 and colony formation assay were performed to demonstrate ligustilide treatment inhibited the viability and proliferation ability of NSCLC cells in vitro. Caspase-3/-7 activity assay and nucleosome ELISA assay were utilized to show ligustilide promoted the apoptosis of NSCLC cells. Metabolic analysis and qRT-PCR assay were used to demonstrated that ligustilide dampened aerobic glycolysis of NSCLC cells. Nude mice were exposed to 5 mg/kg ligustilide and ligustilide inhibited orthotopic NSCLC growth in vivo. qRT-PCR and Western blot analysis were performed to substantiate the regulatory function of ligustilide to PTEN/AKT signaling in NSCLC cells. Overall, this study revealed that ligustilide regulated the proliferation, apoptosis and aerobic glycolysis of NSCLC cells through PTEN/AKT signaling pathway.

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Nutritional Quality, Sensory Analysis and Shelf Life Stability of Yogurts Containing Inulin-Type Fructans and Winery Byproducts for Sustainable Health.

Iriondo-DeHond, M., Blázquez-Duff, J. M., Del Castillo, M. D. & Miguel, E. (2020). Foods, 9(9), 1199.

The aim of the present study was to evaluate the use of winery byproduct extracts (grape pomace, seed and skin) and a mixture of inulin-type fructans (inulin and FOS) as suitable ingredients for the development of yogurts with antioxidant and antidiabetic properties. Their effect on the physicochemical, textural, microbiological and sensory parameters of yogurts was evaluated during 21 days of refrigerated storage. The incorporation of winery byproduct extracts in yogurt resulted in a significant increase (p < 0.05) in total phenolic content (TPC) and antioxidant and antidiabetic properties, compared to the controls. The grape skin yogurt showed the highest (p < 0.05) TPC (0.09 ± 0.00 mg GAE/g yogurt) and antioxidant capacity (7.69 ± 1.15 mmol TE/g yogurt). Moreover, the grape skin yogurt presented the highest (p < 0.05) inhibition of the activity of the enzyme α-glucosidase (56.46 ± 2.31%). The addition of inulin-type fructans did not significantly (p > 0.05) modify the overall antioxidant capacity or inhibition of the enzyme α-glucosidase of control and winery byproduct extract yogurts. Yogurts containing winery byproduct extracts and dietary fiber achieved high overall acceptance scores (6.33–6.67) and showed stable physicochemical, textural and microbiological characteristics during storage, assuring an optimal 21-day shelf life. According to their antioxidant and antidiabetic properties, we propose the yogurt containing grape skin extract, together with inulin and FOS, as a novel food product for the promotion of sustainable health.

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Excessive supply of glucose elicits an NF‐κB2‐dependent glycolysis in lactating goat mammary glands.

Cai, J., Wang, D., Liang, S., Peng, J., Zhao, F. & Liu, J. (2020). The FASEB Journal, 34(6), 8671-8685.

During lactation, an improper glucose supply often threatens mammary gland (MG) health. However, information is limited on the metabolic trajectories and molecules that regulate lactating MGs with an excessive glucose supply. Based on the network analysis of transcriptome and microRNAs, we found that the oversupply of glucose‐induced severe glucose metabolic disorders in MGs of lactating goats, shifting lactose synthesis to acute fermentative glycolysis which caused increased flux of glucose metabolism into lactate. Moreover, NF‐κB2 played a key role in regulating glycolysis, exhibiting a metabolic shift when MGs had an excessive supply of glucose. In primary mammary epithelial cells, fermentative glycolysis, and intracellular concentration of reactive oxygen species (ROS) were reduced by ganoderic acid A through blocking NF‐κB2, while activation of NF‐κB2 with phorbol myristate acetate (PMA) upregulated fermentative glycolysis and increased cellular ROS accumulation under excessive glucose. Thus, we established an NF‐κB2‐targeting method to reform the metabolic shift toward glycolysis caused by glucose oversupply by integrating NF‐κB2 blockade and intracellular ROS scavenging.

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A comparison of macronutrient-based methods for deriving energy values in human milk.

Perrin, M. T., Spence, E. H., Belfort, M. B., Parker, M. G. & Bode, L. (2020). Journal of Perinatology, 40(11), 1688-1693.

Objective: Energy values for human milk are increasingly available clinically, though there are no standards for deriving these values. We compared published calorie methods using a common set of samples. Study design: Ten human milk samples were measured for gross and digestible macronutrients using laboratory methods. Four calorie conversion factors were used: Atwater general (ATW-GEN); Atwater milk specific (ATW-MILK), human milk specific (HUM-MILK), and combustible conversions (COMBUST). Differences in derived calories were assessed using ANOVA. Results: There was a significant difference (P < 0.001) in calorie values between methods. Gross macronutrients with COMBUST conversion factors produced the highest calorie values (19.4 ± 1.4 kcal/ounce) whereas digestible macronutrients with HUM-MILK conversion factors produced the lowest calorie values (16.3 ± 1.3 kcal/ounce). Mean difference between these values was 3.1 kcal/ounce (95% CI 2.5, 3.7). Conclusion: Mean calorie difference of 3.1 kcal/ounce is clinically important for preterm infants, suggesting the need for standardization.

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A thermophilic fungal GH36 α-galactosidase from Lichtheimia ramosa and its synergistic hydrolysis of locust bean gum.

Xie, J., Wang, B., He, Z. & Pan, L. (2020). Carbohydrate Research, 491, 107911.

A novel GH36 α-galactosidase gene (LrAgal36A) from Lichtheimia ramose was synthesized and highly expressed in Pichia pastoris. The enzyme titer and protein yield for high-density fermentation in a   L fermentor were up to 953.6 U mL−1 and 4.36 g L−1. Purified recombinant LrAgal36A showed the maximum activity at pH 6.0 and 65°C and was thermostable with a half-life of 70 min at 60°C. LrAgal36A displayed the highest specific activity (353.17 ± 4.19 U mg−1) toward p-nitrophenyl-α-d-galactopyranoside (pNPGal) followed by galacto-oligosaccharides and could act slightly on galactomannans. The Km and catalytic efficiency (kcat/Km) of LrAgal36A for pNPGal were 0.33 mM and 1569.50 mM−1 s−1, respectively. LrAgal36A and GH5 β-mannanase from L. ramose showed a significant synergistic effect on the degradation of locust bean gum (LBG), resulting in release more reducing sugars (1.56 folds) and galactose (7.6 folds) by simultaneous or sequential reactions. Due to its hydrolysis properties, LrAgal36A might have potential applications in the area of pulp biobleaching, feed and food processing.

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High Sensitivity Analysis and Food Processing Stability of Rare Sugars.

Miyoshi, M., Kimura, I., Inazu, T. & Izumori, K. (2019). Food Science and Technology Research, 25(6), 891-901.

To evaluate the stability of rare sugars, i.e., sorbose, allose, tagatose and allulose, in food products containing rare sugar syrup (RSS) during cooking, we developed a highly sensitive analysis method using high performance liquid chromatography (HPLC) with corona charged aerosol detector (CAD) and analyzed the rare sugars in a Maillard reaction mixture and in food products available at market. In the Maillard reaction, the amounts of each rare sugar decreased at the initial pH of 6.0. Further, the increase in allulose was accelerated in reaction mixtures at pH 7.5. The stability of rare sugars, which are added to improve food functions during food processing, was greatly influenced by the pH, temperature and heating time. Surprisingly, allulose was retained at the highest level (86.0%–88.5%) under the various cooking conditions, while the other rare sugars were obviously decreased. Therefore, it was suggested that allulose can be maintained under various manufacturing conditions, including under weakly alkaline treatment.

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Identification of the bacteria and their metabolic activities associated with the microbial spoilage of custard cream desserts.

Techer, C., Jan, S., Thierry, A., Maillard, M. B., Grosset, N., Galet, O., Breton, V., Gautier, M. & Baron, F. (2020). Food Microbiology, 86, 103317.

The famous French dessert “ile flottante” consists of a sweet egg white foam floating on a vanilla custard cream, which contains highly nutritive raw materials, including milk, sugar and egg. Spoilage issues are therefore a key concern for the manufacturers. This study explored the bacterial diversity of 64 spoiled custard cream desserts manufactured by 2 French companies. B. cereus group bacteria, coagulase negative Staphylococcus, Enterococcus and Leuconostoc spp. were isolated from spoiled products. Thirty-one bacterial isolates representative of the main spoilage species were tested for their spoilage abilities. Significant growth and pH decrease were observed regardless of species. While off-odours were detected with B. cereus group and staphylococci, yoghurt odours were detected with Enterococcus spp. And Leuconostoc spp. B. cereus group bacteria produced various esters and several compounds derived from amino acid and sugar metabolism. Most Staphylococci produced phenolic compounds. Enterococcus spp. And Leuconostoc spp. isolates produced high levels of compounds derived from sugar metabolism. Each type of spoilage bacteria was associated with a specific volatile profile and lactic acid was identified as a potential marker of spoilage of custard cream-based desserts. These findings provide valuable information for manufacturers to improve food spoilage detection and prevention of chilled desserts made with milk and egg.

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Fortified blended food base: effect of co-fermentation time on composition, phytic acid content and reconstitution properties.

Shevade, A. V., O’Callaghan, Y. C., O’Brien, N. M., O’Connor, T. P. & Guinee, T. P. (2019). Foods, 8(9), 388.

Dehydrated blends of dairy-cereal combine the functional and nutritional properties of two major food groups. Fortified blended food base (FBFB) was prepared by blending fermented milk with parboiled wheat, co-fermenting the blend at 35°C, shelf-drying and milling. Increasing co-fermentation time from 0 to 72 h resulted in powder with lower lactose, phytic acid and pH, and higher contents of lactic acid and galactose. Simultaneously, the pasting viscosity of the reconstituted base (16.7%, w/w, total solids) and its yield stress (σ0), consistency index (K) and viscosity on shearing decreased significantly. The changes in some characteristics (pH, phytic acid, η120) were essentially complete after 24 h co-fermentation while others (lactose, galactose and lactic acid, pasting viscosities, flowability) proceeded more gradually over 72 h. The reduction in phytic acid varied from 40 to 58% depending on the pH of the fermented milk prior to blending with the parboiled cereal. The reduction in phytic acid content of milk (fermented milk)-cereal blends with co-fermentation time is nutritionally desirable as it is conducive to an enhanced bioavailability of elements, such as Ca, Mg, Fe and Zn in milk-cereal blends, and is especially important where such blends serve as a base for fortified-blended foods supplied to food-insecure regions.

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Transcription factor E2F4 is a positive regulator of milk biosynthesis and proliferation of bovine mammary epithelial cells.

Zhen, Z., Zhang, M., Yuan, X. & Li, M. (2020). Cell Biology International, 44(1), 229-241.

The transcription factor E2F4 is a key determinant of cell differentiation and cell‐cycle progression, but its function and regulatory mechanism are not completely understood. Here, we report that E2F4 acts as a positive regulator of the biosynthesis of milk components and proliferation of bovine mammary epithelial cells (BMECs). Overexpression of E2F4 in BMECs resulted in the upregulation of β‐casein, triglyceride, and lactose levels and increased cell proliferation, whereas E2F4 knockdown by small interfering RNA had the opposite effects. We further detected that overexpression of E2F4 significantly increased the messenger RNA expression of mTOR, SREBP‐1c, and Cyclin D1, and increased protein levels of SREBP‐1c, and Cyclin D1, and the ratio of p‐mTOR/mTOR, whereas E2F4 knockdown had the opposite effects. E2F4 was almost entirely located in the nucleus, and we further identified, via ChIP‐qPCR analysis, that mTOR, SREBP‐1c, and Cyclin D1 were E2F4 target genes, and exogenous administration of methionine, leucine, β‐estradiol, and prolactin markedly increased the protein levels of E2F4 and its binding to the promoters of these three genes. In summary, our data reveal that E2F4 responds to extracellular stimuli and regulates the expression of mTOR, SREBP‐1c, and Cyclin D1 for milk biosynthesis and proliferation of BMECs.

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Accuracy and reliability of infrared analyzers for measuring human milk macronutrients in a milk bank setting.

Perrin, M. T., Festival, J., Starks, S., Mondeaux, L., Brownell, E. A. & Vickers, A. (2019). Current Developments in Nutrition3(11), nzz116.

Background: Infrared (IR) analysis is an emerging technology that may be a useful tool for milk banks to manage the nutrient variability in donor human milk. Objective: To evaluate the accuracy, reliability, and comparability of commercial infrared analyzers for measuring human milk macronutrients in a milk bank setting. Methods: Three nonprofit milk banks received blinded test kits of human milk that had been assessed using reference methods. Four infrared instruments were used to measure macronutrients as follows: 1 filtered mid-IR, 2 Fourier-transformed full-spectra mid-IR, and 1 near-IR. Twenty-five unique samples were read concurrently for the accuracy arm. An identical sample was read daily for 1 mo for the reliability arm.Results: Values for R2 describing relationships with reference methods for total fat, crude protein, and lactose, were as follows: filtered mid-IR, 0.98, 0.94, and 0.48; Fourier-transformed full-spectra mid-IR, 0.97, 0.93, and 0.36 for instrument 1 and 0.98, 0.98, and 0.31 for instrument 2; and near-IR 0.93, 0.93, and 0.12. There was no significant difference between instruments for crude protein and total fat measurements. There were significant differences in carbohydrate measurements between instruments. For 1 mo of daily measurements in the reliability arm, CVs for filtered mid-IR were ≤4.6%, for Fourier-transformed full spectra mid-IR were ≤1.7%, and for near-IR were ≤5.1%. Conclusions: Infrared analysis is an accurate and reliable method for measuring crude protein and total fat in a milk bank setting. Carbohydrate measurements are less accurate and are significantly different between instruments, which will likely lead to differences in derived calorie values.

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Development of a dehydrated fortified food base from fermented milk and parboiled wheat, and comparison of its composition and reconstitution behavior with those of commercial dried dairy‐cereal blends.

Shevade, A. V., O'Callaghan, Y. C., O'Brien, N. M., O'Connor, T. P. & Guinee, T. P. (2019). Food science & Nutrition, 7(11), 3681-3691.

Dehydrated blends of milk and cereal are reconstituted and consumed as a nutritious soup or porridge in many regions; the composition and reconstitution behavior of the blends are likely to impact on nutritional quality and consumer acceptability of the soup/porridge. Experimental samples of dried fermented milk‐bulgur wheat blend (FMBW) and commercial samples of dried dairy‐cereal blends, namely kishk, tarhana, and super cereal plus corn–soy blend (SCpCSB) were compared for composition, color, water sorption, and reconstitution characteristics. FMBW blends had higher contents of protein, Ca, lactose and lactic acid, lower levels of salt (NaCl) and Fe, and a lighter, more‐yellow color (higher L* and b*‐color co‐ordinates) than tarhana or kishk. Compared with SCpCSB, FMBW had numerically higher levels of protein, lactose, and lactic acid, lower levels of Ca, Fe, Zn, and Mg, and lower pH. Tarhana had highest mean levels of starch, and on reconstitution (133 g/kg) had highest water holding capacity, viscosity during pasting and cooling, yield stress (σ0), consistency coefficient (K), and viscosity on shearing from 20 to 120 s−1 at 60°C. Reconstituted FMBW, kishk, and SCpCSB had similar pasting and flow behavior properties. Overall, the composition (starch, protein, Ca, Mg), pasting and flow behavior characteristics of FMBW were closer to those SCpCSB and kishk than to tarhana. The results suggest that the FMBW powder, on appropriate supplementation with Ca, Fe, Zn and Mg, could be used for the development of customized fortified blended foods for specific groups.

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Fermentability of a Novel Galacto-Oligosaccharide Mixture by Lactobacillus spp. and Bifidobacterium spp.

Kittibunchakul, S., Maischberger, T., Domig, K. J., Kneifel, W., Nguyen, H. M., Haltrich, D. & Nguyen, T. H. (2018). Molecules, 23(12), 3352.

This study aimed to investigate the specific growth stimulation of certain desired intestinal bacteria by a novel galacto-oligosaccharide mixture, which was produced with a β-galactosidase from a potential probiotic Lactobacillus isolate that contained mainly oligosaccharides of β-1,3 and β-1,6 glycosidic linkages (termed Lb-GOS) using single-strain fermentations. The composition of this Lb-GOS mixture was 33.5% disaccharides, 60.5% trisaccharides, 4.8% tetrasaccharides, and 1.0% pentasaccharides with a negligible amount of monosaccharides, lactose, and lactobionic acid (0.3%). Eight Lactobacillus spp. strains and three Bifidobacterium spp. strains were used in single-strain fermentations to determine the fermentation activity scores of this Lb-GOS preparation compared to two commercially available prebiotic mixtures, 4′GOS-P and Vivinal GOS (V-GOS). The highest scores were obtained when L. reuteri Lb46 and the two Bifidobacterium strains, B. animalis subsp. Lactis Bif1 and Bif3, were grown on these galacto-oligosaccharide mixtures. In addition, the Lb-GOS mixture was found to have higher fermentation activity scores; hence, it stimulated the growth of these probiotic strains more than 4′GOS-P and V-GOS, which may be attributed to the different glycosidic linkage types that are found in the Lb-GOS mixture compared to the other two commercial preparations. These findings suggested that the Lb-GOS mixture that is described in this work should be of interest for the formulations of new carbohydrate-based functional food ingredients.

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Insignificance of lactose impurities on generation and structural characteristics of thermally stabilised whey protein-pectin complexes.

Protte, K., Weiss, J. & Hinrichs, J. (2018). International Dairy Journal, In Press.

We studied the impact of lactose impurities (0, 130, 150 mm) on micro- and macrostructural characteristics of thermally stabilised whey protein-pectin complexes (WPPC) by varying biopolymer concentration (chigh = 5.0% WPI + 1.0% pectin; cmed= 2.75% WPI + 0.55% pectin; cllow = 0.5% WPI + 0.1% pectin), shear rate (0, 150, 500 s-1) and scale (lab/pilot plant). We demonstrated that ≤ 150 mm lactose had no significant effect on the microstructure of WPPC, as investigated by fluorescence spectroscopy and browning measurements. Unfolding of β-lactoglobulin within WPPC depended on the biopolymer concentration, being strongest at chigh. Measured browning was attributed to reactions between whey proteins and neutral sugars in pectin side chains. Particle size was unaffected by lactose, but showed an increase with biopolymer concentration and a decrease with shear rate. Thus, WPPC can likely be generated using whey powders with lactose impurities or other protein sources of lower purity.

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Kinetics of lactose fermentation in milk with kombucha starter.

Kanurić, K. G., Milanović, S. D., Ikonić, B. B., Lončar, E. S., Iličić, M. D., Vukić, V. R. & Vukić, D. V. (2018). Journal of Food and Drug Analysis, In Press.

The aim of this research was to investigate the effect of new, non-conventional starter culture on the kinetics of the lactose transformation during milk fermentation by kombucha, at pH 5.8; 5.4; 5.1; 4.8; and 4.6, at two different temperatures 37°C and 42°C. Milk fermentation at 42°C lasted significantly shorter (about 5 h, 30 min) compared to the fermentation at 37°C. Changes of lactose concentration at the both temperatures are consisting of two retaining stages and very steep decline in-between. The analysis of the rate curves showed that the reaction rate passes through the maximum after 9 h, 30 min at 37°C and after 4 h at 42°C. The sigmoidal saturation curve indicates a complex kinetics of lactose fermentation by kombucha starter.

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Bistability and Nonmonotonic Induction of the lac Operon in the Natural Lactose Uptake System.

Zander, D., Samaga, D., Straube, R. & Bettenbrock, K. (2017). Biophysical Journal, 112(9), 1984-1996.

The Escherichia coli lac operon is regulated by a positive feedback loop whose potential to generate an all-or-none response in single cells has been a paradigm for bistable gene expression. However, so far bistable lac induction has only been observed using gratuitous inducers, raising the question about the biological relevance of bistable lac induction in the natural setting with lactose as the inducer. In fact, the existing experimental evidence points to a graded rather than an all-or-none response in the natural lactose uptake system. In contrast, predictions based on computational models of the lactose uptake pathway remain controversial. Although some argue in favor of bistability, others argue against it. Here, we reinvestigate lac operon expression in single cells using a combined experimental/modeling approach. To this end, we parameterize a well-supported mathematical model using transient measurements of LacZ activity upon induction with different amounts of lactose. The resulting model predicts a monostable induction curve for the wild-type system, but indicates that overexpression of the LacI repressor would drive the system into the bistable regime. Both predictions were confirmed experimentally supporting the view that the wild-type lac induction circuit generates a graded response rather than bistability. More interestingly, we find that the lac induction curve exhibits a pronounced maximum at intermediate lactose concentrations. Supported by our data, a model-based analysis suggests that the nonmonotonic response results from saturation of the LacI repressor at low inducer concentrations and dilution of Lac enzymes due to an increased growth rate beyond the saturation point. We speculate that the observed maximum in the lac expression level helps to save cellular resources by limiting Lac enzyme expression at high inducer concentrations.

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