Short communication: characterization of soluble thiols in bovine milk

Enzyme-free colorimetric detection of biothiols based on the photoinduced oxidation of 3,3',5,5'-tetramethylbenzidine

Realizing the rapid and on-site detection of biothiols in complex biological and food samples using simple assays and devices remains a major challenge. In this study, biothiols containing sulfhydryl groups were found to be able to inhibit the photo-triggered oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Based on the discovery, using the commercially available and low-cost TMB as the chromogenic substrate, an enzyme-free colorimetric approach was developed for the rapid determination of biothiols. The method does not involve the introduction of any natural enzymes, nanoenzymes, and external oxidants. The mechanisms of the photoinduced oxidation of TMB and the detection of biothiols were proposed. Furthermore, a smartphone-based portable device integrated with test strips was constructed by the 3D printing technique. This device can simultaneously meet the requirements of the photocatalytic oxidation reaction of TMB and the detection of biothiols. The entire process only takes less than 5 min. The successful detection of cysteine in urine and milk samples demonstrates the great potential of the device in the on-site assays.

The association of maternal dietary quality and the antioxidant-proxidant balance of human milk

Background

Human milk composition varies over time within an individual mother as well as between lactating mothers due to several factors including maternal health, diet, and nutritional status. Therefore, improving nutrition status during gestation and breastfeeding is crucial for improving the health of both mothers and infants. Diet can enhance the oxidant-antioxidant balance of human milk. This study aimed to investigate the association between human milk oxidant-antioxidant balance with dietary patterns of lactating mothers identified by using principal component analysis.

Method

This cross-sectional study included 350 breastfeeding women between the ages of 20 to 35 years. The dietary intakes of the women in the study were estimated using a validated food frequency questionnaire, which included 65 food items. The oxidant-antioxidant balance of milk samples was assessed using the ferric reducing antioxidant power (FRAP), 2, 2′-diphenyl-1-picrylhydrazyl (DPPH), thiobarbituric acid reactive substances (TBARs), and Ellman’s assay. The milk concentration of total protein, calcium, and triglyceride was also measured using commercial kits.

Result

Two predominant dietary patterns were recognized that we defined as a healthy and unhealthy pattern. There were higher levels of DPPH and thiol in the milk from mothers in the third tertile (highest adherence) of a healthy dietary pattern compared to the first tertile (lowest adherence; p < 0.05). Milk calcium and thiol were significantly lower in the third tertile of mothers with an unhealthy dietary pattern versus the first tertile (P < 0.05). In multivariate multinomial logistic regression analyses adjusted for mother’s age, body mass index (BMI), energy intake, and infant’s sex, adherence to a healthy dietary pattern was associated with higher levels of milk DPPH (OR = 1.32, 95% confidence interval (CI): 1.01, 1.80) and milk thiol (OR = 1.21, 95% CI: 1.10, 1.50). On the other adherence to the unhealthy dietary pattern was correlated with low levels of milk thiol (OR = 1.29; 95%CI: 1.09, 1.59) and milk calcium (OR = 1.28; 95%CI: 1.11, 1.55).

Conclusion

Our findings demonstrated that adherence to a healthy dietary pattern, identified by higher consumption of green vegetables, other vegetables, and fruits is associated with a higher milk oxidant-antioxidant status in breastfeeding mothers.

Genetic and Non-Genetic Variation of Milk Total Antioxidant Activity Predicted from Mid-Infrared Spectra in Holstein Cows

Simple Summary

The total antioxidant activity (TAA) of food is important for human health and results from the contribution of different nutraceutical compounds. Direct determination of TAA in food is time-consuming and expensive. Infrared technologies allow the prediction of difficult-to-measure traits with certain accuracy in several organic matrices, including TAA of bovine milk. In order to understand the background of TAA and identify potential strategies to improve this feature in bovine milk, we explored its non-genetic sources of variation and estimated heritability and correlations with traits of economic interest in a large database of Holstein cows.

Abstract

Food antioxidants enhance products shelf life and stability during technological treatments through the maintenance of their physical and chemical properties. Moreover, they are endowed with several positive effects on human health, including cell membranes preservation, enzyme functionality, and DNA integrity. Milk has been described in relation to a wide array of fat soluble and water-soluble antioxidant compounds, in particular vitamin A, C, and E, lactoferrin and peptides derived from casein and whey proteins. The total antioxidant activity (TAA) of milk is a novel and scarcely explored trait, defined as the sum of antioxidant contributions of the aforementioned compounds. On this background, the aims of the present study were to investigate the variability of milk TAA on a large scale exploiting predictions obtained through mid-infrared (MIR) spectroscopy and to estimate genetic parameters of this trait in Holstein cows. Individual milk samples were collected between January 2011 and December 2018 during the routine milk recording procedure. Samples were analysed for gross composition through MIR spectroscopy and MIR spectra were stored. Milk TAA was then predicted (pTAA) from the stored milk MIR spectra (111,653 test-day records of 9519 cows in 344 herds) using the previously developed prediction model; considering the prediction accuracy, pTAA might be considered a proxy of the TAA determined through the reference method. Overall, pTAA averaged 7.16 mmoL/L of Trolox equivalents, showed a nadir around 40 days after calving and increased thereafter, following a linear trend up to the end of lactation. The lowest pTAA was observed in milk sampled from June to September. Milk pTAA was heritable (0.401 ± 0.015) and genetically associated to fat yield (0.366 ± 0.049), crude protein (CP) yield (0.238 ± 0.052), fat percentage (0.616 ± 0.022) and CP percentage (0.754 ± 0.015). The official selection index of Italian Holstein put the 49% of the emphasis on fat and protein yield and percentage; therefore, it derives that an indirect favourable selection for milk pTAA should be already in progress in Italian Holstein population.

Production of Functional Fermented Milk Beverages Supplemented with Pomegranate Peel Extract and Probiotic Lactic Acid Bacteria

Fermented milk beverages supplemented with pomegranate peel extract and inoculated withLactobacillus plantarumandBifidobacterium longumsubsplongumwere produced. The antioxidant activity of fermented milk beverages supplemented with pomegranate peel 150 mg/L (FMPO 150) and 300 mg/L (FMPO 300) was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). In addition, the polyphenolic profile and sugars content were determined by HPLC analysis, and the volatile compounds were identified using GC-MS analysis. The effects of FMPO 150 and FMPO 300 (10 g/day) on the lipid profile and antioxidant/biochemical status of rats were also evaluated after 4 weeks of oral intake. Antioxidant activity of the fermented milk beverage FMPO 300 was higher than that of FMPO 150. GC-MS analysis of the volatile compounds revealed that diacetyl, acetoin, and acetaldehyde were the major constituents. FMPO 150 and FMPO 300 were efficient in reducing the LDL cholesterol and triacylglycerol and increased the HDL cholesterol in serum. Liver function biomarkers were not affected by the end of treatment (p<0.05). Also, the thiobarbituric acid-reactive substances (TBARS) were decreased, while the activity of antioxidant enzymes in the liver (GSH, CAT, SOD, and GPx) were increased. Hence, the combination of pomegranate peel extract and probiotic lactic acid bacteria in a fermented milk beverage provides not only probiotic benefits but also bioactive phenolic compounds that could be functional and possess therapeutic effects.

Technical note: Development and validation of an HPLC method for the quantification of tocopherols in different types of commercial cow milk

In the present study, a methanol-fluorescence-based HPLC method was validated for its use to quantify α-tocopherol and γ-tocopherol in raw milk, whole UHT milk, partially skimmed UHT milk, whole pasteurized milk, and partially skimmed pasteurized milk. Repeatability and reproducibility, calculated as relative standard deviation of 10 measurements within the same day and 30 measurements across 3 d, respectively, were always below 5% for both tocopherols concentrations and retention times. Recovery was assessed through 3 spiking levels and it ranged from 89 to 107%. The method was able to detect the expected declines in tocopherols in milk exposed to UHT or skimming treatments. Vitamin E, calculated as the sum of α-tocopherol and γ-tocopherol, was similar in whole pasteurized and raw milk, averaging 1.57 and 1.56 mg/L, respectively, followed by whole UHT (1.33 mg/L), partially skimmed pasteurized (0.77 mg/L), and partially skimmed UHT milk (0.61 mg/L).

Short communication: Phenotypic characterization of total antioxidant activity of buffalo, goat, and sheep milk

Free radicals are reactive and unstable waste molecules produced by cells, responsible of damages and alteration on DNA, proteins, and fat. The daily intake of antioxidant compounds, acting against free radicals and their detrimental effects, is essential for human health. Milk contains several compounds with antioxidant activity, and the sum of their reducing potential blocking free radicals development is defined as total antioxidant activity (TAA). This novel trait has been described in literature both in individual and bulk cow milk, but there are no reports from other dairy species. Therefore, the present study aimed to investigate phenotypic variation of TAA in individual samples of buffalo (n = 105), goat (n = 112), and sheep (n = 198) milk. Total antioxidant activity was measured through a reference spectrophotometric method, and expressed as millimoles per liter of Trolox equivalents (TE). The greatest TAA was observed in sheep milk, averaging 7.78 mmol/L of TE and showing also the broadest phenotypic variation expressed as coefficient of variation (13.98%). Significantly lower TAA values were observed for buffalo (7.35 mmol/L of TE) and goat (6.80 mmol/L of TE) milk, with coefficients of variation of 8.18 and 8.47%, respectively. Total antioxidant activity exhibited weak correlations with milk yield and chemical composition. Phenotypic values of TAA presented in this study will be used to assess the ability of mid-infrared spectroscopy to predict this new trait and thus to collect data at the population level.

Development and validation of a near infrared spectrophotometric method to determine total antioxidant activity of milk

In the present study a spectrophotometric method for the determination of total antioxidant activity (TAA) based on ABTS assay was developed and validated on raw milk (RM), whole UHT milk (WUM), partially skimmed UHT milk (SUM), whole pasteurised milk (WM) and partially skimmed pasteurised milk (SM). The most suitable solvent for antioxidant extraction was 80% acetone. Regardless of the type of milk, the coefficient of determination from the linearity test was greater than 0.95. The limit of detection ranged from 0.74 to 6.07μmoll^-1 Trolox equivalents. Repeatability, calculated as relative standard deviation of twenty measurements within a day, and reproducibility, calculated as relative standard deviation of sixty measurements across three days, ranged from 1.24 to 4.04% and from 2.18 to 3.52%, respectively. Preservative added to RM had negligible effects on the TAA of milk. The greatest TAA was measured for SM followed by SUM, RM, WM and WUM.

Short communication: Selecting the most informative mid-infrared spectra wavenumbers to improve the accuracy of prediction models for detailed milk protein content

The objective of this study was to investigate the ability of mid-infrared spectroscopy (MIRS) to predict protein fraction contents of bovine milk samples by applying uninformative variable elimination (UVE) procedure to select the most informative wavenumber variables before partial least squares (PLS) analysis. Reference values (n=114) of protein fractions were measured using reversed-phase HPLC and spectra were acquired through MilkoScan FT6000 (Foss Electric A/S, Hillerød, Denmark). Prediction models were built using the full data set and tested with a leave-one-out cross-validation. Compared with MIRS models developed using standard PLS, the UVE procedure reduced the number of wavenumber variables to be analyzed through PLS regression and improved the accuracy of prediction by 6.0 to 66.7%. Good predictions were obtained for total protein, total casein (CN), and α-CN, which included αS1- and αS2-CN; moderately accurate predictions were observed for κ-CN and total whey protein; and unsatisfactory results were obtained for β-CN, α-lactalbumin, and β-lactoglobulin. Results indicated that UVE combined with PLS is a valid approach to enhance the accuracy of MIRS prediction models for milk protein fractions.