Streamlined analysis of lactose-free dairy products

Screening of α-amylase/trypsin inhibitor activity in wheat, spelt and einkorn by high-performance thin-layer chromatography

α-Amylase/trypsin inhibitor proteins (ATI) are discussed as possible triggers for non-celiac gluten sensitivity. The potential of high-performance thin-layer chromatography (HPTLC) was studied for the first time to analyse the inhibitory properties of ATIs from flour of wheat, spelt, and einkorn. Inhibition by each flour of the digestive enzymes trypsin or α-amylase was determined by the reduction of released metabolisation products in comparison to non-digested flour, and positive (acarbose) and negative (water) controls. Firstly, amylolysis was carried out in miniaturized form on the HPTLC surface (HPTLC-nanoGIT) after in-vial pre-incubation of the amylase with the inhibitors from flour. α-Amylase inhibition was evident via the reduction of released saccharides, as analysed by normal phase HPTLC. A strong influence of the flour matrix on the assay results (individual saccharides) was evident, caused by an increased amylolysis of further polysaccharides present, making HPTLC analysis more reliable than currently used spectrophotometric sum value assays. The detection and visualization of such matrix influence helps to understand the problems associated with spectrophotometric assays. Only maltotriose was identified as a reliable marker of the amylolysis. The highest α-amylase inhibition and thus the lowest saccharide response was detected for maltotriose in refined spelt, whereas the lowest α-amylase inhibition and thus the highest saccharide response was detected for maltotriose in refined wheat. A comparison of refined and whole grain flours showed no clear trend in the responses. Secondly, trypsin inhibition and proteolysis were performed in-vial, and any inhibition was evident via the reduction of released peptides, analysed by reversed-phase HPTLC. Based on the product pattern of the proteolysis, einkorn and whole wheat showed the highest trypsin inhibition, whereas refined wheat and refined spelt showed the lowest inhibition. Advantageously, HPTLC analysis provided important information on changes in individual saccharides or peptides, which was more reliable and sustainable than spectrophotometric in-vial assays (only sum value) or liquid column chromatography analysis (targeting only the ATI proteins).

Quantitative saccharide release of hydrothermally treated flours by validated salivary/pancreatic on-surface amylolysis (nanoGIT) and high-performance thin-layer chromatography

The susceptibility of hydrothermally treated flour products to amylolysis was studied. The human salivary α-amylase and porcine pancreatin enzyme mixture containing α-amylase were used on-surface to investigate the release of glucose, maltose, and maltotriose. On the same adsorbent surface (all-in-one), their high-performance thin-layer chromatography separation and detection via selective chemical derivatization was performed. For the first time, the all-in-one nanoGIT system was studied quantitatively and validated for the simulated static oral and intestinal on-surface amylolysis of ten different hydrothermally treated flours and soluble starch. Differences were detected in the digestibility of refined and whole flours from wheat, spelt, and rye as well as from einkorn, amaranth, emmer, and oat. Amaranth released the lowest amount of saccharides and spelt the highest in both oral and intestinal digestion systems. The results suggest that consumption of whole grain products may be beneficial because of their lower saccharide release, with particular attention to rye.

Advances in Low-Lactose/Lactose-Free Dairy Products and Their Production

With increasing health awareness worldwide, lactose intolerance has become a major concern of consumers, creating new market opportunities for low-lactose/lactose-free dairy foods. In recent years, through innovating processes and technologies, dairy manufacturers have significantly improved the variety, and functional and sensory qualities of low-lactose and lactose-free dairy products. Based on this, this paper first covers the pathology and epidemiology of lactose intolerance and market trends. Then, we focus on current advantages and disadvantages of different lactose hydrolysis technologies and improvements in these technologies to enhance nutritional value, and functional, sensory, and quality properties of lactose-free dairy products. We found that more and more cutting-edge technologies are being applied to the production of lactose-free dairy products, and that these technologies greatly improve the quality and production efficiency of lactose-free dairy products. Hopefully, our review can provide a theoretical basis for the marketing expansion and consumption guidance for low-lactose/lactose-free dairy products.

Miniaturized open-source 2LabsToGo screening of lactose-free dairy products and saccharide-containing foods

The open-source 2LabsToGo system is the only one in its nature. It combines in one miniaturized instrument all relevant steps normally performed in a chemical and biological laboratory. For the first time, the applicability of the 2LabsToGo system was studied for screening 17 food products. As examples, saccharides were analyzed in eight products of different matrix complexity, and the absence of lactose was studied in nine lactose-free dairy products. Derivatization including homogeneous reagent application and plate heating via the 2LabsToGo system was explored for saccharide detection, and its performance was investigated. The visual detection sensitivity of lactose was comparable to previous studies. The precision of lactose in milk matrix (%RSD 4.6%) as well as the coefficient of determination of the calibration function (0.9995) were highly satisfying. The obtained lactose content of milk (4.5%) was plausible. Screening eight saccharide-containing food samples showed the saccharides in agreement with the expectations for the respective food product. The lactose content of nine different lactose-free dairy products was proven to be below the 0.1% lactose limit value. As proof-of-principle and for verification, these screening results obtained with the miniaturized 2LabsToGo system were reproduced using conventional state-of-the-art instrumentation, which led to the same results. However, instrumental costs were comparably low for the 2LabsToGo system. The application of the new 2LabsToGo system was successfully shown for saccharide screening, which is attractive to the field of quality control or official food control.

Planar chromatography - Current practice and future prospects

Planar chromatography, in the form of thin-layer or high-performance thin-layer chromatography (TLC, HPTLC), continues to provide a robust and widely used separation technique. It is unrivaled as a simple and rapid qualitative method for mixture analysis, or for finding bioactive components in mixtures. The format of TLC/HPTLC also provides a unique method for preserving the separation, enabling further investigation of components of interest (including quantification/structure determination) separated in both time and space from the original analysis. The current practice of planar chromatography and areas of development of the technology are reviewed and promising future directions in the use of TLC/HPTLC are outlined.

2LabsToGo─Recipe for Building Your Own Chromatography Equipment Including Biological Assay and Effect Detection

A complete recipe for building your own chromatography equipment from readily available materials is introduced. It combines sample separation (chemistry laboratory) with biological effect detection (biology laboratory). This hyphenation of two disciplines is necessary for prioritizing important compounds in complex samples. Among the thousands of compounds therein, it is often not clear which compounds are the important ones. On the same separation surface, additional detection of biological effects enables and guides substance prioritization. The newly developed open-source 2LabsToGo system for chemical and biological analysis is completely solvent-resistant and, due to miniaturization, environmentally friendly regarding the consumption of materials. It produces comparable results but is 10 times more compact (26 cm × 31 cm × 34 cm), 10 times lighter (6.8 kg), and 55 times less expensive (€ 1717) than current sophisticated commercial devices. As a proof of concept of the first 2LabsToGo system, the quality of different water samples was analyzed since clean water is becoming increasingly rare. In water, most of the thousands of substance signals or features can neither be identified nor classified toxicologically. However, methods that exploit this hyphenated strategy provide answers to such essential safety issues. Drinking or tap water did not show bioactive or toxic compounds, which was expected, whereas biogas or landfill water samples did. The hyphenated 2LabsToGo strategy is affordable and extremely useful for all laboratories with limited equipment but pressing challenges. It is ready to be used in various analytical tasks and applications.

Fast detection of apricot product frauds by added pumpkin via planar chromatography and chemometrics: Greenness assessment by analytical eco-scale

The European Commission requires that fruit products distributed on the market meet standards of high quality and authenticity. For the quality assessment of apricot products susceptible to food fraud, an environmentally friendly, simple and cost-effective analytical profiling was developed by high-performance thin-layer chromatography multi-imaging (HPTLC-FLD/Vis). The new phytochemical profiling was applied for analysis of authentic samples (7 apricot and 5pumpkin samples) and simulated adulterated products (11 mixture samples prepared by addition of 2.5-53% pooled pumpkin to pooled apricot). Based on the analytical eco-scale assessment, the HPTLC-FLD/Vis method was proven as an excellent green analytical method with low energy and solvent consumption. Chemometric data analysis confirmed the difference between apricot and apricot-pumpkin mixtures based on the phytochemical profile. Chemical markers responsible for their differentiation were identified. The results indicated that frauds by adding pumpkin to apricot products can be detected at added contents as low as 2.5%.

Combining high performance thin layer chromatography with minispectrometer-fiber optic probe-coupled to smartphone for in place analysis: Lactose quantification in several matrices

An in place colorimetric method has been proposed for estimation of the quantity of lactose in several matrix (milk, water effluents and surfaces). Analyzing the amount of this carbohydrate it can be control the product, the cleanliness of the parts of the dairy companies and it can avoid contamination of milk products produced there. This method combines the use of HPTLC for sugars separation with novel analytical devices as minispectrophotometer with fiber optic coupled to a smartphone. In order to measure the lactose a colorimetric reaction has been used. Variable volumes of samples or stock solutions were deposited in nano-silica gel layer, a mobile phase of acetonitrile:water:acetic acid was used for carbohydrate separation and a solution of thymol (0.05 g Thymol in 95 mL of EtOH and 5 mL H₂SO₄) was used for revealed the carbohydrate spot. Finally, the reflectance of samples and stock solutions were measured. The achieved limits of detection were 0.03 mg mL^-1 and 0.003 mg mL^-1 for the working concentration range and the analysis at traces level respectively.

On-surface autosampling for liquid chromatography-mass spectrometry

An on-surface multi-purpose autosampler was built for liquid chromatography-mass spectrometry (LC-MS) based on the autoTLC-MS interface, taking advantage of open-source hard- and software developments as well as 3D printing. Termed autoTLC-LC-MS system, it is introduced for orthogonal hyphenation of normal phase high-performance thin-layer chromatography with reversed phase high-performance LC (HPLC) and high-resolution MS (HRMS). For verification of its functionality, a multi-class antibiotic mixture was applied as a calibration band pattern on an adsorbent layer and detected by the Bacillus subtilis bioassay. This effect-image was uploaded as a template in the updated TLC-MS_manager software. The clicked-on antibiotic zones were sequentially eluted without intervention from the planar counterpart (without bioassay) via a monolithic HPLC column into the HRMS system. For elution of antibiotics of 7 structural classes at 5 different calibration levels, the new on-surface autosampler achieved intra-day precisions of 2.1-14.1%, while inter-day precisions ranged 2.5-16.1% (all n = 3). The new hyphenation offers potential for planar sample clean-up prior to HPLC, concentration of liquid samples, increase of peak capacity and proof of peak purity or isomers. The integrated autoTLC-LC-MS system enabled high sample throughput, efficiency and reproducibility for the first time through fully automated TLC-LC-MS sequence operation. Its contact-closure signal functionality, versatile 3D printed planar sample holder and open-source software made it readily adjustable for new analytical tasks. Undoubtedly, any planar material can be investigated for leachables, such as textiles, foils, papers and other packagings, as well as planar biological samples for ingredients.

Reducing lactose content of milk from livestock and humans via lactose imprinted poly(2-hydroxyethyl methacrylate-N-methacryloyl-i-aspartic acid) cryogels

Lactase, which can cause lactose intolerance in its deficiency, is a vital enzyme concerning digestion. To overcome lactose intolerance for patients with digestion problem depending of this kind of issue, lactose in food should be removed. In this study, lactose imprinted poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-aspartic acid), poly(HEMA-MAsp), cryogels were synthesized to reduce the amount of lactose content of milk samples. Occurrence of desired bounds, structural integrity, and surface characteristics were analyzed via Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), scanning electron microscope (SEM), micro computed tomography (CT), and confocal microscope methods. Water retention characteristic were tested in solution with different electrolytic nature. Adsorption parameters were optimized in an aqueous medium. The adsorption performance of imprinted cryogels was studied in milk samples obtained from cow, sheep, goat, buffalo, and from human volunteers at different intervals after birth. Amount of lactose adsorbed in aqueous media and milk sample from humans were 322 (56.7%) and 179.5 (5.94%) mg lactose/g polymer, respectively. Selectivity studies revealed an approximately 8-fold increase in adsorption rate of molecularly imprinted cryogels as compared to that of nonimprinted cryogels. In addition, competitive adsorption was conducted using lactose-imprinted cryogels in aqueous media containing lactose, glucose, and galactose molecules resulting in adsorption rates of 220.56, 57.87, and 61.65 mg biomolecule/g polymer, respectively.

Determination of Carbohydrates in Lactose-Free Dairy Products to Support Food Labelling

Milk and its derivatives are the basis of human nutrition since childhood. Given their importance within a balanced diet, the determination of carbohydrates in milk and its derivatives is fundamental for two reasons: one of alimentary origin related to intolerances and the other one of technological origin, especially for PDO (Protected Designation of Origin) products. The dietetic approach, including lactose-free products, has a crucial role in the management of lactose intolerance, but labelling and compositional rules indicating the absence or reduced presence of lactose in food are currently not harmonised at Union level. Considering the above-mentioned issues and the absence of official methods for the determination of low sugar concentrations, we propose a new and simple IC-HRMS method to detect carbohydrates in milk and different lactose-free derivatives, which can allow the definition of concentration limits useful to characterise products suitable for specific dietary regimes.

HI-HPTLC-UV/Vis/FLD-HESI-HRMS and bioprofiling of steviol glycosides, steviol, and isosteviol in Stevia leaves and foods

Food products and botanicals on the global market need to be investigated in a more comprehensive way to detect effects, falsifications or adulterations. This is especially true for such ones containing Stevia leaves, Stevia extracts, or steviol glycosides. A multi-imaging profiling was developed exploiting hydrophilic interaction liquid chromatography (HILIC). A minimalistic sample preparation, different mixtures of acetonitrile and water/buffer on the silica gel phase as well as derivatization reagents and optional hyphenation with high-resolution mass spectrometry were exploited. The hydrophilic interaction high-performance thin-layer chromatography (HI-HPTLC) development took 10 min for 48 analyses. It was used to screen Stevia leaf extracts and 20 different food products. For the first time, the biological and biochemical profiling of Stevia leaf products by HI-HPTLC-UV/Vis/FLD-assay pointed to 19 different bioactive compound bands found in the more natural multicomponent Stevia leaf extracts, whereas most of these activities were not existent for the steviol glycosides. The chemically isolated, purified, and EU-regulated steviol glycosides ease risk assessment and food product development. However, multipotent botanicals may have subtle impact on homeostasis via several metabolic pathways, providing benefits for the consumer's health. Analyzed side by side by means of the effect-directed profiling, their individual activity profiles were visualized as image and individual substances of importance were pointed out. Multi-imaging (comprehensive detection) plus non-targeted bioprofiling (focus on known and unknown bioactivity) allows for a fast detection of questionable product changes that occur along the global food chain and are particularly related to food safety. Graphical abstract.

Impact of Natural and Artificial Sweeteners Compounds in the Sensory Profile and Preference Drivers Applied to Traditional, Lactose-Free, and Vegan Frozen Desserts of Chocolate Flavor

The study developed traditional and light chocolate-flavor frozen dessert formulations, aimed at the general public, lactose intolerants, and vegans, and evaluated influences on quantitative sensory profiles and consumer acceptance with the replacement of sucrose by sweeteners in low-calorie versions. Twelve samples with different matrices were studied, sweetened with sucrose, sucralose, and stevia. The ideal concentration of sucrose (9%: dairy samples and 15%: vegan samples) was determined by the JAR scale. The sweetness equivalence was determined by the magnitude estimation method. The physical-chemical parameters were evaluated: pH, overrun, melting, and texture. The sensory profile evaluated through Quantitative Descriptive Analysis (QDA). The QDA data were correlated with acceptance data by partial least squares regression (PLS). The results showed that the substitution of traditional milk by lactose-free milk in the formulation did not change the characteristics of the chocolate ice cream. The use of sweeteners presented differences for milk flavor, bitter taste, bitter residual, and melting. The use of stevia extract was characterized by the presence of bitter taste, residual sweet and bitter that inhibited the perception of milk flavor, but not directly impacting the acceptance by consumers. The sucralose presented a profile closer to the sucrose, presenting lower intensity for the undesirable attributes such as bitter taste and residual bitter. There was no significant difference in the use of soy or rice protein in vegan versions, however, the use of sweeteners and body agents negatively impacted consumers' acceptance by attenuating the flavor of vegetable protein and raising gummy coating during the melting. PRACTICAL APPLICATION: This study shows the development and sensory profile of frozen chocolate desserts. Traditional and modified samples have also been produced for consumers with dietary restrictions such as vegans, vegetarians, lactose intolerants, and diabetics. Throughout the sensory and statistical analysis, it was identified how to replace sucrose by the natural glycoside sweetener of steviol, as well as the impact on the sensory profile and the acceptance of the different formulations. The results found may provide important information for researchers in food industries who need to produce frozen chocolate desserts for vegans, vegetarians, lactose intolerant, and diabetic consumers. Stevia and sucralose were good substitutes for sucrose in the formulation of frozen desserts without lactose, but not in vegan versions (with rice and soy protein).

Lovastatin in lactone and hydroxy acid forms and citrinin in red yeast rice powders analyzed by HPTLC-UV/FLD

For the analysis of pigment-rich red yeast rice products, a fast quantitative high-performance thin-layer chromatography (HPTLC) method was newly developed and validated. The active ingredient lovastatin, present in lactone (LL) and hydroxy acid forms (LH), as well as the mycotoxin citrinin were analyzed in 19 red yeast rice products, including powders, dietary supplements, and Chinese proprietary medicines (Xuezhikang and Zhibituo). The HPTLC method including sample preparation allows a high throughput of matrix-rich samples (10 min per analysis) and is highly cost-efficient (running costs of 0.5 Euro per analysis). For a fast protocol, application volumes up to 10 μL were selected although higher application volumes will lower still the LODs, which were 30 mg/kg for LL and LH as well as 4 mg/kg for citrinin. Thanks to the minimalistic sample preparation, the overall mean recovery rate was good (109.9% ± 5.9%; repeated measurements of the three analytes per fresh sample preparation at three spike levels). Repeated calibrations (five per analyte) in the red yeast rice matrix showed highly satisfying determination coefficients (≥ 0.9991; mean 0.9996). For three analytes at three concentration levels, the obtained mean intermediate precisions in red yeast rice matrix analyzed over the whole procedure including sample preparation were highly satisfying (≤ 2.6%). Citrinin was not detectable in the samples down to the given LOD of 4.0 mg/kg for the 10-μL sample volume applied. The mean content of lovastatin in 15 RYR powders was 8.7 g/kg, with a rang of 1.5-26.2 g/kg. The content of lovastatin in Zhibituo tablets and Xuezhikang capsules was determined to be 2.7 and 11.1 g/kg, respectively. The two commercially available RYR dietary supplement samples showed the highest lovastatin contents of 40.7 and 41.4 g/kg. By these figures of merit, the HPTLC method was proven to be suited for the control of such matrix-rich, fermented food. Graphical abstract.

Vulnerability of anthocyanins to the components of a thin-layer chromatographic system and comprehensive screening of anthocyanes in alimentary products

The aim of this study was to revisit the TLC authentication of alimentary products concept based on analysis of anthocyanes with the foodstuffs of plant origin. To this effect, we used two anthocyanins (cyanin and keracyanin) and two anthocyanidins (pelargonidin and delphinidin) as phytochemical standards. The first step was to develop a novel method making use of the RP-18 F_254s stationary phase (which ensures mixed-mode retention mechanism with the localized adsorption on the non-bonded silanols) and acetic acid as the mobile phase component. Importantly, similar TLC systems are currently used for the analysis of anthocyanes. Individual steps of our method development enabled a deeper insight in vulnerability of anthocyanins to external conditions resulting in hydrolysis thereof. In this study, it was impossible to fully separate the products of hydrolytic degradation of the test anthocyanins in a single development run and it was only triple development which ensured distinct and symmetrically shaped chromatographic spots, further scrutinized with use of mass spectrometry. The identity of the hydrolytically split fractions was additionally studied with use of the p-aminobenzoic acid (PABA) test. To obtain calibration curves, triple development was employed for cyanin, keracyanin, and pelargonidin, while delphinidin was developed in one development run. The respective LOD and LOQ values were: for spot (i) derived from the cyanin standard, 0.005 and 0.016 μg spot^-1; for spot (ii) derived from the cyanin standard, 0.006 and 0.017 μg spot^-1; for spot (i) derived from the keracyanin standard, 0.092 and 0.274 μg spot^-1; for spot (ii) derived from the keracyanin standard, 0.035 and 0.104 μg spot^-1; for the pelargonidin standard, 0.013 and 0.040 μg spot^-1; and for the delphinidin standard, 0.036 and 0.108 μg spot^-1. The developed method was used to identify and quantify cyanin, keracyanin, pelargonidin and delphinidin in selected alimentary products (syrups, juices and herbal infusions), keeping in mind that the obtained numerical results were of semi-quantitative nature only.

High-performance thin-layer chromatography analysis of steviol glycosides in Stevia formulations and sugar-free food products, and benchmarking with (ultra) high-performance liquid chromatography

A high-performance TLC (HPTLC) method was newly developed and validated for analysis of 7 steviol glycosides in 6 different types of food and Stevia formulations. After a minimized one-step sample preparation, 21 samples were developed in parallel, allowing an effective food screening. Depending on the sample application volume, the method was suited to analyze food sample concentrations in the mg/kg range. LOQs of stevioside in natural yoghurt matrix spiked at 0.02, 0.13 and 0.2% were determined by the calibration curve method to be 12ng/band (peak height). ANOVA was successfully passed to prove data homogeneity in the working range (30-600ng/band). The accuracy (recovery tolerance limit, 92-120%), repeatability (3.1-5.4%) and intermediate precision (4.0-8.4%) were determined for stevioside in milk-based matrix including sample preparation and recovery rates at 3 different concentration levels. For the first time, the recording of HPTLC-ESI-MS spectra via the TLC-MS Interface was demonstrated for rebaudioside A. HPTLC contents for rebaudioside A were compared with results of two (U)HPLC methods. The running costs and analysis time of the three different methods were discussed in detail with regard to screening of food products.