Stefania Barzaghi

Sugars as a perturbation of the water matrix

Near infrared (NIR) and nuclear magnetic resonance (NMR) spectroscopy studies were performed to determine the behaviour of water during an osmotic process of apple spheres in concentrated sugar solutions. The osmotic dehydration is a process of water removal from cellular structures through immersion in a hypertonic solution. Relationships between sugars and water were studied using both two-dimensional correlation, calculated on NIR spectra recorded during the process, and NIR–NMR outer product analysis (OPA). We found that there was a shift of 7nm towards higher wavelengths in the maximum absorbance of the first overtone range of the water O–H stretching, due to the increase of hydrogen bonds implicated in the binding of the sugars progressively increasing in concentration during water removal. The absorptions detected by two-dimensional correlation, using processing time as the dynamic variable, belong to the elements which have more OH free as indicated from the outer product analysis, i.e. free water at 1936 nm followed by bonded water at 1393 nm and 1518 nm and sugars at 2131 nm, respectively.

Near infrared monitoring of mineralisation of liquid dairy manure in agricultural soils

Liquid dairy manure is a major organic input to cultivated soils. Therefore, a method for monitoring the mineralisation of slurries should be a useful tool for managing soil fertilisation. In order to examine whether the biodegradation of cattle sludge can be monitored by near infrared (NIR) spectroscopy, soil samples from a laboratory incubation experiment were analysed using this rapid and inexpensive method. Five different cattle slurries were added to three soils with increasing clay content in such an amount as to give 130 ppm of total nitrogen. The resulting 18 experimental treatments (three control soils and 15 soil-slurry combinations) were incubated for 180 days under optimal temperature and soil water content. Each treatment was sampled at 0, 2, 8, 12, 16, 21, 29, 41, 72, 121 and 180 days: the respired CO2 was captured in alkali traps and mineral N was extracted using 1 M KCl. Three replicates of each sampling were analysed individually. The resulting 648 samples, air dried and ground at 0.5 mm, were analysed by NIR spectroscopy using an Antaris (Thermo Nicolet) Fourier transform-NIR spectrometer. Although the slurries and soil mineralised carbon represent only a very small part of the total soil organic carbon, the mineralisation of carbon can be clearly monitored by NIR spectroscopy in both amended and unamended soils. Whereas NO3–N evolution was difficult to predict using NIR data, the results for NH4–N were more encouraging. Using measurements of CO2–C respired, a two-pool mineralisation model was developed and the simulated concentration of carbon pools in the soils were used for the development of NIR equations. The results obtained in this work have demonstrated that NIR is a useful tool for monitoring the carbon mineralisation process when cattle sludge is incorporated into agricultural soils.

NIR and other luminometric methods to monitor the primary clotting phase of milk

The rapid routine method currently used to monitor the ability of milk to coagulate does not provide information on the primary clotting phase. The purpose of this work was to assess if the principal critical events related to the primary clotting phase could be detected by NIR and by other methods based on the interaction of light and material (fluorescence spectroscopy, tristimulus colorimetry) that provide a quick response. Six different coagulation tests were carried out. Reconstituted skim milk powder was used as standard substrate and the same liquid calf rennet solution was added. Milk NIR spectra were collected at 35°C using an InfrAlyzer 500 (Bran+Luebbe). Spectra were taken every 70 seconds, from rennet addition up to about 10 minutes after clotting time. Data were processed by IDAS-PC software to find the most discriminant wavelengths in highlighting spectral differences. For fluorescence tests, the primary clotting phase was monitored collecting samples at different times and stopping the enzymatic reaction at 0°C in an ice-bath. Spectrofluorimetric titrations were carried out by using ANS as hydrophobic probe and a Luminescence Spectrometer LS-B. Protein Surface Hydrophobycity (PSH) values were calculated. The ANS relative distribution was also monitored after ultracentrifugation at 0°C. In this case ANS was added to milk before rennet addition. Colorimetric assays were carried out by using a tristimulus colorimetry and data collected at the same time as NIR spectra. Differences in luminosity values were calculated. The clotting time was calculated using both a Formagraph Instrument and by visual observation of coagulation. NIR data show two critical events during the primary clotting phase, confirmed by the other techniques used. The first appears a few minutes before clotting. The second, in accordance with the visual observation of coagulation, detects the clotting point, before Formagraph in corrispondence of micellar aggregation. Interesting results are obtained by plotting selected NIR 2nd derivative absorbance values against time; this establishes a trend of coagulation, which is also detectedby the other techniques. The interrelationship among the different techniques is discussed and spectral data are interpreted in terms of water bonds and/or different amounts of free water due to the formation of new products and/or protein structure rearrangements.

Quantification of casein fractions and of some of their genetic variants in phosphate buffer by near infrared spectroscopy

Milk casein and casein fraction contents have a great influence on milk rennet properties and cheese yield so that the selection of dairy cattle with genetic characteristics suitable for milk transformation is of great interest to dairy farms and firms. The possibility of a rapid and accurate determination of these parameters would be very useful to predict milk aptitude to cheese making. This work aimed to determine casein fractions and their genetic variants content using near infrared (NIR) spectroscopy in reconstituted casein samples by comparing the performance of different NIR equipment (a monochromator instrument and a Fourier transform instrument) and different modes of measurement (reflectance and transflectance) in order to evaluate the best operative conditions for this application. Fifty-eight raw milk samples, collected from different farms in the Asturias region, Spain, were analysed for protein (TP%) and non caseinic nitrogen (NCN%) content using the Kjeldahl method. Casein content was calculated as the difference between TP and NCN content. Casein fractions (αs0-, αs1-, αs2-, κ-casein) and genetic variants of β-casein (βB- βA1-, βA2-casein) were determined by a capillary electrophoresis system. Samples were ultra-centrifuged to obtain native casein and then reconstituted in phosphate buffer (pH = 6.8) at the same original milk concentration, previously determined by the Kjeldahl method. Spectra were collected at 37°C with a FT-NIR instrument in transflectance mode and a monochrometer in both transflectance and reflectance mode. Partial least square (PLS) analyses performed on transflectance spectra showed good prediction ability for all variables—(min R2 = 0.80 for κ-casein; max R2 = 0.94 for βA2–casein), with the exception of αs2-casein. NIR spectroscopy has the ability to determine and quantify casein genetic variants and could be used to select milk for its final purpose and to predict the aptitude of milk to cheese-making.

Testing the suitability of different high-performance liquid chromatographic methods to determine aflatoxin M1 in a soft fresh Italian cheese.

Aflatoxin M1 (AFM1) is a toxic undesirable compound in milk. AFM1 affinity for caseins causes a concentration effect during milk process for dairy transformation. In spite of this, no official method of analysis, nor maximum tolerance level for aflatoxin M1 in cheese have been established. Thus, the aim of this work was to test the suitability of different HPLC methods for the AFM1 quantification in soft cheese samples at three different contamination levels (low, medium and high, at respectively nearly 30, 100 and 250 ng/kg). Nine participants were selected among Italian laboratories accredited by the Italian accreditation body (ACCREDIA) for HPLC toxin analysis. They were asked to analyze samples applying the method routinely used. The different applied methods were compared, and precision and accuracy parameters were evaluated. The main differences among HPLC procedures were registered at the level of extraction step. The use of an enzymatic digestion for the extraction of the toxin from cheese seemed to be particularly advantageous and the use of immunoaffinity columns seemed to be determinant for the improvement of sensitivity at low contamination levels. In general, the applied methods well discriminated the 3 levels of contamination, even though they performed better at the medium and high concentration levels (100 and 250 ng/kg) than at the low one (30 ng/kg). In fact relative standard deviation for reproducibility at low level was higher (60.1%) than the same value at medium and high levels (22.8% and 28.9%, respectively).

Near infrared spectroscopy for the control of osmo–air dehydrated apple rings

The aim of this work was to investigate the feasibility of near infrared (NIR) spectroscopy both in quantifying the residual water content of osmo-air dehydrated apple rings and in differentiating them on the basis of the sugar solution used in the osmotic pretreatment so identifying the osmotic syrup used. In order to achieve this, a set of products obtained by different processing conditions was created. Apple rings were dipped for different lengths of time (30, 60 and 90 min) in three different sugar solutions at the same water activity (aw = 0.90): sucrose (59% wt /wt), maltose (62% wt /wt) and a mixture (53% wt /wt) of fructose, glucose and sucrose having the same composition as apple. Air drying was then performed at different temperatures (70°, 80°, 90°C) and the obtained osmo-air dehydrated apple rings were packed in polypropylene film under vacuum in order to avoid water absorption phenomena. NIR spectra, in the range 10,000–4000 cm−1, were recorded directly on packed apple rings using a FT-NIR spectrometer equipped with fiber optic probe. In calibrating the residual water content the coefficient of determination (R2) was 0.93, the RPD value was 3.33 and RER value was 13.79, which could be considered, for our purposes, suitable for controlling the dehydration process. Moreover, applying a classification statistic method on NIR data, such as PLS discrimination analysis, it was also possible to identify correctly which sugar solution was used in the osmotic pre-treatment independently of the conditions used. Two-dimensional correlation analysis was also carried out, in order to investigate how the ratios between the main constituents, sugars and water, involved in the osmo-air dehydration varied as a function of the process variable used.

Influence of the presence of bioactive compounds in smart-packaging materials on water absorption using NIR spectroscopy and aquaphotomics:

Food packaging plays an active role in the environment/packaging/food system, and new solutions take into account new concepts of smart, active, and/or eco-friendly food packaging materials. On this point of view, the active packaging system should be capable of interacting with the food, for instance by the release of active molecules that will provide protection against microbial spoilage, and simultaneously be ‘natural’. A full exploitation of the antimicrobial and antioxidant properties of propolis, in order to achieve a significant prolongation of the shelf-life, can meet these needs. Moreover, fast methods able for classifying, sorting, and identifying the quality and the stability characteristics associated with the different materials are requested along the food chain in order to validate their properties. This study aimed the identification of bioactive compounds from Italian propolis in smart packaging materials by applying the aquaphotomics approach. The Aquagrams results highlighted that the absorption differences at 1410 nm are able to identify the paper sheets obtained by the incorporation of the active compounds. A second Aquagrams plot was built up for sheets measured on polythene layer. Results showed different water patterns at 1438, 1440, and from 1474 to 1518 nm. These data confirm that the water absorption in NIR range can be affected by the presence of chemical groups derived from the active compounds of propolis, which are able to interact with water spectral response.

The Applicability of near Infrared Spectroscopy for Monitoring Properties of Food Packaging Materials

This paper reports the results of some preliminary experiments to assess the use of NIR spectroscopy in measuring the quality and the stability of a new, active food packaging material based on propolis and comparing it to paper and polythene–paper sheets.

A portable microNIR instrument as a screening tool in discriminating fruit based beverages prepared with cow ricotta cheese whey by-products.

PROCEEDINGS OF THE 17TH INTERNATIONAL CONFERENCE ON NEAR INFRARED SPECTROSCOPY FOZ DO IGUASSU BRAZIL 18-23 OCTOBER 2015 IntroductIon Ricotta cheese whey (RCW) is obtained from the production of a typical Italian cheese named “Ricotta” which is made by heating the acidified whey to at least 90°C for a few minutes, in order to cause a heat-induced coagulation of whey proteins, that are separated by mechanical means and drained in perforated moulds1. RCW is the residual liquid, that still has some nutritional value consisting of few proteins and peptides, a strong organic content, especially due to lactose and high saline concentration. RCW-fruit based beverages are a novel type of healthy drinks, in which the nutritional components of fruit are combined with proteins and minerals of the dairy RCW by-product. Some effort have been already done to produce whey based beverages2,3, but to our knowledge RCW has never been considered as an ingredient in the formulation of fruit-based nutritional drinks. Moreover, varying the fruit component as well as the type of technological process to obtain Ricotta cheese from whey, different functional properties can be achieved. This work aimed at verifying the ability of a diode array microNIR in discriminating RCW-fruit based beverages prepared from four types of clear juices (pear, strawberry, blueberry, apple) and two RCWs, considering as technological factors the proportion of RCW to fruit juice, the influence of the pasteurization step and the RCW type.