Romdhane Karoui

Mid-Infrared Spectroscopy Coupled with Chemometrics: A Tool for the Analysis of Intact Food Systems and the Exploration of Their Molecular Structure-Quality Relationships - A Review

Public interest in food quality and methods of production has increased significantly in recent decades, due in part to changes in eating habits, consumer behavior, and the increased industrialization and globalization of food supply chains.1 Demand for high levels of quality and safety in food production obviously requires high standards in quality assurance and process control; satisfying this demand in turn requires appropriate analytical tools for food analysis both during and after production. Desirable features of such tools include speed, ease-of-use, minimal or no sample preparation, and the avoidance of sample destruction. These features are characteristic of a range of spectroscopic methods including the mid-infrared (MIR). While it is true that near-infrared (NIR) spectroscopy has achieved greater uptake by the food industry,2 reported applications of MIR in this sector have increased over the past decade or more. Foods represent significant analytical challenges. They are highly complex, variable and can be found in a number of different physical states: these include solids, dilute solutions, emulsions, foams, highly visco-elastic forms, and glassy

Effect of heat treatment of rennet skim milk induced coagulation on the rheological properties and molecular structure determined by synchronous fluorescence spectroscopy and turbiscan.

Heat treatment applied to milk induces denaturation of whey proteins, leading to a complex mixture of whey protein and whey protein coated casein micelles. The present paper investigates the effects of heat treatment (60 and 80°C during 20min) and rennet-induced coagulation temperature (30 and 40°C) determined by rheology, synchronous fluorescence spectroscopy (SFS) and turbiscan measurements. The gelation times determined by rheology and SFS increased with the increase of heat treatment applied to milk. The rise in temperature induced a decrease in the maximum curd firming rate and an increase in the viscosity of the investigated milk samples. The principal component analysis (PCA) applied, separately, to the SF and turbiscan spectra showed a clear discrimination between: (i) raw milks and heated milks; and (ii) milks renneted at 30°C from those renneted at 40°C. The results showed the ability of SFS as a rapid and non-destructive technique for the: (i) monitoring network structure and molecular interaction during the coagulation process; and (ii) determination of gelation time of rennet-induced coagulation of studied milk samples.

Use of front face fluorescence for monitoring lipid oxidation during ageing of cakes

Front face fluorescence spectroscopy coupled with chemometric tools was used as a useful tool for the monitoring of sponge cakes freshness, produced at the pilot scale, during ageing (i.e. 1, 3, 6, 9, 16, and 20days). The fluorescence emission spectra were acquired in the 340-490nm and 390-680nm after excitation at 325 and 380nm, respectively, while excitation spectra (250-390nm) were scanned after emission at 410nm. The primary and secondary products of lipid oxidation were also determined on the same cakes. The principal component analysis (PCA) applied to the each spectral collection obtained after excitation at 325 and 380nm and emission at 410nm allowed a clear discrimination of cakes according to their ageing. A high correlation between the intensity of fluorescence at 521nm and the p-anisidine values was observed since squared correlation coefficient of 0.73 was obtained. The results showed that fluorescence spectroscopy could be used as a powerful tool for the evaluation of cake freshness throughout storage.

Monitoring changes in whiting (Merlangius merlangus) fillets stored under modified atmosphere packaging by front face fluorescence spectroscopy and instrumental techniques.

Quality assessment of whiting (Merlangius merlangus) fillets stored in normal air (control group) and modified atmosphere packaging (MAP1: 50% N2/50% CO2 and MAP2: 80% N2/20% CO2) for up to 15 days at 4 °C was performed. The physico-chemical [pH, drip loss, moisture content, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS) and peroxide value (PV)], textural (i.e., hardness, fragility, gumminess, chewiness, springiness, cohesiveness), and color (i.e., L(∗), a(∗), b(∗)) parameters were determined. Front face fluorescence spectroscopy (FFFS) emission spectra were also scanned on the same samples with excitation set at 290 and 360 nm. The results indicated that MAP treatment, particularly MAP1 had an obvious preservative effect on fish quality by reducing pH value, TBARS and TVB-N contents, and retarding the softening of fish texture compared to control samples. Principal component analysis (PCA) applied to physico-chemical and instrumental data sets showed a clear discrimination of fish samples according to both their storage time and condition. A complete (100%) of correct classification was obtained by the concatenation of spectral, physico-chemical, and instrumental data sets. The results demonstrated that storage under MAP can be recommended to improve quality of whiting fillets, which in turn, can be evaluated by FFFS as a rapid and non-destructive technique.

Use of Front-Face Fluorescence Spectroscopy to Differentiate Sheep Milks from Different Genotypes and Feeding Systems

The objective of the present study was to assess the potential of front-face fluorescence spectroscopy coupled with chemometric tools for the evaluation of the quality of milk samples according to the feeding system and genotype. Fifty (n = 50) ewes milk samples were scanned after excitation set at 250, 290, 322, and 380 nm and emission set at 410 nm. Thirty out of the 50 samples composed the first trial and were obtained from two different genotypes (i.e., Comisana versus Sicilo-Sarde); the second trial was composed of 20 samples obtained from the Sicilo-Sarde genotype with two different feeding systems in pen (soybean versus scotch bean). Milk samples were divided into four groups named Sicilo-Sarde with pasture feeding (Spas), Comisana with pasture feeding (Cpas), Sicilo-Sarde feeding on scotch bean (Ssco), and Sicilo-Sarde feeding on soybean (Ssoy). The factorial discriminant analysis was applied to the: (i) four groups (i.e., Spas, Ssco, Ssoy, and Cpas) and (ii) three groups composed only of Sicilo-Sarde genotype (i.e., Spas, Ssco, and Ssoy). Considering the four groups, the best result was obtained with the excitation vitamin A spectra since correct classification amounting to 76% was observed. When the factorial discriminant analysis was performed with the three groups belonging to the Sicilo-Sarde genotype, the best result was obtained again with vitamin A spectra (i.e., emission and excitation spectra) since 88.6% of correct classification was observed. Concatenation technique applied to the five fluorescence spectra improved the rate of classification between the four groups since 44 out of 50 samples were correctly classified. No misclassification was observed between milk samples collected from ewes with pasture feeding from the pen feeding. It was concluded from the obtained results that fluorescence spectroscopy could be considered as a powerful tool for differentiating between raw milks according to both genotype and feeding system.

Classification of Soils into Different Moisture Content Levels based on VIS-NIR Spectra

Soil moisture content (MC) affects the accuracy of the visible (VIS) and near infrared (NIR) spectroscopic measurement of other soil properties e.g. carbon, nitrogen, etc. This study was conducted to subtract the MC contribution to VIS-NIR spectra by classifying soil spectra into different MC groups. A mobile, fiber-type, VIS-NIR spectrophotometer (Zeiss Corona 1.7 visnir fiber), with a measurement range of 306.5 – 1710.9 nm was used to measure the light reflectance of two sample sets; one (275 samples) collected from a single field and the other (360 samples) collected from multiple fields in Belgium and northern France. The Partial Least Squares (PLS) regression analysis and Factorial Discriminant Analysis (FDA) were applied on the VIS-NIR spectra in order to quantify MC and classify spectra into different MC groups, respectively. The PLS for the single-field sample set provided better estimation of MC (R2=0.98) than for the multiple-field sample set (R2=0.88). For the single-field sample set, spectra were successfully classified into six MC groups with correct classification (CC) of 94.1% and 95.6% for the calibration and validation data sets, respectively. Due to large variability of the multiple-field sample set, soils were successfully classified into 3 MC groups only. The CC obtained were 88.1% and 79.7% for the calibration and validation sets, respectively. These results suggested that the FDA can be successfully used to classify soil VIS-NIR spectra into different MC levels, particularly when soil variability is minimal.

Efficiency of Rosemary and Basil Essential Oils on the Shelf-Life Extension of Atlantic Mackerel (Scomber scombrus) Fillets Stored at 2°C

The objective of the present study was to evaluate the impact of rosemary and basil essential oils (EOs) on the quality of Atlantic mackerel fillets stored at 2°C up to 15 days. Atlantic mackerel (Scomber scombrus) fillets were periodically evaluated to assess their textural, color, physicochemical, and spectral characteristics. The results indicated that rosemary and basil treatments were effective for inhibiting the formation of total volatile basic nitrogen (TVB-N) and lipid oxidation products during storage. Based on TVB-N values, the shelf life of Atlantic mackerel fillets treated with rosemary and basil EOs was extended by 2 and 5 days, respectively, compared to the control group. Similar results were obtained with thiobarbituric acid-reactive substance analysis, which demonstrated an extended shelf life of Atlantic mackerel immersed with rosemary and basil EOs of 2 and 3 days, respectively, compared to the control group. The factorial discriminant analysis applied on the concatenated first five principal components corresponding to the physicochemical, textural, color, and fluorescence measurements allowed clear discrimination of the three groups, because a correct classification rate of 93.3% was obtained. Therefore, treatment with basil and rosemary EOs, as natural biopreservative compounds, could present a high-potential application in the seafood industry.

Potential of Multispectral Imager to Characterize Anisotropic French PDO Cheeses: A Feasibility Study

The present study was aimed to investigate the potential of multispectral images coupled with chemometric tools (PLSDA and PLS-R) for: (1.) discriminating different French blue veined cheeses belonging to four brand products (Fourme d’Ambert, Fourme de Montbrison, Bleu d’Auvergne, and Bleu des Causses) and (2.) predicting some of physicochemical (pH, ash, dry matter, total nitrogen, water soluble nitrogen, Ca2+, Na+, Cl−, and P) and rheological properties (softening and dropping points). The results obtained showed that multispectral imaging system applied to anisotropic blue cheeses succeeded to: (1.) discriminate cheeses based on their blue veins features in spite of the visual similarity of their structure and appearance with percentage of correct classification varying between 30 and 100%; and (2.) predict selected parameters (i.e., Ca2+, Cl−, WSN, dropping, and softening points) since R2cv ≥ 0.62 and RPD ≥ 1.62 were obtained. Moreover, the predictive results suggested that the image texture of cheese was strongly related to its physicochemical composition and rheological characteristics (softening and dropping points).

Application of Fourier-transform mid infrared spectroscopy for the monitoring of pound cakes quality during storage

The aim of the present study was to investigate the ability of MIR and texture analyzer to evaluate the quality of pound cake samples produced with palm oil and rapeseed oil throughout storage. The MIR spectra analyzed by using principal component analysis (PCA) showed a clear separation of pound cakes as a function of the storage time and the nature of the used oil in the recipe. By applying partial least square regression (PLSR), excellent prediction was obtained for hardness (R2 = 0.91; RPD = 2.26), while an approximate qualitative prediction was found for springiness (R2 = 0.73; RPD = 2.07), cohesiveness (R2 = 0.67; RPD = 1.31) and resilience (R2 = 0.65; RPD = 1.24). It could be concluded that the MIR spectroscopy could be used as a rapid and non-destructive technique for monitoring texture of pound cakes throughout storage as well as for the prediction of their hardness.

Chapter 15 – Eggs and Egg Products

Publisher Summary The (Vis)/near-infrared (NIR) spectroscopy provides significant information about the quality of egg and egg products, including the detection of blood, and meat spots, and hatching as well as the composition of egg products. The NIR spectroscopy has been used successfully in determining egg quality during storage. The mid-infrared spectroscopy (MIR) can be used as a rapid technique for the determination of eggshell quality. The MIR provides better results than egg size parameters. In addition, fracture force, maximal deformation, and shell stiffness are found to be predicted with comparable accuracy by both MIR and egg size parameters. NIR reflectance, among other spectroscopic techniques, is used for the determination of moisture, fat, and protein in spray-dried whole egg. A standard error of performance of 0.15%, 0.20%, and 0.28% is obtained for moisture, protein, and fat, respectively, using a calibration based on three wavelengths. NIR transmission can be used for the measurement of protein, total lipid, and total solid contents of liquid egg products. NIR reflectance is used for the prediction of the physicochemical composition of freeze-dried egg yolk samples from laying hens fed with four different diets enriched with different sources of n-3 polyunsaturated fatty acids.