Evaluation of immunoglobulins in bovine colostrum using laser induced fluorescence

Toward commercial applications of LED and laser-induced fluorescence techniques for food identity, quality, and safety monitoring: A review

The assessment of food safety and quality is a matter of paramount importance, especially considering the challenges posed by climate change. Convenient, eco-friendly, and non-destructive techniques have attracted extensive attention in the food industry because they can retain food safety and quality. Fluorescence radiation, the process by which fluorophore emits light upon the absorption of ultraviolet or visible light, offers the advantages of high sensitivity and selectivity. The use of excitation-emission matrix (EEM) has been extensively explored in the food industry, but on-site detection of EEMs remain a challenge. To address this limitation, laser-induced fluorescence (LIF) and light emitting diode-induced fluorescence (LED-IF) have been implemented in many cases to facilitate the transition of fluorescence measurements from the laboratory to commercial applications. This review provides an overview of the application of commercially available LIF/LED-IF devices for non-destructive food measurement and recent studies that focus on the development of LIF/LED-IF devices for commercial applications. These studies were categorized into two stages: the preliminary exploration stage, which emphasizes the selection of an appropriate excitation wavelength based on the combination of EEM and chemometrics, and the pre-application stage, where experiments were conducted on scouting with specific excitation wavelength. Although commercially available devices have emerged in many research fields, only a limited number have been reported for use in the food industry. Future studies should focus on enhancing the diversity of test samples and parameters that can be measured by a single device, exploring the application of LIF techniques for detecting low-concentration substances in food, investigating more quantitative approaches, and developing embedded computing devices.

Reflection-enhanced laser-induced fluorescence spectroscopy to improve the analytical sensitivity in liquids

The current work demonstrates a novel approach to enhancing the analytical sensitivity of the laser-induced fluorescence (LIF) technique in liquids. An increase in the fluorescence spectral band intensity of about sixfold compared to the conventional LIF has been achieved. Such betterment has been accomplished by having the fluorophore liquid in a cuvette having a reflecting mirror-like side facing the exciting incident laser beam. The silvered or aluminized reflecting side of the cuvette was tested. The pilot test of the proposed cuvette was performed using an excitation laser light of 405 nm wavelength and five mW average power on chlorophyll-a (Chl-a) samples of different concentrations. As a result, a pronounced improvement in the Chl-a fluorescence spectral band intensity is achieved. Such a novel approach, the reflection-enhanced laser-induced fluorescence (RELIF), has been used to analyze six Egyptian brands of extra virgin olive oil (EVOO). Compared to the LIF measurement results on the same EVOO, the RELIF was superior in terms of the fluorescence-spectrum intensity enhancement factor. Both Ag and Al coatings of the cuvette revealed similar results. Statistical analysis of the measured fluorescence spectra via the partial least square regression (PLSR) method for LIF and RELIF revealed a higher coefficient of determination R² for both RELIF measurements (with silver and aluminum coating) than for LIF. The proposed novel RELIF approach can be utilized for other fluorophore liquids at higher analytical sensitivity than conventional LIF. On the other hand, the RELIF technique is straightforward, cost-effective, and does not complicate the traditional LIF setup.

Temporal kinetics of bovine mammary IgG secretion into colostrum and transition milk

Neonatal calf survival and health is predominantly dependent on sufficient consumption of immunoglobulin G (IgG) and the resulting transfer of passive immunity (TPI). In this study, we investigate the potential for continued IgG secretion and temporal kinetics of mammary IgG output in sequential milkings performed at 0, 4, 16, 28, 40, and 52 hr postcalving in Holstein dairy cows. For colostrum (0 hr), we also scrutinize the relationships between IgG concentration, volume, refractometer readings (˚Bx values, Brix) and concentration of sugars (lactose and glucose). Mammary transcripts postpartum (0 hr) indicated that active IgG secretion continues beyond the first milking (colostrum; n = 4 to 5). IgG measurements at the different timepoints indicated that colostrum represents only 25.1% of the total IgG produced across the 6 sequential milking timepoints, with a substantial 48.9% being secreted into transition milk over the next 3 timepoints (4-, 6-, and 28-hr) combined. The differences on the basis of IgG concentrations across 0-, 4-, and 16-hr milking timepoints were not statistically significant (P = 0.1522; n = 9). For colostrum, volume remained highly variable, even with induced let-down prior to milking (n = 27). Nonetheless, colostrum IgG secretion was significantly co-regulated with volume (R2 = 0.915; P < 0.001; n = 18), an association that was stronger than that measured for lactose (R2 = 0.803; P < 0.001; n = 18) and glucose (R2 = 0.467; P = 0.002; n = 17). Comparing colostrum ˚Bx values to absolute IgG concentrations showed no correlation (R2 = 0.127; P = 0.07; n = 27); biochemical separation of colostrum components indicated that both proteins and nonprotein solutes could affect ˚Bx values (P < 0.0001 for both; n = 5). This suggests that ˚Bx values do not reasonably indicate IgG concentration to serve as a measure of "colostrum quality." Additionally, our finding that early transition milk (4-, 6-, and 28-hr) can contribute substantially more IgG than colostrum forces a rethink of existing feeding paradigms and means to maximize TPI in calves. Collectively, our results reveal the remarkable value of early transition milk and caveats to colostrum assessments that could advance application in enhancing neonatal calf health.