Rapid and High Throughput Detection of Pathogenic Bacteria in Food Samples

Author Institution: Department of Food Science and Technology, The Ohio State Universit

The potato : composition, non-enzymatic browning and anthocyanins

Chipping varieties and model systems were used to determine the role of potato constituents on chip color. Composition was evaluated by HPLC and chip color measured using a ColorQuest colorimeter. Reducing sugar (RS) content did not completely explain color quality when present in low concentrations (<60 mg/lOOg). Levels of ascorbic acid, glutamine and a chlorogenic acid isomer, along with RS, showed high correlation with color. Sucrose was a poor estimator of chip color. Model systems used leached potato slices infiltrated with solutions containing sucrose, RS, ascorbic, chlorogenic and amino acids. Linear association of RS with L* and hue angle and quadratic relationship with chroma of chips were found. Ascorbic acid affected chroma and hue at low RS levels while chlorogenic acid was not involved in color development. Red potatoes {Solarium tuberosum and Solarium stenotomum) were evaluated as potential source of natural red colorant. Cultivars (33) were screened for anthocyanin content and qualitative composition. Monomeric anthocyanin content, determined by pH differential, ranged between 4 and 40 mg/lOOg fresh weight (fw) tuber. Varieties 5847-1 and ND04069-4 showed high anthocyanin content (>35 mg/lOOg). Anthocyanin composition was characterized by HPLC, spectral analysis and Mass Spectroscopy (MS). The major anthocyanin was pelargonidin-3-rutinoside-5-glucoside acylated with p-coumaric acid. The presence of glycoalkaloids (α-solanine and α-chaconine) was detected by MS and quantified by HPLC. Varieties NDO4069-4 and 5847-1 showed glycoalkaloid levels of 13 and 7 mg/lOOg fw, respectively. Glycoalkaloids were precipitated from pigment concentrates by alkaline treatment. The best results were obtained at pH 8.0 with 30% monomeric anthocyanin degradation and 90% glycoalkaloid precipitation. The color and pigment stability of chemically related anthocyanin extracts (red-fleshed potatoes and radishes), the effect of pigment purity, and temperature were evaluated in model juices (pH 3.5). Color (CIELch) and anthocyanin degradation was monitored for 65 wks of storage. All model juices showed color similar to FD&C Red # 40. Excellent stability was obtained with all treatments in refrigeration. Anthocyanin structure and extraction method affected pigment stability. At 25°C, higher stability was obtained on juices colored with chemically purified radish anthocyanins (22 wk half-life) and lowest with potato vegetable juice (10 wk half-life)

Monitoring Turkish white cheese ripening by portable FT-IR spectroscopy

The biochemical metabolism during cheese ripening plays an active role in producing amino acids, organic acids, and fatty acids. Our objective was to evaluate the unique fingerprint-like infrared spectra of the soluble fractions in different solvents (water-based, methanol, and ethanol) of Turkish white cheese for rapid monitoring of cheese composition during ripening. Turkish white cheese samples were produced in a pilot plant scale using a mesophilic culture (Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris), ripened for 100 days and samples were collected at 20-day intervals for analysis. Three extraction solvents (water, methanol, and ethanol) were selected to obtain soluble cheese fractions. Reference methods included gas chromatography (amino acids and fatty acid profiles), and liquid chromatography (organic acids) were used to obtain the reference results. FT-IR spectra were correlated with chromatographic data using pattern recognition analysis to develop regression and classification predictive models. All models showed a good fit (RPre ≥ 0.91) for predicting the target compounds during cheese ripening. Individual free fatty acids were predicted better in ethanol extracts (0.99 ≥ RPre ≥ 0.93, 1.95 ≥ SEP ≥ 0.38), while organic acids (0.98 ≥ RPre ≥ 0.97, 10.51 ≥ SEP ≥ 0.57) and total free amino acids (RPre = 0.99, SEP = 0.0037) were predicted better by using water-based extracts. Moreover, cheese compounds extracted with methanol provided the best SIMCA classification results in discriminating the different stages of cheese ripening. By using a simple methanolic extraction and collecting spectra with a portable FT-IR device provided a fast, simple, and cost-effective technique to monitor the ripening of white cheese and predict the levels of key compounds that play an important role in the biochemical metabolism of Turkish white cheese

Raman Spectroscopy for Food Quality: Assessment Uncovering Adulteration and Ensuring Authenticity

The globalization of the food market, the prevalence of economically motivated adulteration, and the scarcity of high-value food sources have posed significant challenges to ensuring food authenticity in the industry. The assessment of food authenticity has now become a matter of utmost importance, necessitating the adoption of rapid and robust methods. While well-established techniques are available for analysis, many are not always feasible because of the need for high-priced instrumentation and proficient operators, excessive time requirements, and the destructive nature of the methods. However, Raman spectroscopy has been positioned as an attractive technology offering high-speed and nondestructive fingerprinting capabilities to monitor sample characteristics of foods. Improvements in optical technology and portable instruments have allowed field-deployable devices and have made it practical to detect adulteration from production to the market. An extensive literature has demonstrated the convenience and efficacy of these instruments in fulfilling the needs of the food industry. This chapter highlights the recent advancements in research studies focusing on the utilization of Raman spectroscopy for the rapid determination of food adulteration and authentication. These developments showcase the potential of Raman spectroscopy as a valuable tool in addressing the challenges posed by food fraud. The ongoing progress in Raman spectroscopy and its applications in food authenticity assessment represents a significant step forward in combating adulteration and ensuring the integrity of our food supply. Further research and technological advancements in this field will enhance the capabilities of Raman spectroscopy, providing the industry with increasingly reliable, efficient, and practical methods to combat food adulteration and authenticate the foods we consume

Advanced spectroscopy-based phenotyping offers a potential solution to the ash dieback epidemic

Natural and urban forests worldwide are increasingly threatened by global change resulting from human-mediated factors, including invasions by lethal exotic pathogens. Ash dieback (ADB), incited by the alien invasive fungus Hymenoscyphus fraxineus, has caused large-scale population decline of European ash (Fraxinus excelsior) across Europe, and is threatening to functionally extirpate this tree species. Genetically controlled host resistance is a key element to ensure European ash survival and to restore this keystone species where it has been decimated. We know that a low proportion of the natural population of European ash expresses heritable, quantitative resistance that is stable across environments. To exploit this resource for breeding and restoration efforts, tools that allow for effective and efficient, rapid identification and deployment of superior genotypes are now sorely needed. Here we show that Fourier-transform infrared (FT-IR) spectroscopy of phenolic extracts from uninfected bark tissue, coupled with a model based on soft independent modelling of class analogy (SIMCA), can robustly discriminate between ADB-resistant and susceptible European ash. The model was validated with populations of European ash grown across six European countries. Our work demonstrates that this approach can efficiently advance the effort to save such fundamental forest resource in Europe and elsewhere

Peroxidase and lipoxygenase activities and their effect on the stability of polyunsaturated fatty acids in two different varieties of sweet corn (Zea mays L.), Jubilee and GH 2684, during frozen storage

The effect of different blanching treatments and packaging materials on the enzymatic (lipoxygenase and peroxidase) activity and fatty acid stability of two different varieties of sweet corn on the cob (Jubilee and GH 2684) was evaluated during nine months of frozen storage at -23.3°C. The initial moisture content in the kernels of the two sweet corn varieties averaged 72.5%. After nine months of frozen storage the moisture content in the kernels of corn depended greatly on the packaging material used. The ears stored in Cryovac B and E bags showed the best moisture retention (72.2% final moisture content), followed by the polyethylene bags (71.4%) while the ears stored without packaging material showed severe dehydration (70.1%). The peroxidase and lipoxygenase activities were determined using spectrophotometric assays on a crude extract obtained from liquid nitrogen powdered corn. Both unblanched varieties of sweet corn showed similar initial peroxidase specific activity and general behavior during the nine months of frozen storage. The presence of lipoxygenase isozymes with different thermal stabilities in both varieties was suggested by the higher lipoxygenase specific activity found in Jubilee after freezing and nine months of frozen storage (0.135 units/mg protein) compared with the GH 2684 variety (0.115 units/mg protein). Complete inactivation of lipoxygenase was obtained after 9 minutes steam blanching at 100°C. Peroxidase was more heat resistant showing some remaining specific activity after 9 minutes steam blanching with a complete inactivation after 15 minutes steam blanching. No regeneration of either enzyme was observed during the nine months of frozen storage suggesting a permanent disruption of the active site of both enzymes. Relative fatty acid content was determined by gas chromatographic analysis of fatty acids methyl esters. The major fatty acids present in both varieties were palmitic (14.93%), stearic (2.79%), oleic (31.54%), linoleic (46.87%) and linolenic (1.89%) acids. Good stability of the polyunsaturated fatty acids was observed during the nine months storage at -23.3°C, with autoxidation as the main mechanism responsible for the decrease in the relative percent of polyunsaturated fatty acids. Some enzymatic oxidation also occurred, decreasing the linolenic acid content. The control of the degradation of polyunsaturated fatty acids depended mostly on the frozen storage temperature (-23.3°C) and not on the oxygen permeability of the different packaging materials. The results obtained in our study suggested that blanching of the ears of sweet corn had an important effect on reducing the enzyme activity but little effect on the polyunsaturated fatty acid degradation after 9 months of storage at -23.3°C