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Microbial screening is a primary concern for many products. Traditional techniques based on standard plate counts (SPC) are accurate, but time consuming. Furthermore, they require a laboratory environment and qualified personnel. The Impedance Technique (IT) looking for changes in the electrical characteristics of the Sample Under Test (SUT) induced by bacterial metabolism represents an interesting alternative to SPC since it is faster (3-12 hours vs 24-72 hours for SPC) and can be easily implemented in automatic form. With this approach, the essential parameter is the time for bacteria concentration to reach a critical threshold value (about 107 cfu∙mL-1) capable of inducing significant variations in the SUT impedance, measured by applying a 100 mV peak to peak 200 Hz sinusoidal test signal at time intervals of 5 minutes. The results of this work show good correlation between data obtained with the SPC approach and with impedance measurements lasting only 3 hours, in the case of highly contaminated samples (106 cfu∙mL-1). Furthermore, this work introduces a portable system for impedance measurements composed of an incubation chamber containing the SUT, a thermoregulation board to control the target temperature and an impedance measurement board. The mix of cheap electronics and fast detection time provides a useful tool for microbial screening in industrial and commercial environments.

Olive oil is a very important product due to its nutritional value, sensory and antioxidant properties. National and international regulations define basic quality parameters (such as acidity and peroxide index) to discriminate high quality oils (extra virgin olive oil) from those of lower quality. The standard procedures to measure acidity and peroxide index feature manual titration requiring laboratory environment and trained personnel. In this paper a novel technique, based on electrical impedance spectroscopy, is presented and implemented as a low-cost, mobile instrument to be used everywhere and by anybody, with substantial improvements of the current quality control of olive oil producers of any dimension. The presented method is validated on 39 olive oil samples with different levels of acidity, peroxide index and total phenolic content. The results show that the conductance of an emulsion of olive oil with a hydro-alcoholic solution is correlated with the oil acidity. Furthermore, since, for the same oil, the emulsion conductance varies with the oil storage conditions (because of increases in the peroxide index), the presented technique could also be used to evaluate product ageing.

Bacterial detection is of primary importance in many fields, such as food and environmental monitoring. Measurements of bacterial concentration are traditionally carried out by means of the Standard Plate Count technique, a reliable method for microbial screening that, however, features long response time and is carried out by qualified personnel in microbiology laboratories. The impedance technique for bacterial concentration detection represents a method very competitive with Standard Plate Count in terms of response time (3-12 hours vs. 24-72 hours) as well as for the possibility to be realized in automatic form. This paper presents an embedded portable biosensor system for the measurement of bacterial concentration in cow’s raw milk. The possibility to perform measurements “on the field”, hence without the need to ship samples to distant laboratories, and to transmit the data on wireless communication systems or on the Internet represents a substantial advantage in terms of time and cost, thus making the presented system an important tool for in-situ bacterial screening.

Sine wave signals are widely used in electronic applications such as digital oscilloscopes calibration, speech analysis and electrochemical sensors. In particular, impedance based microbial biosensors detect bacterial concentration by stimulating the sample with a sinusoidal test signal and measuring its electrical characteristics. Thus, for reliable microbial biosensing, fast and accurate sine wave analysis is mandatory. Many algorithms for the estimation of sinusoidal parameters exist that provide accurate estimate but are based on time consuming iterative procedures and/or need good starting values for the sine parameters. In this paper a linear non iterative algorithm based on the least squares method is presented that allows sinusoidal voltages analysis in a fast and efficient manner. The algorithm has been tested either with simulation analysis either with real impedances and the results proved to be accurate enough for reliable bacterial concentration measurement.

The quality of olive oil is essentially determined by the product free acidity and peroxide value, while the total phenol content is also important for a high antioxidant capacity. Generally, these parameters are measured with laboratory analysis, that are expensive and may require a few days. Thus, a cheap and easy technique usable by untrained personnel, “on-site” and producing results “in real time” during production is desirable, particularly as far as small olive oil mills and packaging centers are concerned. This paper describes a technique to determine peroxide value and total phenol content in olive oil, that is based on the measurement of optical density of an emulsion between a suitable chemical reagent and a small quantity of the oil of interest. The optical density is measured by illuminating the sample with a LED with peak wavelength of 569 nm for peroxide value and 835 nm for total phenol content. The experimental results show good correlation (R2 = 0.883 and 0.895 for peroxide value and total phenol content, respectively) between data measured with the standard methodology and the technique of this work, implemented also in the form of a portable embedded system.

Bacterial screening is very important in water environmental monitoring, since the presence of dangerous pathogens can seriously endanger human health. Microbial concentration detection is performed by Standard Plate Count technique, which is reliable but is characterized by long response time and is not suitable to be implemented in automatic form. This work presents a portable sensor implemented as an electronic embedded system featuring disposable measurement cells and based on impedance measurements, that is suitable to measure bacterial concentration in water samples. The system provides much faster response than standard technique (3 – 12 hours depending on the contamination level vs. 24 – 72 hours of the standard technique) and can be used for in-situ microbial test without the need to ship samples to a laboratory for analysis. Water samples from different sources (rivers, wastewaters, watercourses) have been tested using the presented system. Enriched medium has been added to the sample to favour bacterial growth. Three different media have been tested (Lauria Bertani, Mc Conkey Broth, Lactose Broth) and data have been compared in relation to microbial growth rate and selectivity towards bacterial group (e.g. coliforms). The obtained experimental data showed good correlation with Plate Count technique.

Electrical characterization of products is gaining increasing interest in the food industry for quality monitoring and control. In particular, this is the case in the ice-cream industry, where machines dedicated to store ice-cream mixes are programmed “ad hoc” for different groups of products. To this purpose, the present work shows that essential product classification (discrimination between milk based and fruit based ice-cream mixes) can be done by means of a technique based on the measurements of non-linear response in the electrical behavior of the electrode-electrolyte interface. The addition of pH measurements allows to further reach the three parts classification occasionally required for advanced applications. The proposed idea is validated by means of measurements on 21 ice-cream mixes, different for producers and composition.

Virgin olive oil is an important ingredient of the Mediterranean diet highly appreciated for its beneficial health effects due to the presence of mono-unsaturated fatty acids and antioxidant properties. The olive oil quality is defined by many parameters, among which acidity and peroxide index and according to international regulations, these two determinations are carried out in laboratory environment, by means of manual titration. This kind of method, however, cannot be used on oil production sites, where, instead, it would be desirable to know the main characteristics of the oil for proper product classification. In this paper a new technique to measure olive oil acidity by electrical conductance is presented that allows for fast, cost-effective and on-site measurements. Such a technique has been validated with a set of 55 olive oil samples. Two different oil emulsions have been used and compared for the measurements: based on a hydro-alcoholic solution (60% ethanol 40% distilled water) and distilled water, respectively. The data show that the electrical conductance of the emulsion with hydro-alcoholic solution is a strong function of the olive oil acidity, that can be estimated with good accuracy (R2 = 0.9308). The experiments with distilled water, instead, exhibit no significant correlation between oil acidity and emulsion conductance that, however, is found to provide information about peroxide index, polyphenols content and filtration technique. Furthermore, using both types of emulsions to compensate for conductance variations other than free fatty acids the accuracy in acidity determination can be improved reaching R2 = 0.9786.

The freezing process is very important in ice cream production affecting quality, taste and yield of the finished product. Batch freezer machines use different control techniques to tightly control the freezing process, based on monitoring of the temperature and/or the viscosity (i.e. consistency) of the product. Temperature control, however, features low sensitivity and need calibration for different product compositions, while product viscosity is essentially inferred from dasher motor load, sensitive to power line fluctuations, volume of product and dasher motor characteristics. In this context, this paper presents a novel technique based on measurements of the product electrical characteristics, tightly linked to temperature and viscosity. The experimental results presented in this work clearly indicate that the proposed technique provides a suitable, non destructive tool to monitor ice cream quality product that overcomes the drawbacks of the standard methods, thus representing an advance in the state of the art for freezing control.