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The quality and authenticity of milk are of paramount importance. Cow milk is more allergenic and less nutritious than ewe, goat, or donkey milk, which are often adulterated with cow milk due to their seasonal availability and higher prices. In this work, a silicon photonic dipstick sensor accommodating two U-shaped Mach–Zehnder Interferometers (MZIs) was employed for the label-free detection of the adulteration of ewe, goat, and donkey milk with cow milk. One of the two MZIs of the chip was modified with bovine κ-casein, while the other was modified with bovine serum albumin to serve as a blank. All assay steps were performed by immersion of the chip side where the MZIs are positioned into the reagent solutions, leading to a photonic dipstick immunosensor. Thus, the chip was first immersed in a mixture of milk with anti-bovine κ-casein antibody and then in a secondary antibody solution for signal enhancement. A limit of detection of 0.05% v/v cow milk in ewe, goat, or donkey milk was achieved in 12 min using a 50-times diluted sample. This fast, sensitive, and simple assay, without the need for sample pre-processing, microfluidics, or pumps, makes the developed sensor ideal for the detection of milk adulteration at the point of need. [ABSTRACT FROM AUTHOR]

Oxytetracycline (OTC) is a widely employed antibiotic in veterinary treatment and in the prevention of infections, potentially leaving residues in animal-derived food products, such as milk, that are consumed by humans. Given the detrimental effects of prolonged human exposure to antibiotics, it has become imperative to develop precise and sensitive methods for monitoring the presence of OTC in food. Herein, we describe the development and results of a preliminary label-free electrochemical aptasensor with antifouling properties designed to detect OTC in milk samples. The sensor was realized by modifying a gold screen-printed electrode with α-lipoic acid–NHS and an amine-terminated aptamer. Different electrochemical techniques were used to study the steps of the fabrication process and to quantify OTC in the presence of the Fe(CN)64−/Fe(CN)63− redox couple The detectable range of concentrations satisfy the maximum residue limits set by the European Union, with an limit of detection (LOD) of 14 ng/mL in phosphate buffer (BP) and 10 ng/mL in the milk matrix, and a dynamic range of up to 500 ng/mL This study is a steppingstone towards the implementation of a sensitive monitoring method for OTC in dairy products. [ABSTRACT FROM AUTHOR]

Salmonella is one of the leading causes of foodborne illnesses worldwide, with poultry products being a major source of contamination. Thus, the detection of salmonella in commercial poultry products is crucial to minimize the effects on public health. Electrochemical sensors are promising tools for bacteria detection due to their sensitivity, simplicity, and potential for on-site analysis. In this work, a three-dimensional (3D) printed electrochemical immunosensor for the determination of Salmonella typhimurium in fresh chicken through a sandwich immunoassay employing biotinylated anti-S. typhimurium antibody followed by streptavidin labeled with Cd/Se ZnS quantum dots (QDs) is presented. The device features three carbon-black polylactic acid electrodes and a holder, and the quantification of S. typhimurium is performed by anodic stripping voltametric (ASV) determination of the Cd(II) released after acidic dissolution of the QDs. To enhance sensitivity, an electroplated bismuth film was deposited on the working electrode, achieving a detection limit of 5 cfu/mL in a total assay time of 25 min, whereas 5 h of sample pre-enrichment was required for the detection of 1 cfu/25 mL of chicken rinse and chicken broth. The method is accurate, with %recovery values ranging from 93.3 to 113% in fresh chicken samples, and repeatable with intra- and inter- assay coefficient of variations <2 and 5%, respectively, indicating the suitability of the proposed immunosensor for the detection of S. typhimurium at the point-of-need. [ABSTRACT FROM AUTHOR]

Cow milk is more allergenic than milk from other species, and therefore the adulteration of ewe or goat milk with cow milk can pose a serious threat to consumers. In this work, a silicon-based photonic immunosensor, which includes two U-shaped Mach–Zehnder Interferometers (MZIs), was employed for the detection of ewe and goat milk adulteration with cow milk through the immunochemical determination of the milk. The method was fast and sensitive with a detection limit of 0.04 μg/mL bovine k-casein (which corresponds to approximately 0.06% cow milk) in ewe or goat milk, respectively, and with a total assay time of 12 min. [ABSTRACT FROM AUTHOR]

Aflatoxin M1 (AFM1) is the hydroxylated form of Aflatoxin B1 (AFB1) and is expelled in the milk of both humans and animals following the consumption of AFB1-contaminated food. AFM1 has been categorized as a Group 1 carcinogen by the International Agency for Research on Cancer. Consequently, the European Commission has established a maximum allowable concentration of 50 pg/mL for AFM1 in dairy products and milk. Here, a rapid and sensitive approach for detecting AFM1 in bovine milk is presented. The analytical setup comprises a broad-band white LED, a spectrophotometer, and a silicon photonic probe, all interconnected by a bifurcated optical fiber [1]. Additionally, a laptop powers the system and facilitates signal monitoring through specialized software. The silicon photonic probe is equipped with two Mach–Zehnder interferometers: one functionalized with AFM1-bovine serum albumin conjugate, and the other with bovine serum albumin to serve as a blank. The analysis involves immersing the probe directly into a mixture of anti-AFM1 antibodies and the sample, followed by sequential immersion into biotinylated anti-rabbit IgG antibody and streptavidin solutions. The entire assay process takes 12 min, and the limit of detection in undiluted milk is 20 pg/mL, below the EU maximum allowable limit of 50 pg/mL. The assay demonstrates accuracy, with %recovery values ranging from 87.5 to 112%, and repeatability, with intra/inter-assay coefficients of variation below 7.6%. Given its analytical performance and compact instrumentation, the proposed immunosensor proves to be an ideal solution for precise on-site determination of AFM1 in milk samples. [ABSTRACT FROM AUTHOR]