Pure N(2) gas was introduced in the headspace of test bottles containing raw milk that were then stored at either 6.0, 7.0, or 12.0 degrees C. Treatment with N(2) significantly reduced the growth of total bacteria, and the growth of bacterial subgroups such as psychrotrophs, enterobacteria, protease- and lipase-producing bacteria, and Listeria spp, and completely excluded Bacillus cereus growth on MYP plates. The inhibitory effect was maximal at 6.0 degrees C, and bacterial growth could be halted at this temperature for 11 days. At 12.0 degrees C, N(2) was able to inhibit growth during the first 48 h. No alarming or undesirable effects, such as the excessive growth of anaerobes or lactobacilli, were observed during the course of the study. The same treatments also halted the growth of one bacterial isolate in pure culture that expressed multiresistance to antibiotics. The continuous flushing of raw milk with pure N(2) gas in a so-called open system that allows gas exchanges with the environment positively impacted the microbiological quality of the raw milk at a temperature range of 6.0-12.0 degrees C. This procedure should therefore be considered as a possible complementary method to refrigeration in controlling bacterial growth and the spoilage potential of both psychrotrophs and mesophiles in raw milk.
As a fermented product, tarhana is the dry form of yogurt-cereal mixture and represents an important part of the diets of many people in different countries including Turkey. In the present study, the effects of the addition of baker's yeast on the quality and functional properties of tarhana were investigated. Tarhana was produced under laboratory conditions (uncontrolled and controlled conditions) using two formulas. Some physicochemical, functional, and sensory properties of the samples were analysed. An increase was found in the acidity value of all samples during the fermentation period. The addition of baker's yeast affected the functional properties (water absorption capacity, foaming capacity, foaming stability, emulsifying activity) of the samples (P < 0.05). The tarhana samples produced by the addition of yeast and under controlled conditions had shorter fermentation times and better sensory properties. This research suggests that the addition of baker's yeast and the employment of controlled conditions can be recommended in the production of the commercial type of tarhana.
A new lactose biosensor was developed by preparing a suitable copolymer of polypyrrole and poly(3,4-ethylenedioxythiophene) synthesized using the electropolymerization method. Pyrrole and 3,4-ethylenedioxythiophene monomers were deposited in the presence of sodium dodecylbenzene sulphonic acid on a platinum disc electrode, which was used as the working electrode. The sensor is based on the serial reactions of b-galactosidase and galactose oxidase immobilized on a copolymermodified platinum disc electrode. Successful synthesis of the enzyme-immobilized copolymer was confirmed by FT-IR spectrometry, SEM, and electrochemical analysis. The response of the enzyme electrode to lactose was determined by cyclic voltammetry at 1 0.40 V. The response time of the biosensor was found to be from 8 to 10 s, and the upper limit of the linear working portion was found to be at a lactose concentration of 2.30 mM with a detection limit of 1.4 3 10 25 M. The apparent Michaelis-Menten constant was found to be 0.65 mM of lactose. The effects of interferents were also investigated. Lactose concentrations determined by the biosensor were in good agreement with those measured by the reference methods. Our results show that the developed biosensor has a significant potential to the determination of lactose concentration in milk.
In this study, a new lactose biosensor has been developed in which the 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer is used as a transducer. The EDOT/Th copolymer was deposited on the glassy carbon electrode to be used as the working electrode. In addition to the working electrode, the three-electrode system was used in both the electrochemical synthesis and in the biosensor measurements. Lactase (β-galactosidase) that catalyzes the breakdown of lactose into monosaccharides (glucose and galactose) and galactose oxidase that catalyzes the oxidation of the resulting galactose were attached to the copolymer by a cross-linker on the modified working electrode. The response of the enzyme electrode to lactose was determined by cyclic voltammetry (CV) at +0.12 V. Enzyme electrode optimization parameters (pH, temperature, enzyme concentration, etc.) were performed. Fourier transform infrared spectroscopy, scanning electron microscopy and CV methods were used to support copolymer formation. In addition, the characteristics of the enzyme electrode prepared in this study (Km, 0.02 mM; activation energy Ea, 38 kJ/mol; linear working range, up to 1.72 mM; limit of detection, 1.9 × 10−5 M and effects of interferents [uric acid and ascorbic acid]) were determined.
Traditional Turkish couscous, a cereal-based product, is made by covering bulgur with milk and flour. Traditionally Turkish couscous was produced from different flours (soyflour and oat flour) and eggs. The nutrient composition of traditional couscous was 90.6% dry matter, 11.27% protein, 2.58% fat, 71.80% carbohydrate, 42.25 mg sodium, 365.62 mg potassium, 2.73 mg iron and 48.30 mg calcium. The calorie content of traditional couscous is about 1487.41 kJ 100 g )1 . The addition of soy and oat flours increased protein content and Ca, K and Fe levels. Sensory properties were also affected. Panellists preferred traditional couscous and couscous with eggs or soyflour over couscous with oat flour.
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