جستجوی مقالات مرتبط با کلیدواژه "آب لیمو" در نشریات گروه "صنایع غذایی"

Key lime juice can be a non-fermenting product with high acidity and a rich source of ascorbic acid and phenol compound. In order to maintain the quality of the product, it is important to choose a suitable method for processing this food.
The use of modern non-thermal methods to produce high quality products should be considered. In this research, by designing and constructing a continuous pulsed electric field (PEF) system, the effect of this method on the degradation of pectin methyl esterase (PME), ascorbic acid, total phenol compound, cloudiness index, color changes and sensory evaluation in key lime juice is discussed. In this research, a bipolar square wave of 10 microseconds and a constant frequency of 1000 is used. In the processing chamber of this device, two cases of stainless steel with length and thickness of 10 and 0.5 ml, respectively, were used. Key lime juice was processed for 500, 571, 666, 800 and 1000 microseconds with Field intensity of 22.22, 33.33, 44.44 and 55.55 kV per cm. In general, by increasing the field from 22.22 to 55.55 kV / cm at a constant time, the process of reducing the degradation of PME enzyme is normally increased by 25%. Applying the highest electric field of 55.55 in 1000 microseconds caused 14% ascorbic acid degradation compared to fresh samples. With increasing pulsed electric fields, the cloudy index of the sample and browning index have increased. The use of high intensity pulsed electric field increased the degradation of PME enzyme and the cloudy index and reduced lightness compared to the fresh sample. Preservation of sensory properties of key lime juice developed with PEF during shelf life showed that the non-thermal pulsed electric field method can act as a promising approach in products with high acidity and enzyme degradation.

Ultraviolet radiation was used in the present study to process lemon juice. The designed UV system had five UV-C lamps and irradiation was performed based on the distance of the lamps (10, 20, and 30 cm) from the fluid layer and the circulation time (10, 20, and 30 minutes) of lemon juice in the system. Non-irradiated sample was also considered as a control treatment. The control and irradiated samples were filled in dark polyethylene bottles and stored at ambient temperature for 90 days. Immediately after irradiation and during the storage period, parameters such as pH, titratable acidity, total soluble solids, ascorbic acid content, color indices (L*, a*, and b*), browning index, as well as sensory attributes were evaluated. The pH, acidity, and total soluble solids did not show a definite trend. The results showed that among the color indices, L* decreased significantly, but a* and b* increased significantly during the storage period. The rate of color changes in irradiated samples from a distance of 10 cm was higher than other treatments. Irradiation also significantly reduced the ascorbic acid content of irradiated samples from a distance of 10 cm compared to other samples and control. However, the browning of irradiated samples from 10 cm distance was significantly less than that of irradiated samples from 20 and 30 cm distance. The score of the panelists indicated that irradiation and storage time altered the quality characteristics of lemon juice. The panelistschr(chr('39')39chr('39')) scores showed more acceptance of irradiated samples from 20 and 30 cm distance compared to irradiated samples from 10 cm distance. In general, the designed system in this study is not recommended for lemon juice processing due to the destructive effect of UV-C radiation on the content of ascorbic acid.

Industrial lemon juice may contain unauthorized additives that can lead to various diseases in society. As a result, it is highly important to use effective methods to identify the fake lemon juice. In this study, for the first time in our country, detection of cheating in industrial lemon juice in Golestan province is presented by analyzing organic acids, including citric acid, isocytic acid, malic acid, and also determining the ratio between citric acid and isocytic acid using liquid chromatography-mass spectrometry. The accuracy of the proposed method was confirmed by analyzing natural lemon juice samples. The limits of detection and quantification were 2 and 5, 0.02 and 0.05, 0.2 and 0.5 mg L-1 for citric acid, isocytic acid, malic acid, respectively. Industrial lemon juice samples were selected from commercially available brands, and fake samples were detected by comparison of the amounts of organic acids with the authorized values set by the European Standard. The results showed that the proposed method is very effective and sensitive in detecting cheating samples of industrial lemon juice.

In this study، physicochemical (pH، acidity، brix، vitamin C، SO2 and formalin number) and sensory properties of PET containers packed Lemon juice were evaluated. The samples were stored at 20 and 40 ◦C. During the ten weeks of preservation، physicochemical and sensory properties were measured in three replicates every two weeks. The results showed that the two storage temperatures (20 and 40 ◦C) had not any significant effect on pH، acidity، brix and formalin number (p≥0. 05). The amount of vitamin C and SO2 were less in the 40◦C stored samples compare with the 20◦C stored samples. The results of sensory evaluation indicate that the PET containers packed samples are acceptable in both storage temperatures (20 and 40 ◦C) during the ten weeks of storage.