JWSS - Journal of Water and Soil Science

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Physicochemical characteristics of potato (Solanum tuberosum L.) are very important for storage and processing qualities. The amount of reducing sugars (glucose and fructose) and organic acids at harvest, during and after storage is the most important factor. In this study, three potato cultivars (Moran, Marfona and Agria) were collected, dry cleaned and graded into three sizes. They were analyzed for specific gravity and dry matter content. Potato tubers were stored at 4°C and about 85% R. H. for 15 weeks and then reconditioned at room temperature (25±l)°C for 4 weeks. During the storage period of tubers, sugars (sucrose, glucose and fructose) were analyzed on a weekly basis, but citric, D-malic and D-pyroglutamic were analyzed on a monthly basis by high performance liquid chromatography (HPLC). Data were analyzed statistically in a completely randomized design with sampling and Duncans multiple range test.

The total sugar and organic acid contents of tubers significantly increased during the 15 weeks of storage at 4°C and decreased after reconditioning at room temperature. The size of tubers did not affect the accumulation of total sugars. Dry matter content and specific gravity of Agria tubers were higher than those of both Moran and Marfona. Also accumulation of reducing sugars was lower in Agria than in Moran and Morfona initially and after the storage and reconditioning periods. Therefore, Agria must be suitable for processing into chips or dry powder.

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For Iranian fermented cheese processing and ripening, different lactic acid bacteria (LAB) that affect on the physicochemical properties and hence the organoleptic characteristics of the cheese is used. Determination of physicochemical changes of cheese, particularly, organic acids is of importance. In this study five cheese formulas with five different group of cheese starters were processed and ripened in 8% brine during two months at 12±1 °C. HPLC analysis of organic acids were accomplished, using SCR-101H column with U. V. detector at 214 nm and quantified with high purity standards concerning each organic acid recovery. Pyruvic, orotic, citric, propionic, lactic, butyric and acetic acids were analyzed after 1, 10, 20, 30, 40, 50 and 60 days of processing and storage. Each determined organic acid exhibited a specific profile changes during cheese ripening.

Lactic acid was dominant organic acid in all samples. Total organic acids were increased significantly after 30 days of storage, but decreased up to the end of ripening. The profile changes of organic acids which was similar in all samples with different amounts related to dominant lactic acid with about 80-90% of the total organic acids. The aromatic mesophile group, CH-N-O1(including Lactococci and Leuconostocs) and Lactobacillus casei and also the mixed mesophiles plus thermophile starters group, CH-1 (including Lactobacillus bulgaricus and Streptococcus salivarius ssp. thermophilus) caused a significant decrease in citric acid and increase in acetic and propionic acid in related cheese samples compared with other cheeses (P < 0.01). But cheese containing only thermophiles or the mixed thermophile and mesophile (code 54) revealed a significant increase in butyric acid. In all samples the changes in pyruvic acid content was irregular. The ripening period of cheese samples were determined by the stepwise regression analysis in relation to their exact amount of organic acids.

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The changes of main sugars and organic acids of Red delicious and Golden delicious apples from Semirom region in Isfahan Province were determined by high performance liquid chromatography (HPLC). The apples were harvested, graded and packed in three kinds of wood, car-board and perforated polyethylene film packages and stored for eight months at 0±0.5^oC and 90 to 95% relative humidity for further analysis. Sucarose, glucose and fructose, as well as citric and L-malic acids were detected and quantified in all packed samples. The obtained data were analyzed with factorial experiment in completely randomized design and mean were compared by Duncan^,s muliple range test. The results showed that fructose was dominant in both cultivars in all packages compared to other sugars. Golden delicious apples contained more sucrose and less glucose than Red delicious. All sugars decreased in packed apple samples during the storage period. The dominant organic acid of both cultivars was L-malic. Citric acid increased to its maximum level in Red or Golden delicious after one or two months of storage, respectively, and then decreased gradually by the end of storage period. In general, apples kept in perforated polyethylene films exhibited the best physiochemical properties during eight months of cold storage.