Showing 4 results for Freezing
A. Nezami, A. Bagheri, H. Rahimian, M. Kafi, M. Nasiri Mahalati,
Volume 10, Issue 4 (1-2007)
Abstract
The present experiment was aimed to evaluate the freezing tolerance of two cold tolerant (MCC426 and MCC252) and a cold susceptible (MCC505) chickpea genotypes. The study was carried out in a split-plot factorial design with three replications. Factorial arrangement of genotype and acclimation (acclimation and non acclimation) were imposed as main plot and temperatures (0, -4, -8, -12, 16, -20ºC) as subplot. The effect of freezing temperature (FT) on plant survival was significantly different among genotypes (p<0.05). According to the average effects of acclimation and FT, the plant survival in MCC426 and MCC252 was 40% and 31% respectively more than in MCC505. Lethal temperature for 50% response (LT50) and temperature resulting in 50% lower dry matter (DMT50) in MCC426 were –10.8ºC and
–8.4ºC, respectively and were lower than the other genotypes. Acclimation increased the freezing tolerance such that MCC426 tolerated up to –12ºC without any mortality, however, at this temperature, plant mortality rates in MCC252 and MCC505 were 25.7% and 67.7%, respectively. Plant regrowth was affected by the intensity of FT, such that plant dry weight (PDW) and stem height (SH) in –12ºC decreased about 63% and 50%, respectively, compared with non - frozen control plants. The most freezing damage was observed in MCC505, -12ºC treatment caused 90% decreases in PDW and SH, but at this temperature, PDW and SH in MCC425 decreased 55% and 49% and in MCC252, the reduction was about 60%and 54%, respectively. It seems that the use of controlled experiments would contribute to the evaluation of freezing tolerance and screening programs in chickpea germplasm for the estimation of LT50 and DMT50 .
M. Yousofi,
Volume 12, Issue 45 (10-2008)
Abstract
Freezing is one of the most important climatic factors affecting almond products in Isfahan province. Therefore, it is important to use a rapid method for assessing the resistant cultivars and wild species of these plants. Evaluation of electrolyte leakage (EL) from freezing damaged tissues of almond is an appropriate method for this purpose. In the present work, the effect of freezing on the rate of electrolyte leakage of 10 cultivated almonds (Amygdalus communis cultivars) and one wild species (A. scoparia) was evaluated in Isfahan province. The perfect and mature flowers of all samples were selected at random, and examined under natural (in nature) and artificial (in laboratory) freezing treatments in 3 replicates. All measurements were done using an Ec meter instrument and the mean of obtained data was analyzed statistically via ANOVA and Tukey's tests. In each treatment, increase in the rate of electrolyte leakage of treated samples in relation to the controls was taken as a criterion for comparison. Total Dissolved Solids (TDS) of the flowers of all samples were also measured, with an accuracy of 0.001, under natural freezing conditions. The mean of TDS was 390.8±33.5 mg/L among cultivated almonds (maximum in Safari cultivar with 439±29.3 mg/L and minimum in Kababi cultivar with 355±35.3 mg/L) and 362±55.8 mg/L in the wild almond (a little less than that of the cultivated ones). Linear regression test showed that there was no correlation between TDS and the rate of electrolyte leakage from freezing damaged tissues of the studied samples. Furthermore, the results showed that the cultivars of Tageri (with 7.47% increasing), Azar (with 19.2% increasing) and Rabie (with 22% increasing) are respectively more resistant than other cultivars under natural freezing, and the cultivars of Rabie (with 60.7% increasing), Tageri (with 67.6% increasing) and Hag Mirzaie (with 71% increasing) are more resistant than other cultivars under artificial treatment. These results are in agreement with the experimental observations in the studied area. The freezing tolerance of wild species (with 48.7% and 73% increasing, respectively) was moderate in both natural and artificial freezing treatments.
M Mousavi Nasab, Gh Mesbahi, L Maghsodi,
Volume 12, Issue 46 (1-2009)
Abstract
Pectin is a hydrocolloid with different characteristics and applications. In this study, the cryoprotective effect of pectin on frozen surimi was investigated. In this research, Kapoor surimi was made for the first time in Iran. Surimi was mixed with 1% pectin solution with the ratio of 1 to 3 (w/v). Then, pectin-containing surimi samples and control samples were packaged, frozen and stored at -20oC. Water binding capacity (WBC), salt extractable protein and drip loss of samples were measured at after 0, 2 and 4 months of storage. The results showed that the loss of WBC in pectin-containing surimi and control samples was 20% and 58%, respectively, after 4 months storage at -20oC. It means pectin could improve the WBC up to 38% in the frozen product. The loss of SEP in pectin containing surimi samples was 21% and in control samples was 25% after 4 month frozen storage, indicating pectin was again effective in maintaining the quality of frozen products. Furthermore, the increase in drip loss in pectin containing surimi was about 7% and in control samples 37%. In this case pectin also helped to decrease the loss of water soluble nutrients. Overall, the results indicate that pectin as a cryoprotectant can improve the quality of frozen surimi.
N Vahedi, M Mazaheri Tehrani, F Shahidi,
Volume 13, Issue 48 (7-2009)
Abstract
In this study, the effect of “Osmodehydrofrozen” fruit addition on sensory, physical, chemical and microbiological properties of concentrated yoghurt and its quality during storage was evaluated. This research was done in two stages. At the first stage, fruit percentage, type and addition time (before and after fermentation) was determined. The results indicated yoghurts containing 10% apple or 13% strawberry, which was added before fermentation had a better quality. Because of high osmotic activity of apple, the synersis was lower in apple yoghurt in comparison with strawberry yoghurt. According to osmotic activity of both fruits, the synersis value was much lower than that of fruit yoghurts, which contained untreated fruits. Taste value was higher in strawberry yoghurt and texture and mouth feel values were higher at low percentages of fruit. The results of the second stage (quality evaluation during storage) indicated that storage had a significant effect on pH, acidity, synersis, taste and texture (P<0.05). In samples which contained apple, coli forms disappeared after 7 days of storage. In samples that contained strawberry, coli forms disappeared after 7 days of storage.
