بررسی تغییرات برخی خواص فیزیکی و شیمیایی میوه زیتون طی انبارمانی

Introduction: The maintenance of the quality of fresh produce is still a major challenge for the consumers. The most important qualitative attributes contributing to the marketability of fresh fruit a reappearance, color, texture, flavor, nutritional value and microbial safety. Storage conditions of product after harvest and storage duration are important factors with specific effect on products qualitativeproperties such as acidity, soluble solids materials, phenolic compounds and density. The amount of soluble solids materials is an important qualitative factor that is directly related to fruit quality and ripening.The existence of phenolic compounds, phenol absorption and changes phenol in product has caused changes in color. Shape, size, arithmetic mean diameter, geometric mean diameter, mass, volume, density, and sphericity coefficient are some of the physical properties of products that are crucial to analyze the behavior of matter in the handling.Furthermore, adequate knowledge about the physical properties of the products is of high importance in machines design, transportation and processing of product.
Materials and Methods: In this study, two types of olives, which were bitter and sweeten with 1.5%NaOHbefore the storage, were collected and their physical properties (length, width, thickness, arithmetic and geometric mean diameter, sphericity coefficient, mass, volume, density and primary moisture) were evaluated. Then, tostudy the effect of storage duration,the sweetened olives were stored at two temperatures (25℃ and 4℃temperature of the refrigerator) for 3 months,and during this period, sampling was performed at 10-dayintervals and the amount of total acidity (TA was determined by diluting each 1 ml aliquot of strawberry juice in 10 ml distilled water and then titrated to pH 8.1 using 0.1 N NaOH), total soluble solids materials (TSS was determined by a handheld refractometer device and expressed as ° Brix), phenolic compounds and the density weremeasured. The study was carried out as factorial based oncompletely randomized designwith twoindependent factors of temperature and storage time.
Results and Discussion: Results obtained for physical properties showed that the means of length, width andthickness insweet olive were 9.72, 1.34 and 1.11%respectivelyhigherthan bitter type. Penetration and absorption of NaOH and processing methods of the product can be considered among the possible causes of this increase. Linear regression relations between physical properties for sweet and bitter olives showed that mass and volume of fruit areestimated accurately according to the main dimensions. The results of data variance analysis also showed thatdensity and soluble solids materialswere significantly affected by themain and interaction effects of the twofactors at 1% probability level. Moreover, the main effect of storage time on total acidity and phenolic compoundswassignificant at 5% and 1% levels, respectively. With increasing storage time, density of sweet olive increased and soluble solids materials and phenolic compounds decreased. Acidity changes of olive during storage fluctuated, and an increase was found in the values of density and soluble solids materials along with theincrease of storage temperature from 4℃ to 25℃.With respect to density, the third month of storage showedhigherincrease compared toother months, and maximum value was reported for sweet olive in temperature of 25℃ and 19thday. Increase ofstorage duration resulted in the reduction of moisture content,whichin turns leads to the reductionof product volume and increase of density. The reductionfound in acidity in the second and third months of storage resultedfrom maturation and ripening processes of the fruit. Organic acids are a source of energy,which are consumed in the time ofmetabolism increaseand fruit ripening.Decreasein phenolic compounds also occurs as the result ofphenol penetration from olive flesh into the water - salt solution.
Conclusion: Results of this study showed that length, width, thickness, mass and volume of sweet olive weregreaterthan bitter type, but,by contrast,sphericity coefficient was higher in bitter olive. Moreover, storage time, increase caused an increase in thedensity of sweet olive and decrease insoluble solids materials and phenolic compounds.There was fluctuation inacidity during different storage times. An increase was found in the values of density and soluble solids materials along with the increase in storage temperature from 4℃ to 25℃.