Moisture sorption isotherms of pistachio nut paste were determined at 4 and 20°C by using gravimetric method with saturated salt solutions. The moisture content of pistachio nut paste increased sharply at higher water activities as the temperature increased. Mathematical models of Brunauer et al., Anderson, Oswin, Halsey, Henderson, Ku¨hn, Filonenko & Chuprin and Peleg were evaluated to determine the best fit for the experimental data. In this study, Peleg model was found to be adequate model for pistachio nut paste. By using Clausius-Clapeyron equation, the heat of sorption was determined. As moisture content increased the heat of sorption decreased.
Deterioration due to chemical and microbiological changes is the most important problem encountered in the production and consuming period of the traditional and modern red pepper paste. On the other side, it is stated in the literature that the olive leaf is an effective natural preservative for similar deteriorations. However, a research related to the preservative effect of olive leaf on pepper paste has not yet been presented in the literature. In the study, olive leaf extract (OLE) was added at different concentrations to the industrial sweet pepper paste and preservative effect of OLE was measured to complete the mentioned deficiency in the literature. However, the experimental results were not suitable for modeling since it contained too much local optimum. Therefore, the experimental results corresponding to not tested independent variable combinations were predicted by bicubic interpolation method. Then, the predicted values were transformed into images to visual determination of significant changes associated with OLE concentrations and storage days. According to the findings, the OLE supplementation between 2.5 and 3.5 g/kg provides optimum microbiological preservation along 15 days for the pepper paste stored as cover‐open. However, OLE supplementation did not cause any physicochemical or color changes for pepper paste stored as cover‐open. Also, there was no significant microbiological, physicochemical or color changes determined for the pepper paste stored as cover‐closed. As a result, OLE supplementation between 2.5 and 3.5 g/kg suggested to preserve the canned pepper paste microbiologically after the consumption has started. Thus, the effect of the OLE on pepper paste was determined and presented to the literature.
Practical application
OLE supplementation between 2.5 and 3.5 g/kg inhibits the microbiological growth in pepper paste stored as cover‐open. Thus, the canned pepper paste supplemented with OLE can be protected microbiologically after start of consumption. Olive leaf that is originally wasted also can be evaluated.
The ingredients and components of herbal resources are of great importance in terms of medicinal/aromatic properties. It is stated that the existence of various diseases, the use of plants for their treatment and the specific properties of each are increasing day by day (Baytop, 1999). The variety of products obtained from these herbal sources especially forest plants which can be consumed as food and transformed into commercial products is increasing nowadays.The Pinaceae family has the most species in terms of characteristics and has a wide distribution up to the last tree border of the Northern Hemisphere, North America, Asia and Europe where there are 13 genera and more than 200 taxa within these family of Pinaceae (Roushfort, 2000). It is stated that the family has 9 species belonging to 4 genera and 22 taxa related to these species in Turkey
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