LOCATION EFFECTS ON OXIDATIVE STABILITY OF CHÉTOUI VIRGIN OLIVE OIL

The effect of growing area on the natural antioxidant and oxidative stability of Chétoui virgin olive oil was studied. Total phenolic content, tocopherol composition, fatty acid composition and oxidative stability were analyzed. The results obtained in this study showed that Chétoui virgin olive oil composition is greatly influenced by growing environment, i.e., mainly by the climatic and pedologic factors. The cumulative rainfall appears to have a major influence on phenolic and o‐diphenol content. Among studied samples, Amdoun oil had the highest total phenolic content, which exceeded 700 mg/kg. Moreover, it contained the highest amounts of o‐diphenols 286.08 ± 6.74 mg/kg and total tocopherols 405.65 ± 4.17 mg/kg. The amounts of total phenols and o‐diphenols showed a good correlation (P ≤ 0.001) with stability while tocopherols showed a very low relation to oxidative stability.     

APPLICATION OF EXPERIMENTAL DESIGN METHOD TO THE OIL EXTRACTION FROM OLIVE CAKE

Olive cake is an important solid waste of the olive oil production. It still contains a certain quantity of oil that can be recovered by means of solvent extraction. In this study, two-level full factorial design was performed to evaluate the effects of four variables and their interactions on the oil extraction by the ethanol 96.0% in a batch reactor. The variables included size of particles, temperature, and time of contact and solvent-to-solids ratio. The statistical analysis of the experimental data showed that the extracted oil mass depends on all the examined variables. It also depends on the interactions between size of particles and solvent-to-solid ratio and size of particles and temperature. The experimental data were in good agreement with those predicted by the model.

PRACTICAL APPLICATIONS

Olive cake is solid waste of the olive oil industry that is available in large amounts in many Mediterranean countries and at very low cost. It can be treated or valorized, enabling at the same time the solution to environmental problems caused by the olive oil production process. The economic interest that it presents is especially because of the residual oil that it contains and that can be recovered by solvent extraction. However, this solid–liquid extraction depends on several parameters: the ones inherent to the products (structure and properties of the sample, nature of extraction solvent); and the others to the extraction process (time of contact, temperature of extraction, solvent-to-solid ratio, stirring velocity). The experimental design method enables to determine the most important variables and their interaction in the extraction process at the same time performing a low number of experiments.     

EFFECT OF BREAK TEMPERATURE AND HOLDING TIME ON PECTIN AND PECTIC ENZYMES IN TOMATO PULP

SUMMARY –The effect of break temperature and holding time on chemical and physical properties of canned tomato pulp and on the activity of polygalacturonase (PG) and pectin esterase (PE) was investigated. Samples preheated above 200°F were slightly higher in pH value and lower in titratable acidity than those preheated at 160°F and 140°F. The gross viscosity and serum viscosity of the canned tomato pulp increased as break temperature increased. A slight increase in serum viscosity was also observed when holding time was lengthened. The effect of break temperature on serum viscosity was much greater than that of holding time. The total pectin content of the tomato pulp as well as that of the serum increased as the break temperature increased. The same observation holds true for the effect of holding time on the total pectin content of the tomato pulp and tomato serum. This was explained by the inactivation of pectic enzymes at higher break temperature and longer holding periods. The level of PE and PG activity in the frozen tomato pulp decreased as break temperature and holding time increased. No PE activity was detected in samples preheated at 180°F for 15 sec. Samples preheated at 220°F for 15 sec showed no PG activity, while those preheated at 200°F for 15–87 sec still show some PG activity with a retention of about 3.54–5.68%. PG in tomatoes may be inactivated by giving the macerated fruits a hot break temperature higher than 200°F. The critical conditions for inactivation of PE (180°F for 15 sec) and of PG (220°F for 15 sec) found in the course of this investigation are supported by the data obtained on pectin analysis and serum viscosity.     

FATIGUE CRACK GROWTH IN THE TENSION STEEL OF REINFORCED CONCRETE

Abstract— A technique is presented for the determination of the constants C and n used in fatigue crack growth analysis. The initial flaw depth should be known but continuous access to the fracture zone during a test is not required. A case history is also given in which the technique is applied to the fatigue of a steel reinforcing bar embedded in a concrete beam. The derived values of the crack growth constants C and n are checked by a simple application of the Miner Rule.     

PHENOLIC COMPOUNDS, TOCOPHEROLS AND OTHER MINOR COMPONENTS IN VIRGIN OLIVE OILS OF SOME TUNISIAN VARIETIES

The phenols, α‐tocopherols, fatty acids and oxidative stability of six monovarietal virgin olive oils (VOOs) were determined. Fourteen phenolic compounds were detected and quantified by solid phase extraction and reversed phase‐high performance liquid chromatography. Dialdehydic form of elenolic acid linked to tyrosol and hydroxytyrosol, oleuropein and ligstroside aglycones were the main components in all samples. Pinoresinol was the most abundant component in lignan fraction. The total phenol content of these monovarietal oils varied from 66.82 mg/kg in “Neb Jmel” oil to 662.74 mg/kg in “El Hor” oil. A wide range of α‐tocopherol contents was also noticed; it varied from 141.94 mg/kg in “Semni” variety to 364.23 mg/kg in “Jdallou” variety. With regard to pigments, chlorophylls and carotenoids were found at variable concentrations: with median values of 11.33 and 3.10 mg/kg, respectively. Among the studied varieties, “Oueslati” and El Hor were characterized by the lowest levels of palmitic and linoleic acids and the highest values of oleic acid.     

EFFECT OF PARTIAL REPLACEMENT OF SUCROSE BY CORN SYRUP ON QUALITY AND STABILITY OF CANNED APPLE SAUCE

SUMMARY— Apple sauces were made from Gravenstein apples under normal commercial processing conditions, using pure sucrose and combinations of sucrose and 62 D.E. corn syrup as sweeteners. Products were tested for storage stability of 68 and 86°F. Undesirable chemical and physical changes occurred rapidly at 86°F as indicated by the increase of hydroxymethyl furfural, darkening of serum color, decrease in consistency and increased can corrosion. This was accompanied by lower organoleptic color and ffavor scores. It appeared that the quality and storage stability of apple sauce were influenced more by higher storage temperatures and longer storage duration than by the type of sweeteners used in making the apple sauce. For a longer shelf fife and better quality retention, canned apple sauce should be stored at 68° F or lower. Results of this investigation indicate that corn syrup can be used lo replace 25% of the added sucrose in processing apple sauce.