Shelf life determination of Yayik butter fortified with spice extracts

Sage ( Salvia officinalis L.), cinnamon ( Cinnamomum zeylanicum ), rosemary ( Rosmarinus officinalis L.), clove ( Syzygium aromaticum L.), sumac ( Rhus coriaria L.), oregano ( Origanum vulgare L.), ginger ( Zingiber officinale ), caraway ( Cuminum cyminum L.) and thyme ( Thymus vulgaris L.) extracts were added at two concentrations (0.2 and 0.5%) to yayik butter. The butter samples were stored at two different temperatures, 4°C and 25°C. Product acceptability was monitored following the Weibull Hazard sensory method where the end of shelf life was the time at which 50% of panellists found the product unacceptable. Ginger, thyme and cinnamon extracts increased the shelf life of yayik butter and were comparable to the synthetic preservatives sorbic acid and BHA. The shelf life of the samples stored in the refrigerator was approximately twice as long as the samples stored at room temperature.     

Effect of heat treatment of skim milk and final fermentation pH on graininess and roughness of stirred yogurt

The effects of heat treatment of skim milk (95°C/80 s, 95°C/256 s, 110°C/40 s, 110°C/180 s, 130°C/20 s and 130°C/80 s) and final fermentation pH of yogurt (4.8 and 4.4) on physical characteristics of stirred yogurt were investigated. Physical properties, including graininess and roughness, of stirred yogurt were determined during storage at 4°C for 15 days. Number of grains, perimeter of grains, visual roughness, storage modulus and yield stress decreased, when heating temperature or final fermentation pH increased. For practical applications, processing parameters such as heat treatment and fermentation pH can be optimized to improve quality or modified to create fermented milk products with different physical properties.     

EFFECT OF SOME HERB ESSENTIAL OILS ON LIPOLYSIS IN WHITE CHEESE

The influence of some herb essential oils on the lipolysis of white cheese was examined. The essential oils of Sirmo (wild Allium sp.), thyme (wild Thymus sp.) and mint (wild Mentha sp.) were added individually or in combinations to cheeses. The cheese samples were ripened for 90 days at 5C. Lipolysis rate increased from the beginning to the sixtieth day of ripening, then decreased up to 90 days in cheese samples. The highest lipolysis rate was observed in the control sample while the lowest was in thyme and sirmo-thyme added samples. Differences between cheese samples and ripening periods were found to be statistically significant (P<0.01) in terms of fatty acids production rates. Sirmo and mint essential oils did not affect the lipolysis of white cheese. The sensory acceptability ofsirmo and mint essential oils added cheeses was superior to that of other samples.     

Aspects Regarding the Use of Probabilistic Models for Isothermal Full Film Rough Line Contacts

This article presents a method to improve the classical probabilistic EHL models by incorporating deterministic EHL results. We first provide a review of the latest developments in the probabilistic approach for the solution of a mixed EHL problem, as well as a review of the latest deterministic EHL results that can impact the probabilistic formulations. Next, we present a probabilistic algorithm for the computations of the load supported by the fluid, the elastically deformed asperities, and the plastically deformed asperities in a mixed EHL contact. The Chang-Etsion-Bogy elastoplastic micro contact model is used together with a corresponding probabilistic fluid flow model. We also present an approach in which the elastic roughness deformation induced by the oil film can be incorporated into the probabilistic model via the use of the amplitude reduction technique.     

Heat Inactivation Kinetics of Apple Polyphenoloxidase and Activation of its Latent Form

Heat inactivation kinetics of crude polyphenoloxidase (PPO) from six apple cultivars (Golden Delicious, Starking Delicious, Granny Smith; Gloster, Starcrimson and Amasya) were studied at three temperatures (68°, 73° and 78°C). PPO activity initially increased and then decreased with heat, following a first order kinetic model. Increase in activity indicated presence of latent PPO. Regression coefficients for the linear portions of inactivation curves were computed to determine inactivation parameters. Reaction data at 78°C revealed that PPO in Amasya was the least and Starking Delicious the most heat-stable. Rate constants for heat inactivation at 78°C ranged from 15.99–28.27. 10^?2 min^?1. Activation energies varied between 54.7–77.2 kcal. mol^?1 with z values of 7.1–10.0C°.PPO in apples was generally more heat-stable than PPO in most fruits.