Poly (L-lactic acid) Modified by N, N -bis(Stearic acid)-1,4-Dicarboxybenzene Dihydrazide: Studies of Crystallization, Melting Behavior and Thermal Decomposition

In this study, a new organic nucleating agent N, N -bis(stearic acid)-1,4-dicarboxybenzene dihydrazide (PASH) to improve crystallization behavior of poly(L-lactic acid) (PLLA) along with the effect of PASH on melting behavior, thermal stability of PASH-nucleated PLLA was holistically reported. The melt-crystallization process illustrated that PASH as an effective heterogeneous nucleating agent could boost PLLA�s crystallization rate, but increasing PASH concentration and cooling rate conversely inhibited melt-crystallization process of PLLA in this study. With respect to melt-crystallization process, a larger amount of PASH leaded to a shift of cold-crystallization peak to lower temperature level. Isothermal crystallization revealed, in comparison to pure PLLA, that the half time of overall crystallization of PLLA/PASH was significantly decreased with PLLA containing 3 wt% PASH having the minimum t1/2= 67.3 s at 105şC. The different melting behaviors of PLLA/PASH under different conditions were attributed to the nucleating effect of PASH within PLLA. In particular, the melting behavior at a heating rate of 10�C/min after isothermal crystallization depended primarily on the crystallization temperature. Whereas, the impact of crystallization time on melting behavior was negligible. Nonetheless, the melting behavior was influenced by the heating rate after non-isothermal crystallization. The thermal stability of PLLA was detrimental with the addition of PASH owing to a typical drop in onset thermal decomposition temperature.

Pengaruh Trietanolamin Dan Asam Stearat Terhadap Mutu Fisik Dan Stabilitas Mekanik Krim Sari Buah Tomat

Tomatoes contain lycopene which is an antioxidant. Antioxidant preparations can be made in the form of a cream with components of an oil phase, a water phase and an emulsifier. Emulsifiers that can be used are triethanolamine (TEA) and stearic acid. This study aims to determine the effect of triethanolamine and stearic acid as emulsifiers on the physical quality and mechanical stability of tomatoes extract cream. The use of triethanolamine and stearic acid with a ratio of 2%:5%; 3%:10%; 4%:15%. The test are the physical characteristics of tomatoes extract cream included organoleptic, homogeneity, cream type, pH, viscosity, spreadability, adhesion, protection and mechanical stability using the centrifugation method. The results of the phytochemical screening of tomatoes extract were positive for triterpenoids. The test results of the three cream formulas are odorless, semi-solid form, light orange to white color, homogeneous, cream type M/A, pH 5.25 - 6.26; viscosity 5,376 cP - 14,370 cP, spreadability 4 - 5,067 cm, adhesion 4 - 11.6 seconds, protection power 2 - 5.2 seconds. The three cream formulas did not undergo phase separation. The higher concentration of TEA and stearic acid had an effect on viscosity, pH value, adhesion, dispersibility and protection, but had no effect on organoleptic, homogeneity, cream type, and stability. tomatoes extract cream with a concentration of TEA:stearic acid 2%:5% gave the best physical quality.

Melting, Crystallization, and In Vitro Digestion Properties of Fats Containing Stearoyl-Rich Triacylglycerols

Fats containing the stearoyl-rich triacylglycerols (TAGs) of 1,2-distearoyl-3-oleoylglycerol (SSO) and 1,3-dioleoyl-2-stearoylglycerol (OSO) were synthesized via the lipase-catalyzed acidolysis of tristearin (SSS)-rich fat and oleic acids, followed by solvent fractionation. Their physicochemical properties and in vitro digestibilities were compared. The SSS-, SSO-, and OSO-rich fats comprised 81.6%, 52.9%, and 33.1% stearic acid, respectively, whereas oleic acid comprised 2.9%, 37.5%, and 56.2%, respectively. The SSS-, SSO-, and OSO-rich fats contained the TAGs of SaSaSa (100.00%), SaSaMo (86.98%), and MoSaMo (67.12%), respectively, and the major TAGs were SSS, SSO, and OSO, respectively. Melting and crystallization temperatures were higher and fat crystals were larger and densely packed in the descending order of SSS-, SSO and OSO-rich fats. Both in vitro multi-step digestion and pH-stat digestion were more rapid for OSO- than SSO-rich fat. Oleic acid was digested faster than stearic acid during the initial digestion, then the rate decreased, whereas that of stearic acid increased over prolonged digestion. Fats that were richer in stearoyl at the sn-1,3 position of TAG melted and crystallized at higher temperatures, had a densely packed microstructure of large fat crystals and were poorly digested. Stearic acid imparts the essential physical attributes of melting and crystallization in solid fats, and the low digestible stearoyl-rich fat would be a viable substitute for trans fatty acids in food lipid industry.