Mahović Poljaček Sanja, Tomašegović Tamara, Strižić Jakovljević Maja, Jamnicki Hanzer Sonja, Murković Steinberg Ivana, Žuvić Iva, Leskovac Mirela, Lavrič Gregor, Kavčič Urška, Karlovits Igor
Faculty of Graphic Arts, University of Zagreb, Getaldićeva 2, 10000 Zagreb, Croatia.
Faculty of Chemical Engineering and Technology, University of Zagreb, Trg Marka Marulića 19, 10000 Zagreb, Croatia.
Polymers (Basel). 2024 Aug 9;16(16):2259. doi: 10.3390/polym16162259.
Starch-based pH-sensing films with bacterial nanocellulose (BNC) and red cabbage anthocyanins (RCA) as active components were investigated in this research. Their structural, physical, surface and colorimetric properties were analyzed, mainly as a function of BNC concentration. The aim of the research was to relate the changes in the intermolecular interactions between the components of the films (starch, anthocyanins and BNC) to the physical, surface and colorimetric properties that are important for the primary intended application of the produced films as pH indicators in smart packaging. The results showed that maize starch (MS) was more suitable as a matrix for the stabilization of anthocyanins compared to potato starch (PS). PS-based films showed a lower value of water contact angle than MS-based films, indicating stronger hydrophilicity. The swelling behavior results indicate that the concentrations of BNC in MS-based films (cca 10%) and the concentration of about 50% BNC in PS-based films are required if satisfactory properties of the indicator in terms of stability in a wet environment are to be achieved. The surface free energy results of PS-based films with BNC were between 62 and 68 mJ/m and with BNC and RCA between 64 and 68 mJ/m; for MS-based films, the value was about 65 mJ/m for all samples with BNC and about 68 mJ/m for all samples with BNC and RCA. The visual color changes after immersion in different buffer solutions (pH 2.0-10.5) showed a gradual transition from red/pink to purple, blue and green for the observed samples. Films immersed in different buffers showed lower values of 2 to 10 lightness points (CIE L*) for PS-based films and 10 to 30 lightness points for MS-based films after the addition of BNC. The results of this research can make an important contribution to defining the influence of intermolecular interactions and structural changes on the physical, surface and colorimetric properties of bio-based pH indicators used in smart packaging applications.
本研究对以细菌纳米纤维素（BNC）和红甘蓝花青素（RCA）为活性成分的淀粉基pH传感薄膜进行了研究。分析了它们的结构、物理、表面和比色性质，主要作为BNC浓度的函数。该研究的目的是将薄膜成分（淀粉、花青素和BNC）之间分子间相互作用的变化与物理、表面和比色性质联系起来，这些性质对于所制备薄膜作为智能包装中的pH指示剂的主要预期应用非常重要。结果表明，与马铃薯淀粉（PS）相比，玉米淀粉（MS）更适合作为稳定花青素的基质。基于PS的薄膜的水接触角值低于基于MS的薄膜，表明其亲水性更强。溶胀行为结果表明，如果要在湿环境中获得令人满意的指示剂稳定性，则基于MS的薄膜中BNC的浓度约为10%，基于PS的薄膜中BNC的浓度约为50%。含BNC的基于PS的薄膜的表面自由能结果在62至68 mJ/m之间，含BNC和RCA的在64至68 mJ/m之间；对于基于MS的薄膜，所有含BNC的样品的值约为65 mJ/m，所有含BNC和RCA的样品的值约为68 mJ/m。浸入不同缓冲溶液（pH 2.0 - 10.5）后，观察到的样品的视觉颜色变化显示出从红色/粉色到紫色、蓝色和绿色的逐渐转变。添加BNC后，浸入不同缓冲液中的薄膜，基于PS的薄膜的明度值（CIE L*）降低了2至10个点，基于MS的薄膜降低了10至30个点。本研究结果可为定义分子间相互作用和结构变化对智能包装应用中使用的生物基pH指示剂的物理、表面和比色性质的影响做出重要贡献。
