Fabrication of antibacterial food packaging from polyvinyl alcohol/sodium caseinate composite films cross-linked with lactic acid

IF 3.8 4区工程技术 Q2 CHEMISTRY, APPLIED

Journal of Vinyl & Additive Technology Pub Date : 2024-07-24 DOI:10.1002/vnl.22137

Naz Doğa Dülger, Sema Samatya Yilmaz, Hüseyin Uzuner, Ayse Aytac

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引用次数: 0

Abstract

In this study, Polyvinyl Alcohol (PVA)/Sodium Caseinate (NaCAS) were cross-linked by mixing with Lactic acid (LA) in different proportions (0.5%, 1%, 2%, and 4%). Composite films were obtained from the prepared solutions using the solution casting method. The obtained composite films were appeared as slightly opaque and lightly yellowish, but mostly transparent. As the amount of LA increased, the polarized microscope surface images of the composite films became rougher. It was explained that cross-linking occurred with the aldehyde groups (CHO) determined in the Fourier transform infrared spectroscopy (FTIR) analysis. The increasing 5% weight loss temperature of the films because of cross-linking also increased the thermal strength. In X-ray diffraction analysis (XRD), the 2θ peak intensity of the 2% LA-added film, which had the highest cross-link density, was indicated to be the lowest. It was reported that 4% and above the LA contribution rate negatively affects the physical and mechanical properties of the PVA/NaCAS matrix. The pure PVA/NaCAS film had 30.08 MPa tensile strength and 1.49% tensile strain. The film with 2% LA added showed the tensile strength value closest to the pure film with 23.89 MPa. With a 6.52% value, the film containing 2% LA showed the lowest moisture retention behavior. Pure PVA/NaCAS film, which has a hydrophilic structure with a contact angle of 57°, gained hydrophobic ability with the addition of LA. The 1% LA-added film exhibited the highest hydrophobic behavior with a contact angle value of 99°. With the LA additive, an increase in the contact angle values of the composite films was observed between approximately 61% and 74%. In addition, the water vapor permeability (WVTR) with 582.37 g/m² day value of pure PVA/NaCAS composite film decreased after the addition of LA. It was degraded to 322.72 g/m² day WVTR value in the 1% LA-added film. 100% antibacterial activity against both E. coli and S. aureus was observed in composite films containing 1% or more LA additive. The resulting films were suggested to be used as active food packaging with antibacterial effects.

Highlights

LA can be used as a crosslinking agent for PVA/NaCAS blends.
2% LA contribution has shown the highest cross-linking density.
4% LA and higher LA contribution would negatively affect the mechanical properties of the matrix.
High antibacterial activity was obtained against both E. coli and S. aureus in films containing 1% or more LA.

Abstract Image

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用乳酸交联聚乙烯醇/酪蛋白酸钠复合膜制作抗菌食品包装

在这项研究中，聚乙烯醇（PVA）/酪蛋白酸钠（NaCAS）与不同比例（0.5%、1%、2% 和 4%）的乳酸（LA）混合交联。用溶液浇铸法从制备好的溶液中获得复合薄膜。得到的复合薄膜呈现轻微的不透明和淡黄色，但大部分是透明的。随着 LA 含量的增加，复合薄膜的偏光显微镜表面图像变得粗糙。傅里叶变换红外光谱（FTIR）分析表明，醛基（CHO）发生了交联。由于交联，薄膜的 5% 失重温度升高，热强度也随之增加。在 X 射线衍射分析（XRD）中，交联密度最高的 2% LA 添加薄膜的 2θ 峰强度最低。据报道，4% 及以上的 LA 添加率会对 PVA/NaCAS 基质的物理和机械性能产生负面影响。纯 PVA/NaCAS 薄膜的拉伸强度为 30.08 兆帕，拉伸应变为 1.49%。添加了 2% LA 的薄膜的拉伸强度值最接近纯薄膜，为 23.89 兆帕。含 2% LA 的薄膜的保湿性能最低，仅为 6.52%。纯 PVA/NaCAS 薄膜具有亲水结构，接触角为 57°，而添加了 LA 的薄膜则具有疏水能力。添加了 1% LA 的薄膜具有最高的疏水性，接触角值达到 99°。添加了 LA 后，复合薄膜的接触角值增加了约 61% 至 74%。此外，添加 LA 后，纯 PVA/NaCAS 复合薄膜的水蒸气渗透率（WVTR）下降，日值为 582.37 g/m2。在添加了 1% LA 的薄膜中，其 WVTR 值降至 322.72 g/m2 天。在含有 1%或更多 LA 添加剂的复合薄膜中，对大肠杆菌和金黄色葡萄球菌的抗菌活性都达到了 100%。亮点 LA 可用作 PVA/NaCAS 混合物的交联剂。LA 含量为 2% 的交联密度最高。LA 含量为 4% 或更高会对基质的机械性能产生负面影响。含有 1% 或更多 LA 的薄膜对大肠杆菌和金黄色葡萄球菌都具有很高的抗菌活性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Vinyl & Additive Technology 工程技术-材料科学：纺织

CiteScore

5.40

自引率

14.80%

发文量

审稿时长

>12 weeks

期刊介绍： Journal of Vinyl and Additive Technology is a peer-reviewed technical publication for new work in the fields of polymer modifiers and additives, vinyl polymers and selected review papers. Over half of all papers in JVAT are based on technology of additives and modifiers for all classes of polymers: thermoset polymers and both condensation and addition thermoplastics. Papers on vinyl technology include PVC additives.