Preparation of polylactic acid/TiO2/GO nano-fibrous films and their preservation effect on green peppers

Polylactic acid (PLA)/nano-TiO₂(TiO₂ NPs)/Graphene oxide (GO) nano-fibrous films were prepared by ultrasonic assisted electrostatic spinning technology, and the effects of TiO₂ NPs:GO mass ratio and ultrasonic power on film morphology and mechanical, thermal, barrier and antibacterial properties were investigated. The addition of TiO₂ NPs and GO can significantly increase the tensile strength and elongation at the break of PLA nano-fibrous films, and improve the water barrier properties of the nano-fibrous films. The antibacterial experiment showed that the inhibition rates of the nano-fibrous films against Escherichia coli and Staphylococcus aureus after 24 h exposure to UV irradiation reached 94.4 ± 1.8% and 92.6 ± 1.7% At the same time, the fresh-keeping packaging experiment of green peppers at room temperature, through the determination of hardness, soluble solids, chlorophyll content to determine the degree of decay of green pepper, it showed that PLA/TiO₂ NPs/GO nano-fibrous films can better maintain the sensory quality of green peppers, delay the rate of spoilage of green peppers, and prolong the preservation period of green peppers.

Ultrasound-assisted extraction of bioactive compounds from Malva sylvestris leaves and its comparison with agitated bed extraction technique

The effects of ultrasound-assisted extraction (UAE) variables-namely extraction temperature (40-60 °C), ultrasonic power (50-150 W), and sonication time (40-60 min)-on the extractive value (EV) of bioactive phenolics from Malva sylvestris leaves were investigated and optimized using Response surface methodology. The effects of extraction solvents (ethanol, ethyl acetate, and n-hexane) on EV, free radical scavenging activity (FRSA), total phenolic content (TPC), and major bioactive phenolics were studied using agitated bed extraction (ABE), and the results were compared with the UAE findings. Under the optimal UAE conditions (48 °C, 110.00 W, and 48.77 min) the experimental EV was 279.89 ± 0.21 mg/g with 71.12 ± 0.15% DPPH_sc, 73.35 ± 0.11% ABTS_sc, and a TPC of 152.25 ± 0.14 mg GAE/g. Ethanolic ABE results in higher EV (320.16 ± 0.25 mg g^-1) compared to UAE, while the FRSA and TPC values were reduced. HPLC analysis revealed that the concentration of bioactive phenolics increased significantly (p < 0.05) under the optimal UAE conditions.

Ultrasound treated potato peel and sweet lime pomace based biopolymer film development

Treatment and management of food processing waste is a major challenge for food industry. Potato processing industry generates tremendous amount of peel and consider it as zero valued waste. Again, pomace generated after juice extraction from sweet lime pulp is considered as waste and not properly utilized. Whereas these waste could be utilized for the development of biodegradable packaging film to overcome environmental issues. Composite films were prepared with varying proportion of potato peel powder (PP) and sweet lime pomace (SLP) in the ratio of 0:1(A), 0.5:1(B), 1:1(C), 1:0.5(D), 1:0(E) with an ultrasound treatment of 45min, and 0:1(F), 0.5:1(G), 1:1(H), 1:0.5(I), 1:0(J) with an ultrasound treatment of 60min. Ultrasound was applied for 45 and 60min to film forming solutions to break down biopolymer particles small enough to form a film. All the films were analyzed for their barrier and mechanical properties. It was observed that increasing ultrasound treatment times gives better result in film properties and less PP content also gives better film properties, from these observations film G prepared with 0.5:1 (PP:SLP) showed better characteristics among all other films. Water vapor permeability, moisture absorption, water solubility, breakage strength and elongation capacity of G film were reported as 7.25×10^-9g/Pahm, 12.88±0.348%, 38.92±0.702%, 242.01±3.074g and 7.61±0.824mm respectively. However, thermal decomposition for film G took place above 200°C. The film forming solution of selected G film, added with clove essential oil (1.5%) as an antimicrobial agent was wrapped on bread and stored it for 5days. The film was successful in lowering the weight loss, reducing the hardness and inhibition of surface microbial load from bread sample.

Applications of power ultrasound in food processing

Acoustic energy as a form of physical energy has drawn the interests of both industry and scientific communities for its potential use as a food processing and preservation tool. Currently, most such applications deal with ultrasonic waves with relatively high intensities and acoustic power densities and are performed mostly in liquids. In this review, we briefly discuss the fundamentals of power ultrasound. We then summarize the physical and chemical effects of power ultrasound treatments based on the actions of acoustic cavitation and by looking into several ultrasound-assisted unit operations. Finally, we examine the biological effects of ultrasonication by focusing on its interactions with the miniature biological systems present in foods, i.e., microorganisms and food enzymes, as well as with selected macrobiological components.

Power Ultrasound

The use of ultrasound as a processing aid has been explored in various industrial sectors for over fifty years, but the application of this physical energy in food processing is relatively new. In this article, the current research and development activities of power ultrasound centered on food and bioprocessing applications are summarized. The mode of action of ultrasonication is attributed to several mechanical and chemical actions caused by cavitation, which include localized hot spots, formation of shock waves, microsteaming, and liquid jets, as well as the production of chemical species that will also impact the process kinetics and food quality attributes. Means to enhance cavitation activity is addressed. The research needs for the future development of ultrasound food processing are also discussed.