Determining the mechanism of pulsed electric field for improving meat quality : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Pulsed electric field (PEF) is a novel non-thermal technology that has recently attracted the attention of meat scientists and technologists due to its ability to modify membrane structure and enhance mass transfer. Several studies have confirmed the potential of PEF for improving meat tenderness in both pre-rigor and post-rigor muscles during ageing. However, there is a high degree of variability between studies and the underlying mechanisms for the reported outcomes are not clearly understood. While some studies have suggested physical disruption as the main cause of PEF induced tenderness, enzymatic nature of the tenderization seems to be the most plausible mechanism. Several studies have suggested the potential of PEF to mediate the tenderization process due to its membrane altering properties causing early release of calcium ions and early activation of the calpain proteases. However, experimental research is yet to confirm this postulation. The changes in the calpain activity and protein profile of beef from older animals during ageing is poorly explored and further understanding of biochemical processes is needed to design useful approaches for tenderization. Relatively few experiments have examined the effects of ageing on the quality of beef from older animals. To elucidate the changes in the calpain activity and protein profile of beef from culled dairy cows during ageing, cold-boned Semimembranosus (n=6) and Biceps femoris (n=6) were vacuum packaged and stored for 14 days at 4±1 °C. A significant (P<0.05) effect of ageing was observed on the pH, shear force and myofibrillar fragmentation index of both the muscles. Casein zymography results indicated the presence of intact and autolyzed forms of calpain 1 and calpain 2. An increase in proteolysis was observed in both the muscles during ageing. Ageing for two weeks resulted in reduction (P<0.05) of the shear force of both muscles by 30%, however, the aged muscles were still excessively tough. To evaluate the impact of PEF on the quality of beef from older animals, cold-boned beef Semimembranosus (n=6) and Biceps femoris (n=6) were processed with two different PEF treatments viz. T1 (5 kV, 90 Hz, 20 µs) and T2 (10 kV, 20 Hz, 20 µs) and were vacuum packaged and stored for 14 days at 4±1 °C along with a non-treated control. Samples from venison Longissimus dorsi (n=6) were also treated with PEF [T1 (2.5 kV, 50 Hz, 20 µs) and T2 (10 kV, 90 Hz, 20 µs)] and were subjected to 21 days of ageing at 4±1 °C. An improvement was recorded in calpain activity of all the samples treated with PEF along with an early activation of calpain 2 in beef. Increased proteolysis of troponin-T and desmin was also recorded, however, no significant (P>0.05) impact was observed on the shear force and myofibrillar fragmentation index of any of the muscles. These results provided an experimental evidence for the enzymatic nature of PEF. PEF has been reported to affect the structural and functional properties of proteins, which suggests that it may influence the digestion of meat proteins. To evaluate the impact of PEF on the protein digestion kinetics, PEF-treated beef Semimembranosus and Biceps femoris [T1 (5 kV, 90 Hz, 20 µs) and T2 (10 kV, 20 Hz, 20 µs)] and venison Longissimus dorsi [T1 (2.5 kV, 50 Hz, 20 µs) and T2 (10 kV, 90 Hz, 20 µs)] were subjected to in vitro simulated gastrointestinal digestion. Both raw (n=3) and cooked (n=3) samples were used separately. Samples were collected at 0, 30, and 60 minutes of gastric digestion and 120 and 180 minutes of intestinal digestion. PEF processing affected the digestion kinetics of all the muscles by modifying the protein profile (SDS-PAGE) of the meat digests and significantly (P0.05) for the PEF treated samples whereas no significant (P>0.05) impact was observed on the release of minerals such as Fe, Zn, Cr, Cu, Mg, Ni, Na or K. PEF processing improved the digestion kinetics of the beef and venison during gastrointestinal digestion simulation in both raw and cooked samples. PEF has been shown to accelerate salt diffusion and enhance mass transfer processes in meat indicating a possibility for its application in sodium reduction management. By influencing the cellular and membrane permeability and by affecting structural and functional properties of proteins, PEF is expected to improve the salt diffusion and possibly sodium perception during chewing. The potential use of PEF to reduce sodium in processed meat was investigated using beef jerky as a model system (n=6). Beef jerky was prepared using different levels of NaCl viz. 2.0% (control), 1.2% (T1) and 1.2% along with PEF-processing (T2, 0.52 kV/cm, 10 kV, 20 Hz, 20 µs). A significant (P0.05) with control and more than 84% of the panellists preferred T2 samples over T1 for saltiness. No undesirable effects of PEF were observed on colour, yield (%) and oxidative and microbial stability. These results suggest that PEF has a sodium-reduction potential that can play a role in public health. The general scope of the present project was to elucidate how PEF affects the meat quality during ageing and to explore the possible application of PEF in protein digestion and sodium reduction. It was expected that this project will decipher the mechanisms of how PEF affects meat quality and protein digestion and elucidate a possible role of PEF in sodium reduction. Research on PEF-assisted sodium reduction and its role in protein digestion is unavailable in the literature

Storage stability of chocolate can be enhanced using locust protein-based film incorporated with \u3cem\u3eE. purpurea\u3c/em\u3e Flower Extract-based Nanoparticles

The study aimed to develop a locust protein (Loct-Prot)-based film to enhance the lipid oxidative and storage stability of chocolate. The E. purpurea flower extract based-nanoparticles (EFNPs) were developed using ultra- sonication (500 W and 20 kHz for 10 min) following a green method of synthesis. The EFPNs were incorporated at different levels [T0 (0%), T1 (1.0%), T2 (1.5%), and T3 (2.0%)] to impart bioactive properties to the Loct-Prot- based films which were used for packaging of white chocolate during 90 days trial. The addition of EFPNs increased (P \u3c 0.05) the density of the Loct-Prot-based film which in turn decreased (P \u3c 0.05) the transmittance (%) and WVTR (water vapour transmission rate, mg/mt2) with increasing levels of addition. While brightness (L*) showed a decrease, redness (a*) and yellowness (b*) increased with increasing concentration of EFPNs. No significant (P \u3e 0.05) effect was recorded on other physicomechanical parameters of the film. The addition of EFPNs (P \u3c 0.05) increased the mean values of all the antioxidant and antimicrobial parameters (total flavonoid and phenolic contents, FRAP, DPPH, and ABTS activities, antioxidant release and inhibitory halos) of the film. The presence of Loct-Prot-based film decreased the lipid (TBARS and free fatty acids) and protein (total carbonyl content) oxidation of the chocolate samples during storage. A significant (P \u3c 0.05) increase was observed in the antioxidant properties [FRAP (μM TE/100 g) and DPPH and ABTS activities (% inhibition)] of the chocolate samples after one month and the sensory and microbial qualities towards the end of the storage. The gastroin- testinal digestion simulation showed a positive impact on the antioxidant properties of the chocolate. Based on our results, Loct-Prot-based film incorporated with EFPNs can be used to enhance the storage stability of chocolate during storage

Aloe vera and carrageenan based edible film improves storage stability of ice-cream

publishedVersio

Rubia cordifolia based novel edible film for improved lipid oxidative and microbial stability of meat products

submittedVersio

Development of composite meat chocolate fortified with calcium and plant extracts

acceptedVersio

High-pressure processing of fish and shellfish products: Safety, quality, and research prospects

Seafood products have been one of the main drivers behind the popularity of high-pressure processing (HPP) in the food industry owing to a high demand for fresh ready-to-eat seafood products and food safety. This review provides an overview of the advanced knowledge available on the use of HPP for production of wholesome and highly nutritive clean label fish and shellfish products. Out of 653 explored items, 65 articles published during 2016-2021 were used. Analysis of the literature showed that most of the earlier work evaluated the HPP effect on physicochemical and sensorial properties, and limited information is available on nutritional aspects. HPP has several applications in the seafood industry. Application of HPP (400-600 MPa) eliminates common seafood pathogens, such as Vibrio and Listeria spp., and slows the growth of spoilage microorganisms. Use of cold water as a pressure medium induces minimal changes in sensory and nutritional properties and helps in the development of clean label seafood products. This technology (200-350 MPa) is also useful to shuck oysters, lobsters, crabs, mussels, clams, and scallops to increase recovery of the edible meat. High-pressure helps to preserve organoleptic and functional properties for an extended time during refrigerated storage. Overall, HPP helps seafood manufacturers to maintain a balance between safety, quality, processing efficiency, and regulatory compliance. Further research is required to understand the mechanisms of pressure-induced modifications and clean label strategies to minimize these modifications

<i>Aloe barbadensis</i> Based Bioactive Edible Film Improved Lipid Stability and Microbial Quality of the Cheese

An attempt was made to develop a bioactive edible film using carrageenan and A. vera gel for enhancing the storage quality of cheese using kalari, a popular Himalayan cheese, as a food-model system. The film was evaluated for various physicomechanical and oxidative properties (ABTS (2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonate)) and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activities, total flavonoid and phenolic contents). Based on preliminary trials, 1% A. vera gel was found to be optimum. The addition of the gel resulted in a significant decrease in moisture content, transparency, solubility, and water-vapor transmission rate and increased the thickness and density of the film. The film showed antimicrobial properties against E. coli and significantly (p < 0.05) decreased the lipid-oxidation (thiobarbituric acid reactive substances, free-fatty acids, and peroxide values) and increased microbial-quality (total-plate, psychrophilic, and yeast/molds) of the samples during 4-week refrigerated storage (4 ± 1 °C). The film also exhibited a significant positive impact on the sensory quality of the cheese, indicating the potential for commercial applications for quality control of cheese during storage

Storage stability of chocolate can be enhanced using locust protein-based film incorporated with E. purpurea flower extract-based nanoparticles

The study aimed to develop a locust protein (Loct-Prot)-based film to enhance the lipid oxidative and storage stability of chocolate. The E. purpurea flower extract based-nanoparticles (EFNPs) were developed using ultrasonication (500 W and 20 kHz for 10 min) following a green method of synthesis. The EFPNs were incorporated at different levels [T0 (0%), T1 (1.0%), T2 (1.5%), and T3 (2.0%)] to impart bioactive properties to the Loct-Prot-based films which were used for packaging of white chocolate during 90 days trial. The addition of EFPNs increased (P  0.05) effect was recorded on other physicomechanical parameters of the film. The addition of EFPNs (P < 0.05) increased the mean values of all the antioxidant and antimicrobial parameters (total flavonoid and phenolic contents, FRAP, DPPH, and ABTS activities, antioxidant release and inhibitory halos) of the film. The presence of Loct-Prot-based film decreased the lipid (TBARS and free fatty acids) and protein (total carbonyl content) oxidation of the chocolate samples during storage. A significant (P < 0.05) increase was observed in the antioxidant properties [FRAP (µM TE/100 g) and DPPH and ABTS activities (% inhibition)] of the chocolate samples after one month and the sensory and microbial qualities towards the end of the storage. The gastrointestinal digestion simulation showed a positive impact on the antioxidant properties of the chocolate. Based on our results, Loct-Prot-based film incorporated with EFPNs can be used to enhance the storage stability of chocolate during storage

Enhancing the lipid stability of foods of animal origin using edible packaging systems

International audienceFoods of animal origin are prone to oxidation due to their high lipid content and fatty acid profile. Edible packaging systems have evolved as a new way of preserving animal-derived foods and have been reported to retard lipid oxidation using antioxidant molecules from side-streams, waste, and agricultural by-products. Studies have evaluated previously undocumented film materials and novel bioactive molecules as additives for edible packaging for animal-derived foods. However, none of the studies is specifically focused on evaluating the packaging systems available for enhancing lipid stability. This paper thoroughly examines and discusses the application of edible packaging containing novel antioxidant molecules for controlling the lipid oxidation of animal-derived foods. The paper analyses and interprets the main findings of the recently published research papers. The materials and active principles used for enhancing lipid stability have been summarised and the underlying mechanisms discussed in detail. Studies should aim at using cheaper and readily available natural ingredients in future for the production of affordable packaging systems