Carmen Gomes

Quantification of bioactive compounds in pulps and by-products of tropical fruits from Brazil

This study aimed to quantify the levels of resveratrol, coumarin, and other bioactives in pulps and by-products of twelve tropical fruits from Brazil obtained during pulp production process. Pineapple, acerola, monbin, cashew apple, guava, soursop, papaya, mango, passion fruit, surinam cherry, sapodilla, and tamarind pulps were evaluated as well as their by-products (peel, pulps leftovers, and seed). Total phenolic, anthocyanins, yellow flavonoids, β-carotene and lycopene levels were also determined. Resveratrol was identified in guava and surinam cherry by-products and coumarin in passion fruit, guava and surinam cherry by-products and mango pulp. These fruit pulp and by-products could be considered a new natural source of both compounds. Overall, fruit by-products presented higher (P<0.05) bioactive content than their respective fruit pulps. This study provides novel information about tropical fruits and their by-products bioactive composition, which is essential for the understanding of their nutraceutical potential and future application in the food industry.

Poly (DL‐lactide‐co‐glycolide) (PLGA) Nanoparticles with Entrapped trans‐Cinnamaldehyde and Eugenol for Antimicrobial Delivery Applications

UNLABELLED Eugenol and trans-cinnamaldehyde are natural compounds known to be highly effective antimicrobials; however, both are hydrophobic molecules, a limitation to their use within the food industry. The goal of this study was to synthesize spherical poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped eugenol and trans-cinnamaldehyde for future antimicrobial delivery applications. The emulsion evaporation method was used to form the nanoparticles in the presence of poly (vinyl alcohol) (PVA) as a surfactant. The inclusion of antimicrobial compounds into the PLGA nanoparticles was accomplished in the organic phase. Synthesis was followed by ultrafiltration (performed to eliminate the excess of PVA and antimicrobial compound) and freeze-drying. The nanoparticles were characterized by their shape, size, entrapment efficiency, and antimicrobial efficiency. The entrapment efficiency for eugenol and trans-cinnamaldehyde was approximately 98% and 92%, respectively. Controlled release experiments conducted in vitro at 37 °C and 100 rpm for 72 h showed an initial burst followed by a slower rate of release of the antimicrobial entrapped inside the PLGA matrix. All loaded nanoparticles formulations proved to be efficient in inhibiting growth of Salmonella spp. (Gram-negative bacterium) and Listeria spp. (Gram-positive bacterium) with concentrations ranging from 20 to 10 mg/mL. Results suggest that the application of these antimicrobial nanoparticles in food systems may be effective at inhibiting specific pathogens. PRACTICAL APPLICATION Nanoencapsulation of lipophilic antimicrobial compounds has great potential for improving the effectiveness and efficiency of delivery in food systems. This study consisted of synthesizing PLGA nanoparticles with entrapped eugenol and trans-cinnamaldehyde. By characterizing these new delivery systems, one can understand the controlled-release mechanism and antimicrobial efficiency that provides a foundation that will enable food manufacturers to design smart food systems for future delivery applications, including packaging and processing, capable of ensuring food safety to consumers.

Understanding E. coli internalization in lettuce leaves for optimization of irradiation treatment

Irradiation penetrates food tissues and effectively reduces the number of food microorganisms in fresh produce, but the efficacy of the process against internalized bacteria is unknown. The objective of this study was to understand the mechanisms of pathogen colonization of plants relative to lettuce leaf structures so that radiation treatment of fresh leafy vegetables can be optimized. Leaves of iceberg, Boston, green leaf, and red leaf lettuces were cut into pieces, submerged in a cocktail mixture of two isolates of Escherichia coli (Rifampicin resistant), and subjected to a vacuum perfusion process to force the bacterial cells into the intercellular spaces in the leaves. Sixty bags containing 20g of lettuce each were tested. The inoculated leaves were gamma irradiated (Lanthanum-140, 0.16kGy/h) at 0.25-1.0-kGy (surface dose values), with increments of 0.25kGy at 15 degrees C. Microbial analysis was performed right after irradiation, including non-irradiated leaf pieces (controls). A dose uniformity ratio (max/min dose) of 2.8 was set to confirm the effect of non-uniform dose distribution. Calculated D(10)-values varied between 48 and 62% based on the dose distribution from the entrance dose. However, despite the subtle differences in composition and structure among the four lettuce varieties, the D(10)-values were not significantly different. Irradiation up to 1.0-kGy resulted in 3-4-log reduction of internalized E. coli on the lettuce leaves. The SEM images suggest that the contamination sites of pathogens in leafy vegetables are mainly localized on crevices and into the stomata. This study shows that irradiation effectively reduces viable E. coli cells internalized in lettuce, and decontamination is not influenced by lettuce variety. Ionizing irradiation effectively reduced the population of internalized pathogen in a dose-dependent manner and could be used as an effective killing step to mitigate the risk of foodborne disease outbreaks.

Microencapsulated antimicrobial compounds as a means to enhance electron beam irradiation treatment for inactivation of pathogens on fresh spinach leaves.

UNLABELLED Recent outbreaks associated to the consumption of raw or minimally processed vegetable products that have resulted in several illnesses and a few deaths call for urgent actions aimed at improving the safety of those products. Electron beam irradiation can extend shelf-life and assure safety of fresh produce. However, undesirable effects on the organoleptic quality at doses required to achieve pathogen inactivation limit irradiation. Ways to increase pathogen radiation sensitivity could reduce the dose required for a certain level of microbial kill. The objective of this study was to evaluate the effectiveness of using natural antimicrobials when irradiating fresh produce. The minimum inhibitory concentration of 5 natural compounds and extracts (trans-cinnamaldehyde, eugenol, garlic extract, propolis extract, and lysozyme with ethylenediaminetetraacetate acid (disodium salt dihydrate) was determined against Salmonella spp. and Listeria spp. In order to mask odor and off-flavor inherent of several compounds, and to increase their solubility, complexes of these compounds and extracts with β-cyclodextrin were prepared by the freeze-drying method. All compounds showed bacteriostatic effect at different levels for both bacteria. The effectiveness of the microencapsulated compounds was tested by spraying them on the surface of baby spinach inoculated with Salmonella spp. The dose (D₁₀ value) required to reduce the bacterial population by 1 log was 0.190 kGy without antimicrobial addition. The increase in radiation sensitivity (up to 40%) varied with the antimicrobial compound. These results confirm that the combination of spraying microencapsulated antimicrobials with electron beam irradiation was effective in increasing the killing effect of irradiation. PRACTICAL APPLICATION Foodborne illness outbreaks attributed to fresh produce consumption have increased and present new challenges to food safety. Current technologies (water washing or treating with 200 ppm chlorine) cannot eliminate internalized pathogens. Ionizing radiation is a viable alternative for eliminating pathogens; however, the dose required to inactivate these pathogens is often too high to be tolerated by the fresh produce without undesirable quality changes. This study uses natural antimicrobial ingredients as radiosensitizers. These ingredients were encapsulated and applied to fresh produce that was subsequently irradiated. The process results in high level of microorganism inactivation using lower doses than the conventional irradiation treatments.

Pre-heating and polyphenol oxidase inhibition impact on extraction of purple sweet potato anthocyanins

Purple sweet potatoes (PSP) have been used as a natural food colorant with high acylated anthocyanins concentrations. Commercially extracting pigments from PSP can be challenging due to firm texture and high polyphenol oxidase (PPO) content. These studies evaluated hot water immersions (30, 50, 70, and 90°C for 10 min) as pre-heating treatments and addition of PPO inhibitors (citric acid, oxalic acid, and sodium borate) to aqueous extraction solutions to aid pigment recovery. Predominant PSP anthocyanins included acylated cyanidin or peonidin derivatives. Non-pigmented cinnamates acted as oxidase substrates and induced co-oxidation reactions with anthocyanins. Pre-heating PSP significantly increased polyphenolic yields in a temperature-dependent manner, consistent with tissue softening and PPO inactivation. The use of solvent modifiers in the extraction solution associated with heat helped minimize enzyme action and increased polyphenolic recovery. Minimizing the impact of PPO with heat was critical to the extraction and recovery of PSP anthocyanins, suitable for food use.

Delivery of phytochemicals of tropical fruit by-products using poly (DL-lactide-co-glycolide) (PLGA) nanoparticles: synthesis, characterization, and antimicrobial activity.

Nanoencapsulation offers great potential in natural compounds delivery as it protects them from degradation, improves their aqueous solubility, and delivers active compounds to the action site. Poly (dl-lactide-co-glycolide) (PLGA) nanoparticles of acerola, guava, and passion fruit by-product extracts were synthesized using the emulsion-evaporation method. PLGA with different lactide to glycolide (50:50 and 65:35) ratios were used to determine how polymer composition affected nanoparticles properties and antimicrobial efficiency. Controlled release experiments showed an initial burst followed by a slower release rate for all encapsulated fruit by-products inside PLGA matrix. Nanoparticle properties were more dependent on by-product extract than on PLGA type. Fruit by-products and their nanoparticles were analyzed for antimicrobial activity against Listeria monocytogenes Scott A and Escherichia coli K12. All fruit by-products encapsulated in PLGA inhibited both bacteria at lower (P<0.05) concentration than corresponding unencapsulated fruit by-product. Both PLGA types improved fruit by-products delivery to pathogens and enhanced antimicrobial activity.

Radiosensitization of Salmonella spp. and Listeria spp. in ready-to-eat baby spinach leaves.

The FDA recently approved irradiation treatment of leafy greens such as spinach up to 1 kGy; however, it is important to reduce the dose required to decontaminate the produce while maintaining its quality. Thus, the objectives of this study were: (1) to assess the radiation sensitivities of Salmonella spp. and Listeria spp. inoculated in ready-to-eat baby spinach leaves under modified atmosphere packaging (MAP) and irradiated using a 1.35-MeV Van de Graff accelerator (the leaves were irradiated both at room temperature and at -5 °C); and (2) to understand and optimize the synergistic effect of MAP and irradiation by studying the radiolysis of ozone formation under different temperatures, the effect of dose rate on its formation, and its decomposition. Results showed that increased concentrations of oxygen in the packaging significantly increased the radiation sensitivity of the test organisms, ranging from 7% up to 25% reduction in D(10)-values. In particular, radiosensitization could be effected (P < 0.05) by production of ozone, which increases with increasing dose-rate and oxygen concentration, and reducing temperatures. Radiosensitization was demonstrated for both microorganisms with irradiation of either fresh or frozen (-5 °C) baby spinach. These results suggest that low-dose (below 1 kGy) e-beam radiation under modified atmosphere packaging (100% O(2) and N(2):O(2)[1:1]) may be a viable tool for reducing microbial populations or eliminating Salmonella spp. and Listeria spp. from baby spinach. A suggested treatment to achieve a 5-log reduction of the test organisms would be irradiation at room temperature under 100% O(2) atmosphere at a dose level of 0.7 kGy. Practical Application: Decontamination of minimally processed fruits and vegetables from food-borne pathogens presents technical and economical challenges to the produce industry. Internalized microorganisms cannot be eliminated by the current procedure (water-washed or treated with 200-ppm chlorine). The only technology available commercially is ionizing radiation; however, the actual radiation dose required to inactivate pathogens is too high to be tolerated by the product without unwanted changes. This study shows a new approach in using MAP with 100% O(2), which is converted to ozone to radiosensitize pathogens while improving the shelf life of minimally processed fruits and vegetables. The process results in a high level of microorganism inactivation using lower doses than the conventional irradiation treatments.

Synthesis and Characterization of Nano-Encapsulated Black Pepper Oleoresin using Hydroxypropyl Beta-Cyclodextrin for Antioxidant and Antimicrobial Applications

Previous studies have reported antimicrobial and antioxidant activity of black pepper oleoresin which is associated to its phenolic compounds and piperine. The ability of cyclodextrins to form an inclusion complex with a guest molecule could improve black pepper oleoresin application, bioavailability, and stability in foods. Hydroxypropyl beta-cyclodextrin (HPBCD) inclusion complex with black pepper olereosin were synthesized using the kneading method and characterized for its physico-chemical properties and its antioxidant and antimicrobial activities. Inclusion complex size was 103.9 ± 7.6 nm and indicated to be a polydisperse system. The entrapment efficiency was 78.3 ± 3.6%, which suggests that other constituents in black pepper oleoresin have higher affinities for HPBCD than piperine (major compound in black pepper oleoresin). Thermograms showed the disappearance of oxidation peaks of black pepper oleoresin, proving complex formation with HPBCD. Phase solubility results indicated 1:1 stoichiometric inclusion complex formation and an increase of black pepper oleoresin aqueous solubility with HPBCD concentration. Nano-encapsulation with HPBCD did not affect (P > 0.05) total phenolic content; however, it enhanced (P < 0.05) black pepper oleoresin antioxidant activity. Black pepper oleoresin and its inclusion complex were analyzed for their antimicrobial activity against Escherichia coli K12 and Salmonella enterica serovar Typhimurium LT2. Both free and encapsulated black pepper oleoresin effectively inhibited bacterial growth within the concentration range tested. Black pepper oleoresin encapsulated in HPBCD was able to inhibit Salmonella at lower (P < 0.05) concentrations than its corresponding free extract. Therefore, black pepper oleoresin-HPBCD nanocapsules could have important applications in the food industry as antimicrobial and antioxidant system.

Effect of Oxygen‐Absorbing Packaging on the Shelf Life of a Liquid‐Based Component of Military Operational Rations

Oxygen within the sealed package can reduce the quality of liquid-based food products with high oil content such as hot-filled meal-ready-to-eat (MRE) cheese spread, a component of military operational rations. The aim of this study was to test a novel oxygen absorber-containing laminate material and its ability to maintain and/or extend shelf life of a cheese-spread MRE item. An iron-based oxygen absorber (ABSO(2)RB(R)) activated by moisture was incorporated into the laminate and used to pack hot-filled cheese spread MREs. The kinetics of oxygen absorption due to humidity and temperature were characterized and peel tests performed to ensure pouch seal integrity. Accelerated shelf-life tests of ABSO(2)RB and regular MRE pouches without the O(2)-absorber were conducted for 3 mo at 51.7 degrees C (125 degrees F), and 6 mo at 37.8 degrees C (100 degrees F) by measuring oxygen concentration (Mocon O(2)-analyzer), microbiological, and physicochemical quality characteristics, including color, texture, moisture, free fatty acid (FFA), pH, water activity, and vitamins and A. Pouches stored at 26.7 degrees C (80 degrees F) for 12 mo served as calibrated controls. Consumer tests were conducted in-house and a confirmatory sensory test was conducted at Natick by a trained panel using a 9-point hedonic scale. ABSO(2)RB-laminates maintain the same seal integrity and strength as those of the control samples. The headspace oxygen concentrations in these pouches reached (P < 0.05) < 0.5% in 11 d of storage at 26.7 degrees C (80 degrees F) and remained below this level throughout the storage period (1 y). No microbial growth (aerobic, coliforms, yeast, and molds) was detected (P < 0.05) for both packages. Overall, the ABSO(2)RB-pouches indicate an improved reduction in oxygen and vitamin C retention compared with MRE controls and maintained product quality (physicochemical and organoleptic). ABSO(2)RB-laminates met the accelerated shelf-life requirement of 1 mo at 51.7 degrees C (125 degrees F), and 6 mo at 37.8 degrees C (100 degrees F). This study clearly shows the benefits of using active packaging technology on retaining nutrition and prolonging shelf life of high-fat, liquid content MRE items.

Preparation of Chitosan-Alginate Nanoparticles for Trans-cinnamaldehyde Entrapment.

UNLABELLED Trans-cinnamaldehyde incorporated chitosan-alginate nanoparticles were synthesized using the ionic gelation and polyelectrolyte complexation technique. Alginate, chitosan, calcium chloride, and trans-cinnamaldehyde at predetermined concentrations were complexed electrostatically to optimize particle size and loading efficiency. A final methodology using optimized processing parameters (for example, stirring time, homogenization time, equilibration time, and droplet size) was developed. The best working alginate to chitosan mass ratio was determined to be 1.5:1 at a pH dispersion of 4.7. Particle size (166.26 nm) and encapsulation efficiency (73.24%) were further optimized at this mass ratio using an alginate:calcium chloride mass ratio of 4.8:1, alginate:trans-cinnamaldehyde mass ratio of 37.5:1, a 18 gauge syringe needle, stirring times of 90 min, 15 min of homogenization at 21000 rpm, and equilibration time of 24 h. Optimized nanoparticles showed increased stability (6 wk) and translucency in solution. The final radical scavenging effect of loaded particles in apple juice was 62% and trans-cinnamaldehyde was just as available to react in free form as it was in inclusion complexes. The final nanoparticle system with modified and optimized processing parameters reduced the size by 43.6% and increased entrapment efficiency by 17.2%. Nanoparticles resembled a spherical shell and core type arrangement (that is, spherical, distinct, and regular) and were in the size range of 10 to 100 nm. PRACTICAL APPLICATION Nanoencapsulation of lipophilic antimicrobial and antioxidant compounds has the potential to improve their effectiveness and efficiency of delivery in food systems. Determining a standard nanoparticle synthesis methodology and optimizing entrapment efficiency and particle size prior to characterization studies allows for improved understanding of nanosystems and substantiates results. This study demonstrates the potential to improve current nanoparticle preparation techniques to fine tune critical physical parameters. The results presented in this study can aid in developing new and simple ways to improve nanoparticle formulations and prompt further studies to validate entrapment of lipophilic compounds combinations.