Simultaneous Determination of Preservatives in Dairy Products by HPLC and Chemometric Analysis

Lactic acid bacteria from artisanal raw goat milk cheeses: technological properties and antimicrobial potential

In cheese-making, a starter culture composed of adequately chosen lactic acid bacteria (LAB) may be suitable to ensure the rapid acidification of milk, improve textural and sensory characteristics, and avoid pathogen proliferation. In this work, 232 LAB isolates collected from artisanal goat's raw milk cheeses produced in Portugal were evaluated for their antimicrobial capacity (at 10 and 37°C), as well as their acidifying and proteolytic properties. Among the 232 isolates, at least 98% of those isolated in De Man- Rogosa-Sharpe (MRS) agar presented antagonism against Listeria monocytogenes, Salmonella Typhimurium, or Staphylococcus aureus, whereas less than 28.1% of M17-isolated LAB showed antagonism against these pathogens. M17-isolated LAB displayed better results than MRS ones in terms of acidifying capacity. As for the proteolytic assay, only 2 MRS isolates showed casein hydrolysis capacity. Principal component analyses and molecular characterization of a subset of selected isolates were conducted to identify those with promising capacities and to correlate the identified LAB genera and species with their antimicrobial, acidifying, and/or proteolytic properties. Lactococcus strains were associated with the highest acidifying capacity, whereas Leuconostoc and Lacticaseibacillus strains were more related to antimicrobial capacities. Leuconostoc mesenteroides, Lactococcus lactis, and Lacticaseibacillus paracasei were the predominant organisms found. The results of this work highlight various strains with pathogen inhibition capacity and suitable technological properties to be included in a customized starter culture. In future work, it is necessary to appropriately define the starter culture and implement it in the cheese-making process to evaluate if the in-vitro capacities are observable in a real food system.

Rapid microwave synthesis of N and S dual-doped carbon quantum dots for natamycin determination based on fluorescence switch-off assay

Green, one-pot, quick, and easily synthesized nitrogen and sulfur co-doped carbon quantum dots (N,S-CDs) were obtained from cheap and readily available chemicals (sucrose, urea, and thiourea) using a microwave-assisted approach in about 4 min and utilized as a turn-off fluorescent sensor for estimation of natamycin (NAT). First, the effect of N and S doping on the microwave-synthesized CDs' quantum yield was carefully studied. CDs derived from sucrose alone failed to produce a high quantum yield; then, to increase the quantum yield, doping with heteroatoms was carried out using either urea or thiourea. A slight increase in quantum yield was observed upon using thiourea with sucrose, while an obvious enhancement of quantum yield was obtained when urea was used instead of thiourea. Surprisingly, using a combination of urea and thiourea together results in N,S-CDs with the highest quantum yield (53.5%), uniform and small particle size distribution, and extended stability. The fluorescent signal of N,S-CDs was quenched upon addition of NAT due to inner filter effect and static quenching in a manner that allowed for quantitative determination of NAT over a range of 0.5-10.0μg ml-1(LOD = 0.10μg ml-1). The N,S-CDs were applicable for determination of NAT in aqueous humor, eye drops, different environmental water samples, and bread with excellent performance. The selectivity study indicated excellent selectivity of the prepared N,S-CDs toward NAT with little interference from possibly interfering substances. In-silico toxicological evaluation of NAT was conducted to estimate its long-term toxicity and drug-drug interactions. Finally, the preparation of N,S-CDs, and analytical procedure compliance with the green chemistry principles were confirmed by two greenness assessment tools.

Prevention of Fungal Contamination in Semi-Hard Cheeses by Whey–Gelatin Film Incorporated with Levilactobacillus brevis SJC120

Cheese whey fermented by lactic acid bacteria (LAB) was used to develop an edible film with antifungal properties. Five LAB strains isolated from artisanal cheeses were screened for antifungal activity and incorporated into a whey–gelatin film. Of the strains tested, Levilactobacillus brevis SJC120 showed the strongest activity against five filamentous fungi isolated from cheese and cheese-making environment, at both 10 °C and 20 °C. The cell-free supernatant from L. brevis inhibited fungal growth by more than 80%. Incorporation of bacterial cells into the film did not alter the moisture content, water vapor permeability, or mechanical and optical properties. The whey–gelatin film was also able to maintain the viability of L. brevis cells at 107 log CFU/g after 30 days at 10 °C. In cheeses wrapped with L. brevis film, the size of fungal colonies decreased by 55% to 76%. Furthermore, no significant differences (p > 0.05) were observed in cheese proteolysis or in the moisture, fat, and protein content of the cheese wrapped with films. The results showed that whey–gelatin film with L. brevis SJC120 can reduce the contamination of cheese with filamentous fungi and could be used as an alternative to conventional cheese preservation and packaging.

An environment-friendly approach using deep eutectic solvent combined with liquid-liquid microextraction based on solidification of floating organic droplets for simultaneous determination of preservatives in beverages

With the increase in environmental protection awareness, the development of strategies to reduce the use of organic solvent used during the extraction process has attracted wide attention. A simple and green ultrasound-assisted deep eutectic solvent extraction combined with liquid-liquid microextraction based on solidification of floating organic droplets method was developed and validated for the simultaneous determination of five preservatives (methyl paraben, ethyl paraben, propyl paraben, isopropyl paraben, isobutyl paraben) in beverages. Extraction conditions including the volume of DES, value of pH, and concentration of salt were statistically optimized through response surface methodology using a Box-Behnken design. Complex Green Analytical Procedure Index (ComplexGAPI) was successfully used to estimate the greenness of the developed method and compare with the previous methods. As a result, the established method was linear, precise, and accurate over the range of 0.5-20 μg mL^-1. Limits of detection and limits of quantification were in the range of 0.15-0.20 μg mL^-1 and 0.40-0.45 μg mL^-1, respectively. The recoveries of all five preservatives ranged from 85.96% to 110.25%, with relative standard deviation less than 6.88% (intra-day) and 4.93% (inter-day). The greenness of the present method is significantly better compared with the previous reported methods. Additionally, the proposed method was successfully applied to analysis of preservatives in beverages and is a potentially promising technique for drink matrices.

Microbial and Chemical Characteristics of Doogh (Iranian Fermented Milk Drink)

Background

Regarding the increasing public health concerns about the safety of foodstuffs, the current survey was designed to argue the presence of preservatives (e.g., sodium benzoate (SB), potassium sorbate (PS), and natamycin) and also the level of salt and fungi in 148 samples of yoghurt drink “Doogh.”

Methods

The enumeration of fungi and determination of salt content of samples were performed according to the standard procedures. Preservative determination was performed by reverse phase high-performance liquid chromatography with UV detection (RV-HPLC-UV).

Results

0.1% of the total analyzed samples was above the permitted level of Iranian standard for SB (0%), while PS was not detected in any of them. Furthermore, natamycin in 0.11% of the analyzed samples had more than the permissible level of Iranian standard. Additionally, about 15% of the tested samples was higher than the Iranian standard level for fungi (<102 CFU/mL). The average amount of salt in the tested Doogh samples and also in the examined Kefir samples was significantly (P < 0.001) lower than the standard amount of salt (<0.8 g/100).

Conclusion

In conclusion, the quality of Doogh and Kefir samples were acceptable in terms of salt content. Kefir had a significantly (P ≤ 0.001) lower amount of salt in comparison with Doogh. Taken together, underlining the results of the present study, no significant public health concern would exist respecting the mentioned additives.

A Review of the Preservation of Hard and Semi-Hard Cheeses: Quality and Safety

Cheese is a dairy product with potential health benefits. Cheese consumption has increased due to the significant diversity of varieties, versatility of product presentation, and changes in consumers’ lifestyles. Spoilage of hard and semi-hard cheeses can be promoted by their maturation period and/or by their long shelf-life. Therefore, preservation studies play a fundamental role in maintaining and/or increasing their shelf-life, and are of significant importance for the dairy sector. The aim of this review is to discuss the most effective methods to ensure the safety and sensory quality of ripened cheeses. We review traditional methods, such as freezing, and modern and innovative technologies, such as high hydrostatic pressures, chemical and natural vegetable origin preservatives, vacuum and modified atmosphere packaging, edible coatings and films, and other technologies applied at the end of storage and marketing stages, including light pulses and irradiation. For each technology, the main advantages and limitations for industrial application in the dairy sector are discussed. Each type of cheese requires a specific preservation treatment and optimal application conditions to ensure cheese quality and safety during storage. The environmental impact of the preservation technologies and their contribution to the sustainability of the food chain are discussed.

Development of a natamycin-based non-migratory antimicrobial active packaging for extending shelf-life of yogurt drink (Doogh)

A natamycin-based non-migratory antimicrobial packaging for extending shelf-life of yogurt drink (Doogh) was developed. Firstly, the surface of low-density polyethylene film (LDPE) was modified with acrylic acid at different times of UV exposure (0-10 min) to produce carboxylic functional groups. Then, natamycin was applied to the UV-treated films to bind covalently with the pendent functional groups. The maximum grafting efficiency (81.96%) was obtained for the 6 min treated film. Moreover, surface properties of films were evaluated by Attenuated Total Reflectance/Fourier Transfer Infrared Spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Antifungal activity of different treatments of natamycin grafted film was evaluated against two common spoilage yeasts of Doogh including Rhodotorula mucilaginosa and Candida parapsilosis. Results showed that 6 min treated film provides maximum anti-yeast activity and can be applied to control fungal growth in Doogh. Natamycin-grafted film postponed the yeast spoilage in Doogh and prolonged its shelf-life to 23 days.

Thermo-/pH-responsive preservative delivery based on TEMPO cellulose nanofiber/cationic copolymer hydrogel film in fruit packaging

Hydrogels have great potential in food packaging. However, stimuli-responsive preservative delivery-based hydrogels for emerging active packaging have not yet been explored. Herein, Unprecedented pH/temperature-responsive hydrogel films for emerging active climacteric fruit packaging were developed based on TEMPO-oxidized nanofibrillated cellulose (TOCNFs) from wheat straw with food-grade cationic-modified poly(N-isopropyl acrylamide-co-acrylamide) (CP_NIPAM-AM). TOCNF incorporation into CP_NIPAM-AM revealed desirable enhancement of characterization, antimicrobial properties, and pH/thermal-responsive behaviour. In-vitro delivery and release mechanism studies with natamycin revealed the fastest release rates in preferred low pH media, up to 32.1 times higher than that under neutral conditions via anomalous diffusion. Applying a thermal stimulus increased natamycin release rates, providing 1.5-21% gradual-additional pulses by Fickian diffusion. The final hydrogel film showed efficient decay control in response to stimuli of the climacteric fruit environment with safe, recyclable, and feasible application demonstrating the significant potential to be used as an alternative-sustainable material for stimuli-triggered preservative delivery in climacteric fruit packaging.

Plant compounds for the potential reduction of food waste - a focus on antimicrobial peptides

A large portion of global food waste is caused by microbial spoilage. The modern approach to preserve food is to apply different hurdles for microbial pathogens to overcome. These vary from thermal processes and chemical additives, to the application of irradiation and modified atmosphere packaging. Even though such preservative techniques exist, loss of food to spoilage still prevails. Plant compounds and peptides represent an untapped source of potential novel natural food preservatives. Of these, antimicrobial peptides (AMPs) are very promising for exploitation. AMPs are a significant component of a plant's innate defense system. Numerous studies have demonstrated the potential application of these AMPs; however, more studies, particularly in the area of food preservation are warranted. This review examines the literature on the application of AMPs and other plant compounds for the purpose of reducing food losses and waste (including crop protection). A focus is placed on the plant defensins, their natural extraction and synthetic production, and their safety and application in food preservation. In addition, current challenges and impediments to their full exploitation are discussed.

Invited review: Controlling dairy product spoilage to reduce food loss and waste

Food loss and waste is a major concern in the United States and globally, with dairy foods representing one of the top categories of food lost and wasted. Estimates indicate that in the United States, approximately a quarter of dairy products are lost at the production level or wasted at the retail or consumer level annually. Premature microbial spoilage of dairy products, including fluid milk, cheese, and cultured products, is a primary contributor to dairy food waste. Microbial contamination may occur at various points throughout the production and processing continuum and includes organisms such as gram-negative bacteria (e.g., Pseudomonas), gram-positive bacteria (e.g., Paenibacillus), and a wide range of fungal organisms. These organisms grow at refrigerated storage temperatures, often rapidly, and create various degradative enzymes that result in off-odors, flavors, and body defects (e.g., coagulation), rendering them inedible. Reducing premature dairy food spoilage will in turn reduce waste throughout the dairy continuum. Strategies to reduce premature spoilage include reducing raw material contamination on-farm, physically removing microbial contaminants, employing biocontrol agents to reduce outgrowth of microbial contaminants, tracking and eliminating microbial contaminants using advanced molecular microbiological techniques, and others. This review will address the primary microbial causes of premature dairy product spoilage and methods of controlling this spoilage to reduce loss and waste in dairy products.