Detection of potentially pathogenic Aeromonas isolates from ready‐to‐eat seafood products by PCR analysis

This study provides data on the prevalence of potentially pathogenic Aeromonas spp. in ready‐to‐eat (RTE) seafood products by evaluating the occurrence of Aeromonas spp. and the presence of virulence‐associated genes. Aeromonas spp. was detected in 57/81 (70.3%) RTE seafood samples. Specifically, Aeromonas spp. was highlighted in 19/21 (90.5%) sushi, in 18/21 (85.7%) sea salad, 11/12 (91.7%) surimi and 9/12 (75%) peeled shrimp samples. Aeromonas spp. was not observed in marinated anchovies and octopus salad samples. Then, PCRs aimed at the hlyA, aerA, alt and ast genes, encoding, respectively, haemolysin A, aerolysin, aeromonas labile temperature cytotonic enterotoxin and aeromonas stable temperature cytotonic enterotoxin, demonstrated a widespread distribution of these genes among Aeromonas isolates. The results underline the need to implement an adequate control plan performing an intensive and continuous monitoring to guarantee the human health.     

Effect of oregano and thyme essential oils on the microbiological and chemical quality of refrigerated (4 °C) ready‐to‐eat squid rings

The efficacy of oregano and thyme essential oils (OEO and TEO, respectively) in the quality retention of a refrigerated (4 °C) squid (Loligo vulgaris) ring ready‐to‐eat (RTE) product was studied. Essential oils were added at different concentrations to the coating medium during processing. An inhibitory (P < 0.05) effect of OEO on the microbial activity (aerobes, anaerobes, Enterobacteriaceae, psychrotrophs) of the squid rings was observed, with a more pronounced effect as OEO concentration increased. The addition of OEO also led to an inhibitory (P < 0.05) effect on lipid oxidation, as determined by peroxide, thiobarbituric acid‐reactive substance and interaction compound formation; however, no effect (P > 0.05) of the OEO concentrations on lipid oxidation development was detected. The addition of TEO did not lead to an inhibitory effect (P > 0.05) on the microbial activity of the refrigerated RTE squid, although a slight inhibitory (P < 0.05) effect on lipid oxidation was observed in the batches including the higher TEO concentrations.     

The effect of long‐term storage on amino acid content of ready‐to‐eat entrées

The effect of 24‐month storage at three different temperatures (6 ± 2 °C, 26 ± 2 °C, 37 ± 2 °C) on quality of three types of ready‐to‐eat entrées (MRE) was evaluated by means of amino acid, ammonia, moisture and crude protein contents. Spicy risotto, Pork meat with carrots and potatoes and Pork goulash with pasta, that are included into the Czech combat rations, were selected for the experiment. During storage, all the explored samples did not significantly differ in moisture and crude protein content. Higher losses of amino acids (e.g. sulphuric amino acids, lysine, leucine) were detected with the increasing storage time and temperature. Growing losses of amino acids resulted in rising ammonia content as a product of amino acid degradation process. The biological value expressed by essential amino acid index declined with higher temperature and longer time of storage. The dependence of amino acid losses on moisture content was observed, too.     

Nondestructive and Continuous Monitoring of Oxygen Levels in Modified Atmosphere Packaged Ready‐to‐Eat Mixed Salad Products Using Optical Oxygen Sensors,and Its Effects on Sensory and Microbiological Counts during Storage

The objective of this study was to determine the percentage oxygen consumption of fresh, respiring ready‐to‐eat (RTE) mixed leaf salad products (Iceberg salad leaf, Caesar salad leaf, and Italian salad leaf). These were held under different modified atmosphere packaging (MAP) conditions (5% O₂, 5% CO₂, 90% N₂ (MAPC—commercial control), 21% O₂, 5% CO₂, 74% N₂ (MAP 1), 45% O₂, 5% CO₂, 50% N₂ (MAP 2), and 60% O₂, 5% CO₂, 35% N₂ (MAP 3)) and 4 °C for up to 10 d. The quality and shelf‐life stability of all packaged salad products were evaluated using sensory, physiochemical, and microbial assessment. Oxygen levels in all MAP packs were measured on each day of analysis using optical oxygen sensors allowing for nondestructive assessment of packs. Analysis showed that with the exception of control packs, oxygen levels for all MAP treatments decreased by approximately 10% after 7 d of storage. Oxygen levels in control packs were depleted after 7 d of storage. This appears to have had no detrimental effect on either the sensory quality or shelf‐life stability of any of the salad products investigated. Additionally, the presence of higher levels of oxygen in modified atmosphere packs did not significantly improve product quality or shelf‐life stability; however, these additional levels of oxygen were freely available to fresh respiring produce if required. This study shows that the application of optical sensors in MAP packs was successful in nondestructively monitoring oxygen level, or changes in oxygen level, during refrigerated storage of RTE salad products.     

Control of Listeria monocytogenes Contamination in Ready‐to‐Eat Meat Products

The ubiquitous nature of Listeria monocytogenes and its ability to grow at refrigerated temperature makes L. monocytogenes a significant threat to the safety of ready‐to‐eat (RTE) meat products. The contamination by L. monocytogenes in RTE meat primarily occurs during slicing and packaging after cooking. The effectiveness of post‐package decontamination technology such as in‐package thermal pasteurization, irradiation, and high‐pressure processing are discussed. Formulating meat products with antimicrobial additives is another common approach to control L. monocytogenes in RTE meat. Irradiation is an effective technology to eliminate L. monocytogenes but can influence the quality of RTE meat products significantly. The effect of irradiation or the combination of irradiation and antimicrobials on the survival of L. monocytogenes and the quality of RTE meat is discussed.     

Efficacy of Combined Sous Vide‐Microwave Cooking for Foodborne Pathogen Inactivation in Ready‐to‐Eat Chicory Stems

There is a variety of different food processing methods, which can be used to prepare ready‐to‐eat foods. However, the need to preserve the freshness and nutritional qualities leads to the application of mild technologies which may be insufficient to inactivate microbial pathogens. In this work, fresh chicory stems were packed under a vacuum in films, which were transparent to microwaves. These were then exposed to microwaves for different periods of time. The application of sous vide microwave cooking (SV‐MW, 900 W, 2450 MHz), controlled naturally occurring mesophilic aerobic bacteria, yeasts and molds for up to 30 d when vacuum‐packed vegetables were stored at 4 °C. In addition, the process lethality of the SV‐MW 90 s cooking was experimentally validated. This treatment led to 6.07 ± 0.7 and 4.92 ± 0.65 log cfu/g reduction of Escherichia coli and Listeria monocytogenes inoculated over the chicory stems (100 g), respectively. With an initial load of 9 log cfu/g for both pathogens, less than 10 cfu/g of surviving cells were found after 90 s cooking. This shows that short‐time microwave cooking can be used to effectively pasteurize vacuum‐packed chicory stems, achieving >5 log cfu/g reduction of E. coli and L. monocytogenes.     

Microwave Pasteurization of Cooked Pasta: Effect of Process Parameters on Texture and Quality for Heat‐and‐Eat and Ready‐to‐Eat Meals

Pasta presents a challenge to microwave processing due to its unique cooking requirements. The objective of this study was to determine the effects of microwave processing on pasta physicochemical and mechanical properties. Fettuccine pasta was parboiled for selected times, then pasteurized using a Microwave Assisted Pasteurization System and stored under refrigeration for 1 wk. Samples were analyzed using microscopy, mechanical testing, and chemical analyses after storage. While no significant differences were observed for free amylose among fresh samples, samples parboiled for ≤6 min had significantly higher free amylose, suggesting reduced starch retrogradation. Increased heat treatment increased degree of protein polymerization, observed in microstructures as increased gluten strand thickness and network density. Firmness and extensibility increased with increased parboil time; however, extension data indicated an overall weakening of microwave‐treated pasta regardless of total cooking time. Overall, microwave pasteurization was shown to be a viable cooking method for pasta.     

Frequency and Correlation of Some Enteric Indicator Bacteria and Salmonella in Ready‐to‐Eat Raw Vegetable Salads from Mexican Restaurants

Data about Salmonella presence in ready‐to‐eat raw vegetable salads (REVS) consumed in restaurants or sold as REVS in México is not available. The objective of the study was to measure the frequency of coliform bacteria (CB), fecal coliform (FC), Escherichia coli, and Salmonella in REVS from different types of restaurants and determine the correlations of CB, FC, and E. coli versus Salmonella from frequencies and concentration data. The REVS were purchased from 3 types of restaurants: national chain restaurants (A₁, A₂); local restaurants (B₁, B₂); and small restaurants in local markets (C₁, C₂, C₃). Two restaurants for each A and B, and 3 for C, were included. Forty REVS were purchased at each A and B restaurant, and 20 at each C restaurant. CB were tested by plate count using violet red bile agar, FC and E. coli were detected by the most probable number method and E. coli confirmed using IMViC test; conventional method of culture was used for Salmonella. Of 220 analyzed samples, 100% had CB, 95.5% had FC, 83.2% had E. coli, and 6.8% had Salmonella. E. coli frequency was equal to or exceeded 75% in all the cases: 75% (A₁, C₁, C₂), 80% (B₂), 85% (B₁, C₃), and 100% (A₂). Salmonella frequency was equal to or exceeded 2.5% in all cases: 2.5% (A₁), 5% (B₂, C₂), 7.5% (B₁), and 10% (A₂, C₁, C₃). No correlation was observed between FC or E. coli versus Salmonella in the analyzed salads. All the tested salads were of poor quality microbiologically, and microbiological quality did not differ between the restaurants types.     

Effects of Antimicrobial Coatings and Cryogenic Freezing on Survival and Growth of Listeria innocua on Frozen Ready‐to‐Eat Shrimp during Thawing

Foodborne pathogens such as Listeria monocytogenes could pose a health risk on frozen ready‐to‐eat (RTE) shrimp as the pathogen could grow following thawing. In this study, antimicrobial‐coating treatments alone, or in combination with cryogenic freezing, were evaluated for their ability to inhibit the growth of Listeria innocua, a surrogate for L. monocytogenes, on RTE shrimp. Cooked RTE shrimp were inoculated with L. innocua at 3 population levels and treated with coating solutions consisting of chitosan, allyl isothiocyanate (AIT), or lauric arginate ester (LAE). The treated shrimp were then stored at –18 °C for 6 d before being thawed at 4, 10, or 22 °C for either 24 or 48 h. Results revealed that antimicrobial coatings achieved approximately 5.5 to 1 log CFU/g reduction of L. innocua on RTE shrimp after the treatments, depending on the inoculated population levels. The coating‐treated shrimp samples had significantly (P < 0.05) less L. innocua than controls at each thawing temperature and time. Cryogenic freezing in combination with coating treatments did not achieve synergistic effects against L. innocua. Antimicrobial coatings can help to improve product safety by reducing Listeria on RTE shrimp.     

Development of ready‐to‐eat rice starch‐based puffed products by coupling freeze‐drying and microwave

The rice starch mixtures with varying amylose contents (AC) of 0.12–19.00% weight were prepared by mixing waxy and nonwaxy rice starches. The 5% rice bran oil shortening was added in the starch paste. After gelatinisation, thin slabs of starch pastes were aged at 4 °C for 24 h. The aged slabs were dried by freeze‐drying to obtain 25% moisture content. A microwave oven set to 600 J s^?1 for 90 s was then used for puffing. The crucial factors affecting the snack purchase were texture and nutrition. The relative crystallinity and retrogradation enthalpy (?H_r) of freeze‐dried pellets increased with increasing the AC. From using a differential scanning calorimeter (DSC), endotherms of pellets were shown only when AC > 0.12%. An amylose–lipid complex was shown in pellets with AC ≥ 9.00%. Relationships between the AC and all puffed product properties were linear. Increasing AC provided greater hardness, fracturability, bulk density, but lower expansion ratio. From the sensory evaluation, the panellists preferred the puffed products with 9.00% AC. Increasing the AC gave higher crispness, hardness, brittleness, air cell opacity and density, but resulted in less puffiness. Thus, the microwave drying has the potential to puff a healthy expanded snack but giving the desirable properties depends on AC.     

Microbiological safety of ready‐to‐eat foods in low‐ and middle‐income countries: A comprehensive 10‐year (2009 to 2018) review

Ready‐to‐eat foods (RTEs) are foods consumed without any further processing. They are widely consumed as choice meals especially by school‐aged children and the fast‐paced working class in most low‐ and middle‐income countries (LMICs), where they contribute substantially to the dietary intake. Depending on the type of processing and packaging material, RTEs could be industrially or traditionally processed. Typically, RTE vendors are of low literacy level, as such, they lack knowledge about good hygiene and food handling practices. In addition, RTEs are often vended in outdoor environments such that they are exposed to several contaminants of microbial origin. Depending on the quantity and type of food contaminant, consumption of contaminated RTEs may result in foodborne diseases and several other adverse health effects in humans. This could constitute major hurdles to growth and development in LMICs. Therefore, this review focuses on providing comprehensive and recent occurrence and impact data on the frequently encountered contaminants of microbial origin published in LMICs within the last decade (2009 to 2018). We have also suggested viable food safety solutions for preventing and controlling the food contamination and promoting consumer health.     

Microbial Safety and Shelf Life of UV‐C Treated Freshly Squeezed White Grape Juice

The effects of UV‐C irradiation on the inactivation of Escherichia coli K‐12 (ATCC 25253), a surrogate of E. coli O157:H7, and on the shelf life of freshly squeezed turbid white grape juice (FSWGJ) were investigated. FSWGJ samples were processed at 0.90 mL/s for 32 min by circulating 8 times in an annular flow UV system. The UV exposure time was 244 s per cycle. The population of E. coli K‐12 was reduced by 5.34 log cycles after exposure to a total UV dosage of 9.92 J/cm² (1.24 J/cm² per cycle) at 0.90 mL/s flow rate. The microbial shelf life of UV‐C treated FSWGJ was extended up to 14 d at 4 °C. UV exposure was not found to alter pH, total soluble solid, and titratable acidity of juice. There was a significant effect (P < 0.05) on turbidity, absorbance coefficient, color, and ascorbic acid content. Furthermore, all physicochemical properties were altered during refrigerated storage. The microbial shelf life of FSWGJ was doubled after UV‐C treatment, whereas the quality of juice was adversely affected similarly observed in the control samples.     

Conventional and emergent technologies for honey processing: A perspective on microbiological safety,bioactivity, and quality

Honey is a natural food of worldwide economic importance. Over the last decades, its potential for food, medical, cosmetical, and biotechnological applications has been widely explored. One of the major safety issues regarding such applications is its susceptibility to being contaminated with bacterial and fungi spores, including pathogenic ones, which may impose a hurdle to its consumption in a raw state. Another factor that makes this product particularly challenging relies on its high sugar content, which will lead to the formation of hydroxymethylfurfural (HMF) when heated (due to Maillard reactions). Moreover, honey's bioactivity is known to be affected when it goes through thermal processing due to its unstable and thermolabile components. Therefore, proper food processing methodologies are of utmost importance not only to ensure honey safety but also to provide a high-quality product with low content of HMF and preserved biological properties. As so, emerging food processing technologies have been employed to improve the safety and quality of raw honey, allowing, for example, to reduce/avoid the exposure time to high processing temperatures, with consequent impact on the formation of HMF. This review aims to gather the literature available regarding the use of conventional and emergent food processing technologies (both thermal and nonthermal food processing technologies) for honey decontamination, preservation/enhancement of honey biological activity, as well as the sensorial attributes.     

Effect of Product Dimensions and Surface Browning Method on Salmonella Contamination in Frozen,Surface‐Browned,Breaded Chicken Products Treated with Antimicrobials

Not‐ready‐to‐eat breaded chicken products formulated with antimicrobial ingredients were tested for the effect of sample dimensions, surface browning method and final internal sample temperature on inoculated Salmonella populations. Fresh chicken breast meat portions (5 × 5 × 5 cm), inoculated with Salmonella (7‐strain mixture; 5 log CFU/g), were mixed with (5% v/w total moisture enhancement) (i) distilled water (control), (ii) caprylic acid (CAA; 0.0625%) and carvacrol (CAR; 0.075%), (iii) CAA (0.25%) and ε‐polylysine (POL; 0.5%), (iv) CAR (0.15%) and POL (0.5%), or (v) CAA (0.0625%), CAR (0.075%) and POL (0.5%). Sodium chloride (1.2%) and sodium tripolyphosphate (0.3%) were added to all treatments. The mixtures were then ground and formed into 9 × 5 × 3 cm (150 g) or 9 × 2.5 × 2 cm (50 g) portions. The products were breaded, browned in (i) an oven (208 °C, 15 min) or (ii) deep fryer (190 °C, 15 s), packaged, and stored at –20 °C (8 d). Overall, maximum internal temperatures of 62.4 ± 4.0 °C (9 × 2.5 × 2 cm) and 46.0 ± 3.0 °C (9 × 5 × 3 cm) were reached in oven‐browned samples, and 35.0 ± 1.1 °C (9 × 2.5 × 2 cm) and 31.7 ± 2.6 °C (9 × 5 × 3 cm) in fryer‐browned samples. Irrespective of formulation treatment, total (after frozen storage) reductions of Salmonella were greater (P < 0.05) for 9 × 2.5 × 2 cm oven‐browned samples (3.8 to at least 4.6 log CFU/g) than for 9 × 5 × 3 cm oven‐browned samples (0.7 to 2.5 log CFU/g). Product dimensions did not (P ≥ 0.05) affect Salmonella reductions (0.6 to 2.8 log CFU/g) in fryer‐browned samples. All antimicrobial treatments reduced Salmonella to undetectable levels (<0.3 log CFU/g) in oven‐browned 9 × 2.5 × 2 cm samples. Overall, the data may be useful for the selection of antimicrobials, product dimensions, and surface browning methods for reducing Salmonella contamination.     

Effect of y‐radiation on chives safety and quality

The effect of γ‐irradiation on the quality of chives was evaluated. The samples were irradiated at 1.0 and 2.0 kGy, stored at 4 °C for 10 days and used for microbiological (aerobic mesophilic, moulds and yeasts, E. coli and Salmonella sp), biochemical (vitamin C and lipoperoxide (MDA) contents and superoxide dismutase (SOD) and guaiacol peroxidase (POX) activity) and sensorial evaluation. For irradiated samples, the total counts of aerobic mesophilic and moulds and yeasts showed a reduction of 6 log cycles during storage, and colour analysis showed no significant difference (P > 0.05) for the b*‐value. The contents of vitamin C were not significantly affected by irradiation and storage time. The MDA contents and SOD activity changed insignificantly at both γ‐irradiation levels after storage, while POX was significantly increased (P ≤ 0.05) at 1 kGy. Samples irradiated at 2.0 kGy presented sensorial acceptance after the storage. These results show that γ‐irradiation increases the shelf life of chives without significant changes in their quality.