Tracz et al. (2015) investigated the potential of HPP to destroy a mixed culture of three stains of C. jejuni inoculated in chicken breast under different pressure conditions (200, 300, and 400 MPa) and treatment times (5, 10, and 15 min), where D values were lowest at the highest pressure applied (79). According to the pressure applied, the temperature varies from 0 to 10°C. When the lowest pressure (200 MPa) was applied, C. jejuni exposed resistance and no significant reduction was achieved regardless of the duration of HPP treatment. Gram-negative bacteria are generally more susceptible to pressure compared to Gram-positive bacteria (79). Sheen et al. (2015) reported also that the inactivation of Salmonella spp. in ground chicken was dependent on both treatment time and pressure level applied (80). It was highlighted that even at high pressure (550 MPa), while the highest temperature reached was 28°C, Salmonella recovered and resuscitated over storage at 10°C to achieve ~6 Log CFU/g at day 9 of storage. Therefore, despite the mechanisms noted of surface structure damage or disintegration, internal cell compound disappearance, and appearance of internal voids in the cells, some cells survived the HPP 15-min treatment (80), pointing to a need for combination approaches. Argyri et al. (2018) HPP treatment at 500 MPa for 10 min at 18–20°C resulted in a significant reduction, below detection limit, of both the native microbiota of chicken and a cocktail culture of three different strains of Salmonella (31). Furthermore, Salmonella enteritidis inoculated on chicken at different initial concentration levels stayed below or just at detection limits during the storage at 4°C over 18 days (30). Working with a cocktail of Listeria monocytogenes, also Argyri et al. (2019) perceived the capability of HPP in maintaining safety and extending the shelf life of chicken (30, 32). Xu et al. (2020) reported D₁₀ values for multi-isolated cocktails of extraintestinal pathogenic E. coli (ExPEC) to HPP (400 MPa, 0–25 min) on ground chicken, where 3.26 min was the average and the highest temperature value reached during the treatment was 25°C (81). Increasing the pressure to 600 MPa provided more than 6 log reduction within 3 min with no bacterial recovery after 4 min (81). The inactivation effect of HPP on two different strains of E. coli on ground chicken was assessed while the temperature remained under 40°C, where a significant resistance of uropathogenic E. coli (UPEC) by comparison with intestinal pathogenic E. coli (iPEC) O157:H7 at 450 and 500 MPa was reported (71). Liu et al. (2012) stated that C. jejuni HCJ2316 exhibited high resistance to pressure (2.8 Log CFU/g reduction), whereas the others were more susceptible to treatment and achieved 5 Log CFU/g reduction (82). However, the microbial recovery upon pressure treatment of C. jejuni is iron-dependent (82).

Lipid oxidation is one of the major causes of deterioration of meat during storage. The chicken meat contains a higher amount of unsaturated fatty acids compared to other animal meats, which makes it more susceptible to lipid oxidation. The most common method to determine the lipid oxidation is Thiobarbituric acid reactive substances (TBARS) analysis (24). The lipid oxidation was particularly affected by working pressure; for low pressure (400 MPa and less), significantly less change in TBARS value was reported, while high pressure (500 MPa) have a higher impact on TBARS value (83). Similar effect was observed when chicken breast filets was treated with 450 and 600 MPa, while no significant change in TBARS value was observed at 300 MPa (84). The pressure of 800 MPa has the most detrimental on TABRS value (85).

A synergistic effect was recorded using nisin (200 ppm) and HPP (450 MPa) at 20°C, enhancing the microbial reduction of mechanically recovered poultry meat, specifically, the inactivation of both aerobic mesophile and psychrotroph populations was greater by comparison with HPP treatment on its own (86). Other researchers outlined the strong synergistic effect of combining hydrostatic pressure treatment (250 MPa for 30 min at 25°C) and 1% food additive (citric acid, nisin, and wasabi extract) in completely reducing the microbial concentration of S. enteritidis to undetectable levels (87). Combining HPP (300–400 MPa) with thymol (100–200 ppm) provided a large inactivation effect on separate cocktails of iPEC O157:H7 (0.94–5.16 Log CFU/g) and UPEC (0.41–4.66 Log CFU/g) in ground chicken samples (71).

The cell membrane is commonly referred to as the only target of PEF contributing to bacterial cell death (90). Treatments with PEF display reversible or irreversible damages on the cell membrane by disorganizing the structure, which yields the breakdown of the semipermeable barrier due to formation of pores in the membrane (18), leading to irreversible electro-permeabilization of the cell membrane; however, recovery can occur in optimal conditions (91). Process parameters of pulse frequency and strength of the electric field of PEF have been demonstrated to affect the microbial inactivation (92).

Reduction in population densities of S. enteritidis and S. typhimurium strains suspended in citrate-phosphate buffer was greater with increasing both treatment time and electric field above 9 kV/cm (93). It was demonstrated by Clemente et al. (18) that the treatment of chicken thighs with PEF did not result in any significant reduction of C. jejuni. PEF was not sufficient to reduce cell concentration of S. enteritidis, E. coli, and C. jejuni on raw chicken (92). However, this non-thermal technology is suggested to be suitable for treating process waters used in poultry processing as well as for poultry scald (92).

Several studies have reported the ability of PEF treatment to modify sensory characteristics, texture, and water-holding property of the meat products, further improving the mass transfer properties (94–96). Meat is considered an excellent source of minerals, such as zinc, iron, phosphorus, and calcium (97). PEF induces irreversible electroporation in meat and affects cellular permeability and mass transfer. Studies suggest that PEF-applied products have changes in mineral content when compared to control. Khan et al. (98) examined the effect of low (2.5 kV, 200 Hz) and high PEF (10 kV, 200 Hz) on four nutritionally important minerals (P, K, Fe, and Zn) of raw and cooked chicken breast. For raw chicken, non-significant changes in mineral content were noted; however, with cooking, a decrease in P, K, and Zn was observed and the concentration of Fe was not affected by treatment or cooking. In another study conducted by Khan et al. (99), the authors found higher concentrations of Ni and Cu for both low (2.5 kV, 200 Hz) and high PEF (10 kV, 200 Hz) than control. Thus, it is vital to study the migration of minerals into meat products due to PEF treatment and should be checked under regulatory limits.

Recent work revealed that chicken oyster thigh artificially contaminated by C. jejuni 1,146 DF (final concentration 4.41 ± 0.20 log₁₀ CFU/g) and treated with only PEF (0.25–1 kV/cm) did not demonstrate any significant inhibition potential. However, sequential treatment of PEF (1 kV/cm) and immersion in buffer with oregano EO (15.625 ppm) for 20 min resulted in a significant reduction close to 1.5 log₁₀ CFU/g (18).

There are some limitations of using UV in poultry processing: UV-C light is not absorbed and cannot penetrate the chicken meat surface, which may affect microbial reduction. The antimicrobial efficacy of pulsed UV and UV-C has limitations also in terms of product density and treatment time (104, 107). The bactericidal effect of UV-C irradiation against C. jejuni, L. monocytogenes, and S. typhimurium on chicken breast was dose-dependent, where treatment at 5 kJ/m² reduced L. monocytogenes, C. jejuni, and S. typhimurium, respectively by 1.29, 1.26, and 1.19 log cycles (102). Haughton et al. (105) examined UV effects against S. enteritidis, E. coli, and Campylobacter (C. jejuni and C. coli) when inoculated in liquid matrix, chicken skin and skinless chicken breast, food contact surfaces, as well as packaging materials. Treatment at a high dose equivalent to 0.192 J/cm² provided complete microbial inactivation of Campylobacter strains suspended in a liquid matrix. By contrast, Salmonella and E. coli were more resistant to the similar UV dose (105). Food surface topography can shield microorganisms and limit UV treatment efficacy (104, 107). Isohanni and Lyhs (103) highlighted that although UV treatment was effective in reducing C. jejuni on surface medium by 6.3 log cycles per square centimeter. However, only 0.8 and 0.7 log cycles reduction were achieved on broiler skin and on broiler meat, respectively, with a dose of 32.9 mW/s per square centimeter. UV light seems to works well on smooth surfaces (108). Bacterial multilayer overloading as well as overlapping, and in the presence of cell, organic compounds protect to target bacteria from UV irradiation (104, 107).

UV light can form off-flavors due to the photochemical effect on the lipid fractions of product or due to absorption of ozone and oxides of nitrogen (101). This leads to the development of lipid peroxidation causing off-flavor. The hexanal aldehyde is a volatile secondary lipid oxidation product, and it is indicative of fatty aldehydes by headspace/gas chromatography–mass spectrometry (GC-MS). McLeod et al. (104) detected an increase in hexanal content of the raw chicken filets treated with 10.8 J/cm² in air, which was noted by the sensory panel as a “sunburnt flavor” giving a low sensory score. Interestingly, when the same chicken samples were cooked, the sensory panel was unable to identify the difference, and it scored fairly with the untreated sample (104).

The combination treatment of UV-C light and clove EO was assessed against poultry-related pathogen S. typhimurium biofilms, generated on stainless steel coupon surfaces. Treatment with 1.2 mg/ml of clove EO followed with UV-C (76.41 mJ/cm²) induced a synergistic effect and resulted in no surviving cells (6.8 log CFU/cm²) embedded within the biofilms. It was demonstrated that the contact with clove EO made the cell easily accessible by UV-C due to the morphological damage occurring: flatter structure (109).

The mechanisms of action are connected to cavitation generation, which eventually disturbs the cell permeability as well as causing thinning (111) and damage on the bacterial membrane (112) and “localized heating” (73) that yields cell inactivation. The cell metabolism is disturbed due to ion penetration of the cell cytoplasm upon permeability disruption caused by pressure gradients of ultrasound. These mechanisms are the result of the collapse of cavitation bubbles during the acoustic cavitation (73). A further utility of ultrasound treatments is the “de-agglomeration of bacterial clusters” (73).

Apparent characteristics of target microorganism type, physiological state, and morphology determine the efficacy of ultrasound. The efficacy is also dependent on the surface of food matrix and temperature (111). Moreover, other parameters interfere with efficacy, such as frequency and sonication treatment time (73). The peptidoglycan in the cell membrane of Gram-positive could be a reason behind the resistance to ultrasound by these bacteria compared to Gram-negative (112), and the susceptibility to ultrasound treatment may vary between strains from the same type. The resistance of cells on plates during in vitro experiments to sonication by ultrasound was higher in contrast to the susceptibility of both Campylobacter and Enterobacteriaceae in raw poultry (112).

It was highlighted that chicken breast subjected to high-intensity ultrasound promoted the growth of mesophilic, psychrophilic, and lactic acid bacteria compared to untreated samples, possibly resulting from the release of nutrients (113). However, it was pointed out that the presence of E. coli was lower for samples subjected to longer treatment (30–50 min) compared to non-treated, whereas for S. aureus, it significantly decreased after 50 min. The microbial reduction in previously contaminated chicken wings depends on both treatment time (3–6 min) and sonication environment solution where the treatment was in (1% solution of lactic acid or sterile distilled water). The combination of lactic acid and sonication (40 kHz, 2.5 W/cm²) had a bactericidal effect on all the bacteria tested and was considered suitable for poultry carcass skin decontamination (73). However, combining ultrasound treatment (37 kHz, 380 W, 5 min) with 70% ethanol induced the highest microbial reduction from chicken skin for three types of attachment by S. typhimurium loosely, intermediately, and tightly attached by respectively 2.86, 2.49, and 1.63 log CFU/g (114).

Marinating is mostly used to increase meat tenderness, enhance flavor profile, reduce cooking time, and increase the shelf life of meat. Ultrasound (40 kHz, 22 W/cm²) increased the marination efficiency of chicken breast when treated with 15 and 20 min (115). A similar increase in marination efficiency, cooking yield, and tenderization was reported when broiler chicken was treated for 20 min and 18 h marination (91% water, 6% NaCl, 3% sodium tripolyphosphate) (116). A positive influence of ultrasound frequency (25, 45, and 130 kHz) and treatment time (1, 3, 6, 16, and 24 h) on marination efficiency was also reported for chicken breast, giving higher uptake of sodium chloride (117). Ultrasound improved the marination properties of meat by breaking the integrity of muscle cell or by enhancing the enzymatic reactions in cell (11, 111). Thus, ultrasound can be used as an alternative to standard marination techniques used in the industry.

The exposure of broiler drumstick skin to ultrasonic energy in water and submerged in 1% lactic acid did not show consistent effect in terms of reducing aerobic plate counts. The irregular characteristics of broiler skin surface were proposed as the reason behind the lack of microbial reduction by protecting bacteria in the skin crevices and avoidance of the cavitation (72). In contrast, other work showed the decontamination efficacy of sonication (40 kHz) of chicken wing skin in 1% lactic acid aqueous solution, where the reduction of E. coli, Proteus sp., Salmonella anatum, and P. fluorescens inoculated on the surface of the chicken skin significantly increased with treatment time rising from 3 to 6 min. Except for E. coli, the microbial reduction was higher when sonication was performed in an aqueous solution of lactic acid instead of water. This was explained by the presence of ions penetrating the cytoplasm due to the action of gradient pressure yielding from ultrasound and the presence of free radicals received in sonochemical reactions (73). Combining high-intensity ultrasound with 0.3% oregano EO treatment was the most appropriate combination to achieve the best reduction of lactic acid bacteria (2.30 log₁₀ CFU ml⁻¹), mesophilic populations (3.36 log₁₀ CFU ml⁻¹), and anaerobic bacteria (3.11 log₁₀ CFU ml⁻¹) present in chicken breasts at day 0 of refrigeration. However, the treatment with ultrasound alone was ineffective to control microbial growth during chilled storage, where the release of nutrient was suggested as a reason permitting microbial growth (74).

It is well-documented that cold plasma (CP) has a large potential for controlling microbial quality, extending shelf life, and avoiding post-processing contamination (25). It not only induces bacterial decontamination but also inactivates a broad spectrum of microorganisms including fungi, viruses, and spores (119). Various plasma compounds have critical interventions in the microbial decontamination process like NO₂, NO, O, O₃, OH, H₂O₂, UV photons, charged particles, and electric fields (120). Bacterial cell etching, erosion, morphological alteration, nucleic acid damaging, protein oxidation, and loss of cell viability are the mechanisms of CP to retain microbial safety in foods (121). However, different parameters and mechanisms interfere with the gravity of damage occurring. The antimicrobial effects of CP are a function of process: duration of treatment, gas mixture, mode of exposure (direct or indirect), power source intensity, as well as intrinsic characteristics of product: surface topology, nature of samples treated (liquid, solid, or semisolid), and characteristics of the target cell (122).

In-package CP treatment configuration enhanced the microbial safety, avoided postprocess contamination, and retained toxicological safety of ready-to-eat chicken products (123). Using the Salmonella mutagenicity assay, no genotoxicity was seen in plasma-treated chicken breast (120). Tulane virus (1.08 ± 0.15 log CFU/cube), indigenous mesophilic bacteria (0.70 ± 0.12 log CFU/cube), and Salmonella (1.45 ± 0.05 log CFU/cube) from chicken samples were significantly reduced upon CP treatment (24 kV for 3 min), where increasing voltage (from 22 to 24 kV) and treatment time had a positive impact on the microbiological quality (123). However, the majority of cells showed morphological changes (cell flattened and other distortions) at 2,000 Hz, whereas at 1,000 Hz, only cell clumps appeared, and other cells were hollowed out (124). S. typhimurium, E. coli O157: H7, and L. monocytogenes populations on chicken breast reduced from 5.48, 5.84, and 5.88 log CFU/g, respectively, at 0 min to 2.77, 3.11, and 3.74 log CFU/g at 10-min plasma exposure (120). Other studies highlight the potential of in-package dielectric barrier discharge (DBD) (70 kV) in controlling poultry-related pathogens, namely, Salmonella and Campylobacter, and inhibiting the growth of spoiling bacteria (psychrophiles) from chicken breast treated and stored (5 days/4°C) (23), where increasing CP treatment time to beyond 60 s improved microbial reduction of psychrophiles, while no significant effect was seen against foodborne pathogens. The in situ decontamination potential of plasma-activated water (PAW) against P. fluorescens ATCC13525 previously inoculated on chicken skin pieces was associated with the plasma process parameters of plasma discharge frequency and treatment time (124), where the concentration of plasma-generated reactive species of nitrite, nitrate, peroxide, hydroxyl, and ozone increased with the discharge frequency (124).

The reaction of myoglobin with hydrogen peroxide may produce choleglobin-inducing discoloration of meat. An increase in both L^* and b^* value was observed when chicken breast was treated with flexible thin-layer DBD (123); in contrast, application of DBD applied on chicken breast (110 kV, 60 kHz) showed a decrease in L^* value mainly due to slime formation after 9 days of storage at 4°C (28). However, Zhuang et al. (25) did not report significant changes in L^*, a^*, and b value when chicken breast was treated with 70 kV. The reactive species generated from the plasma can induce lipid peroxidation. Zhuang et al. (2019), Lee et al. (2019), and Moutiq et al. (2020) reported no changes in lipid profile of chicken breast after CP treatment, attributed to plasma reactive species being less damaging on chicken breast as compared to red meat due to variation in fat content (25, 28, 120, 123).

Yeh et al. (2019) considered the combined treatment effect of rosemary (Rosmarinus officinalis) extract (1%) and in-package DBD-CP on poultry ground meat (Table 1) (67). The treatment induced a reduction of the diversity in bacterial communities, and by day 5 of storage at 4°C, the maximum population densities of treated samples were similar to those at day 0 (67). Rosemary extract had a significant effect in reducing the total microbial counts not only of previously plasma-treated chicken patties but also of non-plasma-treated chicken patties (16). Thyme oil/silk fibroin nanofibers treated with CP were proposed as an active packaging approach with antimicrobial potential against S. typhimurium inoculated on poultry meat (chicken meat and duck meat). The inhibition potential of thyme EO/silk fibroin nanofibers treated with CP was reported as higher compared to thyme EO/silk fibroin nanofibers, with an increase in the rate of thyme oil released (23.5–25%) upon plasma treatment clearly noted (57). Sahebkar et al. (2020) found that associating CP (10 min at 32 kHz) and EO (in marinade solutions) treatments of breast chicken filet inoculated with S. aureus and E. coli challenge populations leads to significant microbial reductions by up to 3–4 log CFU/g (68). A synergetic effect was identified by combining three different EOs (Crocus sativus L., Allium sativum L., and Zataria multiflora Boiss.) and CP treatment, where the advantage of combining the EOs with CP was retained after 14 days of storage (68).