Preservatives

Numerous efforts have been made to use additives to reduce the microbial load on fresh poultry. Some of the techniques used have been chilling and washing of carcasses with chlorinated water (35-45), 70% alcohol dipping (46), immersion of carcasses in solutions of poly(hexamethylenebiguanide hydrochloride) (47), dipping in various organic acids (19,48-51), and chilling in polyphosphate solutions (52,53).

It was reported that when Lactobacillus cells were added to chilled water at a concentration of 100 million/ mL, shelf life was increased as much as 3 days. Carcasses immersed in 0.12% lactic acid had a total bacterial count of 400 compared with a control group that had 130,000 organisms/g (50). Sorbic acid was an effective preservative when a 7.5% solution was sprayed onto the chilled poultry parts at 140°F in a ratio of 70:20:10 propylene glycol to water to glycerin (54). Nine acids were studied, and it was concluded that adipic and succinic acid increased the shelf life of broilers by 6 days more than the water-chilled samples when the pH of the chilling solution was 2.5 (49). Another study revealed that dipping cup-up broiler parts in 1% ascorbic acid solution for 3 min retarded microbial growth and increased the refrigerated life for 6 to 7 days compared to that of the control (19). It has been suggested that the use of polyphosphate solutions was effective in controlling the growth of gram-positive micrococci and staphylococci (28).

Of the materials tested for use in preserving chilled poultry carcasses, antibiotics have received the most attention. The addition of antibiotics to the chilling water had been widely accepted in the 1950s and the early 1960s. Chlorotetracycline or oxytetracycline was added to the chilling bath through which the birds passed following evisceration; the results indicated that these antibiotics lengthened the keeping time by at least several days, but that bacteria resistant to the antibiotics (eg, pigmented pseudomonads and certain Alcalilgenes species) grew on the birds and built up in the plant (55). The antibiotics had no effect on yeasts and molds that were also a part of the microflora of poultry carcasses (56). Because of the fact that small residues, about 0.5 ppm, may be left after cooking and the effect that such residues might have on the intestinal flora of humans, permission to use such compounds in foods was withdrawn by the FDA (57).

Potassium sorbate has been extensively investigated as an antibacterial agent for extending shelf life and inhibiting pathogen growth. The effectiveness of a 10% potassium sorbate dip in inhibiting bacterial growth of fresh chicken breast meat inoculated with Salmonella was demonstrated (58). It has also been reported that dipping broiler carcasses in a 5% potassium sorbate dip for 1 min was effective in inhibiting Salmonella and S. aureus (59).

Preparation of germicidal ice incorporated with food additives such as calcium hypochlorite, chloramine benzoic acid, formaldehyde, hydrogen peroxide, sodium propionate, and sodium nitrite for ice-packing purposes have been studied (60). It was proven that ice-containing glycol diformate and sorbic acid were more effective against microbial growth than was common ice or the acronizing process. It has been reported that the average shelf life of broiler parts ice-packed with 0.075% sorbic acid ice and 0.1% potassium sorbate ice was 11.5 and 3.6 days longer than the ice-packed controls (61). Both sorbic acid ice and potassium sorbate ice decreased the incidence of gramnegative rod-type organisms and increased the incidence of gram-positive cocci on broiler parts after 4 days of storage at 2 to 4°C.

Packaging

A number of studies have been made to determine the effect of packaging on the shelf life of poultry carcasses. One study reported that packaging materials had a significant effect on the shelf life of fresh poultry (62). Storage time for poultry carcasses wrapped in cellophane and cellophane—vinylidene chloride copolymer sheets were the same under nonvacuum conditions, but when the air was evacuated, the storage time increased 4 days beyond that obtained without vacuum (63). Fewer pseudomonads were found, but Microbacterium thermosphactum and atypical lactobacilli were a significant part of the spoilage flora on turkeys wrapped in impermeable film at 1°C (64). It has been reported that while the pseudomonads were the main spoilage organisms on the carcasses wrapped in the permeable film, the Alternomonas putrefacians predominated on the carcasses wrapped in the impermeable film.

The influence of packaging materials seems to affect the quality of fresh poultry. Bacterial growth was inhibited by using a shrinkable poly(vinyl chloride) film with a permeability to oxygen of approximately 500 mL/cm2,24 h, 1 atm (65). It was also concluded that shrinkable poly(vinyl chloride) film was better for retaining the quality and shelf life of chicken than any other material that was not air evacuated.

Another effective way of packaging is by employing carbon dioxide treatment. Chickens stored in 10 and 20% carbon dioxide at 1°C effectively extended the shelf life (66). It has been suggested that packaging broiler carcasses in nylon—surlyn film with a carbon dioxide addition rate of 3.6 X 10"4 and 7.22 X 10" 4 m3/kg carcass extended shelf life at 1.1°C of storage to 22 and 27 days, respectively (67). Vacuum-C02 packaging extended the shelf life of broiler carcasses for approximately 7 days when compared to those of the ice-packed controls (4). It was also reported that the major microorganism groups isolated from the spoiled ice-packed samples were members of the Pseudomonas species (93.3%); however, Lactobacillus spp. (74.0%) were found to be the dominant microflora on the vacuum-C02 packaged broilers after 28 days of storage at 1.1 to 3.3°C (4).

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