This study was carried out to investigate the effect of nitrite concentration, and abused chilling temperature against proper chilling temperature on the chemical, microbiological and shelf life of roast beef stored at 4°C and 12°C. Three roast beef treatments were formulated to investigate the effect of nitrite concentration (0.006%, 0.012% and 0.018%) and abused chilling temperature (12°C) against control treatment (0.026% nitrite and storage at 4°C) on the chemical, microbiological and shelf life. Results showed that roast beef containing 0.026% nitrite and stored at 4°C for 25 days had the lowest thiobarbituric acid (TBA) value while the highest TBA values were in the treatment containing 0.006% added nitrite, stored at 12°C. The aerobic plate count, Enterobacteriaceae, lactic acid bacteria (LAB), and spore former count were increased throughout the storage period which was lower in 0.026% and 0.018% containing nitrite treatments while higher in other two treatments. The lowest percentage of nitrite losses during storage was in the samples having 0.026% added nitrite to roast beef. The results emphasized the risk of abused temperature and the importance of keeping this product under efficient and consistent refrigeration during storage and the use of high nitrite concentration to protect it and elongate its shelf life.
Roast beef is a cured, cooked, smoked whole meat piece product. It is usually consumed or served cold after processing. As roast beef is a cured meat product, curing contributes a characteristic pink color, specific texture and flavor, and provides a preservative effect especially against the growth of spores of Clostridium botulinum [
Curing is accomplished by adding mixtures of salt, nitrite, spices and usually a reducing agent such as ascorbate, to meat. A heating step is usually employed some time after the curing process begins as in the case of roast beef [
The observation that the added nitrite decreases rapidly during the curing process leaves no doubt that it is reacting with the components of meat and its role in the curing process is multifunctional [
Shelf life determination of a new product often requires storage for significant periods, and includes samples from early development stages as well as initial production runs. Through the evaluation of stored samples, potential storage problems can be identified and, either eliminated or controlled before the food goes into production. In production, an on-going quality assurance system is equally important, and involves assessment of freshly made products, typically before the production has been released into distribution. Samples stored for up to the assigned shelf life should also be evaluated, so that any change in the storage performance can be noted, and appropriate actions taken if necessary [
To keep meat products safe through the food chain is of great importance. Sodium nitrite is most commonly used in meat curing to help develop a desirable flavor and attractive color. Nitrite retards the development of meat rancidity and unpleasant flavors and odors of meat during storage. Moreover, it is a very effective inhibitor against the growth of spoilage and pathogenic microorganisms [
The objectives of this study were to:
・ Evaluate the effect of nitrite concentration and the chilling temperature on the shelf life of roast beef (ready to eat).
・ Determine the shelf life of roast beef under the selected conditions (nitrite level and chilling temperature).
・ Evaluate the shelf life of roast beef obtained from the producer.
・ Determine the effect of nitrite concentration within the storage chill temperature on the microbiological and oxidative rancidity of the studied roast beef.
Frozen raw beef topside was taken out of the freezer and tempered overnight. The meat blocks were cut into pieces of 10 kg. It was then transferred to the brine injector where the injector delivers a solution of salt, sodium nitrite, potato starch, isolated soy bean protein, sodium ascorbate, sodium tri-poly phosphates, spices and water (
The mixture was cooled to a temperature of 4˚C. The protein improves at cold temperatures, so we cool down the pipes that lead from the mix to the injector. After injection, the beef were transferred to the tumbler, which is also cooled down to 4˚C. The tumbling process takes about one hour under vacuum pressure. Then, the meat pieces were placed into fibrous packages, and the packaging process took place under vacuum, and was controlled by computer, each bag contained 1 kg of meat. The beef, then, was held for certain time at about 6˚C - 7˚C [
Roast beef batches were thermally processed in a steam oven as follows:
The beef in their special fibrous bags was dried for 40 minutes to lower the amount of water. Following drying the beef was liquid smoked at 76˚C; smoking took 1.30 hour, after smoking the beef was dried for 3 minutes. The roast beef was cooked to a core temperature of 74˚C for 4 hours. After cooking the beef was allowed to dry to get a good color. Then the beef was taken out to be cool in the blasted chiller for four hours, to cool from
Ingredients | Treatments | |||
---|---|---|---|---|
A | B | C | D | |
Meat (kg) | 10 | 10 | 10 | 10 |
Water (L) | 7 | 7 | 7 | 7 |
Salt (%) | 7 | 7 | 7 | 7 |
Sodium tripolyphosphate (%) | 2 | 2 | 2 | 2 |
Sodium ascorbate (%) | 0.3 | 0.3 | 0.3 | 0.3 |
Sodium nitrite % | 0.006 | 0.012 | 0.018 | 0.026 |
Potato starch (%) | 5 | 5 | 5 | 5 |
Soybean isolate (%) | 6 | 6 | 6 | 6 |
Spices (%) | 0.9 | 0.9 | 0.9 | 0.9 |
Total (kg) | 17 | 17 | 17 | 17 |
64˚C to 1˚C. After that, the roast beef was kept in refrigerator at 4˚C throughout the duration of the experiment D. B, C and A samples from were taken to be kept at abused temperature (12˚C) (
Moisture, fat and protein were determined directly after storage using Infratech Analyzer (Model Tecator 1265, Sweden) [
The roast beef pH was measured using pH meter (Model WPA, Cambridge) [
The extent of lipid oxidation was determined by the TBA method [
Nitrite residue was determined in duplicate sample for each treatment according to the colorimetric method of AOAC, method number 973.31 [
Number of colony forming units (CFU) of the following microorganisms was counted [
A pour plate method of plate count agar (Hi Media, Bombay, India). Incubation was carried out at 30˚C for 48 hours.
Count was determined on pour plates of lactobacillus deManRogosa (MRS) agar (Hi Media, Bombay, India); incubation at 20˚C - 22˚C for 48 hours. After counting all colonies that grow on the medium as presumptive positive lactic acid bacteria, smears of typical colonies were prepared for Gram stain, catalase test, and oxidase test.
Treatments | A | B | C | D |
---|---|---|---|---|
Cooking temperature (˚C) | 75 | 75 | 75 | 75 |
Chilling storage temperature (˚C) | 12 | 12 | 12 | 4 |
This count was determined using pour plate method of violet red bile glucose agar (Scharlau Chemie, Spain). Incubation was carried out at 37˚C for 24 hours. Then the oxidase test and the oxidation fermentation test (OF) were carried out (ICMSF, 1978).
Was determined using a poured plate method of reinforced Clostridia agar (Hi Media, Bombay, India). Incubation was carried out anaerobically at 35˚C - 37˚C for 20 hours.
Statistical analysis of data was carried out using Statistical Analysis System (SAS) package. Analysis of variance (ANOVA) of the general linear models (GLM) procedure of statistical analysis system. The significant differences between means were determined at p < 0.05 using Duncan Multiple Range Test [
Proximate contents of the roast beef were 78.4% moisture, 1.8% fat, 14.8% protein, and 3% ash.
The pH value of all products was found to be 6.2 which can be expected to be relatively high, attributable to addition of sodium polyphosphate [
The results of the residual nitrite are shown in
The percent of nitrite losses increased with time. Losses in treatments A, B, and C were about 89% during storage period at 12˚C, whereas treatment D which had 0.026% added nitrite during storage period at 4˚C showed 81% of nitrite losses. Higher sodium nitrite concentration, more reactions will occur with meat components especially protein, but there is a limit for protein to react with nitrite, so protein reached the saturation level that means no more protein to react with nitrite.
When nitrite is added to the biologically complex system of meat, it reacts with or is bound to various naturally occurring chemical components such as protein. The heating conditions normally used in the curing pro- cess speeds up these reactions, and when the manufacturing process is complete, only about 10% - 20% of the originally added nitrite is analytically detectable. These so-called residual nitrite level declines further during storage and distribution, as the product moves to the consumer for final preparation and consumption [
TBA values for the stored roast beef which were measured on days 0, 4, 7, 19, 22, and 25 following storage at 4˚C and 12˚C are presented in
Storage time (days) | Treatments | |||
---|---|---|---|---|
A (12˚C, 0.006%) | B (12˚C, 0.012%) | C (12˚C, 0.018%) | D (12˚C, 0.026%) | |
0 | 18.2 | 36.5 | 55.4 | 80.6 |
4 | 14.6 | 29.8 | 45 | 75.4 |
7 | 12.2 | 25.2 | 38.3 | 71.0 |
19 | 9.3 | 19.1 | 29 | 61.4 |
22 | 7.8 | 15.7 | 24 | 52.5 |
25 | 6.2 | 12.4 | 19.6 | 49.4 |
Storage time (days) | Treatments | |||
---|---|---|---|---|
A (12˚C, 0.006%) | B (12˚C, 0.012%) | C (12˚C, 0.018%) | D (12˚C, 0.026%) | |
0 | 0.40 | 0.23 | 0.16 | 0.10 |
4 | 0.60 | 0.42 | 0.30 | 0.13 |
7 | 0.90 | 0.80 | 0.60 | 0.24 |
19 | 1.10 | 0.95 | 0.82 | 0.36 |
22 | 1.30 | 1.10 | 0.98 | 0.42 |
25 | 1.50 | 1.30 | 1.13 | 0.53 |
C, 1.3 mg/kg for treatment B and 1.5 mg/kg for treatment A. In contrast treatment D (0.026% nitrite) did not exceed 0.53 mg/kg.
Nitrite is known to have antioxidant effect in cured meat products [
From these results we can conclude that 0.026% and 0.0180% nitrite have a better antioxidant effect than 0.012% and 0.006% level at the initial and during storage. Moreover, TBA values for abused treatments were higher than refrigerated treatment, so the chemical deterioration is supposed to be faster.
Lipid oxidation of muscle foods results in formation of harmful products like malondialdehyde, degradation of fatty acids, carcinogenesis and formation of metmyglobin in meat products. Moreover, protein oxidation accelerated by free radicals decrease the nutritional value of meat due to loss of essential amino acids and low digestibility of oxidized proteins [
The effects of various preservative combinations upon microbial growth were studied during different storage times. All results are average values of duplicate samples from four treatments and were expressed as log10 CFU/g (colony forming units/g).
However, the APC counts are considered fairly satisfactory when colony counts is 3 - 5 Log10 CFU/g, and unsatisfactory when they reached more than 6 log10 CFU/g [
Treatments | Storage time (Days) | |||||
---|---|---|---|---|---|---|
0 | 4 | 7 | 19 | 22 | 25 | |
A (12˚C, 0.006%) | 3.12 | 3.42 | 5.49 | 7.20 | 7.30 | 7.57 |
B (12˚C, 0.012%) | 2.75 | 3.16 | 4.96 | 6.37 | 6.48 | 6.59 |
C (12˚C, 0.018%) | 2.30 | 2.91 | 4.53 | 5.51 | 5.57 | 5.68 |
D (12˚C, 0.026%) | 2.00 | 2.35 | 2.39 | 3.61 | 3.62 | 4.00 |
treatment 0.012% and 0.006% nitrite roast beef have reached this limit at day 19, indicating that treatment D would be spoiled later after all the other treatments which mean longer shelf life. This means that the increase in APC counts affects the shelf life of the roast beef, also the storage temperature is important to extend the shelf life of the roast beef.
Lactic acid bacteria are the most frequently isolated bacteria from this kind of meat products (roast beef) since they are tolerant to CO2 and low temperature. The adoption of modified atmospheres or vacuum for the packaging of roast beef has shown that lactic acid bacteria generally become numerically dominant in such environments [
These results show the importance of storage temperature in determining Enterobacteriaceae counts which has a direct influence on the product shelf life.
Nitrite has a proven bacteriostatic effect on Enterobacteria [
Treatments | Storage time (Days) | |||||
---|---|---|---|---|---|---|
0 | 4 | 7 | 19 | 22 | 25 | |
A (12˚C, 0.006%) | 2.24 | 2.82 | 3.05 | 3.17 | 3.26 | 3.45 |
B (12˚C, 0.012%) | 2.04 | 2.69 | 2.77 | 3.07 | 3.15 | 3.29 |
C (12˚C, 0.018%) | 1.69 | 2.11 | 2.37 | 2.59 | 2.81 | 3.03 |
D (12˚C, 0.026%) | 1.00 | 1.39 | 1.48 | 1.54 | 1.72 | 1.81 |
Treatments | Storage time (Days) | |||||
---|---|---|---|---|---|---|
0 | 4 | 7 | 19 | 22 | 25 | |
A (12˚C, 0.006%) | 2.13 | 2.98 | 3.42 | 3.42 | 4.09 | 4.12 |
B (12˚C, 0.012%) | 2.06 | 2.79 | 3.35 | 3.37 | 4.08 | 4.09 |
C (12˚C, 0.018%) | 1.48 | 2.67 | 3.25 | 3.30 | 3.72 | 3.76 |
D (12˚C, 0.026%) | 1.00 | 2.48 | 2.79 | 2.89 | 3.43 | 3.57 |
Treatments | Storage time (Days) | |||||
---|---|---|---|---|---|---|
0 | 4 | 7 | 19 | 22 | 25 | |
A (12˚C, 0.006%) | 2.44 | 2.82 | 3.04 | 5.39 | 5.72 | 5.93 |
B (12˚C, 0.012%) | 1.95 | 2.51 | 2.85 | 5.30 | 5.65 | 5.65 |
C (12˚C, 0.018%) | 1.69 | 2.24 | 2.47 | 4.51 | 4.79 | 5.52 |
D (12˚C, 0.026%) | <1 | 1.00 | 1.56 | 1.69 | 1.85 | 1.90 |
anaerobic spore formers count affects the shelf life of roast beef, also the storage temperature is important to extend the shelf life of roast beef.
In refrigerated treatment, clostridium counts were lower than those kept at abused temperature, and there was an increase in its population at the lower nitrite levels. The decrease in inhibition observed in the present research appears to be related to the decline in residual nitrite [
However, significant concerns exist because nitrite may react with amines and amino acids to produce N-nitrosamines, which are known to be a potential carcinogenic and mutagenic [
Moreover, there has been a growing interest in natural ingredients to be used in food and food products as preservatives instead of synthetic chemicals that may cause health hazards, because natural ingredients have greater application for increasing consumer acceptability, palatability, stability and shelf-life of food products. Consequently, search for natural additives, especially of plant origin, has notably increased in recent years [
It could be concluded from the overall results that the added nitrite concentration and chilling temperature had significant effect on the chemical, microbiological and shelf life of roast beef. Abused storage temperature limits the shelf life of roast beef, and the storage under refrigeration (4˚C) extends the shelf life of roast beef. The increased addition of nitrite alone up to 0.018%, without good refrigeration practice (4˚C), also limits the shelf life of roast beef. Addition of 0.026% nitrite with proper refrigeration has resulted in an extension of the roast beef shelf life.
Our deepest thanks are to the employees of the Department of Nutrition and Food Science for their help and support.
Tamador Maayah,Malak Angor,Khaled Al-Marazeeq,Basem Al-Abdullah, (2016) Evaluation of the Shelf Life of Packaged Roast Beef and Some Treatments for Its Extension. Food and Nutrition Sciences,07,205-213. doi: 10.4236/fns.2016.73022