**4. Cholesterol and cholesterol oxides**

It was evident that cholesterol content of the raw and grilled chicken sample was about 39% higher than those of beef sample. This is due to the use of chicken skin which contains high level of cholesterol in chicken burger. Mixed meat samples had cholesterol content which was about 15% lower than chicken and 18% higher than those of beef.

Substitution of the added beef and chicken fat with olive oil resulted in a considerable decrease in cholesterol contents. The reduction in beef and chicken samples was about 53% and 58%, respectively


Each value is the mean of three replicates.

\* Values within the same column with same subscripts are not significantly (p> 0.05) different according to LSD.

\*\* Values within the same row with different superscripts denote significant differences (p< 0.05) between treatments according to LSD, whereas values within the same column with same subscripts denote no significant (p> 0.05) differences among raw and grilled samples according to LSD.

Table 2. Cholesterol content (mg/100 g fat) for the raw and grilled burger samples during storage.

Meat Fat Replacement with Olive Oil 441

Beef Chicken Mixed Beef with olive

C14:0 1.36 1.34 0.58 0.53 0.88 0.76 0.25 0.24 0.29 0.22

C16:0 34.78 31.79 26.71 26.58 30.69 28.87 16.71 15.42 17.25 14.45

C16:1 1.01 1.48 4.72 4.62 3.02 3.73 0.81 1.11 2.68 3.34

C18:0 22.36 20.57 6.13 6.00 12.61 10.48 10.21 8.93 5.86 4.81

C18:1 37.72 39.65 42.84 42.88 39.93 42.88 58.84 63.32 59.92 65.37

C18:2 1.81 3.1 17.82 17.81 11.60 12.03 8.63 8.94 11.97 11.94

C18:3 0.35 0.96 1.10 0.88 0.79 0.83 0.86 0.89 1.26 0.93

C20:0 0.04 traces 0.02 traces 0.02 traces 0.03 traces 0.01 traces

Another strategy for changing fatty acid profile of meat products rather than meat mixing is the replacement of animal fats by vegetable oils. Olive oil is a vegetable oil whose MUFA content is high. The MUFA, PUFA and SFA contents were about 72%, 10% and 13%, respectively. The addition of olive oil in place of beef and chicken fat changed the fatty acids composition of the beef and chicken burgers. The decrease in SFA of beef sample was about 54%, whereas the increase in MUFA and PUFA contents was about 54% and 33.9%, respectively, of their original contents in beef fat. On the other hand, the increase in MUFA was about 32%, whereas the decrease in SFA and PUFA contents was about 30% of their original contents in chicken fat. The decrease in SFA contents in these burger samples was due to the decrease in myristic, palmitic and stearic acid contents, while the increase in MUFA was due mainly to oleic acid, since the addition of olive oil decreased the palmitoleic acid contents. The increase in PUFA content of beef sample was mainly due to the increase

MUFA and PUFA contents showed gradual and significant decrease for all treatments during storage period, especially at the end of storage. This may be due to the oxidation of

In the case of PUFA, the decrease in their contents of beef with olive oil was lower than in beef with tallow (≈ 47%), while chicken samples showed reverse trend, since the decline in

PUFA contents of chicken was about 8% compared to 22% in chicken with olive oil.

Table 4. Means values of fatty acids profile (g/100g fat) for the raw and grilled burger

Each value is the mean of three readings of fatty acids after samples formulation.

in linoleic and to a less extent to the increase in linolenic content.

Treatment

Raw Grilled Raw Grilled Raw Grilled Raw Grilled Raw Grilled

oil

Chicken with olive oil

Fatty acid

Myristic

Palmitic

Palmitoleic

Stearic

Oleic

Linoleic

Linolenic

Arachidic

samples after formulation.

unsaturated fatty acids.


Each value is the mean of three replicates.

\* Means in the same row with the different subscripts denote significant differences among treatments of burger (p< 0.05) according to LSD.

\*\* Means in the same column with different superscripts denote significant differences among raw and grilled burger samples (p< 0.05) according to LSD.

Table 3. Cholesterol values (mg/100g burger) for the raw and grilled burger samples.

Storage time and grilling did not affect cholesterol contents of all treatments, calculated on the fat basis (mg cholesterol/100g fat).

However, cholesterol content calculated on the burgers basis (mg cholesterol/100g burger) showed lower cholesterol in grilled samples compared to the raw one. The reduction was about 23, 21, 23, 25 and 21% for beef, chicken, mixed, beef with olive oil and chicken with olive oil samples, respectively. This reduction might be due to the loss of fat during cooking.

7-ketocholesterol was used in this study as a tracer of the degree of cholesterol oxidation, because of its fast and continuous formation at levels relatively high with respect to the other oxidation products (Park and Addis, 1985). moreover, the chromatographic peak of 7 ketocholesterol does not overlap with other peaks of cholesterol oxides products and components of food matrices (Rodriguez-Estrada, *et al.,* 1997).

In this study, there was no detectable amount of 7-ketocholesterol in all raw and grilled samples, indicating that storage and grilling did not affect the stability of cholesterol against oxidation. This could be explained by the fact that grilling conditions were not severe, since the maximum temperature of grilling was about 75°C and the time of grilling did not exceed 20 minutes. Cholesterol shows high oxidation stability at temperature below 100°C (Kyoichi, *et al.,* 1993). Furthermore, the grilling machine permitted low oxygen level to be in contact with burger during grilling because the upper part of the grill was closed and directly came into contact with the burgers.

### **5. Fatty acids profile**

The effect of formulation, grilling and storage period on SFA, MUFA and PUFA contents of the burgers was observed. As expected, fatty acid composition of burgers reflected the fatty acid composition of the tissues and the fat used for their manufacturing.

It is well known that SFA are considered as a primary cause of hypercholesterolemia, and MUFA provide the body of essential fatty acids and decrease LDL cholesterol in the body (Mattson and Grundy, 1985). On the other hand, the addition of beef meat and fat to chicken burger enhanced its oxidative stability by increasing SFA by 32% and decreasing PUFA content by 34%, approximately. PUFA are easily prone to oxidation generating short chain compounds that deteriorate the sensory properties of the meat products.

Beef Chicken Mixed Beef with

Raw c50.12a a70.82a b59a e23.78a d29a Grilled c38.76b a56b b45.42b e17.77b d23b

\* Means in the same row with the different subscripts denote significant differences among treatments

\*\* Means in the same column with different superscripts denote significant differences among raw and

Storage time and grilling did not affect cholesterol contents of all treatments, calculated on

However, cholesterol content calculated on the burgers basis (mg cholesterol/100g burger) showed lower cholesterol in grilled samples compared to the raw one. The reduction was about 23, 21, 23, 25 and 21% for beef, chicken, mixed, beef with olive oil and chicken with olive oil samples, respectively. This reduction might be due to the loss of fat during cooking. 7-ketocholesterol was used in this study as a tracer of the degree of cholesterol oxidation, because of its fast and continuous formation at levels relatively high with respect to the other oxidation products (Park and Addis, 1985). moreover, the chromatographic peak of 7 ketocholesterol does not overlap with other peaks of cholesterol oxides products and

In this study, there was no detectable amount of 7-ketocholesterol in all raw and grilled samples, indicating that storage and grilling did not affect the stability of cholesterol against oxidation. This could be explained by the fact that grilling conditions were not severe, since the maximum temperature of grilling was about 75°C and the time of grilling did not exceed 20 minutes. Cholesterol shows high oxidation stability at temperature below 100°C (Kyoichi, *et al.,* 1993). Furthermore, the grilling machine permitted low oxygen level to be in contact with burger during grilling because the upper part of the grill was closed and directly came

The effect of formulation, grilling and storage period on SFA, MUFA and PUFA contents of the burgers was observed. As expected, fatty acid composition of burgers reflected the fatty

It is well known that SFA are considered as a primary cause of hypercholesterolemia, and MUFA provide the body of essential fatty acids and decrease LDL cholesterol in the body (Mattson and Grundy, 1985). On the other hand, the addition of beef meat and fat to chicken burger enhanced its oxidative stability by increasing SFA by 32% and decreasing PUFA content by 34%, approximately. PUFA are easily prone to oxidation generating short chain

acid composition of the tissues and the fat used for their manufacturing.

compounds that deteriorate the sensory properties of the meat products.

Table 3. Cholesterol values (mg/100g burger) for the raw and grilled burger samples.

\*Treatment\*\*

olive oil

Chicken with olive oil

Characteristic

Each value is the mean of three replicates.

the fat basis (mg cholesterol/100g fat).

into contact with the burgers.

**5. Fatty acids profile** 

grilled burger samples (p< 0.05) according to LSD.

components of food matrices (Rodriguez-Estrada, *et al.,* 1997).

of burger (p< 0.05) according to LSD.


Each value is the mean of three readings of fatty acids after samples formulation.

Table 4. Means values of fatty acids profile (g/100g fat) for the raw and grilled burger samples after formulation.

Another strategy for changing fatty acid profile of meat products rather than meat mixing is the replacement of animal fats by vegetable oils. Olive oil is a vegetable oil whose MUFA content is high. The MUFA, PUFA and SFA contents were about 72%, 10% and 13%, respectively. The addition of olive oil in place of beef and chicken fat changed the fatty acids composition of the beef and chicken burgers. The decrease in SFA of beef sample was about 54%, whereas the increase in MUFA and PUFA contents was about 54% and 33.9%, respectively, of their original contents in beef fat. On the other hand, the increase in MUFA was about 32%, whereas the decrease in SFA and PUFA contents was about 30% of their original contents in chicken fat. The decrease in SFA contents in these burger samples was due to the decrease in myristic, palmitic and stearic acid contents, while the increase in MUFA was due mainly to oleic acid, since the addition of olive oil decreased the palmitoleic acid contents. The increase in PUFA content of beef sample was mainly due to the increase in linoleic and to a less extent to the increase in linolenic content.

MUFA and PUFA contents showed gradual and significant decrease for all treatments during storage period, especially at the end of storage. This may be due to the oxidation of unsaturated fatty acids.

In the case of PUFA, the decrease in their contents of beef with olive oil was lower than in beef with tallow (≈ 47%), while chicken samples showed reverse trend, since the decline in PUFA contents of chicken was about 8% compared to 22% in chicken with olive oil.

Meat Fat Replacement with Olive Oil 443

In the mixed treatment we expected that cooking loss value will be between beef and chicken sample values, but unexpected result was obtained, the outcome showed that mixed treatment had the highest cooking loss in weight. More investigation is needed to explain the results.

The highest cooking loss was found after three months of storage which might be due to the weakness of protein matrix to entrap moisture and fat during storage, moreover, this weakness of protein matrix results in decrease of water and lipid holding capacity and

Cooked burgers from each treatment were evaluated by 18 panelists from the sensory evaluation team at the Department of Nutrition and Food Technology. The panelists were both male and female, and were of different ages; they were requested to taste each sample separately without comparing it with other samples. Panelists were familiarized with the questionnaire form used. The samples were evaluated for desirability in appearance, color, tenderness, flavor, juiciness and overall acceptability using a 9-hedonic scale test as described by LARMOND (1991), varying from 9 (like extremely) to 1 (dislike extremely).

The sensory evaluation results showed that all the sensory characteristics did not exceed the range like moderately, or fell to dislike slightly*.* This low score given by the panelists for all samples might be attributed to the fact that the prepared burgers were free of any added ingredients or additives that are usually added to these type of products such as spices, salt, protein derivatives of vegetable origin, dietary fibers, antioxidants, flavor enhancers and other additives which result in enhancing the sensory characteristics and the stability of the

Since the fat content of all burger treatments was about 15%, these products might contain

Mixing of chicken with beef meat enhanced the sensory characteristics of the beef. In general, mixed sample had sensory scores higher than beef sample, and were close to the chicken sample. Mixed formulation was the most stable with respect to the sensory characteristics during the storage period. Freshly prepared mixed formulation samples had appearance and color scores (6.94 and 6.89, respectively) higher than those of the beef and chicken samples.(6.11 and 6.83, respectively for appearance) and (5.67 and 6.61, respectively for color). This may be due to the dilution of the redness color of beef meat as well as the dilution of the yellowness of the chicken meat which resulted in moderate appearance and color between beef and chicken meats (between redness and yellowness), since beef meat

Appearance and color are related sensory qualities, so this modification in color of the mixed treatment affected the appearance, which in role affected the panelist's evaluation.

Tenderness evaluation of meat and meat products by panelists is correlated mainly with juiciness. Therefore, close scores of tenderness and juiciness of beef chicken and mixed treatments were observed. Tenderness and juiciness scores of the mixed formulations were significantly higher than those of beef, and very close to those of chicken. This indicated that tenderness and juiciness are strongly related to the type of meat more than to other factors.

stability, which might be due to denaturation of protein during frozen storage.

Pieces of bread and water were used to neutralize the taste between samples.

up to 20-30% of fat to give the desirable succulence and texture.

contains more myoglobin than chicken.

**7. Sensory evaluation** 

meat products.


Each value is the mean of three replicates.

\* Values within the same column with different subscripts are significantly (p< 0.05) different according to LSD.

\*\* Values within the same row with different superscripts denote significance different (p< 0.05) among raw and grilled sample according to LSD

Table 5. Effect of formulation, storage time and grilling on fatty acids profile (g/100g fat) of the burger samples.

Grilling significantly decreased SFA, and increased MUFA contents of all samples, except for MUFA contents of chicken sample which remained constant. PUFA contents, in general, increased in most samples, but in some cases there was no clear trend.
