How Does Replacement of Beef with Agushie Impact the Nutritional and Eating Quality of Beef Burgers?

Study Location and Experimental Materials

The experiment was conducted at the Meat Science and Processing Unit of the Department of Animal Science, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana. Beef (boneless) was purchased from the Kumasi Abattoir Company Limited and stored in a freezer at -18°C prior to usage. Agushie and other non-meat ingredients used were obtained from the Kumasi central market.

Experimental Procedure

Preparation of Burgers: All undesirable particles in agushie were removed by hand picking and discarded, after which it was washed thoroughly with distilled water and blended with a kitchen blender. The frozen beef was cut into smaller pieces and minced using a table top meat grinder (MADO Superwolf, Germany) through a 5mm grinder disc. The minced beef and blended agushie were allotted to four treatments namely, T1 (Control), T2, T3 and T4 in which agushie was included at 0% 13% 26% and 39% respectively. All spices used were not varied for each treatment and each was formed into burger. Five (5) kg of burgers were produced per treatment and the four treatments produced were replicated three times, vacuum packaged after overnight chilling, labelled appropriately and frozen at -18°C for further analysis.

Parameters Measured

Cooking Yield and PH (Acidity): Cooking yield of burgers were determined as described by Akwetey WY, et al. [8] using the following formula:

Acidity (pH) of blended burger treatment samples were directly determined using an electronic pH meter with a probe (Mettler, Toledo).

Proximate Composition

Moisture, protein, fat, ash and fibre contents were determined according to the methods described by Association of Official Analytical Chemists [9].

Eating (Sensory) Attributes

Nine (9) samples (100g each) per treatment were taken out of the freezer at random and thawed at 2°C overnight, fried in vegetable oil, cut into four equal parts and served to thirty (30) consumers made up of students of KNUST and Teaching Assistants of the Department of Animal Science for sensory evaluation. The vegetable oil used was changed after frying each treatment sample and the sensory evaluation was based on appearance, taste, flavour, juiciness, texture, mouth feel and acceptability of burgers produced with and without agushie. A 9-point Hedonic scale (1=dislike extremely, 2 = dislike very much, 3= dislike moderately, 4=dislike slightly, 5= neither like nor dislike, 6= like slightly, 7= like moderately, 8= like very much, 9= like extremely) was used for the evaluation. Treatments samples were coded with three-digit random numbers in order to ensure fairness in assessment and to ensure realization of sincere results from the panel. Water was provided to each panel member to rinse his/her mouth between tasting and scoring the profiles of the burgers in order the prevent carry-on effects from one sample to another. The sensory area was adequately lighted with white fluorescence lamps and there was no awful odour that could possibly detract the attention of panel members.

Statistical Analysis

All data generated from the study were subjected to One-way Analysis of variance (ANOVA) using SPSS [10] and significant differences between treatment means (p<0.05) were determined by Duncan’s test of homogeneity.

Proximate Composition, PH and Cooking Yield

Results obtained for percentage moisture, protein, fat, ash, and fibre of the burgers with and without agushie are shown in Table 1. There were significant differences (p<0.05) between moisture content of the control (T1) and agushie- treated burgers. Moisture content reduced significantly (p<0.05) from T1 (53.73%) to T4 (46.77%). Adebayo OF, et al. [11] also reported reduced moisture contents in ‘agushie_-_ treated ‘ogri’ condiment, but Akofur SDH [12] observed increasing moisture levels (50.30-54.60%) in agushie- treated meatloaves. The difference in moisture content in this study compared to what was reported by Akofur SDH [12] could be attributed to the fact his study was about emulsified products (meatloaf) which involved the addition of relatively more water during formulation compared to beef burgers in this study.

From Table 1 the levels of protein increased with increasing levels of agushie in burger formulations and the control (without agushie) recorded significantly (p<0.5) lower protein contents (20.49%) compared to all the agushie- treated burgers. Akofur SDH [12] reported that agushie has

30% protein whiles FAO [13] stated that beef has up to 22% protein. The increasing levels of protein with increased use of agushie in this study confirm the findings of Dzadu L [14] when agushie was used in frankfurter-type sausage formulations. Thus suggesting that, agushie could be used in meat formulations in order to increase protein contents.

There were also significant differences (p<0.05) between fat contents of T1 (control) and the agushie-treated burgers. It was observed that fat contents increased significantly (p<0.05) from T1 (13.66%) to T4 (17.95%); however, the fat contents of T1 and T2 were not different. Agushie has been reported to have lower fat content Bankole SA, et al. [15] compared to beef AAC [16], hence the observed increased fat contents in the agushie-treated burgers in study were not readily understood. But Akofur SDH [12] also reported increasing levels of fat in agushie-treated meatloaf. It could probably be due to the fact that agushie, being a vegetable, might have higher affinity for the vegetable oil used in frying the burgers compared to beef.

Ash contents in the control (T1) and T2 were not significant different (p>0.05), but the contents of ash observed in both T1 and T2 were significantly (p<0.05) lower than T3 and T4.

Table 1: Proximate composition, cooking yield and pH of burgers produced with and without agushie. ᵃᵇᶜ Means in the same row with different superscripts are significantly different (p<0.05). T1=100% ground beef (or 0% agushie), T2, T3 and T4 contained 13%, 26%, and 39% agushie respectively in place of ground beef. Mixed spice comprised of powdered red pepper (10g/kg), black pepper (5g/kg) and powdered ginger (10g/kg) meat. *pH (no unit).

reatment T1 recorded lower ash contents of 2.41% while values in the agushie-treated burgers increased from 2.56% (T2) to 3.77% (T4). These observations are similar to the report by Egbebi AO [17] (3.70%), but lower than what was reported by Akofur SDH [12] (4.60% to 5.53%). Akofur SDH [12] reported that agushie has 3% ash content whiles beef has 1.2% ash [13].

The contents of crude fibre showed significant differences (p<0.05) between the control (T1) and the agushie-treated burgers. Treatment T1 and T2 were similar in fibre contents but their values were significantly lower (p<0.05) compared to T3 and T4; both of which were also similar. Fibre contents in this study ranged from 0.24% (T1) to 0.98% (T4). Contrarily Akofur SDH [12] and Egbebi AO [17] reported higher values of 4.54% in agushie-treated ‘ogri’ and 5.53% in agushie_-_treated meatloaf respectively. The higher levels of fibre in agushie-treated burgers could help alleviate diet-related constipations by improving bowel movements in consumers.

The results obtained for cooking yield and acidity

(pH) are also shown in Table 1. Significant differences (p<0.05) existed in the pH values across treatments. All the pH values observed in the agushie_-_treated burgers were higher compared to the control. The reported values of pH ranged from 6.14(T1) to 6.55(T4). These increases in pH with increased use of agushie resulted in significantly (p<0.05) higher cooking yields in all the agushie-treated beef burgers compared to the control because pH in meat and meat products increase with water holding capacity [18], which also is positively correlated with cooking yield. Also, the cooking yield of meat is dependent on contraction of myofibrillar proteins that form the muscle matrix, leading to expulsion of water and, to a lesser extent fat. However, the proportion of these losses will depend on the type of cooking; which was similar for all burger treatment types in this study. The cooking yields observed in this study ranged from 60.66% (T1) to 79.06% (T4), indicating that all things been equal, meat processors could benefit more when they produce and sell agushie-treated burgers since meat products are sold on weight basis.

Eating Characteristics of Burgers Produced With or Without Agushie

Table 2 shows the results for the sensory properties of burgers produced with and without agushie. No significant differences (p>0.05) were found across treatments in terms of appearance, flavour, taste, juiciness, texture and acceptability. Though T2 and T3 seemed to be more acceptable to the panel, the observed differences in the scores were not statistically different.

Table 2: Effects of using agushie on eating characteristics of burgers. T1=100% ground beef (or 0% agushie), T2, T3 and T4 contained 13%, 26%, and 39% agushie respectively in place of ground beef. Mixed spice comprised of powdered red pepper (10g/kg), black pepper (5g/kg) and powdered ginger (10g/kg) meat. (Sensory scale,1=dislike extremely to 9= like extremely).