Chemical and Technological Evaluation of Avocado Fruit Wastes for Enhancing Functional Properties of Some Foods

During food industry a large proportion of raw materials are removed as wastes, or by-products which are rich in many functional components that are good for human health such as nutraceuticals and bioactive compounds (Helkar et al., 2016).

Avocado (Persea americana Mill) is the most important and unique edible fruit of the Lauraceae family which is a dicotyledonous evergreen plantand belongs to the genus Persea which has more than 150 species. Although it originates from Mexico and Central America, it has recently produced and consumed worldwide like Mediterranean countries (Melgar et al., 2018; Araújo et al., 2018; Colombo and Papetti, 2019; Bahru et al, 2019).

In 2022, global avocado production amounted to about 8,978,275 metric tonnes, up 4.8% from 8,570,284 tonnes in 2021. Mexico was the largest producer, accounting for over 28% of global production. Mexico, Colombia, Peru, Dominican Republic, Kenya and Indonesia are the top seven countries of the world production (FAO, 2024).

Regretfully, Egypt is not one of the largest avocado producing countries, but a few varieties have been successfully grown in the 1950s and 1960s, which were grown in limited areas in the Delta.  Certain areas of Egypt have just started growing avocados, especially El-Beheira Governorate, which provides 95% of Egypt’s avocado production (El-Beheira Directorate of Agriculture, 2019).

Avocado fruit is regarded as a super food (complementary & functional) that can supply various nutrients and phytochemicals found in many bitter-tasting vegetables and sweet-tasting, sugar-rich fruits. Eating avocados is associated with stronger immune systems, and defense against oxidative damage caused by cellular metabolic activities (Ortiz-Avila et al., 2015; Comerford et al., 2016).

Avocado is consumed directly as fresh pulp or processed to extract oil and several products (guacamole, packaged chunks and slices, dried or dehydrated avocado). Direct consumption and processing of avocado, generates large amounts of wastes such as peel, seeds and defatted pulp which make up between 21–30% of the fruit weight and cause environmental problems and are generally discarded without any additional applications (López-Cobo et al., 2016; Dalle Mulle Santos et al., 2016 ; Araújo et al., 2018; Figueroa et al., 2018).

 Avocado wastes possess interesting biological properties and are rich fiber, protein and different bioactive compounds such as chlorophylls and polyphenols which have anti oxidative activities. Both of peels and seeds have higher than pulp and hence used as natural additives to increase food quality. Therefore, they have a great potential as a source of functional ingredients in food, cosmetic and other industries (Rodrıguez- Carpena et al., 2011; López-Cobo et al., 2016; Dalle Mulle Santos et al., 2016; Araujo et al., 2018; Colombo and Papetti, 2019). One of the most important aspects of the food industry is waste management. Thus, the conversion of byproducts into health-promoting products shows financial advantages for workers, stakeholders, and the nation (Helkar et al., 2016). Therefore, the present study aimed to determine the proximate composition, minerals, dietary fiber, bioactive components and antioxidant activity of avocado fruit wastes (peel and seed) and its utilization in producing some functional foods (biscuits & burger).

MATERIALS AND METHODS

MATERIALS: 

Avocado (Persea americana Mill) fruits variety "Hass" were obtained from Al-Sulaymaniyah Farm, Alex-Cairo Desert Road,Al-Nubaira, Egypt in December 2021.  The fruits were harvested before the ripening stage, selected on the basis of size uniformity, absence of physical damage and visible decay. Each fruits was wrapped in papers and left at room temperature to ripen (7- 9 days). Figure (1) shows avocado fruit parts. The ripe fruits were washed with tap water, drained, cut manually to obtain their edible and non-edible portions (pulp, peel and seeds, respectively) and stored at 4±1ºC. The pulp was separated manually from the peel and seed.

  All chemicals used were of analytical grade, and were purchased from El-Gamhouria Company, for chemical and medical requisites, Alexandria, Egypt. Wheat flour ( extraction 72%), liquid milk, sugar, shortening, butter, baking ammonia, salt, vanillin, pepper powder , glass jars and polyethylene bags used as packaging materials for the preparation and formulation of food products  all were purchased from local markets in Alexandria, Egypt.

Figure (1): General appearance of  avocado fruit parts.

METHODS:

Preparation of avocado (Persea americana Mill)waste powder:

Using a sharp knife the peels were cut into small pieces. The seeds were minced by means of a grater. All parts were dried to a constant weight in an oven at 50°C for 48 h. Then were ground using an electrical mill (SEB 21260), sieved to obtained particle size of 60 mesh and kept in low density polyethylene bags and stored at 4±1°C.

Chemical Analysis:

Proximate chemical composition including moisture content, crude protein, crude ether extract, crude fiber and total ash were determined according to the methods of AOAC (2007). Nitrogen free extract (NFE) was calculated by difference.  Minerals were determined according to the   method of (AOAC, 2007). Ca, Mg, Fe, Mn, Cu and Zn were determined by atomic absorption spectrophotometric (Perkin-Elmer Instrument Model 2380). K and Na were determined by flame photometer. Dietary fiber fractions including neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), cellulose and hemicelluloses were analyzed using the method of Goering and Van Soest (1970).Total phenolics content was determined according to the methodology proposed by Abirami et al. (2014). The total flavonoids content was determined using the methodology proposed by Barros et al.  (2011). Scavenging activity by DPPH assay was determined according to the procedure based on Brand-Williams et al. (1995). The ABTS⁺ free radical scavenging activity of samples was estimated using the method of   Hwang and Do Thi (2014).

Utilization of avocado waste in some functional products:

Preparation of biscuits:

Biscuits were prepared from blends of wheat flour containing 0, 5, 10 and 20% of seed powder (SPW) and 5,10 and 15% of peel powder (PPW ), using the method described by Smith (1972).  The formula used for preparing biscuits is shown in Table (1).

Table (1). Ingredients used for preparing biscuits containing different concentrations of avocado waste.

SPW: Seed powder.

PPW: Peel powder.

Preparation of beef burger:

    Different percentages of SPW and PPW (5, 7.5, 10 and 15%)   substitution as partial part from minced meat were used in preparing beef burger according to Mabrouk (2014). Beef burger ingredients as shown in Table. (2).

Table (2). Ingredients used for preparing beef burger containing different concentrations of avocado waste.

SPW: Seed powder.

PPW: Peel powder.

Biscuit characteristics:Biscuit characteristics were evaluated according to Hooda and Jood (2005) with the following measurements: Average weight of six pieces (g), diameter of 6 pieces (mm) and thickness of 6 pieces (mm). Spread ratio was calculated by dividing the average value of diameter (mm) by the average value of thickness (mm).

Burger characteristics: Shrinkage % and cooking loss %were determined according to the method of Mabrouk (2014) using the following equations:

 Shrinkage % = A₁ –A₂ /A₁ x100.

  Where: A₁: Area of the sample before grilling.   A₂: Area of the sample after grilling.

 Cooking loss % = F- G /F x100

  Where:   F: Fresh burger sample weight (g).          G: Grilled burger sample weight (g).

Sensory evaluations:  Colour, texture,flavour, appearance  and total acceptability of the prepared products including,biscuit and beef burger were assessed by 10 panelists of Food Technol. Lab., Food Technol. Research Inst., Agriculture Research Center, of Sabahia, Alexandria, Egypt. Ten trained panelists were asked to evaluate the samples according to the method described by Hooda and Jood (2005) on hedonic scale consisting of 9 points where 1 (Extremely dislike) to 9 (Extremely like).

Statistical analysis: Data were statistically analyzed by a general linear model procedure of the Fisher’s protected least-significant difference (PLSD) test using SAS, 2004 (SAS Institute, Inc., Cary, NC) (SAS, 2004). This test combines ANOVA with a comparison of differences between the means of the treatments at the significance level of P ≤ 0.05.

RESULTS AND DISCUSSION

           In the present study, the evaluation of nutritional value and utilization of   avocado fruit waste required to determine the proximate chemical composition, mineral content and some bioactive compounds of peel and seed as main wastes in addition to estimate the weight composition of these parts. The average weight of peel and seed represented 13.24 and 16.11% of the total weight of avocado fruit, respectively. These means that about 30% of the fruit weight accounts as non-edible portion (peel and seed). Thus, approximately third of the total fruit weight represents as a waste after processing. These findings are consistent with those reported byDa Silvaet al.(2022).

Proximate chemical composition:

        The proximate chemical composition of peels and seeds of avocado fruit is represented in Table (3). Peels contained : 12.42% moisture, 5.70% crude protein (CP), 11.68% crude ether extract (CE), 40.36% crude fiber (CF), 2.02% ash and 40.24% NFE, while seeds  had 10.96% moisture, 4.97% CP, 3.03% CE, 4.20% CF, 4.31% ash and 83.49% NFE on d.w. These results indicated that peels had higher CP, CE, ash and CF values than seeds, while seeds had higher ash and NFE than peel. There were significant differences between all the components of peel and seed   proximate composition.

Table (3). Proximate chemical composition of avocado fruit waste on dry weight basis.

Means ±SD; the values having different letters within a row are significant (p ≤ 0.05(.

 * Nitrogen free extract calculated by difference; dry basis (%).

Many studies have shown that the highest component present in the avocado seed is carbohydrates, in the range of 44.7 to 79.5% (Araújo et al.,2018 ; Alkhalaf et al.,2019) of which approx. 91% of all carbohydrates are starch ( Tesfaye et al.,2018), followed by protein   ranges from 2.64  to as much as 23% (Ifesan et al.,2015; Egbuonu et al.,2018 ),whereas the fat content ranges from 0.71 to 14.1%,  ash content ranges from 1.6 to 2.83%  (Mahawan et al., 2015 ; Ifesan et al., 2015; Siol and Sadowska, 2023).The variation in proximate composition of the avocado fruit peel and seed that were reported by previous authors due to the variations in stage of ripening , the harvesting time, variety, cultivation climate, beside other factors.

Mineral content:

Avocado fruit wastes (seed and peel) are good sources of minerals, particularly potassium, magnesium and calcium as well as minor amounts of iron, copper, manganese and zinc. It was observed that the mineral contents varied widely in avocado fruit parts with the seeds and peel exhibiting higher contents than pulp (Da Silva et al., 2022).

Mineral content of peel and seed are represented in Table (4). These results indicated that all the determined elements of seed had values higher than that of peel. The following minerals; potassium, calcium, sodium and magnesium were the macro elements meanwhile micro elements; iron, copper, zinc and manganese in seeds were found to be much higher in concentration than the peels.

Table (4): Mineral content of avocado fruit waste on dry weight basis.

*FDA (2019), the daily values for Americans 4 years and older age.

Means ± SD on a dry weight basis.

The values having different letters within a row are significant (p ≤ 0.05(.

Potassium was the predominant element (2769.61 and 1445.03 mg/100 g) in the seed and peel, respectively, followed by calcium (269.90 and 121.81 mg/100 g), sodium (142.89 and 92.15 mg/100 g) and magnesium (49.49 and 42.91 mg/100 g); where the seeds showed higher significant values than the peels in this respect.  Cowan and Wolstenholme (2016) reported that the high potassium and low sodium diets are good for preventing cardiovascular diseases.

Regarding the micro-elements, iron was found to have the highest concentration (13.40 and 8.84 mg/100 g) in the seed and peel, respectively, followed by copper (11.43 and 7.43 mg/100 g), zinc (5.40 and 2.31 mg/100 g), and manganese (1.14 and 0.72 mg/100 g). The findings indicate that avocado fruit wastes (peels and seeds)  are good sources of minerals, and can be processed into a variety of products, including dry soup and snack crackers (Mousa et al., 2021).

Dietary fiber fractions:

   Table (5) represents the dietary fiber fractions of avocado fruit waste (peel and seed).  The values of these fractions could be ranked in descending orders as follows neutral detergent fiber (NDF) 47.17%, acid detergent fiber (ADF) (40.39%) and acid detergent lignin (ADL) (17.26%) for peel. The fractions values of the seed were significantly lower than peel being 23.84, 7.15 and 3.52%, respectively. It's clear that, there were pronounced variation between the values of NDF, ADF and ADL of peel and seed. All the values of peel were higher than that of seed

Table (5): Dietary fiber fractions of avocado waste (peel and seed)

Means ± SD on a dry weight basis.  

The values having different letters within a row are significant (p ≤ 0.05).

It was reported by Negesse (2009) and Marcos et al. (2020) that the dietary fiber fractions of avocado peel were higher than those of seed being (26.1 and 11.5), (23.3 and 10.4) and (12.5 and 3.48) g/100 g for NDF, ADF and ADL, respectively. 

On the other hand,NDF, ADF and ADL content of  avocado seed in the  present study had lower concentration than avocado seed fiber residues found  by Barbosa-Martín et al. (2016)  that they ranged between  (39.66 to 40.44), (20.63 to 21.21) and (12.99 to 13.47) g/100 g  for NDF, ADF and ADL, respectively.

Rivera–González et al. (2019)  showed that  high dietary fiber  content promote  beneficial  health  effects  as antioxidant activity,  reduced blood cholesterol and  changes on  the insulinaemic and   glycemic    responses. The difference and variation in dietary fiber content of the avocado fruit peel and seed that were reported by previous authors may be referred to fruit variety, different environmental conditions, and ripeness, beside other factors.

Bioactive components and antioxidant activity

Table (6) presented the avocado seed and peel powder bioactive compounds.  It was clear that seed contain significant higher amounts of phenolic and flavonoid contents being (37.97 mg GAE /g and 18.94 mg QE /g, respectively) than peel (25.56 mg GAE /g and 13.65 mg QE /g, respectively). This agrees with the results reported by Wang et al. (2010) and Ferreira da Vinha et al.  (2013).

Table (6): Total phenolics, flavonoids content and antioxidant activity of avocado fruit waste (dw).

Means ± SD on a dry weight basis.  

The values having different letters within a row are significant (p ≤ 0.05).

The total polyphenolic contents of avocado peel in our study were within the range of 21.74 to 1252.31 mg GAE/100 g DW reported by Morais et al. (2015). While, the total polyphenolic contents ofseed were lower than that reported by Siol and Sadowska (2023).

Table (6) shows the antioxidant activity of extracts of avocado fruit waste (peel and seed) as assessed by DPPH and ABTS⁺ radical scavenging. The radical scavenging activity on DPPH was expressed as IC₅₀.. Table (6) revealed that seed extract exhibited the highest activity followed by peel extract. The mean values of IC₅₀ as µg/ ml were 9.31 and 12.90, respectively.  The lower IC₅₀ value means stronger scavenging DPPH free radicals. In general the antioxidant activity of seed extract was significantly higher than that of peel extract. The DPPH scavenging activity of avocado fruit parts is associated with their phenolic and flavonoid contents, thus, seed extract showed the highest DPPH radical scavenging activity compared to peel.

The ABTS⁺ method was used to confirm the results from the DPPH test since it is based on a similar antioxidant mechanism and the results are shown in Table (6). The results clearly confirmed that seed extract contained more antioxidants followed by peel extract which were 16.10 and 11.71 mg Trolox Equiv/g dw, respectively. This is consistent with Rodríguez-Carpena et al. (2011).  Generally, the antioxidant activity depends on several factors such as species, maturity stage, climate and environmental conditions, handling, extraction method...etc. according to Villa-Rodríguez et al. (2011).The results implied that bioactive compounds from the seed and peel might be potential resources for the development of antioxidant function dietary food.

The avocado wastes (seed and peel) are a good source of carbohydrate, dietary fiber, minerals, bioactive compounds as well as higher antioxidant properties. In addition, anti-inflammatory, hypoglycemic, antihypertensive, and analgesic effects are reported in the literature. The addition of avocado seeds to candy, cakes, snacks and a beverage alternative to coffee and has been previously explored (Siol and Sadowska, 2023).

Biscuit products:

                Biscuits are very attractive food   product   for many of people, especially for vulnerable groups. Biscuits are the most popularly consumed bakery items , because of low cost value among other processed foods, varied taste, easy availability and longer shelf life ( Hooda and Jood, 2005 ; Ajila  et al., 2008 ). In the present study, the wheat flour was replaced by 5, 10, 15 and 20% of seed powder (SPW) and 5, 10 and 15 % peel powder (PPW). The organoleptic properties and the appearance of these formulated biscuits are given in Table (7) and Fig. (2).

Table (7). Organoleptic properties of biscuits containing avocado fruit seed and peel powders.

SPW: Seed powder, PPW: Peel powder, Means ± SD.

Means in a column   not sharing the same letter are significantly different at p ≤ 0.05.

Capital  letter for differences between properties of biscuits with different concentration of SPW.

Small letter for differences between properties of biscuits with different concentration of PPW.

The scores of panelists showed that all samples were accepted. The scores of organoleptic properties were slightly decreased, by increasing the level of SPW and PPW. There were no significant differences between the three levels of SPW (0, 5 and 10 % (and two levels of PPW (0 and 5%) in all properties as they were highly accepted as control. While, increasing SPW to 15 and 20% caused significant decrease as well as PPW at 10 and 15%, but still moderately accepted.

Figure (2). General appearance of biscuits substituted with SPW and PPW powder at different levels.   SPW: Seed powder, PPW: Peel powder.

Physical properties of biscuits

Physical properties such as weight, diameter, thickness and spread ratio of biscuits are summarized in Table (8). These results indicated that there were slight differences in the physical characteristics between the biscuits which were made from 100% wheat flour and those made from wheat flour with 5, 10, 15 and 20% replacement of avocado seed powder and 5, 10 and 15 % replacement of avocado peel powder. It was observed that the weight of biscuits decreased gradually from 23.08 to 21.62 g with increasing the proportion of avocado seed powder. Also there was an obvious decrease in diameter from 42.76 to 38.00 mm; while, thickness of biscuits was slightly decreased by increasing the concentration of avocado seed powder.  The same observations were also found for biscuits made from wheat flour with 5, 10 and 15% replacement of avocado peel powder as shown in Table (8).

Table (8): Physical characteristics of biscuits containing different concentrations of avocado seed and peel powders.

SPW: Seed powder, PPW: Peel powder , Means ± SD.

Means in a column not sharing the same letter are significantly different at p ≤ 0.05.

Capital letter for differences between properties of biscuits with different concentration of SPW.

Small letter for differences between properties of biscuits with different concentration of  PPW.

The spread ratio is an important characteristic for determining the quality of biscuits. Biscuits with higher spread ratios are the most desirable (Chauhan et al., 2016). The spread ratio of all SPW and PPW biscuits containing differ concentrations showed no significant differences from control.  Ajila et al. (2008) and Ashoush and Gadallah (2011) observed low value of spread ratio for biscuits incorporated with mango peel powders and by Kohajdová et al . (2014) for biscuits incorporated with grapefruit and apple fiber. This may be due to the dilution of gluten (Kohajdová et al., 2014).

The results of the physical properties of biscuits showed that supplementation of whole wheat flour with avocado seed and peel powder gave slight difference between the samples as they all compared favourably with the control. The above results confirmed the successful use of avocado seed powder up to 20% and avocado peel powder up to15% replacing wheat flour in preparing biscuit with satisfactory acceptable quality.

Proximate chemical analysis of biscuits substituted with seed and peel powders

Generally, the moisture content of biscuits increased significantly (P < 0.05) by increasing the level of SPW and PPW incorporation which could be related to the increased in water absorption of dietary fiber present in seed and peel with high percentage as shown in Table (5). As observed in Table (9), incorporation of PPW in the biscuit samples significantly increased fat, protein with no significant compared to control and highly increased  fiber content while incorporation of SPW in the biscuit samples significantly increased fat and fiber content but reduced the protein content. This may be due to the low protein contents of avocado seed as shown previously in Table (3).  As was expected, there was significant increase in the fiber content of the biscuit samples. The values increased from 3.1% in control sample to 8.19% in sample incorporated with 15% PPW.  Crude fiber composition is a measure of the quality of indigestible cellulose, pentose, lignin, and other indigestible materials (Akajiaku  et al., 2018). Despite having little nutritional value, crude fiber aids in the increased absorption of some other micronutrients and utilization of nitrogen) Obinna-Echem et al., 2020).

Table (9): Moisture, protein, fat, fiber, total phenolic content and anti-oxidant activity ofbiscuits containing different concentrations of avocado seed and peel powders.

SPW: Seed powder, PPW: Peel powder, Means ± SD.

Means in a column not sharing the same letter are significantly different at p ≤ 0.05.

Capital letter for differences between properties of biscuits with different concentration of SPW.

Small letter for differences between properties ofbiscuits with different concentration of PPW.

Regarding to total phenolic content, the results revealed that there was an improvement in the phenolics content with increasing the levels of SPW and PPW. The results in Table (9) showed that increasing the levels of SPW and PPW gradually increased the content of phenolics contents compared to control biscuit sample. Biscuit treatments containing 20% SPW had the highest total phenolic (26.42 mg GAE /g). Even though there was some loss in the phenolic content during processing, there was an increase in phenolic content in biscuits by the incorporation of SPW and PPW. The same behavior was observed with the partial replacement of cookies and snacks flour with avocado seed powder (Novelin et al., 2022; Siol and Sadowska, 2023).  Also, all the levels of SPW and PPW incorporated in biscuits showed an excellent ability in radical scavenging activity (42.04 - 67.52%), while it was only 33.89% in the case of the control (Table 9). Thus, the incorporation of SPW and PPW into biscuits increases health benefits by increasing antioxidant properties.

Beef burger

     Beef burger is one of the most popularly meat products. From the obtained results of chemical, nutritional and functional properties of avocado fruit waste (seed and peel), it was suggested to use seed and peel powders in beef burger ranging between 5% to 15% substitution. Table (10) represents the organoleptic properties and Table (11) shows some physical characteristics of beef burger while, Figs. (3-A & 3-B) illustrate the appearance of beef burger before and after cooking.

Table (10): Organoleptic properties of beef burger containing different concentrations of avocado seed and peel powders.

SPW: Seed powder, PPW: Peel powder , Means ± SD.

Means in a column not sharing the same letter are significantly different at p ≤ 0.05.

Capital letter for differences between properties of Beef burgerwith different concentration of SPW.

Small letter for differences between properties ofBeef burger with different concentration of PPW.

Figure (3-A):General appearance of  beef burger containing different concentrations of avocado fruit  seed powder (SPW).

Figure (3-B): General appearance of beef burger containing different concentrations of avocado fruit peel powder (PPW).

Organoleptic properties

                 The organoleptic properties of all replacement levels of seed and peel powder were accepted. The data in Table (10) showed the changes in sensory properties of beef burger prepared with the different levels of substitution. As a matter of fact, the scores of organoleptic properties were reduced by increasing the level of substitution.

      Statistical analysis revealed that there were no significant differences between control and 5% replacement in all the organoleptic properties, while, raising the replacement to 7.5 and 10% peel powder and 10 and 15% seed powder showed decreased significant difference  but still within the level of acceptability and far  from the rejection level. On the other hand, beef burger produced using seed powder with the same levels of peel powder substitution was more acceptable.

                The results showed improvement by replacing meat with seed powder at 5 and 10% while peel powder by up to 7.5%. Incorporation of seed and peel powder in beef burger improves the amount of beneficial components they contain and the eye-catching appearance of the finished product. Therefore, the beef burger replacement with 5 and 10% SPW, 7.5% PPW) can be recommended as a good quality beef burger with acceptable sensory quality.

Physical characteristics

    The data in Table (11) show that the control sample had the highest percentage of cooking loss and percentage shrinkage. It was observed that the incorporation of seed and peel powder in producing beef burger decreased both percentage of grilling loss and shrinkage. The seed powder at 15% showed the lowest (P ≤ 0.05) mean value of the percentage ofcooking loss and shrinkage (10.85 and 15.52%, respectively). While the control sample showed the highest (P ≤ 0.05) mean value (22.46 and 32.81%, respectively).

As expected, beef burger samples with low cooking loss showed the highest reduction in shrinkage. A significant (P ≤ 0.05) decrease in percentage cooking loss and shrinkage were observed by increasing the increment of seed and peel powder percentage in the products. Similar effects were also reported on using black eye bean flour, chickpea flour and lentil flour (Serdaroğlu et al., 2005) and dietary fiber from rice bran (Choi et al., 2007).

Table (11): Physical characteristics of beef burger containing different concentrations of avocado fruit seed and peel powders.

SPW: Seed powder, PPW: Peel powder , Mean±SD.

Means in a column not sharing the same letter are significantly different at p ≤ 0.05.

Capital letter for differences between properties of Beef burgerwith different concentration of SPW.

Small letter for differences between properties ofBeef burger with different concentration of PPW.

Turhan et al. (2009) stated that the burgers shrank during cooking due to the meat protein denaturation and fluid (moisture and fat) loss. The addition of fibers and non-meat protein ingredients may reduce diameter shrinkage and weight loss. Also, Alakali et al. (2010) reported that loss of weight occurring during cooking might be due to moisture evaporation and drainage of melted fat and juices.

Proximate chemical analysis of beef burger substituted with seed and peel powders

The data in table (12) represent moisture, crude protein, crude fat, crude fiber, total phenolic contents and anti-oxidant activity of beef burger as affected by replacement of meat with avocado seed and peel powders. Statistical analysis between treatments indicated that there were significant differences among all treatments. Moisture content decreased significantly by increasing the level of SPW and PPW incorporation as compared to control. An obvious increase in protein and fat content was noticed by increasing the level up to 10% with SPW and PPW incorporation, which could be related to the decrement in moisture content. While treatment with 15% SPW showed minimum protein and fat content compared to control (Table 12) this may be due to the low crude protein and fat contents of seed powder, while, increasing percentage of seed powder caused decreased crude protein and fat contents in beef burger. 

Table (12): Moisture, protein, fat, fiber, total phenolic content and anti-oxidant activity ofbeef burger containing different concentrations of avocado seed and peel powders.

SPW: Seed powder, PPW: Peel powder , Mean ±SD.

Means in a column not sharing the same letter are significantly different at p ≤ 0.05.

Capital letter for differences between properties of Beef burgerwith different concentration of SPW.

Small letter for differences between properties ofBeef burger with different concentration of PPW.