Nutritional composition of fruit residue powder and cookies
The nutritional composition of pomegranate peel powder, grape must powder and cookies were assessed (Table 2 and 3). It was observed that pomegranate peel powder had higher total carbohydrates and moisture whereas other parameters like total protein, crude fibre, ash, fat, free fatty acids and calorific value were higher in grape must powder.
Total carbohydrate
The total carbohydrate content was high in S
8 cookies (60.17 g/100 g) and it was low in S
5 cookies (52.23 g/100 g). Total carbohydrate contents of maida, wheat and pearl millet controls were 66.38, 63.30 and 60.62 g respectively. As per the recommendations of nutrition experts, an average human should consume 282 g of carbohydrates per day and the major portion of recommended level of carbohydrate is obtained from the regular diet. Hence the supplementary food or snacks should contain low carbohydrate content. The fortification of fruit waste powder had lowered the level of carbohydrate in the cookies. From the results, it was found that the carbohydrate content of the fortified cookies is less when compared to control cookies. The addition of fruit residue powder considerably decreased total carbohydrate. Addition of guava peel flour
(Bertagnolli et al., 2014) and eggfruit peel flour with wheat flour
(Perez and Germani, 2007) reduced the carbohydrate level of the cookies.
Crude fibre
Crude fibre has less energy value and the fibre content of the samples varied from 2.09% in S1 to 4.03% in S5 cookies. The fibre content increased with the addition of pomegranate peel powder and grape must powder. Pearl mill
et also contains a relative proportion of fibre which aids in slow release of sugar
(Rai et al., 2008). According to
Okpala and Akpu (2014), increasing the amount of orange peel powder greatly enhanced the fiber content of the bread. Similarly,
Ikuomola et al., (2017) reported that cookies prepared from wheat flour and fortified with malted barley bran had higher fibre content than control. In another study, the addition of grape pomace powder (0 to 5 and 0 to 10 g/100 g) to wheat flour increased the total dietary fiber content of fortified bread
(Tolve et al., 2021).
Fat content
The fat content of the samples ranged from 19.22 to 24.90 g/100 g (Table 3). The S5 cookies recorded higher fat content (24.90 g) and cookies fortified with grape must comparatively recorded higher fat content than other cookies. The grape seed is a rich source of fat and it contains 90% monounsaturated fatty acid
(Sousa et al., 2014). An average healthy adult who is aiming to maintain the current weight requires 40 to 60 g of fat consumption per day. The fat content has a direct relation to the calorific value. The USDA reports that 35% of the calories are obtained from fat which states that 97 g of fat per day is to be consumed in a 2500 calorie diet and up to 66 g of fat consumption per day is required in a 2000 calorie diet.
Free fatty acids (FFA)
The free fatty acid content of the cookies ranged from 0.79% to 1.16%. The FFA content in cookies fortified with (S6) registered the highest value (1.16 %) and lowest in S1 (0.79). Free fatty acids speed up the rate of hydroperoxide decomposition, acting as pre-oxidants in oils. Thus, high FFA content in the food may cause further oxidation and leads to development of offensive taste and flavour. If the free fatty acid content of food is high, rancidity takes place quickly. The quality deterioration of cookies is due to moisture loss, oxidation, textural alteration and spoilage during prolonged storage
(Adegoke et al., 1998). During storage, development of off-flavours is the indicator of product oxidation that can be identified by measuring FFA levels. Cookies possess higher risk of oxidative changes because of higher fat contents due to the addition of butter. Incorporation of antioxidant prevents quality degradation by retarding or inhibiting oxidative reactions
(Reddy et al., 2005). It has been noted that there is controversy about the use of synthetic antioxidants in terms of their safety for human health
(Nanditha and Prabhasankar, 2008). Pomegranate peel powder is a plentiful source of phytochemicals more specifically ellagitannis that impart characteristic free radical scavenging properties.
Total protein
Significantly higher protein (14.6 g) was found in treatment S5 and the minimum protein content (8.1 g) was recorded in the treatment (S
1). This is due to the incorporation of grape must powder which is rich in protein (11%) as compared to conventional cookies. Increase in the protein content in the fortified cookies with increase in the level of fortification was reported by
Paul and Bhattacharyya (2015) in cookies fortified with pomegranate juice and peel powder. Though the protein content of residue powder is higher, the protein content of cookies was reduced. This may be due to denaturation of protein that takes place during baking of cookies
(Nakov et al., 2020).
Calorific value
The calorific value is reported to be higher in S
1 which is 492.73 kcal and found to be lower in S
7 (385.84 kcal). More percent of carbohydrate in S
1 is responsible for the highest calorific value whereas comparatively lower calorific value in cookies prepared from wheat flour, pearl millet flour and fortification with pomegranate peel powder and grape must powder might be due to more ash and crude fibre which do not add any calories. The findings of the present study were well supported by
El-Sharnouby et al., (2012) in nutritional quality of biscuits supplemented with wheat bran and date palm fruits.
Moisture content
The moisture content was high in S
5 (9.36%) and it was reported to be low in S
8 (4.65%). The moisture content has its direct influence in the storability. Generally, cookies have less moisture content when compared to other value-added products. Cookies will have better shelf-life conditions if they possess low moisture content and are packed and stored properly (
i.
e., packaging in moisture and vapour proof material). The grape must incorporated cookies are having high moisture content and decreased hardness. Water absorption increased with the addition of grape must at the level of 5% as it contains more fibre. Addition of mango peel powder, apple fibre, lemon and orange peel to the wheat dough produced the similar effect
(Ajila et al., 2008; Kohajdova et al., 2011; Kohajdova et al., 2014). Increased water absorption is due to the higher number of hydroxyl groups in the structure of dietary fibre, which enables more water interactions through hydrogen bonding
(Kohajdova et al., 2011).
Ash content
The average ash content of the cookies was reported to be high in S
5 (3.20 g/100 g) and found to be low in S
1 (0.95 g/100 g). The ash content of grape must powder (GMP) was 3.70 g/100 g and the ash content increases with the addition of GMP. Higher ash content indicates that the flour contains more of the germ, bran and outer endosperm. Lower ash content means that the flour is more highly refined and so the ash content of refined maida is 0.95 g. The higher ash content in the fortified cookies may be due to higher mineral content present in fruit residue powder
(Bello et al., 2022).
Total phenol and antioxidants
The total phenolic content ranged from 90 mg to 160 mg. The presence of phenolics on account of their ability to donate hydrogen atom is one of the reported reasons for high free radical scavenging properties of fruit waste powder. Correlation between phenolics concentration and antioxidant activity has been previously justified by
Chidambara et al., (2002) and
Zahin et al., (2010). Due to fruit residue powder’s high level of bioactivity, there was a simultaneous rise in the total phenolic content and antioxidant activity of cookies after the concentration of fruit powder was increased
(Zlatanovic et al., 2019). In the present study, wheat flour cookies fortified with 5% pomegranate peel powder recorded the highest total phenol content. The antioxidants content also ranged from 8.84% and 90.75%. The cookies prepared from combination of wheat flour and pearl millet flour and fortified with pomegranate peel powder and grape must powder resulted in the highest antioxidant content.
Sensory analysis
Addition of pomegranate peel powder at 5% level did not manifest any undesirable organoleptic response and the product remained acceptable. S
1 ranked first in terms of colour, texture, flavour and taste and S
5 ranked second in overall acceptability (Table 4 and Fig 2).
Gayas et al., (2012) observed the mean overall sensory acceptability scores of more than 8.50 for biscuit samples incorporated up to 5% carrot pomace powder indicated the commercial scope for manufacturing good quality vegetarian biscuits with carrot pomace powder and defatted soy flour. The colour of control cookies made of maida flour was found to be brighter and those made with pomegranate peel powder and grape must powder contributed dark colour as they possess anthocyanin which on baking leads to formation of dark colour on reaction with reducing sugars present
(Nakov et al., 2020).