Nutritional and functional properties of cookies enriched with defatted peanut cake flour

Abstract Peanut is the most important oil seed in the world and is becoming a valuable source of plant protein and other important functional ingredients. The present study was designed to explore the nutritional, microbiological, and sensorial properties of the functional cookies enriched with defatted peanut cake flour (DPCF). Peanut seeds were roasted in a microwave, and oil was extracted using a mechanical extruder. The leftover peanut cake residues were collected and utilized for the development of cookies. The mechanical grinder was used to grind the peanut cake into flour. Afterward, DPCF was added at different levels (0, 3, 7, 10, and 14%) to prepare functional and therapeutic cookies. The cookies were tested for their biochemical (proximate, mineral, and antioxidant), microbiological (Mold count), physical, and sensorial attributes. The results showed that the mineral content i.e. calcium, iron, magnesium, zinc, manganese, phosphorus, and potassium in the wheat and DPCF were 21, 1.21, 23, 0.80, 0.73, 137, 134.62 and 178.5, 3.81, 49.68, 5.28, 4.95, 730, 1266.50 mg/100 g, respectively. The antioxidant profile of functional cookies was found to be best in the T4 (14% peanut cake flour) TPC (4.33 ± 0.08 GAE mg/g) and DPPH (1.11 ± 0.06 AAE mg/g), whereas the Control sample has the lowest TPC (1.04 ± 0.02 GAE mg/g) and DPPH (0.18 ± 0.01 AAE mg/g). The thickness, diameter and spread ratio were 3.94–5.54, 31.09–24.98 and 7.82–5.1 mm, respectively. In conclusion, defatted peanut cake flour (DPCF) is a great option to be added in precise amounts (14% of the total) to fill the nutritional gap in cookies.


Introduction
Food crops have occupied an important place in human nutrition as they remain the major sources of macro and micro nutrients for a large proportion of the world population, particularly in developing countries. The peanut is taxonomically classified as Arachis hypogaea L., worldwide known as groundnut. Peanut is a legume crop generally grown for its consumable seeds. Commercially, peanut production is considered of great importance, ranging from small to large scale, mainly grown in the subtropics and tropical areas around the globe (Variath & Janila, 2017). It usually grows underground; while keeping this certain characteristic into account, the botanist Carl Linnaeus named the species hypogaea, which means "under the earth" (Biljwan et al., 2019). However, it is recognized as legume and grain mainly due to its high oil content. A significant change in the consumption pattern was observed both in developed and developing economies (Van Su et al., 2020). The major proportion of peanuts being produced in developing regions around the globe is primarily employed for the extraction of oil due to its bioactive potential and further utilized to meet domestic needs merely, particularly in developing countries; meanwhile, in developed regions (Northern America, Europe, Australia, and Japan), it is being expanded as a nutritional food commodity (Godswil, 2019).
Peanut meal or peanut cake is recognized as the by-product acquired after the extraction of oil by means of mechanical pressing and can be identified by its light gray to brownish flakes with different sizes having smooth and curved surfaces. The size of peanut meal flakes is normally ranging from 1.5 to 40 mm in diameter (Zoulias et al., 2000). In addition, peanut meal or cake is observed to contain significantly higher amounts of protein in it and it is mainly employed for animal feed purposes. High protein contents along with low fiber and significantly higher oil residues with the absence of any kind of anti-nutritional factors make peanut meal a novel potential food ingredient (Smith & Barringer, 2015). Due to its cost-effectiveness peanut cake can be utilized to replace soybean meal which can be employed in the development of proteindense food derivatives.
Moreover, contamination with certain toxic molds or fungi such as aflatoxins (Sharma et al., 2016) or their secondary metabolites may present in the peanut meal that may possess high food quality complications; however, it should be observed through FAO guidelines and established threshold to eliminate any existing hazards (Floret et al., 2021). Nutrient-depleting and harmful chemicals may be present in raw peanuts. Aflatoxin, protease inhibitors, hemagglutinin, goitrogen, saponin, and phytic acid are some of the chemicals that have so far been found. Three strategies can be used to deal with the potential health risks brought on by aflatoxin contamination of food and feed. These are avoidance, elimination, and inactivation. Whatever strategy or technique is used, it needs to possess the following qualities: A process must meet the following criteria: (a) It must be cost-effective; (b) the aflatoxin must be eliminated, and the by-products of that elimination must not be toxic; (c) the process should not reduce the product's nutritional value; (d) the process must be quick and easy to use so that it can be used in different locations with unskilled laborers; and (e) the process must not pollute the environment (Dong et al., 2011;Natarajan, 1980). Aflatoxin inactivation by chemical means in peanut products has good potential. Aflatoxin destruction was accomplished with the aid of specific chemical processes. Many of these processes are not currently commercially viable, except ammoniation, which is being used to salvage toxic meal in the United States (Dong et al., 2011;Gardner et al., 1971) In the context of protein quality, groundnut is considered a cost-effective source. Major counterparts of peanuts contain a significant amount of protein which is relatively higher in comparison to any existing oil nut composition and its application for the development of protein-fortified food derivatives is increasing at a significant pace (Adegunwa et al., 2019). Based on dry weight (per 100 g) analysis, groundnuts were observed to have fiber (8.0 g), water (1.55 g), protein (23.68 g) as well as fat contents (49.67 g), and carbohydrates (21.51 g) while providing total energy of 244 kJ (Settaluri et al., 2012). In addition, groundnuts were also examined to contain essential micronutrients, e.g., vitamins and minerals in the percentages of 0.77 g and 0.018 g, respectively, which are much needed for the proper development as well as growth (Taylor et al., 2009). Peanuts contain many constituents required for human nutrition. The high nutritional value of peanuts is primarily due to the presence of relatively higher levels of biologically active compounds such as tocopherols, flavonoids, phytosterols, resveratrol, and their ease of digestion (Bodoira et al., 2022). The fat contents of peanuts have been extensively studied. In general, peanuts contain approximately 50 to 55 percent of fat contents, from which 30% is linoleic acid and 45% is oleic acid. The latter is released by lipid oxidation and is sensitive to tastelessness (T. L. Dharsenda & Dabhi, 2020). Among particular interest is the oleic/linoleic ratio currently used as an index of industrial consumption stability and shelf life. It is expected that the use of high-oleic nuts instead of conventional nuts will increase the shelf span and consequently improves the oxidative stability of peanut derivatives (Amoniyan et al., 2020).
Cookies are one of the bakery products that people of all ages consume. These are usually prepared from refined wheat flour, which has fewer essential nutrients but is a good source of fat and carbohydrates. The nutritional value can be enriched by using multigrain flour, which adds protein, fiber, and minerals to the product. The protein content of cookies can be increased by using peanut meal (Etiosa et al., 2018). It is one of the most important oils and protein crops in the world. It contains 30% of protein with all the indispensable amino acids. Peanut meal is a rich source of protein, and these proteins are unique among plant proteins because of their high biological value and the presence of essential amino acids such as lysine which is a limited amino acid in most cereals as well as in oil-bearing nuts (Zin et al., 2014). Due to the extraction of peanut oil, which is used in the manufacturing of numerous food products, the output of peanuts in Pakistan has increased to a level of 100,000 tons (Iqbal et al., 2013). The defatted peanut flour that is left over after extraction is a serious problem and is typically sold for use in animal feed (Arbach et al., 2021). In the current study, a concerted effort has been made to evaluate the nutritional and bioactive characteristics of peanut cake flour; meanwhile, functional cookies were prepared by introducing different levels of peanut cake flour. Developed cookies supplemented with peanut cake flour were examined for their biochemical, mineral, bioactive as well as sensory profile. In order to ensure that sufficient quality protein is available to the masses suffering from the threat of protein energy malnutrition, the results of the current research intervention are critical in supporting the use of peanut protein isolates in the manufacture of various baked products.
Partially defatted peanut cake is an inexpensive and underutilized by-product from the peanut oil industry which is rich in protein along with other essential nutrients and offers the same health and dietary benefits of peanuts but with less fat. The concentration of essential nutrients from this material could increase its value, and it could become a source of new protein with applications in different industries and processes. Therefore, the aim of this study was to find out the best concentration for the preparation of nutrient-rich cookies from peanut cake flour.

Procurement of raw material
In this study peanuts were procured from the local market, and shells were removed and then packed in a sealed plastic bag to avoid any further contamination until further analysis at the Food Analysis Lab, University Institute of Food Science and Technology, The University of Lahore. Meanwhile, the chemical reagents required for this study were purchased from Merck (Germany) and Sigma-Aldrich Chemical Co. (St. Louis, MO, USA).

Roasting of peanuts
Peanut seeds were microwaved to roast in a convection microwave oven. After microwaving, the seed was allowed to cool down at ambient room temperature; then the skin was removed by hand. After removing the skin, peanuts were packed in a plastic bag and sealed to avoid any moisture transfer from the environment (Liu et al., 2019).

Extraction of oil
In this study, peanut oil was extracted by utilizing a laboratory-scale mechanical extruder (Extrutech E325 (Sabetha, KS), a single-screw extruder, which has a barrel diameter of 254 mm, a screw diameter of 83 mm, and a barrel length-to-diameter ratio of 9:1). After oil extraction peanut cake was collected as remaining residues and was packed until further analysis.

Defatted peanut cake flour Formulation
Defatted peanut cake (DPC) was ground to make fine powder or flour. For this purpose, a conventional mechanical grinder was used (Sieve size 0.5-2.0 mm). Further, this powder was stored in a sterile glass jar to prevent any moisture contamination until the development of functional cookies (Federal & Ilaro, 2019).

Composition analysis of raw material
Wheat flour and defatted peanut cake flour samples were analyzed for their proximate and mineral composition as suggested by the methods described by Iji et al. (2017).

Functional product development
For this purpose, a standard recipe of soft whole-wheat flour (having an extraction rate of 100%) was used for the preparation of cookies. skim milk was used as a whole-milk substitute in cookie recipes. All of the cookies took between 10 and 15 minutes to mix. After mixing, the cookie dough was molded into the appropriate form in a commercial baking oven, where it was then baked for 15 minutes at a temperature of 180 to 185 °C. Cookies were placed in airtight plastic bags after being allowed to cool at room temperature ( Figure 3).
Further, defatted peanut cake flour was added at different levels (0%, 3%, 7%, 10%, and 14%) in the wheat flour for the preparation of cookies as shown in Table 1.

Proximate content
In this present study, the moisture, crude ash, crude protein, crude fat, crude fiber and NFE (nitrogen-free extract) contents of prepared cookies were examined as described by the methods in Adeloye et al. (2020). All of the ingredients used in the formulation (in grams) and their respective proportions were taken into account when calculating the calories in cookies. Finally, the process of converting grams to calories was carried out. The US Food and Drug Administration (FDA) recommends using 4, 9, and 4 calories per gram of carbohydrate, fat, and protein, respectively, to calculate caloric content for nutritional labeling. Before calculating calories, the whole amount of dietary fiber was removed from the total amount of carbohydrates (Ostermann-Porcel et al., 2017).

Mineral assessment
Digestion is mainly done to remove any organic biomass present in the sample for a clear assessment of heavy metals (inorganic) content. For this purpose, wet digestion was employed in this study. Accurately, 0.2 g of the sample was taken into the digestion conical flask followed by 10 ml of concentrated nitric acid (HNO 3 ) as well as 5 ml of sulphuric acid (H 2 SO 4 ). Meanwhile, a blank sample was also prepared by adding 10 and 5 ml of nitric acid and sulphuric acid, respectively, in the absence of a sample in a digestion conical flask (De Camargo et al., 2014). Atomic Absorption Spectrophotometer (AAS) and flame photometer were employed for the detection of different mineral concentrations.

Physical properties of functional cookies
Each cookie's diameter and thickness were measured using a vernier caliper in triplicate, and the average was determined for each measurement, while to examine the spread ratio of cookies the following equation was used (Ao, 2017).

2, 2-diphenyl-1-picryl hydrazyl (DPPH assay)
The antioxidant activity was examined by method (2, 2-diphenyl-1-picryl hydrazyl) as prescribed by Mphahlele et al. (2016) with slight modifications as mentioned above. For this purpose, accurately 15 μl extracts were added into a test tube followed by 735 μl methanol and 750 μl 0.1 mM DPPH solution and thoroughly mixed until the extract dissolved in methanol. Then, the mixture was incubated for exactly 30 min in the dark to avoid any exposure to light. The absorbance was measured at 517 nm by employing an Ultraviolet visible spectrophotometer. A suitable calibration curve was prepared using ascorbic acid as a standard solution. The obtained results were expressed as mM ascorbic acid (AA) equivalent g −1 of extracts.

Total phenolic contents
Total Phenolic Content (TPC) was determined using the Folin-Ciocalteu reagent. Briefly, 0.1 mL sample extract was mixed with 7.9 mL water and 0.5 mL 2 N Folin-Ciocalteu reagent for 5 min. Then, 1.5 mL of 20% sodium carbonate solution was added. The final mixture was left for 2 hr for color development at room temperature. The absorbance was measured at 765 nm. TPC was quantified using gallic acid as standard.

Mold count
The pour plate method as described by (Zhu et al., 2015) was used. The sample dilution weighing (0.1 ml) was transferred from each dilution to the corresponding plate, and 15 ml of sterile Sabouraud Dextrose Agar (SDA) medium was poured and mixed thoroughly with the inoculum by rocking the plate. The plates were incubated at ambient temperature for three days after which colonies formed were counted and expressed as colony-forming units per gram (cfu/g) (Ling et al., 2016).

Sensory evaluation
The organoleptic properties of the cookies including Taste, Colour, Texture, Aroma, and Overall acceptability were assessed by 20-member panelists screened among staff and students and instructed regarding the evaluation procedures in both written and verbal formats before the cookie's evaluation. Each panelist was given the cookie samples to taste and compare various treatments on 9-point hedonic scale where 9 represents like extremely, 5 represents neither like nor dislike and 1 represents dislike extremely.

Statistical analysis
The data obtained from each parameter were subjected to statistically analyzed by using Statistical Package for Social Sciences (SPSS) to check the level of significance by using analysis of variance (ANOVA) with Tukey test, means, and standard deviation. The level of Significance was p ≤ 0.05.

Physico-chemical properties of wheat and peanut cake flour
The mean values regarding the physicochemical properties of wheat and defatted peanut cake flour (DPCF) are presented in Table 1. The results explored that the average moisture content in Wheat flour and defatted Peanut Cake flour was 12.88 ± 0.05 and 7.61 ± 0.10 g/100 g, respectively. Moisture content in peanuts is initially low which may increase their shelf-life span. Meanwhile, before the development of flour; Peanut seeds were oven-roasted to reduce the water activity to a further possible extent and increase its acceptability as a novel food constituent, whereas the average protein content in Wheat flour (10.43 ± 0.05) g/100 g and defatted peanut cake flour (46.67 ± 0.64) g/100 g was observed. Protein levels in grain and peanut flours are of great importance due to their inherent functional characteristics, i.e., absorption of water, stretchiness, and viscoelasticity, as well as dough strength, loaf volume, texture, and cohesiveness of dough. Another study conducted by the Seth and Kochhar (2018) found similar findings and mentioned that peanut flour, which is prepared from crushed, partially defatted peanuts, has exceptionally low levels of cholesterol and saturated fat. It is a very rich source of protein.
Fat content outcomes showed that the average fat content in Wheat flour and defatted peanut cake flour was (0.98 ± 0.02) and (4.32 ± 0.04) g/100 g, respectively. Fat is considered a great tenderizer in baked derivatives. Meanwhile, fat acts as a coating agent on protein molecules against water that can consequently slow down the gluten development. In addition, fat content is utilized to shorten the gluten strands. While results regarding the crude fiber content elucidated that the average crude fiber content in Wheat flour and defatted peanut cake flour are 2.75 ± 0.04 and 5.10 ± 0.01 g/100 g, respectively. The fiber content refers to whole grains mainly in the preparation of crackers, muffins as well as tortillas, and cookies. Nuts are full of dietary fiber which can be consumable by a human. In the context of the development of nutritionally enhanced baked foods, fiber content from nuts is a potential constituent. Fiber plays an important role in the normal functioning of the human body by promoting health-benefit aspects, particularly, reducing digestion-related complications. The findings regarding the ash content showed that the ash content in Wheat flour and defatted peanut cake flour are 0.97 ± 0.02 and 4.90 ± 0.04 g/100 g, respectively. Meanwhile, the NFE (nitrogen-free extract) content in Wheat flour was 72.01 ± 0.18 and in defatted peanut cake flour, 31.41 ± 0.83 g/100 g was observed. The results are in agreement with the findings of Yadav et al. (2013) during the study of bread enriched with de-oiled peanut meal flour (DPMF). Another study conducted by the Herawati and Kamsiati (2019) found similar results. The current findings are also in line with the study conducted by (Geraldo, 2021;Sibt-E-Abbas et al., 2020).

Effect of adding DPCF on the biochemical profile of cookies
The results regarding the proximate content of the functional cookies are presented in Table 3. Moisture content mainly serves as a dispersing agent for other constituents, i.e., sugar, salt as well as yeast. In addition, moisture is essential for yeast fermentation and reproduction. Regarding the outcomes, on average T 0 (4.89 ± 0.03 g/100 g, T1 (4.67 ± 0.04 g/100 g), T2 (4.36 ± 0.02 g/100 g), T3 (4.14 ± 0.03 g/100 g) and T4 (3.84 ± 0.04 g/100 g) was found. Whereas the maximum moisture content (4.91) g/100 g was detected in the T0 (Control), the least moisture level was examined in T4 (3.8 g/100 g). The results presented that by adding Defatted peanut cake flour moisture content of cookies significantly decreased as compared to the cookies developed with only wheat flour and further found in the following order (Wheat: PCF) of T 0 (100:00) >T1 (97:03) >T2 (93:07) >T3 (90:10) >T4 (86:14) at level (P < .05). These outcomes were found to be in engagement with the results described by (Ijarotimi, 2022). Another study conducted by Wang and Wu (2022) discovered that adding defatted peanut flour to cookies tended to raise their water, protein, and lysine contents. As a result, adding defatted peanut flour greatly increased the nutritional value of gluten-free cookies.
Fat is considered a great tenderizer in baked derivatives. Meanwhile, fat acts as a coating agent on protein molecules against water that can consequently slow down the gluten development. In addition, fat content is utilized to shorten the gluten strands. Regarding the outcomes, on average T 0 (22.80 ± 0.04) g/100 g, T1 (22.93 ± 0.01) g/100 g, T2 (23.10 ± 0.02) g/100 g, T3 (23.23 ± 0.06) g/ 100 g and T4 (23.42 ± 0.07) g/100 g was found. Whereas the maximum fat content (23.44) g/100 g was detected in T4, the least fat level was examined in T 0 (Control) sample (22.79 g/100 g). It showed that by adding defatted peanut cake flour the fat content of cookies significantly increased as compared to the cookies developed with only wheat flour and further found in the following order (Wheat: PCF) of T 0 (100:00) <T1 (97:03) <T2 (93:07) <T3 (90:10) <T4 (86:14) at level (P < .05). These outcomes were found in engagement with the results described by (Yu et al., 2021).
The caloric value of the functional cookies ranged from 458 to 515 Kcal/100 g. The highest calories were observed in the T4 (515 ± 0.4), whereas the lowest caloric value of functional cookies were observed in the T O (458 ± 0.4). The results are in line with the findings of Kulthe et al. (2014).

Mineral profile of functional cookies
The results regarding the mineral content of the functional cookies are presented in Table 4. Defatted peanut cake flour is reported to exhibit a rich mineral profile such as calcium, iron, magnesium, zinc as well as manganese. This inherent characteristic of nuts; makes them a potential constituent for the development of functional food derivatives (Etiosa et al., 2017). On the other hand, all-purpose wheat flour is examined to contain very low concentrations of essential minerals that are much required for the proper growth and development of the human body.

Sensory evaluation of functional cookies
In Figure 2 sensorial evaluations of different treatments (T 0 , T1, T2, T3, and T4) were presented. Particularly, in product development, sensory evaluations are considered of great significance because it directly affects the consumer's choice.
It was observed that by adding defatted peanut cake flour concentrations in the development of cookies the overall acceptability was found to be decreased gradually. Meanwhile, results from T1 (8.60), T2 (8.50), and T3 (8.40) having 3%, 7%, and 10% Defatted peanut cake flour levels, respectively, exhibit that Defatted peanut cake flour can be added in certain amounts to fulfill the nutritional gap generated by normal cookies primarily prepared with wheat flour while without losing any of its sensory attributes at level (P < .05). The results are in agreement with the findings of Yadav et al. (2013) during the study of bread enriched with de-oiled peanut meal flour (DPMF).

Conclusions
Defatted peanut cake flour is a great source of essential nutrients including minerals, proteins and bioactive compounds that can be used as a partial replacement for wheat flour in the preparation of functional cookies. Furthermore, the study exhibits that defatted peanut cake flour can be added in certain amounts (14%) to fulfill the nutritional gap generated by normal cookies primarily prepared with wheat flour without losing any of its nutritional and sensorial attributes. The overall acceptability and other sensorial parameters presented that the T1 is most likely preferred by the maximum panelist.