Physio-chemical property of value-added cookies with partial replacement of wheat flour by fruit pomace flour

Introduction

Fruit processing industries generate substantial quantities of solid by-products, primarily in the form of pomace, peels, and seeds. Apple (Malus domestica) and pineapple (Ananas comosus) processing for juice extraction yields up to 25-35% and 40-50% of the raw fruit weight as pomace, respectively [1,2] . Disposal of fruit pomace presents severe environmental challenges and economic burdens if unmanaged. However, these by-products are rich sources of dietary fiber, minerals, bio-active phenolics, and natural organic acids [3,4] . Converting fruit pomace into dried pomace flour presents a sustainable strategy for waste valorization and functional food formulation [5] . Bakery products, particularly cookies and biscuits, are widely consumed snack foods due to their long shelf-life, convenience, and affordability [6] . Standard commercial cookies are typically manufactured from refined wheat flour, which is high in digestible carbohydrates but low in dietary fiber and micronutrients [7] . Partial replacement of refined wheat flour with fruit pomace flour offers an effective route to enhance the nutritional value of bakery products [8,9] . This investigation evaluates the physico-chemical property of value-added cookies formulated by blending wheat flour with apple and pineapple pomace flours. and 120-day ambient storage.

Materials and Methods

Raw Material Preparation

Fresh, mature apples and pineapples were procured from the local market in Meerut, UP, India. The fruits were thoroughly washed with running tap water to eliminate adhering dust and soil particles. Juicing was performed to separate the juice from the pomace. The fresh pomace was blanched at 85 °C for 2 min to inactivate endogenous enzymes [10] . Blanched pomace was dried in a tray dryer at 60 °C for 10-12 h until the moisture content dropped to approximately 5%. The dried pomace was ground using an electric grinder, sieved through a 60-mesh screen to yield fine Apple Pomace Flour (APF) and Pineapple Pomace Flour (PPF), and stored in airtight glass jars under ambient conditions. Other bakery ingredients-wheat flour (WF), baking powder, refined vegetable oil, granulated sugar, and High-Density Polyethylene (HDPE) film-were purchased locally.

Formulation and Cookie Processing

Cookies were developed using the creaming method according to four treatment combinations:

The basic formulation per 100 g flour blend contained 45 g edible vegetable oil, 60 g powdered sugar, and 1.25 g baking powder. Vegetable oil and sugar were creamed together in a whipping machine for 2 min at medium speed. Sieved flours and baking powder were folded into the cream and kneaded with water to form a uniform dough. The dough was rolled to a standard thickness, cut into circular shapes using a cookie cutter, and baked in a deck oven at 180 °C for 18 min. After cooling on wire racks at room temperature, the cookies were sealed in HDPE polythene pouches and stored at ambient temperature for 120 days.

Analytical Measurements

• Physico-Chemical Properties: Moisture content was determined gravimetrically by hot-air oven drying at 105 °C [15] . Total ash was determined using a muffle furnace (Sandeep Instruments) at 550 °C [16] . Crude protein (𝑁 × 6.25) was analyzed using an automated Kjeldahl digestion and distillation system (Kelplus-KES20LE, Pelican Instruments) [17] . Crude fat was extracted using petroleum ether in an automated Soxhlet extraction system (Socsplus, Pelican Instruments) [18] . Crude fiber was estimated using an automated fiber analyzer (Fibraplus, Pelican Instruments) through sequential acid (0.255 N H 2 SO 4 ) and alkali (0.313 N NaOH) digestion [19] . • pH and Carbohydrates: pH was measured using a digital pH meter (Biogen Scientific) calibrated with pH 4.0 and 7.0 buffer solutions [16] . Total carbohydrate was calculated by difference [20] :

Statistical Analysis

All experiments were conducted in triplicate using a Completely Randomized Design (CRD). Data were analyzed using MS Excel and SPSS software (Version 20.0). Analysis of Variance (ANOVA) and Duncan's Multiple Range Test (DMRT) were used to test for significant differences among treatment means and storage periods at 𝑝 ≤ 0.05 and 𝑝 ≤ 0.01.

Results and Discussion

Moisture Content

The moisture content of fresh cookies (Day 0) ranged from 2.45% (𝑇 0 ) to 2.96% (𝑇 3 ) (Table 1). Higher incorporation levels of fruit pomace flour significantly increased the initial moisture levels (𝑝 ≤ 0.01), driven by the high water-binding capacity of fruit dietary fibers [21] . Over the 120-day ambient storage period, moisture content increased steadily across all treatments, reaching 3.23% in 𝑇 0 and 3.63% in 𝑇 3 . This upward trend is attributed to atmospheric moisture absorption through the HDPE packaging material [22] .

Ash Content:

Initial total ash content increased significantly with higher replacement levels, from 0.98% in 𝑇 0 to 1.81% in 𝑇 3 (Table 2). This increase highlights the mineral richness of apple and pineapple pomace compared to refined wheat flour [23] . During 120 days of ambient storage, ash content declined slightly but significantly across all samples (𝑇 0: 0.98% to 0.89%; 𝑇 3: 1.81% to 1.72%), likely due to moisture gain and chemical interaction with minor mineral constituents over time. 3 0.98 a,v ± 0.005 0.96 a,w ± 0.003 0.95 a,x ± 0.003 0.93 a,y ± 0.009 0.89 a,z ± 0.005 0.94 ± 0.005 76.27 * * 𝑇 1 3 1.25 b,v ± 0.003 1.23 b,w ± 0.009 1.20 b,x ± 0.006 1.18 b,y ± 0.006 1.17

Crude Protein Content

Freshly prepared cookies demonstrated a minor increase in crude protein with fruit pomace incorporation (𝑇 0: 7.33% vs. 𝑇 3: 7.96%; Table 3). Over the 120-day storage period, protein content decreased across all formulations (𝑇 0: 7.33% to 7.24%; 𝑇 3: 7.96% to 7.76%). This reduction during ambient storage can be attributed to non-enzymatic browning (Maillard reaction) and slow protein degradation [24] .

Fat Content

Fat content at Day 0 ranged from 21.74% in 𝑇 0 to 23.22% in 𝑇 3 (Table 4). During 120 days of ambient storage, fat levels showed a slight decrease across all treatments (𝑇 0: 21.74% to 21.51%; 𝑇 3: 23.22% to 23.06%). This reduction during storage is generally attributed to lipid oxidation and hydrolysis into free fatty acids triggered by absorbed moisture and trace oxygen within the package [25] .

Dietary Fiber Content

Dietary fibre increased substantially with fruit pomace incorporation, from 1.12% in the control (𝑇 0 ) to 3.83% in the 𝑇 3 formulation at Day 0 (Table 5). This marked enhancement reflects the elevated cellulose, hemicellulose, and pectin contents inherent to apple and pineapple pomace matrices [26] . During 120 days of storage, dietary fibre decreased slightly (𝑇 0: 1.12% to 1.00%; 𝑇 3: 3.83% to 3.68%), likely due to minor breakdown of soluble fiber constituents over extended storage [27] . 3 1.12 a,w ± 0.020 1.11 a,w ± 0.015 1.06 a,x ± 0.012 1.02 a,xy ± 0.015 1.00 a,y ± 0.015 1.06 11.86 * * 𝑇 1 3 3.21 b,w ± 0.023 3.18 b,wx ± 0.024 3.16 c,wx ± 0.026 3.12 b,xy ± 0.021 3.08 b,y ± 0.015 3.15 5.16 * * 𝑇 2 3 3.49 c,w ± 0.021 3.44 a,wx ± 0.026 3.40 b,xy ± 0.021 3.36 (a-d) and row (v-z) differ significantly (p ≤ 0.05).

pH Values

The pH of fresh cookies dropped significantly with fruit pomace supplementation (𝑇 0: 7.03 vs. 𝑇 3: 6.00; Table 6), driven by natural organic acids (malic and citric acids) present in apple and pineapple pomace [28] . Over 120 days of ambient storage, pH values dropped steadily across all samples (𝑇 0: 7.03 to 6.45; 𝑇 3: 6.00 to 5.48). This progressive acidification is primarily associated with the accumulation of free fatty acids from lipid hydrolysis and moisture pickup [29] .

Total Carbohydrate Content

Total carbohydrate content at Day 0 ranged from 67.85% in 𝑇 0 to 74.25% in 𝑇 3 (Table 7). Among the composite formulations, carbohydrate content decreased as the proportion of fruit pomace increased (𝑇 1: 76.11% down to 𝑇 3: 74.25%), corresponding to the inverse increase in ash, fiber, and protein fractions. Over the 120-day ambient storage period, carbohydrate levels showed a slight downward trend across all treatments (𝑇 0: 67.85% to 67.21%; 𝑇 3: 74.25% to 73.54%), which directly reflects the percentage recalculation following moisture uptake during storage [30] .

Conclusion

This study demonstrates the viability of utilizing apple pomace flour (APF) and pineapple pomace flour (PPF) as functional ingredients to partially replace refined wheat flour in composite cookies. Incorporating equal blends of APF and PPF up to 30-40% significantly enhances the dietary fiber (up to 3.83%), ash (up to 1.81%), and protein content (up to 7.96%) of the product compared to 100% wheat flour control cookies. During 120 days of ambient storage in HDPE polythene packaging, moisture content increased from 2.45-2.96% to 3.23-3.63%, accompanied by minor decreases in ash, protein, fat, crude fiber, pH, and carbohydrate levels (𝑝 ≤ 0.01). Despite these storageinduced changes, all composite cookies maintained acceptable quality attributes over the entire 120-day evaluation period. Overall, substituting 30% to 40% wheat flour with fruit pomace flour offers a commercially feasible strategy for producing fiber-rich, nutrient-dense cookies while advancing sustainable fruit-waste valorization in the food industry.

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