Abstract This study aimed to develop a functional ingredient using pomace from selected pineapple varieties in the Philippines. In a preliminary trial, cabinet- and freeze-drying methods were compared to determine the ideal drying technique for preparing pineapple pomace powder (PPP) as a functional ingredient. Pomace samples were collected from three pineapple varieties: Smooth Cayenne, MD2 and Queen. The collected pomace samples were dried, ground, sieved, and analyzed for bioactive compounds, including total phenolic content (TPC), total flavonoid content (TFC), ascorbic acid content (AAC), total dietary fiber (TDF), and antioxidant activity using DPPH, FRAP, and ABTS assays. The PPP with the highest concentration of bioactive compounds was selected for developing the functional ingredient. The physicochemical properties of the developed PPP were also evaluated. The findings revealed that freeze-drying resulted in a significantly higher drying rate and lower moisture content compared to cabinet-drying. Among the three pineapple varieties, the freeze-dried MD2 pomace exhibited the highest concentrations of bioactive compounds and antioxidant activity. The study concluded that freeze-drying the MD2 pineapple pomace was the most effective for developing a functional ingredient. The resulting freeze-dried PPP had a moisture content of 9.65%, water activity of 0.35, pH of 3.89, titratable acidity of 2.70% as citric acid, total soluble solids of 2.6°Brix, and a light-yellow color based on CIE Lab color space values (L* = 84.44, a* = 0.34, and b* = 27.29).

Keywords: Functional ingredient, Pineapple pomace, Bioactive compounds, Dietary fiber, Antioxidant activity

Funding: The authors are grateful for the research funding provided by the University of the Philippines Los Baños - Basic Research Program.

Citation: Panganiban, M. T., Pagatpatan, C. M. L., Tengco, J. M. J., and Reginio Jr., F. C. 2025. Development of a functional ingredient using pomace from selected pineapple [Ananas comosus (L.) Merr.] varieties in the Philippines. Natural and Life Sciences Communications. 24(2): e2025029.

INTRODUCTION

Pineapple is considered one of the most significant commercial fruit crops, contributing greatly to global agricultural production while securing the nutrition and livelihoods of local farmers (FAO, 2021). Globally, the Philippines ranks second among the leading pineapple-producing countries (Statista, 2022). Several pineapple cultivars are grown in the Philippines, including Smooth Cayenne, Red Spanish, Sweet 16, Queen, and MD2 (PCAARRD, 2022.; Hermoso, 2022). These varieties are commonly consumed fresh or processed into canned fruit or juice, preserves, and pies valued for their refreshing flavor and aroma.

Pineapple pomace, the residue collected after juice processing, is often regarded as waste. However, improper disposal of pineapple waste can harm the environment due to the increased demand for biological and chemical oxygen (Hamzah et al., 2021). On a positive note, pineapple pomace contains a significant amount of bioactive compounds, including dietary fiber, vitamins, minerals, phytochemicals, and antioxidants (Montalvo-Gonzales et al., 2018). These bioactive compounds provide various health benefits, such as aiding digestion, reducing inflammation, offering antioxidant protection, and promoting cardiovascular health (Ali et al., 2020). Incorporating pineapple pomace into the diet has the potential to enhance the nutritional value of consumers' daily food intake.

In the Philippines, non-communicable diseases (NCDs) such as cancers, cardiovascular diseases, and diabetes account for a significant proportion (67%) of deaths (DOST-FNRI, 2020). Surveys indicate that NCD-related risk factors, including elevated blood pressure and blood glucose, remain prevalent among adults aged 20 years and older (DOST-FNRI, 2020). The typical Filipino diet, which often includes large amounts of processed foods, contributes to unhealthy eating patterns. These, along with other lifestyle-related risk factors, lead to conditions such as elevated pressure, high blood lipids, elevated blood glucose, overweight, and obesity (DOST-FNRI, 2020).

Studies have also shown that consumers are seeking functional solutions to support long-term dietary and lifestyle changes (Baker et al., 2022; Franklyn-Miller, 2024; French, 2024; Gordon-Seymour, 2022). They are adopting proactive and preventive approaches to protect their health by selecting health-promoting foods in the market. In fact, the global demand for functional foods is steadily increasing and is projected to grow at a compounded annual growth rate of 8.5% from 2022 to 2032 (Franklin-Miller, 2024).

Thus, the research aimed to develop pineapple pomace powder (PPP) as a functional ingredient by determining the ideal drying method and applying it to the pineapple pomace with highest bioactive compounds and antioxidant activity. Developing functional ingredients from pineapple pomace offers multiple benefits, including addressing waste management challenges, improving the nutritional profile of processed foods by incorporating pomace as a functional ingredient, and contributing to solutions for health and nutrition problems in the Philippines and in other countries.

MATERIAL AND METHODS

The study employed a single-factorial design in determining the most effective drying method in preparing pineapple pomace powder (PPP). The treatment variables were cabinet- and freeze-drying while the response variables included drying characteristics, such as achieving a moisture content of 15.5% or lower in the shortest possible drying time. The ideal drying method was used in drying the pomace samples from three locally grown pineapple varieties, namely Smooth Cayenne, MD2, and Queen. The concentrations of bioactive compounds were analyzed and compared. The pomace sample with the highest concentration of bioactive compounds was selected for the development of a functional ingredient. The physicochemical properties of the developed PPP were then determined.

Raw materials and chemicals

Pineapple [Ananas comosus (L.) Merr.] pomace samples were collected from selected pineapple varieties. Mature and ripe pineapple samples, with approximately 70–80% of the eyes turned yellow, were sourced from different regions across the Philippines. The varieties used in the study include Smooth Cayenne from Calauan, Laguna; MD2 from South Cotabato, Mindanao; and Queen from Daet, Bicol. The selection of pineapple varieties was based on the variety commonly used in processing of pineapple juice in the Philippines.

The enzymes used such as ⍺-amylase (3,000 U/ml, thermostable), ⍺-amyloglucosidase (3260 U/ml), and protease (from Bacillus licheniformis) were obtained from Megazyme International Ltd. (Wickow, Ireland). Meanwhile, DPPH (2,2-Diphenyl-1-picrylhydrazyl), Folin-Ciocalteu’s phenol reagent, gallic acid, quercetin, TPTZ (2,4,6-Tri (2-pyridyl)-s-triazine), and Trolox ((±)-6-Hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid) were acquired from Sigma-Aldrich Ltd. (St. Louis, MO, USA). Lastly, ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) was purchased from Roche Diagnostics (Manheim, Germany). Other reagents and chemicals used were of analytical grade.

Sample preparation

The pineapple pomace samples were prepared based on the procedure described by Montalvo-González et al. (2018), with slight modifications. A total of 45 kg of each pineapple variety was washed, peeled, sliced, and subjected to a pulper finisher and filtered to separate the pomace from the juice, yielding a 15% pomace recovery. The pomace was washed with water at 55°C for 5 minutes with a water-to-pomace mass ratio of 2:1 to remove contaminants and achieve partial enzyme inactivation while preserving the bioactive compounds of the samples. After washing, 1 kg of pomace was pressed, collected, and dried using a cabinet-dryer (TEW Electric Heating Equipment Co. Ltd., Taiwan) and freeze-dryer (GECAR Machine Solution, Inc., Philippines). The collected dried samples were ground, sieved, and analyzed for drying characteristics and quantification of bioactive compounds.

Drying of pineapple pomace

The drying methods such as cabinet-drying and freeze-drying were used as treatment variables while the drying characteristics, such as achieving the target moisture content of 15.5% or lower in the shortest drying time were used as response variables. The target moisture value was based on the Codex Standard (152-1985) for wheat flour. The collected pineapple pomace samples were dried following the method described by Zubia et al. (2023), with slight modifications. These samples were divided into two sets. The first set was dried using a freeze-dryer with the primary drying stage set at a temperature of -30°C for 27 hours. The other set of pineapple pomace was further divided into three and subjected to cabinet-drying at 40°C, 50°C, and 60°C. The dried pineapple pomace samples were ground, sieved through a 30-mesh stainless steel sieve, packed in polyethylene plastic bags, labeled, and stored in the freezer at -20°C until further analysis.

Drying characteristics of pineapple pomace powder

The determination of moisture content was carried out using the air oven-drying method, following AOAC method 925.10 (AOAC, 2019). One (1) g of the sample was weighed in tared crucibles and dried in an oven at 100 ± 5°C for at least 5 hours or until a constant weight was achieved. The drying ratio, and average drying rate were calculated based on the equation used by Munjaji et al. (2022):

where: w1 is the weight of samples before drying (g), w2 is the weight of samples after drying (g), DR is the drying rate (g/min), Wr is the amount of moisture removed (g), T is the time taken (h), and Wd is the total dried  weight of sample (g).

Quantification of bioactive compounds content and antioxidant activity

Extraction of Bioactive Compounds. The pineapple pomace powder extracts (PPPE) were prepared using a combination of methods described by Bansod et al. (2023) and Zubia et al. (2023) with modifications. One (1) g of pineapple pomace powder was added to 5 ml of a solvent mixture consisting of a 50:50 (v/v) solution of ethanol and distilled water, acidified with citric acid to obtain a final pH of 4.5 in a 10-ml test tube. The solvent mixture was sonicated (Ultrasonic Cleaner 8892, Cole-Parmer, U.S.A.) for 30 minutes and centrifuged for 20 minutes at 4,000 rpm. The supernatant was filtered using Whatman^® No.1 filter paper (Sigma-Aldrich, U.S.A.). The extraction and filtration were repeated to collect a total of 20 ml of filtrate. The collected filtrate was quantitatively transferred to a 25-ml volumetric flask and diluted to the mark using the solvent mixture. Extracts were portioned into 2 ml aliquots and stored at -4°C until used for analysis.

Total phenolic content (TPC). The TPC of PPPEs was determined following the Folin-Ciocalteu assay using a UV-visible spectrophotometer (ISO, 2005 and Zubia et al., 2023) with slight modifications. Approximately, 0.15 ml sample extract was mixed with 0.75 ml of 10% (v/v) Folin-Ciocalteu reagent and 0.6 ml of 7.5% (w/v) sodium carbonate. The mixture was kept in a dark room at room temperature for 60 minutes. Blanks were prepared using distilled water instead of the PPPE. Gallic acid was used as a standard for the calibration curve. The absorbance was measured at 765 nm using a UV-visible spectrophotometer (UV 1900i, Shimadzu, Japan). The concentration of the sample was determined using the linear equation of the gallic acid standard curve, expressed as gallic acid equivalents per 100 g of dry weight (mg GAE/100g DW).

Total flavonoid content (TFC). The TFC of PPPEs was according to Chandra et al. (2014) method, using an aluminum chloride colorimetric assay, with slight modifications. Briefly, 0.75 ml PPPE was mixed with 0.75 ml of 2% aluminum chloride. The solution was incubated at room temperature for 60 minutes and the absorbance was measured at 420 nm wavelength. Quercetin was used as a standard for the calibration curve with a concentration of 1 to 100 μg/ml. The total flavonoid content of the extract was expressed as mg quercetin equivalents per 100 g of sample in dry weight (mg QE/100 g DW).

Ascorbic acid content (AAC). The AAC of PPPEs was measured according to Jose et al. (2022) procedure using a titration method. The samples were extracted for AAC analysis by mixing 0.5 g of PPP with 20 ml of 4% oxalic acid. The mixture was placed in a magnetic stirrer for 15 minutes, filtered using Whatman^® No.1 filter paper (Sigma-Aldrich, U.S.A.), and quantitatively transferred to a 25-ml volumetric flask. The collected filtrate was diluted with 4% oxalic acid. To prepare the ascorbic acid solution, 0.1 g of ascorbic acid was weighed and dissolved in 100 ml of 4% oxalic acid. The quantification of ascorbic acid was performed by mixing 5 ml of working standard in a 50-ml Erlenmeyer flask containing 10 ml of 4% oxalic acid. This solution was titrated against the dichlorophenolindophenol (DCPI) solution, which was prepared by dissolving 0.1 g sodium dichlorophenol indophenol in 100 ml distilled water. The endpoint was indicated by the appearance of a faint pink color. For sample analysis, 5 ml of sample extract was added to a separate flask containing 10 ml of 4% oxalic acid. The solution was titrated against the DCPI solution, and the appearance of a faint pink color indicated the endpoint. The ascorbic acid content of samples was caclulated using the equation below and expressed as mg ascorbic acid per 100 g of sample in dry weight (mg AA/100 g DW).

Total dietary fiber (TDF). The TDF of PPP was determined using enzyme-gravimetric method following the AOAC Method 991.43 (AOAC, 2000), with slight modifications. Approximately, 0.5 g of each sample was weighed and added in a dilution bottle with 50 ml of pH 6, 0.08M phosphate buffer and 50 μl α-amylase. The solution was placed in a hot plate and heated to 100°C for 40 minutes while stirring constantly to undergo gelatinization, hydrolysis and depolymerization of starch. After heating, the mixture was cooled to 60 °C for 30 minutes, added with 100 μl protease, and incubated for 30 minutes. The mixture was acidified to 4.0–4.7 using 0.5 N HCl, added with 200 μl α-amyloglucosidase, and incubated for 30 minutes. The mixture was filtered using a crucible lined with Celite (Sigma-Aldrich, U.S.A.) and a suction. The filtrate was transferred to a 500-ml beaker while the residue was washed with 15 ml each of 78% ethanol, 95% ethanol, and acetone twice. The dried residue was dried overnight at 100 °C. After drying, the residue was weighed and calculated for % IDF. Meanwhile, the filtrate was heated to 60°C for 30 minutes and added with four equal portions of heated (60°C) 95% ethanol. The mixture was filtered using Whatman^® No.1 filter paper (Sigma-Aldrich, U.S.A.). The residue was collected and dried overnight at 100°C. The weight of the dried residue was used for the calculation of SDF. The TDF was calculated by adding the obtained IDF and SDF values.

 2,2-Diphenyl-1-1 picrylhydrazyl (DPPH) radical scavenging activity. The DPPH radical scavenging activity of PPPEs was analyzed using the method described by Zubia et al. (2023) with slight modifications. The 0.75 ml of diluted extract was mixed with 0.75 ml of 120 µM methanolic solution of DPPH. The solution was allowed to stand for 30 minutes at room temperature in a dark room. The absorbance was measured at 517 nm with Trolox as the standard. A 1.5 ml of absolute methanol was used as a blank. The DPPH radical scavenging activity of the samples was expressed as mg Trolox equivalent per 100 g sample in dry weight (mg TE/100g DW).

Ferric-reducing antioxidant power (FRAP). The FRAP of PPPEs was determined using the method described by Zubia et al. (2023) and Castillo-Israel et al. (2020), with slight modifications. FRAP reagent was prepared by mixing the 300 mM acetate buffer with a pH of 3.6, 10 mM 2,4,6,-tripyridyl-S-triazine (TPTZ) solution, and 20 mM ferric chloride with a ratio of 10:1:1 (v/v/v). The solution was placed in the incubator for 30 minutes at 37°C. The diluted extract of 0.15 ml was mixed with 1.36 ml FRAP reagent and incubated for 5 minutes at 37 °C. Trolox was used as a standard and the absorbance was measured at 620 nm. The results were expressed as mg Trolox equivalents per 100 g of sample in dry weight (mg TE/100g DW).

2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity. The ABTS radical scavenging activity of PPPEs was determined using the method described by Zubia et al. (2023) with slight modifications. The ABTS solution was prepared by mixing 7 mM ABTS^●+ with 2.45 mM potassium persulfate solution with a ratio of 1:1. The solution was left to stand in a dark room for 16 hours and was diluted with distilled water to obtain an absorbance of 0.70 ± 0.02 at 734 nm. The assay was analyzed by adding 1.35 ml of the ABTS solution in a test tube containing 0.15 ml of diluted extract. The solution was incubated at room temperature for 15 minutes before measuring absorbance at 734 nm. Trolox was used as the standard (0.8 to 12 µg/ml) and of the results were expressed as mg Trolox equivalents per 100 g of sample in dry weight (mg TE/100g DW).

Physico-chemical properties of freeze-dried MD2 pineapple pomace powder

pH. The pH of the samples was measured by diluting 1 g of each sample with 10 ml distilled water using a pH meter (Milwaukee, USA) following the method adopted by Sifat et al. (2021) and AOAC method 973.41 (AOAC, 1998).

Titratable acidity. The titratable acidity of the samples was determined as described by Sifat et al. (2021) and AOAC method 942.15 (AOAC, 1998), with slight modifications. One (1) g of each sample was mixed with 10 ml distilled water in a beaker. The sample solution was titrated with 0.1N sodium hydroxide and 2 drops of phenolphthalein as indicator.  The % acidity was computed and reported as g of citric acid per 100 g of sample.

Water activity (Aw). The Aw was determined by filling the sample dish with approximately 2 g of sample and measuring Aw using a water activity meter (LabSwift-aw, Novasina, Lachen, Switzerland) following the method described by Zubia et al. (2023).

Total soluble solids (TSS). The TSS of the sample was measured in ^○Brix scale by placing small amount of reconstituted 1 samples in 10 ml distilled water into the glass prism of the handheld refractometer (Master-53 Atago, Tokyo, Japan) following the method described by Sifat et al. (2021).

Instrumental color. The color profile of the sample was measured using a handheld chromameter (CR-400 Chroma Meter, Konica Minolta, Japan) at 25°C based on the method described by Zubia et al. (2023) with modifications. The instrument was calibrated using a white color standard. Approximately 10 g of the samples were placed in a petri dish, and color readings were taken at different areas on the surface of the sample. Data were expressed according to CIELAB system where, L* indicates brightness from dark (0) to light (100), a* for redness (+) to greenness (-), and b* for yellowness (+) to blueness (-). The chroma (C*) and hue angle (H°) angle were calculated using the following equations:

Statistical analysis

All analyses were performed with at least three replicates and results were expressed as mean ± standard deviation (SD). Data were first subjected to Levene’s test to assess homogeneity of variance and the Shapiro-Wilk test for normality. Then, a one-way Analysis of Variance (ANOVA) was conducted with a significance level of 0.05. Tukey’s Honestly Significant Difference (HSD) test was used as a post-hoc analysis to identify which means significantly differed at the 95% confidence level. All statistical analyses were performed using Jamovi (Version 2.3, Jamovi Project, 2022).

RESULTS

Effect of drying methods on the drying characteristics of PPP

Drying pineapple pomace using different drying methods led to varying drying characteristics as shown in Table 1. Results showed that the moisture content and drying rate of freeze-dried samples were significantly different from those of samples dried in a cabinet-dryer at 40°C, 50°C, and 60°C. Among the drying methods used, freeze-drying had the highest drying rate and shortest drying time, taking just 27 hours to reach the target moisture content of 15.5% or lower. The cabinet-drying at 40°C had the longest drying time and did not meet the target moisture content.

Table 1. Drying characteristics of freeze-and cabinet-dried Smooth Cayenne pineapple pomace.

Note: Values are presented as mean ± standard deviation (SD). In each column, mean values with different superscripts indicate significant differences at (P < 0.05) (n=3).

Selection of pineapple variety based on bioactive compounds content and antioxidant activity

The selection of pineapple variety for developing a functional ingredient using pineapple pomace was based on the concentrations of bioactive compounds and antioxidant activity (Figure 1). Results indicate that the MD2 variety consistently surpassed the other two pineapple varieties, showing significantly higher TPC, TFC, AAC, TDF, and antioxidant activity.

The highest TPC was observed in MD2 and Queen pomace, with concentrations of 316.23 ± 25.18 mg GAE/100 g DW and 303.11 ± 8.61 mg GAE/100 g DW,  respectively, followed by Smooth Cayenne variety at 173.22 ± 11.94 mg GAE/100 g DW. The TFC of pomace also differed significantly among the varieties. The MD2 pomace had the highest TFC, with a concentration of 106.72 ± 9.35 mg QE/100 g DW, followed by Smooth Cayenne at 56.31 ± 5.42 mg QE/100 g DW, and Queen at 45.32 ± 2.93 mg QE/100 g DW.

The highest AAC was recorded in MD2 pomace, with a concentration of 38.95 ± 5.06 mg AA/100g DW, followed by Queen with 16.49 ± 0.98 mg AA/100g DW, and Smooth Cayenne with 14.52 ± 1.41 mg AA/100g DW.  This indicates that the AAC of MD2 pomace was significantly higher compared to that of Queen and Smooth Cayenne.

The highest TDF values were observed in MD2 and Smooth Cayenne, with concentrations of 48.61 ± 1.75% and 46.45 ± 0.99%, respectively, followed by Queen with a concentration of 41.18 ± 0.40%. The TDF contents of Smooth Cayenne and MD2 were significantly higher compared to Queen.

Furthermore, the highest antioxidant activity was observed in MD2 and Queen varieties, with concentrations of 150.56 ± 6.87, 395.40 ± 24.03, and 266.39 ± 11.09 mg TE/100g DW; and 157.93 ± 10.76, 389.62 ± 25.76, and 273.56 ± 26.18 mg TE/100g DW  for the DPPH, FRAP, and ABTS assays, respectively.  The trends in antioxidant activity, as measured through DPPH, FRAP, and ABTS assays, were consistent across the three varieties, demonstrating that both Queen and MD2 exhibited significantly higher antioxidant activity compared to Smooth Cayenne.

Figure 1. Total phenolic contents (mg GAE/100g DW), total flavonoid contents (mg QE/100g DW), ascorbic acid contents (mg AA/100g DW), total dietary fiber (%), DPPH radical scavenging activities, ferric-reducing antioxidant power, and ABTS radical scavenging activities (mg TE/100g DW) of freeze-dried pineapple pomace (n=3).

Physicochemical properties of freeze-dried MD2 pineapple pomace powder

The physicochemical properties of freeze-dried MD2 PPP is summarized in Table 2. Results showed that the freeze-dried MD2 PPP had a moisture content of less than 10% and low water activity. It was slightly acidic, with a pH below 4.6 and a minimal concentration of citric acid. In terms of color attributes, the freeze-dried MD2 PPP displayed a light yellow color with L* value approaching 100 and a positive b* value. Furthermore, the chroma and hue angle measurements showed low saturation and intensity of color.

Table 2. Physicochemical properties of freeze-dried MD2 pineapple pomace powder.

Note: Values are presented as mean ± standard deviation (SD) (n=3).

DISCUSSION

The drying parameters were critical factors influencing the quality of PPP. As indicated in the results, the freeze-drying method was significantly more effective than cabinet-drying in terms of drying characteristics. Freeze-drying not only achieved a significantly shorter drying time compared to cabinet-drying but also resulted in a higher drying rate. The difference in the drying process likely explains the variation in outcomes when drying pineapple pomace.

Freeze-drying had an advantage because the process did not directly expose the product to heat. As explained by Gaidhani et al. (2015), freeze-drying removes water as ice through sublimation, followed by desorption of bound water molecules. Sublimation occurs when ice transitions directly to vapor without passing through the liquid phase. In this process, the product is completely frozen at -30 °C, placed under deep vacuum, and dried as heat energy is applied, causing the ice to sublime.

In contrast, cabinet-drying removes water using heated dry air, typically at 60–80 °C, which circulates between the shelves in an enclosed compartment. This temperature often leads to thermochemical reactions, such as the Maillard reaction and caramelization. Additionally, the outer part of the pineapple pomace tends to dry first, while moisture remains in the inner parts, delaying the drying process of pineapple pomace. As a result, achieving the target moisture content at 60°C took 93 hours. A similar finding was reported by Shams et al. (2022) in their study comparing freeze-drying and cabinet-drying of button mushroom, where freeze-dried mushrooms exhibited lower moisture content than cabinet-dried ones. Furthermore, Jovanovic et al. (2020) demonstrated that freeze-drying preserves phytochemicals and their bioactivity in fruit and vegetable powders. Similarly, Zubia et al. (2023) reported high concentrations of TPC and CTC in freeze-dried bignay pomace.

In addition to the drying method, another important factor considered in the study was the variety of pineapple to be used to develop the functional ingredient. Yekoyada et al. (2021) showed that both variety and area of production influence the quality of pineapples. Factors such as genotype, environment, climate, soil characteristics and agricultural practices, all affect pineapple quality. The Smooth Cayenne, Queen, and MD2 cultivars all belong to Ananas comosus (L.) species, are key commercial pineapples. Smooth Cayenne and Queen are traditional pineapple cultivars, while MD2 is a modern cultivar developed as a selective cross between the two. These three varieties are known for their outstanding quality in terms of sweetness, color and aroma. In the Philippines, Smooth Cayenne is commonly grown in Laguna for local consumption, while MD2 and Queen are cultivated in Bicol and South Cotabato and are primarily used by large pineapple manufacturers for export as whole fruit, canned products, or juice. The PPP derived from these varieties varied in bioactive compound concentrations. The MD2 variety consistently surpassed the other two pineapple varieties, showing significantly higher TPC, TFC, AAC, TDF, and antioxidant activity. These findings align with Sun et al. (2016), which identified MD2 as an exceptional cultivar among 11 pineapple cultivars in terms of bioactive compounds.

In terms of TDF, the Smooth Cayenne and MD2 varieties were comparable, while the Queen had significantly lower values. This may be attributed to varietal differences and growing conditions, especially since the three varieties were sourced from different regions in the Philippines. The majority of the TDF in the samples was IDF, with values similar to those reported by Nguyen et al. (2024), who found 42.7 ± 0.3% IDF in pineapple pomace. Ideally, a ratio of 30–50% SDF and 50–70% IDF are recommended proportions for maximizing dietary fiber’s health benefits (Nagarajaiah and Prakash, 2016). Although the pineapple pomace did not meet these ideal proportions, it remained a good source of IDF. Nguyen et al. (2024), Kumari et al. (2020), Devi et al. (2013), and Selani et al. (2014) demonstrated this by incorporating pineapple pomace into biscuits, breads, cookies, and extruded products, respectively. This incorporation also enhanced the TPC, antioxidant activities, and TDF of the developed products.

The developed PPP, intended as a functional ingredient, was produced using freeze-drying with MD2 pineapple pomace. The resulting PPP had a moisture content of less that 10%, a water activity of below 0.85, and a pH of less than 4.6 , meeting the conditions necessary to inhibit microbial activity. These intrinsic properties contribute to an extended shelf life. The titratable acidity, reported as a percentage of citric acid, indicated that the acid flavor of the pineapple was concentrated during freeze-drying. According to Lu et al. (2014), the titratable acidity of whole pineapples was 0.73 %, 0.53 %, and 0.69 % citric acid for Smooth Cayenne, MD2, and Queen, respectively. On the other hand, the TSS of PPP was low, indicating negligible sugar content in the product. In terms of color, the freeze-dried MD2 PPP appeared light yellow.

CONCLUSION

The study identified freeze-drying as the most effective method for transforming pineapple pomace into a functional ingredient, offering superior drying characteristics. Among the three pineapple varieties evaluated, the MD2 variety demonstrated the greatest potential, consistently surpassing Smooth Cayenne and Queen in bioactive compound content and antioxidant activity. These findings highlight the viability of utilizing MD2 pineapple pomace in the production of functional ingredients. Furthermore, the results emphasize the potential of freeze-dried MD2 pineapple pomace to promote waste utilization and support the development of food products with substantial health benefits. 

ACKNOWLEDGEMENTS

The authors thank the Office of the Vice Chancellor for Research and Extension, University of the Philippines Los Baños (UPLB), for funding this project through the Basic Research Program. The authors also acknowledge the valuable contributions of Ms. Cendy Grace C. Boholst and Ms. Zyra Joy L. Aguilar in the preparation of raw materials.

AUTHOR CONTRIBUTIONS

Ms. Panganiban led the conceptualization of the experimental design, the conduct of the experiment, and the manuscript writing. Dr. Reginio Jr. served as a mentor throughout the research and writing process. Ms. Pagatpatan and Ms. Tengco contributed to the data collection, statistical analysis, and written report on the determination of the functional properties of freeze-dried pineapple pomace. All authors have read and approved the final manuscript.

CONFLICT OF INTEREST

The authors declare that they hold no competing interests.

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