Effects of Inulin Supplementation and Electron Beam Irradiation Assisted with Pregelatinization Process on the Quality of Pisang Awak Banana Powder

Featured Application

The integration of drum drying with electron beam irradiation offers a processing route to produce banana-based food powders with improved solubility, rapid reconstitution, and reduced gelation upon cooling. This study positions the approach as a model that can be extended to other starch-based powders requiring improved dispersibility, stability, and functional performance in diverse food applications.

Abstract

Unripe Pisang Awak banana is rich in resistant starch and dietary fiber, which are recognized for supporting digestive health and bowel regularity, yet its limited solubility restricts its application in instant beverages. This study aimed to improve the functional quality of Pisang Awak banana powder (PABP) through drum drying, electron beam irradiation, and inulin supplementation. PABP was produced by tray or drum drying and irradiated at 0, 2, 4, 6, and 8 kGy. Drum-dried powder treated with 8 kGy was identified as optimal and further fortified with inulin at 0–10% (w/w). Compared with tray drying, drum drying with irradiation markedly accelerated rehydration and enhanced solubility. Incorporation of 10% inulin produced the best overall performance, yielding faster reconstitution, greater solubility at 80–90 °C, and lower viscosity values across all pasting parameters. Collectively, the combination of drum drying, irradiation, and inulin addition yielded a banana powder with improved reconstitution and reduced gelation upon cooling. This optimized formulation demonstrates potential as a model for starch-based instant powders, while also contributing to the sustainable utilization of local banana resources.

1. Introduction

Pisang Awak Banana (Musa sapientum) or Namwa Banana is a traditional fruit widely found throughout Thailand and is known for its nutritional benefits that promote holistic health and well-being. Unripe Namwa banana contains a high total starch content of 78.19–81.82% [1], comprising 48–65% of resistant starch depending on cultivar, harvest timing, and processing methods [1,2]. The majority of the resistant starch in unripe bananas is classified as Resistant Starch Type II (RS2) [3], which has been shown to stimulate the secretion of mucin from gastric mucosal cells, which contributes to protecting the stomach lining [4]. Resistant Starch facilitates intestinal movement, decreases the time required for contents to pass through the gut, and promotes greater fecal output, contributing to the prevention of constipation [5].

In Thailand, Namwa Banana is extensively cultivated; however, local farmers frequently encounter low economic returns due to market oversupply [6], particularly from overripe bananas that surpass consumer demand. To mitigate this issue and enhance the value of surplus produce, several food entrepreneurs now market instant banana-based beverages in powdered form, intended for reconstitution with hot water. These products are promoted as functional foods with gut-supportive qualities. Banana powder is rich in resistant starch and dietary fiber, which acts as a prebiotic and supports digestive health while promoting bowel regularity. Moreover, formulations made from unripe banana powder have been shown to enhance gut microbiota abundance and diversity, fostering the growth of beneficial bacteria such as Lactobacillus and Bifidobacterium, which have mechanisms associated with improved gastrointestinal function [7]. Nevertheless, limited solubility remains a key drawback, often resulting in undesirable mouthfeel and throat irritation upon consumption, thereby diminishing consumer acceptance and reducing the product’s competitiveness in the functional food market.

Food irradiation technology, especially using electron beam (e-beam), is a non-thermal preservation method that extends shelf life and reduces microbial contamination, while retaining nutritional and sensory qualities [8]. The World Health Organization has affirmed the safety and nutritional adequacy of irradiated foods for human consumption, based on comprehensive evaluations of numerous toxicological, microbiological, and nutritional studies [9]. Previous studies have demonstrated that irradiation can modify the physicochemical properties of starch, including the reduction in crystallinity, lowering of gelatinization temperature, improvement in solubility, and enhancement of resistant starch content [10,11,12,13,14]. While the direct application of electron beam irradiation (EBI) on banana starch has limited research, numerous studies on other starches have demonstrated that EBI induces significant modifications at the molecular level, affecting physicochemical characteristics such as crystallinity, solubility, viscosity, and digestibility. For instance, wheat starch treated with 10 MeV EBI showed an increase in solubility from 15.19% to 50.48% and improved water/oil absorption, as well as reduced swelling but increased resistant starch content [15]. In addition to the use of irradiation technology to improve solubility in starch-containing food beverages, pregelatinization has been shown to lower the gelatinization temperature of starch, thereby facilitating starch swelling at reduced temperatures. This modification may help alleviate throat irritation during the consumption of banana powder-based beverages. Drum drying is a widely utilized thermal processing technique for the pregelatinization of starch. In this process, starch slurry is applied as a thin film onto the surface of one or two heated, rotating drums. The combined effects of heat and short residence time gelatinize the starch granules, which are subsequently dehydrated into flakes or powder. Drum-dried starch exhibits significantly reduced crystallinity, increased cold-water solubility, and enhanced swelling capacity relative to native starch. These functional attributes render it an ideal candidate for instant food and beverage applications, such as soups, sauces, and powdered drinks, where rapid rehydration and efficient thickening are required [16].

In recent years, there has been increasing interest in the development of healthy beverage products derived from natural plant sources, not only for the alleviation of specific health-related symptoms but also for the enhancement of functional properties. Among various approaches, the incorporation of prebiotics has emerged as an effective strategy to enhance the functional value of such products in response to consumer demand. Prebiotics are a type of dietary fiber that is not digested in the upper gastrointestinal tract but can selectively stimulate the growth and activity of beneficial probiotic microorganisms in the colon, thereby contributing to improved digestive health. Inulin, a well-known prebiotic, is highly water-soluble and thermally stable, making it a suitable ingredient for incorporation into functional health products [17]. Therefore, this study aims to develop a functional banana-based beverage enriched with inulin and improve solubility through electron beam irradiation, assisted with a pregelatinization process, to increase consumer convenience. This development is intended to elevate the quality of Thai banana-derived products to better meet the demands of modern consumers, support local banana farmers through value-added processing, and create new opportunities for health food entrepreneurs in the growing functional food market.

2. Materials and Methods

2.1. Preparation of Pisang Awak Banana Powder (PABP)

2.1.1. Pisang Awak Banana Puree Preparation

Pisang Awak Banana was obtained from Talad Thai fresh market (Pathum Thani province) at the mature stage of 2–3 [2]. The sliced bananas (1 cm thickness) were pretreated by immersing them in 0.5% (w/w) citric acid solution for 5 min and then rinsed with distilled water. The pretreated banana slices were chopped into small pieces and then blended in a blender for 1 min to obtain banana puree [18].

2.1.2. Tray Drying Method

Banana puree was uniformly spread onto stainless steel trays lined with food-grade non-stick sheets, maintaining a thickness of approximately 5–7 mm to ensure consistent drying. The samples were dried in a tray dryer at 75 °C until the moisture content was reduced to below 10% (wet basis). Upon completion of drying, the banana sheets were cooled to ambient temperature, ground using a laboratory-scale grinder, and sieved through a 60-mesh screen to obtain a fine powder. The resulting powder was stored in airtight containers at room temperature until further use [19,20].

2.1.3. Drum Drying Method

The banana puree was dried using a double-drum dryer with externally heated rotating drums maintained at a surface temperature of 140 °C [21]. The puree was continuously fed onto the gap between the two counter-rotating drums, forming a thin film on the heated drum surface. Upon completing one rotation cycle, the dried sheet was mechanically scraped off using a stationary blade attached to the dryer. The resulting banana sheet was cooled to room temperature, ground to a fine powder, and stored under the same conditions as the tray-dried samples.

2.2. Electron Beam Irradiation (EBI)

The EBI was conducted using a method adapted from previous work [22]. Each PABP sample (100 g) was packed in a polyethylene pouch (8 cm × 9 cm) and placed on a conveyor belt for continuous exposure to the electron beam accelerator at room temperature. The irradiation was performed at the Thailand Institute of Nuclear Technology (Public Organization), Pathum Thani, Thailand. The PABP samples, prepared by both tray drying (TD) and drum drying (DD), were irradiated with an electron beam at levels of 0, 2, 4, 6, and 8 kGy and designated as PABP-TD, PABP-TD2, PABP-TD4, PABP-TD6, PABP-TD8, PABP-DD, PABP-DD2, PABP-DD4, PABP-DD6, and PABP-DD8, respectively.

2.3. Physicochemical Properties

2.3.1. Rehydration Time

A 20 g sample was rehydrated in 200 mL of hot water at 90 °C. The mixture was stirred using a magnetic stirrer bar until fully dissolved, and the time required to dissolve completely was recorded as rehydration time [23].

2.3.2. Pasting Properties

A PABP suspension was prepared by mixing 3.5 g of PABP with 25 g of distilled water (based on a 14% moisture basis) in an aluminum canister. The pasting properties were analyzed using a Rapid Visco Analyzer (RVA-4500, Perten Instruments, Stockholm, Sweden) using AACC International Method 76-21.01 and ICC Standard No. 162 (STD1 pasting profile). The temperature profile was created by heating the sample from 50 to 95 °C at a rate of 12 °C/min, holding at 95 °C for 2.5 min, and subsequently cooling to 50 °C at the same rate [24,25].

2.3.3. Solubility Index

Fifty milligrams of PABP were mixed with 5 mL of water and incubated at 50, 60, 70, 80, and 90 °C for 30 min each. After incubation, the mixtures were centrifuged at 4000 rpm for 15 min. The resulting sediments were collected and dried in a hot-air oven at 110 °C for 5 h. The dried residues were then weighed, and the solubility index was calculated using the following equation [26].

$$\mathrm{Solubility}\mathrm{index}(\%)={\displaystyle \frac{\mathrm{weight}\mathrm{of}\mathrm{the}\mathrm{dissolved}\mathrm{solid}\mathrm{in}\mathrm{supernatant}\left(\mathrm{g}\right)}{\mathrm{weight}\mathrm{of}\mathrm{the}\mathrm{sample}\left(\mathrm{g}\right)}} \times 100$$

(1)

2.4. Statistical Analysis

A completely randomized design (CRD) with two replications was used in this experiment, with all measurements in triplicate (n = 3). Data were reported as mean ± standard deviation. Analysis of variance (ANOVA) and significant differences among means were determined using Duncan’s new multiple range test at a significance level of p < 0.05. Statistical analyses were conducted using SPSS for Windows (version 24.0; SPSS Inc., Chicago, IL, USA).

3. Results and Discussion

3.1. Effect of Electron Beam Irradiation Dose on Physicochemical Properties of PABP

Samples of PABP prepared using tray drying and drum drying methods were subjected to electron beam irradiation at doses of 2, 4, 6, and 8 kGy. The non-irradiated and irradiated powders were evaluated based on rehydration time, solubility, and pasting properties to identify the optimal preparation method and irradiation dose for further investigation.

3.1.1. Rehydration Times

The rehydration times of the irradiated PABP from tray drying and drum drying are presented in

Table 1. Rehydration time of PABP prepared by tray drying and drum drying, irradiated with electron beam at doses of 2, 4, 6, and 8 kGy.

Samples	Rehydration Time (mins) Mean ± SD (n = 2)	Percentage of Maximum Rehydration Time of Control Sample (%)
PABP-TD (control)	2.24 ab ± 0.07	100.00
PABP-TD2	2.23 a ± 0.02	99.55
PABP-TD4	2.12 c ± 0.05	94.64
PABP-TD6	2.04 d ± 0.03	91.07
PABP-TD8	1.53 e ± 0.03	68.30
PABP-DD	2.19 bc ± 0.01	97.77
PABP-DD2	1.97 d ± 0.04	87.95
PABP-DD4	1.49 e ± 0.03	66.52
PABP-DD6	1.38 f ± 0.05	61.61
PABP-DD8	1.27 g ± 0.03	56.70

^a–g Mean values in a column with different letters are significantly different (p ≤ 0.05). PABP = Pisang Awak banana powder, TD = Tray drying process, DD = Drum drying process.

. A significant reduction in rehydration time was observed with increasing irradiation dose in both drying methods (p < 0.05). Specifically, the rehydration time of tray-dried PABP decreased from 2.24 min (non-irradiated) to 1.53 min at 8 kGy, while drum-dried PABP showed a reduction from 2.19 min to 1.27 min under the same irradiation dose. These results indicate that drum drying gave a lower rehydration time compared to tray drying. When expressed as a percentage of the maximum rehydration time of non-irradiated PABP, drum-dried samples irradiated at 8 kGy exhibited rehydration times corresponding to 56.70%, whereas tray-dried counterparts reached 68.30%. The lower rehydration time observed in drum-dried samples can be attributed to the physical changes in starch granules caused by the rapid and high temperature dehydration process. Drum drying involves thin-film drying on a hot surface, resulting in extensive starch gelatinization and disruption of granular structure, which enhances the water absorption capacity and reconstitution rate [27]. In contrast, tray drying typically proceeds at lower drying rates and temperatures, leading to incomplete gelatinization and a denser, less porous product structure. Studies on starch-based materials have demonstrated that drum drying results in powders with enhanced rehydration and water absorption properties, primarily because the process induces irreversible swelling of starch granules and disrupts intermolecular hydrogen bonding within the starch molecules [28,29].

3.1.2. Solubility Index

According to the results presented in Figure 1, increasing the irradiation dose led to notable changes in the solubility index of PABP across all tested temperatures. All samples exhibited a progressive increase in solubility with rising temperature from 50 °C to 90 °C. This trend was particularly pronounced in drum-dried samples, especially at higher irradiation doses. For example, at a constant temperature of 60 °C, the solubility of tray-dried samples significantly increased from 31.92% at 2 kGy to 46.89% at 8 kGy (p < 0.05). In contrast, drum-dried samples already exhibited a higher solubility of 54.81% at 2 kGy, which further significantly increased to 59.27% at 8 kGy (p < 0.05). Similar findings have been reported in previous studies [30], where Majzoobi et al. (2011) demonstrated that drum-dried wheat starch exhibited significantly higher solubility and water absorption compared to its native counterpart, primarily due to gelatinization and granular disintegration occurring during the drum drying process. This phenomenon is attributed to direct conductive heat transfer between the starch slurry and the heated surface of the rotating drum, which enables rapid thermal penetration and facilitates starch gelatinization and disruption of crystalline regions, resulting in higher localized temperatures [31]. In contrast, tray drying utilizes indirect convective heat transfer through heated air at comparatively lower temperatures [32], which tends to preserve more of the native starch granule structure and consequently yields lower solubility under comparable conditions.

3.1.3. Pasting Properties

Table 2. Rapid Visco Analysis of PABP prepared by tray drying and drum drying, irradiated with electron beam at 2, 4, 6, and 8 kGy.

Drying Process/ Irradiation Dose	Mean ± SD (n = 2)
	Peak Viscosity (cP)	Trough Viscosity (cP)	Breakdown (cP)	Final Viscosity (cP)	Setback	Final Viscosity (cP)
PABP-TD	1023.14 a ± 17.24	976.13 a ± 17.53	45.27 d ± 0.86	1161.89 a ± 26.93	206.11 b ± 4.24	6.46 b ± 0.19
PABP-TD 2 kGy	630.83 c ± 10.98	568.18 c ± 23.01	70.95 b ± 2.15	674.79 c ± 10.53	107.26 d ± 2.36	5.68 c ± 0.12
PABP-TD 4 kGy	501.35 d ± 12.28	432.09 d ± 11.89	70.65 b ± 1.87	517.95 d ± 24.01	85.79 f ± 2.20	5.21 e ± 0.11
PABP-TD 6 kGy	453.48 e ± 10.23	360.31 e ± 8.90	79.70 a ± 1.51	381.89 f ± 14.66	74.61 g ± 1.68	5.42 de ± 0.22
PABP-TD 8 kGy	388.08 f ± 10.17	308.62 f ± 5.28	77.65 a ± 2.60	383.66 f ± 7.74	68.70 h ± 1.71	5.24 e ± 0.14
PABP-DD	759.21 b ± 19.66	718.49 b ± 15.16	39.36 e ± 0.61	1128.68 b ± 18.31	387.29 a ± 4.09	7.03 a ± 0.09
PABP-DD 2 kGy	309.45 g ± 10.02	294.30 f ± 5.79	11.12 g ± 0.24	419.07 e ± 9.29	128.29 c ± 3.68	5.59 cd ± 0.10
PABP-DD 4 kGy	231.60 h ± 6.69	208.03 g ± 1.94	25.23 f ± 0.29	303.78 g ± 5.75	95.71 e ± 2.24	3.96 f ± 0.13
PABP-DD 6 kGy	210.26 i ± 1.75	167.34 h ± 2.42	44.35 d ± 0.51	250.66 h ± 5.43	79.00 g ± 2.41	3.30 g ± 0.05
PABP-DD 8 kGy	183.04 j ± 6.78	131.07 i ± 3.17	55.84 c ± 0.74	190.10 i ± 3.73	58.31 i ± 2.02	2.25 h ± 0.05

^a–j Mean values in a column with different letters are significantly different (p ≤ 0.05). PABP = Pisang Awak banana powder, TD = Tray drying process, DD = Drum drying process.

summarizes the pasting properties of non-irradiated and irradiated PABP. A marked decrease in the peak was observed with an increasing irradiation dose. Specifically, the peak viscosity of PABP irradiated at 8 kGy decreased from 1023.14 cP to 388.08 cP in tray-dried samples and from 759.21 cP to 183.04 cP in drum-dried samples. Final viscosity followed a similar downward trend, though irradiated tray-dried samples consistently exhibited higher values than drum-dried counterparts at the same dose. These reductions in peak and final viscosity were statistically significant (p < 0.05) and are likely due to irradiation-induced degradation and structural alterations of starch granules. This is consistent with the findings of Trinh and Nguyen (2020) [11], who reported that electron beam irradiation of maize starch at doses ranging from 0 to 7 kGy resulted in starch depolymerization, formation of cross-linkages, and fragmentation of large crystalline regions into smaller ones. Furthermore, peak time decreased with increasing irradiation dose, suggesting faster gelatinization of starch in the irradiated samples. The breakdown viscosity of irradiated PABP exhibited distinct trends depending on the drying method. In drum-dried samples, breakdown viscosity initially decreased from the non-irradiated control to 2 kGy, followed by an increase at higher irradiation doses of 2 to 8 kGy. In contrast, tray-dried samples showed a continuous increase in breakdown viscosity with increasing irradiation dose. When comparing drying methods at the same irradiation levels, irradiated PABP from the drum dryer consistently exhibited higher breakdown values than those from the tray dryer. These differences suggest that drum drying may enhance the susceptibility of irradiated starch to shear thinning during heating. This observation is consistent with the findings of Brasoveanu et al. (2013) [33], who reported enhanced molecular fragmentation and shear sensitivity in corn starch irradiated with electron beams at doses up to 7 kGy. Interestingly, all pasting parameters of PABP samples obtained from the tray dryer were higher than those from the drum dryer at equivalent irradiation doses, with the exception of setback viscosity, which exhibited the opposite trend. The higher setback values observed in drum-dried, pregelatinized starches may reflect a greater tendency for retrogradation, likely due to the increased molecular mobility and structural disruption during drum drying. This finding aligns with previous reports indicating enhanced re-association of starch chains in drum-dried samples [34]. Collectively, these observations support the hypothesis that electron beam irradiation combined with drum drying exerts a synergistic effect on starch structure. Drum drying with electron beam irradiation at 8 kGy was therefore selected for subsequent PABP preparation, as it provided the shortest rehydration time, highest solubility index, and improved pasting behavior, while minimizing gel formation upon reconstitution.

3.2. Effect of Inulin Supplementation Level on Physicochemical Properties of PABP

This part of the study aimed to enhance the functional properties of banana-based beverages by incorporating inulin into drum-dried PABP irradiated at 8 kGy, a condition selected based on prior findings. Inulin was incorporated at concentrations ranging from 2.5% to 10%, and its effects on the solubility index and rehydration time of both tray-dried and drum-dried PABP were investigated.

3.2.1. Rehydration Time and Solubility Index

According to the results presented in

Table 3. Rehydration Time and Solubility Index of Irradiated (8 kGy) Tray-Dried and Drum-Dried PABP as Affected by Inulin Concentration.

Samples	Mean ± S.D. (n = 2)
	Rehydration Time (Min)	Solubility Index (%) 90 °C
PABP-TD 0%	1.5567 a ± 0.04	61.95 i ± 0.90
PABP-TD 2.5%	1.5367 a ± 0.04	66.12 h ± 1.64
PABP-TD 5%	1.4300 b ± 0.04	69.45 g ± 1.75
PABP-TD 7.5%	1.3500 c ± 0.04	72.20 ef ± 1.81
PABP-TD 10%	1.3267 cd ± 0.03	76.60 c ± 1.43
PABP-DD 0%	1.3167 cd ± 0.04	70.49 fg ± 1.13
PABP-DD 2.5%	1.3033 cde ± 0.04	72.93 de ± 1.53
PABP-DD 5%	1.2867 de ± 0.02	74.94 cd ± 0.42
PABP-DD 7.5%	1.2533 ef ± 0.02	81.44 b ± 2.06
PABP-DD 10%	1.2067 f ± 0.02	84.53 a ± 0.46

^a–i Mean values in a column with different letters are significantly different (p ≤ 0.05). PABP = Pisang Awak banana powder, TD = Tray drying process, DD = Drum drying process.

, the incorporation of inulin had a significant effect on both the rehydration time and the solubility index at 90 °C for tray-dried and drum-dried PABP. The samples supplemented with 10% inulin exhibited the highest solubility values in both drying methods. Comparing the solubility index values across different inulin supplementation levels between tray drying and drum drying methods, it was evident that drum drying was more effective in enhancing the solubility of raw PABP at all levels of inulin addition. Concurrently, the rehydration time decreased with higher levels of inulin in both drying methods. Similar observations were reported by Koçer (2022) [35], who demonstrated that inulin addition improved powder dispersibility and reduced caking tendencies. These findings align with the present study, in which inulin incorporation markedly enhanced rehydration rates and solubility indices of PABP, particularly in drum-dried PABP formulations. This effect results from the hydrophilic nature of inulin, which possesses a strong affinity for water and promotes rapid hydration by forming a permeable layer around powder particles, thereby minimizing agglomeration and facilitating efficient water penetration [36,37]. This improvement is particularly advantageous for the development of instant functional banana beverages, as it enhances preparation convenience and consumer usability.

3.2.2. Pasting Properties

The addition of inulin had a significant impact on the pasting characteristics of both drum-dried and tray-dried PABP irradiated at 8 kGy, as summarized in

Table 4. Pasting Properties of Irradiated (8 kGy) Tray-Dried and Drum-Dried PABP as Affected by Inulin Concentration.

Drying Process/ Irradiation Dose/% Inulin	Mean ± S.D. (n = 2)
	Peak Viscosity (cP)	Trough Viscosity (cP)	Breakdown (cP)	Final Viscosity (cP)	Setback	Final Viscosity (cP)
PABP-TD 0%	377.37 a ± 5.74	305.68 a ± 4.39	75.77 a ± 3.00	370.22 a ± 7.63	64.69 a ± 4.45	5.07 c ± 0.31
PABP-TD 2.5%	292.52 b ± 1.27	251.53 b ± 1.30	40.35 c ± 2.33	314.28 b ± 5.85	64.13 a ± 1.37	5.23 c ± 0.14
PABP-TD 5%	269.11 c ± 3.25	239.78 c ± 6.60	28.95 d ± 2.64	295.12 c ± 3.57	61.11 a ± 0.98	5.53 b ± 0.07
PABP-TD 7.5%	249.88 d ± 3.86	214.43 d ± 3.68	30.32 d ± 1.03	270.72 d ± 0.73	54.59 b ± 1.44	5.74 b ± 0.13
PABP-TD 10%	221.96 e ± 1.41	198.61 e ± 3.63	21.82 e ± 3.00	251.14 e ± 6.23	51.45 b ± 2.51	6.00 a ± 0.19
PABP-DD 0%	177.93 f ± 8.33	117.11 f ± 15.00	59.96 b ± 7.35	173.99 f ± 20.78	54.92 b ± 3.96	2.19 d ± 0.09
PABP-DD 2.5%	153.61 g ± 3.93	102.60 g ± 4.79	55.52 b ± 3.76	148.79 g ± 1.61	49.89 bc ± 1.61	1.79 e ± 0.03
PABP-DD 5%	139.70 h ± 6.11	91.45 h ± 2.32	45.86 c ± 1.49	140.65 gh ± 2.83	46.38 cd ± 1.05	1.77 e ± 0.08
PABP-DD 7.5%	121.44 i ± 3.84	85.96 h ± 3.24	32.28 d ± 1.06	129.30 hi ± 3.96	44.24 d ± 3.96	2.35 d ± 0.03
PABP-DD 10%	111.27 j ± 3.07	82.94 h ± 3.44	21.19 d ± 3.61	125.00 i ± 3.84	37.46 e ± 3.49	1.65 e ± 0.03

^a–j Mean values in a column with different letters are significantly different (p ≤ 0.05). PABP = Pisang Awak banana powder, TD = Tray drying process, DD = Drum drying process.

. A progressive decrease in peak viscosity was observed with increasing inulin concentrations, with tray-dried samples exhibiting generally higher viscosity values than drum-dried counterparts at equivalent inulin levels. For instance, tray drying with 8 kGy irradiation and non-inulin supplementation resulted in the highest peak viscosity (377.37 ± 5.74 cP), whereas drum drying with 10% inulin supplementation at the same irradiation level yielded the lowest peak viscosity (111.27 ± 3.07 cP). Trough viscosity and final viscosity followed the same decreasing trend. Additionally, the lower viscosity observed in drum-dried PABP compared to tray-dried samples can be explained by the more extensive gelatinization and structural disruption induced during drum drying. This process involves conductive heat transfer and high surface contact temperatures, leading to greater degradation of starch granule integrity and reduced pasting performance. The reduction in viscosity because of the increase in inulin concentration may be attributed to the partial substitution of starch with inulin, thereby decreasing the overall starch content available for swelling and viscosity development. The breakdown viscosity also significantly decreased with increasing inulin concentration. For instance, the tray drying sample irradiated at 8 kGy without inulin supplementation exhibited the highest breakdown value (75.77 ± 3.00 cP), whereas the tray drying with 10% inulin supplementation under the same irradiation level showed the lowest breakdown value (21.82 ± 3.00 cP). The reduction in breakdown viscosity with increasing inulin concentration may result from the formation of hydrogen bonds between inulin, starch, and water molecules, which disrupt intra-molecular hydrogen bonding among starch chains, particularly amylose, thereby reducing granule disintegration during heating [38]. In addition, the setback viscosity, which is associated with retrogradation and gel formation during the cooling phase, also declined as the inulin level increased. For example, tray drying with 8 kGy irradiation without inulin addition showed the highest setback value (64.69 ± 4.45 cP), while tray drying with 10% inulin yielded the lowest (37.46 ± 3.49 cP). This reduction may be explained by the formation of a hydration layer around starch granules by inulin molecules, which hinders the reassociation of amylose chains and consequently delays retrogradation. These results are consistent with previous studies indicating that increasing inulin concentrations lead to a gradual rise in pasting temperature, along with significant reductions in peak viscosity, breakdown, and setback values [39]. These findings indicate that inulin supplementation enhances the suitability of PABP for instant beverage applications.

In addition to physicochemical properties, previous studies indicate that both electron beam irradiation and inulin supplementation may influence sensory and nutritional attributes. For example, Trinh and Nguyen (2020) observed that high-dose irradiation of maize starch powders led to noticeable darkening, suggesting potential effects on product color [11]. Similarly, Michalska-Ciechanowska et al. (2020) reported that inulin addition in juice powders helped preserve color and bioactive compounds, including phenolics and antioxidant capacity [40]. Other work has shown that inulin can alter sweetness, creaminess, and mouthfeel in starch- or dairy-based systems [41,42]. These findings suggest plausible impacts of irradiation and inulin beyond functionality, underscoring the need for future evaluation of sensory attributes and consumer perception in PABP-based formulations.

4. Conclusions

This study demonstrated that the functional and physicochemical properties of PABP can be enhanced through drum drying, electron beam irradiation, and inulin supplementation. Drum drying yielded shorter rehydration times and higher solubility than tray drying. Increasing irradiation dose, particularly to 8 kGy, further improved rehydration and solubility while reducing viscosity parameters, indicating enhanced dispersibility. Drum-dried PABP irradiated at 8 kGy was identified as optimal and subsequently fortified with 10% inulin, exhibiting the most improved physicochemical profile, with rapid rehydration, high solubility, and reduced gelation upon cooling. These findings provide a basis for developing banana-based powders with improved reconstitution for customer convenience, while the incorporation of inulin provides an additional nutritional benefit as a recognized dietary fiber. While the present work focused on physicochemical characterization, further studies are needed to investigate nutritional and sensory aspects to fully establish the application potential of such formulations.