Materials

White rice, mung beans, and other raw materials (onion, garlic, tomatoes, cooking oil, iodized salt, and fish sauce) were bought from a certified food supplier in Manila, Philippines. Horseradish leaves and dried smoked herring were bought from a local distributor in Imus, Cavite, Philippines. Mylar bags and oxygen absorbers were obtained from EntrePouch (Manila, Philippines), a certified supplier of food-grade packaging materials, to maintain product integrity during storage.

Ingredients preparation

Dried mung beans (2.2 kg) were washed to remove floating beans and other foreign materials. The beans were then presoaked in 4 L of water for 3 min, drained, and boiled in 3.5 L of water for 20 min until tender. After boiling, the water was drained from the mung beans. Concurrently, 1 kg of dried smoked herring was deboned, yielding 350 g of fish meat for use in the dish. Garlic (150 g) and onions (60 g) were peeled and chopped. Tomatoes (450 g) were halved, de-seeded, and cut into 1 cm cubes. Horseradish leaves (110 g) were separated from the stems and prepared for inclusion in the recipe.

A 10 L stainless steel cooking vessel was preheated until residual moisture was eliminated. Subsequently, 150 mL of cooking oil was heated, and chopped onions were sautéed until partially translucent. Minced garlic was then added and sautéed with the onions until aromatic. Deboned, dried, smoked herring was incorporated and cooked until the edges became crisp. Chopped tomatoes were added and sautéed until softened. Pre-drained mung beans were then introduced and mixed thoroughly to ensure uniform incorporation of all ingredients. Two liters of water, 50 mL of fish sauce, and 150 g of iodized salt were added to the mixture and stirred to enhance flavor. The mixture was simmered for 5 min at 80 ± 2°C, after which horseradish leaves were added and further simmered at 80 ± 2°C for 2 min until slightly tender. The prepared sautéed mung bean mixture was transferred into 3 L microwave-safe containers and allowed to cool at room temperature. Separately, 1 kg of white rice was washed until the rinse water was clear and subsequently cooked over low heat with 1,250 mL of water for 15 min, until an al dente texture was achieved. The cooked rice was transferred into a 3 L microwave-safe container and allowed to cool prior to further use.

Freeze-drying of rice and sautéed mung bean meal

Freeze-drying process was done at Freeze Dry Manila, Quezon City, Metro Manila, Philippines. Boiled rice and sautéed mung beans with horseradish leaves and dried smoked herring were separately stored in the freezer at –5°C for 24 hours prior to freeze drying. Boiled white rice (4.297 kg) and sautéed mung beans with horseradish leaves and dried smoked herring (4.914 kg) were freeze-dried using Harvest Right Home Freeze Dryer in Large size. Primary drying or sublimation phase was done at a shelf temperature of –30°C for 10 hours. Secondary drying or desorption phase was done at 50°C for 5 hours. Both the sublimation and desorption phase were set at a chamber pressure of 300 mTorr. The post-dry weights of the white rice and sautéed mung beans with horseradish leaves and dried smoked herring were 1.327 kg and 1.383 kg, respectively.

Packaging

The freeze-dried instant rice and mung bean meal was vacuum packed in 15 × 25 cm single serving aluminum and nylon stand up mylar bags with vacuum pressure of 80 mbar and heat seal temperature of 150°C. Each pack contains 1 g pack of oxygen absorber, 49.4 g freeze dried rice, and 67.6 g freeze dried sautéed mung beans with horseradish leaves and dried smoked herring to yield 1 serving of sautéed mung bean (243 g) [25] computed using the drying ratio of 3.6:1. Drying ratio is the ratio of the pre-dried weight of the cooked food and its post-dry weight [26]. After freeze drying, the white rice decreased its weight from 4.297 kg to 1.327 kg. Moreover, the sautéed mung beans with horseradish leaves and dried smoked herring decreased their weight from 4.914 kg to 1.383 kg. The drying ratios of white rice and sautéed mung beans with horseradish leaves and dried smoked herring were 3.2:1 and 3.6:1, respectively. When rehydrated with water, 49.4 g of freeze-dried rice yielded 1 cup of rice (160 g) and 67.60 g freeze-dried sautéed mung bean yielded 1 serving of sautéed mung bean [27].

Sampling and sample size

For microbiological analysis, the freeze-dried product was analyzed in triplicate (n = 3) to ensure reliability and reproducibility of results.

For physicochemical, proximate, and micronutrient analyses, single representative samples (n = 1) were analyzed to obtain baseline compositional data.

For sensory evaluation, a total of 50 untrained consumer-type panelists were selected using purposive sampling. Each participant evaluated two samples: the control (traditionally prepared rice and Ginisang Monggo) and the experimental (freeze-dried rice and Ginisang Monggo) product.

All samples were immediately sent to the respective laboratories for microbiological, proximate, and nutritional analyses. Samples for sensory evaluation were stored at room temperature at 25°C and were evaluated after securing the microbiological results to ensure safety for consumption.

Microbiological analysis

The microbiological analyses were performed on the freeze-dried instant rice and mung bean meal by Qualibet Testing Services Corporation, Quezon City, Metro Manila, Philippines. The methods used were pour plate method [28] for the aerobic plate count (APC), yeast and mold count, and Compact Dry from Nissui Pharmaceutical Co., LTD. for the Escherichia coli, Salmonella, and Staphylococcus aureus. The results are expressed in colony forming unit per gram (cfu/g) of product.

Physicochemical and proximate analysis

The proximate analyses were performed on the freeze-dried instant rice and mung bean meal by Qualibet Testing Services Corporation, Quezon City, Metro Manila, Philippines. Fat, protein and moisture content, water activity, and ash content were measured based on the standard AOAC methods [29]. The total energy content is computed using the Atwater factor based on the total protein content, fat content, and carbohydrate content of the sample.

Nutritional evaluation

The nutritional evaluation was performed on the freeze-dried instant rice and mung bean meal by Intertek Testing Services Philippines, Inc., Makati City, Metro Manila, Philippines. Iron content was determined using atomic absorption spectrometry (AAS). Vitamin A was determined by high performance liquid chromatography (HPLC). Both analyses were based on the laboratory’s in-house procedure.

Sensory evaluation

One package of the freeze-dried, vacuum-sealed product was rehydrated using 181.9 mL of boiling water measured at 100 ± 2°C using Cooper-Atkins 322-01-1 5 1/2” Probe Thermometer. It was stirred for 20 seconds and allowed to stand for 10 min while covered. Both the rehydrated freeze-dried product and the control sample (traditional rice and sautéed mung bean meal) were cooled to 45°C prior to serving to ensure consistency during evaluation. Sensory acceptability was assessed by panelists based on specific attributes, including appearance, color, aroma, taste, texture, and overall acceptability, using a nine-point hedonic scale (1 = dislike extremely to 9 = like extremely) [30].

A total of fifty panelists were recruited through purposive sampling and randomly assigned, in accordance with predefined inclusion and exclusion criteria. Eligible participants were Filipino citizens, aged 19 years and older, with no known food allergies or sensitivities related to the product. Individuals who did not meet the inclusion criteria, voluntarily withdrew, or failed to complete the sensory evaluation were excluded from the study. Participation was voluntary and supported by an informed consent process, which emphasized the participants’ right to decline or withdraw at any stage without penalty. To maintain respondent anonymity, alphanumeric codes were assigned, and no identifying information was recorded on the evaluation forms.

Ethical consideration

The sensory evaluation was conducted in accordance with ethical standards for research involving human participants and was approved by De Los Santos Medical Center Research Ethics Committee [Ethics Review Board (ERB) Protocol Number 2025-020], Quezon City, Manila, Philippines. All participants provided informed consent prior to participation and were informed of their right to withdraw from the study at any time without penalty. Individuals with known food allergies or sensitivities were excluded to ensure participant safety. Participant anonymity and data confidentiality were maintained through the use of alphanumeric codes, and all data were used solely for research purposes.

Statistical analysis

To determine the acceptability of the freeze-dried product compared to the traditional product, a two-tailed paired t-test was performed at a significance level of p < 0.05 [30].

Microbiological analysis

The microbiological quality of the freeze-dried instant rice and mung bean meal is summarized in Table 1. The APC was estimated at 70 cfu/g. Counts of E. coli, S. aureus, and yeast and molds were all below 10 cfu/g. Salmonella spp. was not detected in the analyzed samples.

Physicochemical and proximate analysis

The proximate composition of the freeze-dried instant rice and mung bean meal, expressed on a dry weight basis per 100 g of sample, is presented in Table 2. The analysis revealed an ash content of 4.20%, crude protein content of 21.69%, fat content of 7.03%, moisture content of 1.55%, and total carbohydrates (calculated by difference) of 65.53%. The estimated total energy value of the product was 412.15 kcal per 100 g of dry sample. Water activity values were at 0.10.

The macronutrient composition of the freeze-dried instant rice and viand is presented in Table 3. On a per-serving basis (117 g individual pack), the product contained 76.67 g of carbohydrates, 25.38 g of protein, and 8.23 g of fat.

Vitamin A and iron analysis

The micronutrient composition of the freeze-dried instant rice and viand is presented in Table 4. Per 117 g serving (individual pack), the product contained 0.35 mg of iron and 10.56 μg retinol equivalents (RE) of vitamin A.

Sensory evaluation

The sensory acceptability of the freeze-dried rice and sautéed mung bean meal was assessed using a nine-point hedonic scale, where 9 corresponded to “like extremely” and 1 to “dislike extremely”. The mean scores and standard deviations for each sensory attribute are presented in Table 5. Overall, the product was deemed acceptable by the panelists across all evaluated attributes, with most scores falling within the “like moderately” range (score of 7), indicating favorable sensory perception.

The sensory evaluation revealed statistically significant differences (p  <  0.05) between the control and the freeze-dried rice and sautéed mung bean meal for appearance, color, taste, and overall acceptability, as presented in Table 6. These results indicate perceptible changes in these attributes attributable to the freeze-drying process. In contrast, no significant differences were observed for aroma and texture between the two samples.

Safety of the food product

Based on the guidelines on the microbiological requirements and assessment of certain prepackaged processed food products [31], the acceptable limits for APC, S. aureus, and yeast and mold count are at ≤ 10² cfu/g; ≤ 10 cfu/g for E. coli, and negative for Salmonella spp. The microbiological results showed low microbial counts and compliance to safety standards, thus considering the product safe for consumption. This low microbial count could be attributed to the heating pre-treatment, low water activity from freeze-drying and absence of oxygen due to vacuum packaging.

Dehydration and freeze-drying (lyophilization) is are effective preservation method as it significantly lowers water activity, thereby inhibiting microbial growth and extending shelf life [32–34]. However, freeze-drying primarily suppresses microbial activity rather than eliminating spoilage organisms entirely [35, 36]. Therefore, pre-treatments, such as use of sodium chloride (NaCl), blanching or heat treatment, and post treatment, such as vacuum packaging, are used to further avoid health risks.

Vacuum packaging removes air or oxygen before sealing, thereby slowing oxidative reactions and inhibiting aerobic microbial growth. This is particularly beneficial for foods that are prone to spoilage when exposed to air. By limiting oxygen availability, vacuum sealing reduces the growth of most spoilage organisms, improving food safety and quality [37, 38].

Nutritional quality of the product

The moisture content of the sample was 1.55% while water activity was 0.10. This is the residual moisture content left after freeze drying along with the oil used for sauteing, which was not removed during lyophilization. Freeze drying is known to significantly decrease moisture content and water activity [24, 39, 40]. The low moisture content reduces microbial risk, ensures better shelf stability, and facilitates transportation due to the reduced weight. This characteristic is ideal for food products’ long-term storage and for disaster response, as it can be transported easier via land, air or sea for distribution to areas affected by disaster.

The ash content of the sample indicated the presence of various minerals. While not a nutrient itself, ash is an indicator of the presence of various essential minerals like sodium, potassium, calcium, magnesium, etc. The value 4.20% could be from the sodium from the salt and fish sauce added to the product as flavoring, iron (as shown in Table 2), and other minerals from the mung bean, rice, and other ingredients. These minerals are essential for daily body functions like muscle function, oxygen transport, electrolyte balance, and bone health, which could contribute to ensuring food security in impoverished areas [16], especially during times of disasters where food and nutrition are scarce. The sample contains 65.53% carbohydrates, aligning with the Department of Science and Technology-Food and Nutrition Research Institute (DOST-FNRI) recommended carbohydrate intake of 55–75% for adults 19 years old and up. This high carbohydrate percentage is from rice and mung beans, as both are good sources of carbohydrates—starch and fiber [41]. The high carbohydrate content provides an instant yet nutritious source of energy for survival situations such as calamities. It also contained 21.69% protein, significantly exceeding the recommended 10–15% of total protein-based energy requirement for adults based on the Philippine Dietary Reference Intakes (PDRI) [42]. Mung beans and smoked herring (tinapa) [43] are good sources of protein. This high protein content makes the product beneficial for preserving muscle mass and supporting immune function during times of crisis. Furthermore, the fat content of the freeze-dried instant rice and mung bean meal was 7.03%. The low-fat profile of the product makes it less prone to lipid oxidation [44] and be beneficial to people with fat restricted diets.

The computed total energy through Atwater factor was 412.15 kcal per 100 g, which is moderately high in relation to the PDRI [42] where males aged 19–59 years old require 2,420–2,510 kcal per day, and female adults need 1,870–1,930 kcal per day. This is advantageous for emergency nutritional needs, since consuming 117 g serving packs containing 482.21 kcal paired with food items that are good sources of iron and vitamin A or by future micronutrient enrichment can fulfil the daily required energy during times of calamities. The acceptable carbohydrate, protein, and fat energy distribution for Filipino adults are 55–75%, 10–15%, and 15–30%, respectively. Based on its macronutrient distribution, the product was high in protein, within the acceptable carbohydrate range, and acceptable in fat content based on its total energy content.

The proximate composition of the freeze-dried instant rice and mung bean meal was notably preserved, consistent with findings for most freeze-dried foods, where nutrient retention remains high [39, 45–47]. Owing to its nutrient-dense profile, this product has strong potential as a primary meal component in short- to medium-term emergency feeding programs. This presents a significant advantage over commonly distributed relief foods, such as instant noodles and canned goods [48], which are typically less nutrient-dense.

Based on the recommended nutrient intake [42], the product had low adequacy for the two micronutrients, iron and vitamin A. The ingredients used for producing the freeze-dried instant rice and mung bean meal had low vitamin A ranging from 0 to 80 μg RE [49]; however, despite the low vitamin A content and despite undergoing processing, it is notable that iron and vitamin A were retained due to freeze drying similar to previous studies wherein vitamins, minerals and other phenolic compounds were retained [33, 50, 51]. Fortification strategies, particularly for iron and vitamin A, should be considered to improve the nutritional value of the meal and better support the micronutrient needs of affected populations during disasters.

Sensory quality of the product

Sensory attributes such as appearance, color, aroma, taste, and texture are critical determinants of consumer acceptance and overall product quality in food products. Appearance was rated slightly above “like slightly”, indicating that the product’s visual quality was acceptable but with room for improvement. Similarly, color was deemed somewhat acceptable, though it did not elicit strong appeal from the panelists. Aroma received ratings between “like moderately” and “like very much”, suggesting that aromatic compounds were effectively retained, producing a desirable scent comparable to the control. Taste was also rated within this range, indicating that the flavor was largely preserved, albeit slightly less intense than the fresh product. Texture ratings similarly fell between “like moderately” and “like very much”, demonstrating successful rehydration and retention of a satisfactory mouthfeel, an important quality in freeze-dried meals. Overall acceptability was close to “like moderately”, suggesting that while the product was generally well-received, minor deficiencies in appearance and color slightly reduced its overall sensory appeal.

The control product’s superior appearance and color aligned with findings by Uscanga et al. (2021) [52], who reported that higher shelf temperatures in freeze-drying can produce perceivable color changes in orange-based products, detectable through colorimetric measurements expressed in ∆E values. These observations underscore the importance of optimizing freeze-drying parameters to maintain visual quality.

The reduced taste scores in the freeze-dried sample may be due to volatile flavor compound loss. Although freeze-drying generally preserves flavor better than conventional hot-air drying, research on broccoli, carrots, and oranges indicates that aroma is often diminished—likely due to a decrease in volatiles during dehydration [41].

Aroma and texture did not differ significantly between samples. This is consistent with the results for freeze-dried orange snacks, where adjustments to pressure and temperature largely influenced color and crispness, while aroma and texture remained relatively stable [53]. Similarly, studies on freeze-dried berries suggest that when optimal shelf conditions are used, texture can be well preserved, even under varying temperatures [54].

Despite the significant differences between the control and freeze-dried product, overall acceptability of the developed product remained respectable as palatability and color were retained due to freeze-drying, similar to yogurts made from freeze-dried soybean peel powder and mung bean peel powder [46] and consumer acceptance of blackcurrant snacks [24, 47]. However, to approach the control’s acceptance levels, process optimization and improvement of formula is recommended.

Although freeze-drying and vacuum packaging are known to extend shelf-life, the long-term stability of the formulated instant rice and mung bean meal was not directly tested in this study. Future research should include accelerated and real-time shelf-life studies under varying storage conditions to validate the product’s longevity and nutrient retention over time.

Conclusion

The study successfully formulated an instant rice and sautéed mung bean meal that utilized the freeze-drying process. The product is not just another freeze-dried meal, but a culturally familiar, nutrient-dense, ready-to-eat complete meal designed for a specific, vulnerable population, but can also be consumed by the general population, especially during times of disaster when food security is a challenge.

Microbiological analysis confirmed that the product was safe for consumption, while proximate analysis demonstrated that it provides a compact, energy-rich composition with substantial carbohydrate- and protein-based energy, suitable for adult consumption in convenient or emergency contexts. Sensory evaluation indicated that the product was generally well accepted, particularly for aroma, taste, and texture, demonstrating the effectiveness of freeze-drying in retaining key sensory attributes. Minor reductions in appearance and color relative to the control highlight areas for potential improvement, suggesting that further optimization of formulation and processing could enhance visual appeal and overall acceptability. The product also has potential for long shelf-life based on low water activity and microbial counts. As such, future research should include accelerated shelf-life testing to establish product longevity under various storage conditions.

Future direction

Future research should focus on optimizing the visual quality of the product, particularly its appearance and color, to enhance overall sensory acceptability. Accelerated and real-time shelf-life studies are recommended to assess the stability of nutrients, sensory attributes, and microbial safety under various storage conditions. Additionally, strategies to further improve flavor and aroma, such as the use of natural enhancers or aroma-retention techniques, could be explored. Nutritional fortification with micronutrients may also be considered to increase the contribution to recommended daily intake. Scaling up production, evaluating cost-effectiveness, and conducting broader consumer acceptance studies across diverse demographic groups will be essential for potential commercial application. Finally, the product’s applicability in emergency relief, institutional feeding programs, or convenience-oriented markets warrants further investigation.