Development of sanitary napkins using corn husk fibres in absorbent layer – an exploratory study

Abstract

Corn husk is an agro waste which poses a problem of its disposal. Hence, fibres were extracted from corn husk to utilize it. The fibres extracted from corn husk were coarse with linear density of 86 deniers, had bundle strength of 1.3 g/d and elongation at break of 18.5%. Water retention of corn husk fibres was also found to be 200%, which makes them suitable as absorbent material. Therefore, the possibility of using corn husk fibres in the absorbent layer of sanitary napkins was explored. Corn husk fibres were mixed with wood pulp in different proportions for use in sanitary napkins. The developed sanitary napkins were evaluated for various physical and hygiene parameters like pH, water retention, absorbency and ability to withstand pressure, disposability, bacterial and fungal bio-burden, and presence of common skin pathogens and compared with other sanitary napkins for all the parameters. The water retention and absorbency of corn husk napkins were comparable to branded napkins, which had higher absorbancy probably due to the presence of SAP in their absorbent layer or difference in the quality of top sheet and technology used to manufacture the napkins. The bacterial and fungal bio-burden for the developed napkins was found to be lowest and within acceptable limits of 1000 c.f.u/ml. The common skin pathogen Staphylococcus aureus and uterine pathogen Candida albicans were found to be absent. Thus, use of corn husk fibres for developing various absorbent hygiene products could be sought as an opportunity for transforming waste to useful products.

Introduction

Utilizing renewable natural resources through value addition is an ideal transition from a petroleum-based economy to bio-based economy. Organic wastes, which are otherwise a challenge to the environment, could prove to be a potential alternative for production of value-added products [1]. Many ligno-cellulosic fibres have been produced from wood or non-wood–based biomass as new alternatives to replace both cotton and polyester production, which burdens the environment and consumes oil resulting in depletion of natural resources. For achieving economic sustainability, the development of alternative means for generating income and wealth, which do not cause hazards to the environment, is essential.

Maize, also known as corn, is the third most important food crop after rice and wheat in India. It is cultivated in all the states in India, except Kerala, throughout the year for various purposes [2]. Corn production in India has been on a constant rise and has reached up to 30.20 million metric tonnes in 2020–21, which is 5% more than the previous year (28.8 million metric tonnes in 2019–20) [3]. If 30 million metric tons of corn is produced in India annually, it could generate approximately 6 million metric tons of husks which could in turn lead to production of about 0.6 million metric tons of fibres [4]. The corn husk which is a bio-waste can be utilized for extraction of fibres for various textile applications.

Sustainability being the imperative aspect of development, many researches have been carried out exploring the possible applications of corn husk in textile and non-textile areas.

Anticipating the enormous scope of corn husk, Bridgehouse ES and Hawthorne WM (1982) pioneered the use of corn husk, generally considered a waste, to manufacture twines and ropes [5]. Various researches on other non-textile applications of corn husk fibres included their use in pulping [6], paper industry [7], composites with poly propylene [8] and low density composites with polyethylene for packaging [9].

A major breakthrough in research on corn husk was achieved by Yang and Reddy [4] who patented the process of extraction of corn husk fibres. The properties of the extracted corn husk fibres were found to be comparable to cotton and linen.

Researchers have been continuously making efforts to refine the process of extraction of corn husk fibres by studying various parameters involved in the process like effect of alkali concentration and treatment time [10,11] on the properties of extracted corn husk fibres and xylanase enzyme on the mechanical properties of fibres extracted from fresh and dried corn husk [12]. Treatment with banana pseudo stem sap was also given to improve thermal stability of corn husk fibres [13].

An extensive study on extracting corn husk fibres using alkali, enzyme and bleaching treatments was conducted by Jain et al. The authors found the extracted fibres suitable for use in developing variety of products such as yarn, rope and hand-made mats [14]. Considering the multifarious applications of corn husk fibres, as reported by various researchers, corn husk fibres were extracted and characterized for their properties [15]. The fibres extracted from corn husk were found to have high water retention; hence their suitability for use in sanitary napkins was explored. They were used in the absorbent layer of sanitary napkins along with wood pulp in different proportions. The developed napkins were evaluated for various physical and hygiene parameters.

Methods and materials

The husk was collected from fully mature cobs of Syngenta Sugar-75, a variety of sweet corn, from Aterna village in Panipat (Haryana). The husk collected directly from fields had very high moisture content. With such high percentage of moisture content, it was highly susceptible to growth of microorganisms, especially fungi, during storage and further processing. Hence, the husk was dried at room temperature and checked for moisture content levels after two and 5 days. The moisture content after 2 days of air-drying was found to be 69.5% while after drying for 5 days, the moisture content had decreased to 10.65% [16]. The moisture content of 10.65% was considered optimum for storage as most of the bast fibres have moisture content of 10% [17]. Considering the above data, the husk was air dried at room temperature and stored in a properly ventilated room.

The fibres were extracted from corn husk using a standardized procedure of treatment with alkali and enzyme [16] which is described as follows:

Alkali Treatment: Corn husk was treated with sodium hydroxide solution at a concentration of 4 g/L and MLR (material to liquor ratio) of 1:40 at 98–100°C for 60 minutes. As the fibres obtained with alkali treatment were quite coarse and harsh in nature, they were further treated with enzyme to make it softer and finer.

Enzyme Treatment: The fibres obtained after alkali treatment were further treated with Pulpzyme HC, a xylanase enzyme, (5% on weight of fibres) for 30 minutes at pH 8–9 and temperature between 55–60°C.

Bleaching: As the fibres extracted from corn husk were yellow in colour, they were bleached using 2 g/L hydrogen peroxide for 60 minutes [16].

The extracted corn husk fibres were characterized and tested for their various physical and mechanical properties.

Estimation of composition of corn husk fibres

[16] The composition of the extracted fibres was determined to understand their behaviour under various conditions.

Cellulose, hemicelluloses and lignin content: The composition analysis of corn husk fibres was done in accordance with TAPPI standards at Cellulose and Pulp Division, Forest Research Institute, Dehradun, Uttarakhand.

Determination of cellulose content: The method used for cellulose estimation in corn husk fibres was TAPPI standard T-203 os-74.

Determination of hemicelluloses (pentosans): Hemicelluloses comprise almost one-third of the carbohydrates in woody plant tissue. TAPPI standard T 223 cm-01 was followed to estimate the hemicellulose content of corn husk fibres.

Determination of lignin content: The procedure followed to estimate lignin content in corn husk fibres was the TAPPI Standard T 222 os-74.

Ash content: It was determined according to IS-199-1989 standard method.

Wax content: It was determined in accordance with IS-199-1973 standard method.

Assessment of physico-chemical properties of corn husk fibres

[16] After the analysis of composition of corn husk fibres, their physical and chemical properties were evaluated using standard test methods.

Fibre fineness: Fibre fineness was measured on Vibroskop which is an automatic instrument for the determination of fibre fineness. This is an indirect method of measurement of fineness of staple fibres.

Bundle strength and elongation at break: Bundle strength is an important parameter to judge the quality and strength of the resultant yarn. A bunch of fibres is tested together for strength and elongation at break using a Stelometer. It is an instrument that tests a flat sample of fibres for tenacity and elongation. The instrument breaks a flat bundle of fibres and indicates the force required to break the fibres on a graduated scale. The elongation is determined on another graduated scale at the breaking point of the fibre sample. A simple calculation is used to determine the tenacity of the sample. The calculation uses the breaking point number (which is indicated on the graduated scale) and the known weight of the sample to determine tenacity. A precision balance is needed in conjunction with the Stelometer to get the weight of the sample. It gives tenacity in grams per tex which was converted to grams per denier by standard formula.

Moisture regain: It was determined according to IS-199 standards.

Development of sanitary napkins using corn husk fibres

Since the water retention properties of corn husk fibres were found to be quite high, their use in the absorbent layer of sanitary napkins was explored. Due to the relative harshness of fibres, they were not used in 100% proportion; instead, they were blended with the wood pulp which was being used conventionally in sanitary napkins. Two blend ratios of corn husk fibres and wood pulp for construction of sanitary napkins were studied, viz. 30:70 and 50:50. The napkins were made in accordance with the norms given in IS: 5405-1980. As this was meant to be an initial exploration, only one type of sanitary napkin , that is, beltless in regular size was constructed. The napkins were manufactured at a unit called Gulmeher Green, Ghazipur Dairy Farm, Delhi. This unit was established to make low cost sanitary napkins in collaboration with an NGO, Aakar Innovations (Navi Mumbai).

Development of sanitary napkins according to BIS 5405-1980 specifications: The process of manufacturing sanitary napkins using corn husk fibres and wood pulp mixture is summarized in Figure 1 [18]. Bleached corn husk fibres were pulverized in a rotor speed mill. In the process of pulverization, a rotor rotating at a speed of 20,000 r/min grinds the corn husk fibres into pulp in 5 min. Pulverized corn husk fibres and wood pulp (virgin pine wood pulp sheet) were thoroughly mixed by passing both of them together in pulverizer 2–3 times.

Figure 1.

Process of manufacturing sanitary napkins using corn husk fibres in absorbent layer.

6–7 g of the blended pulp was then filled manually in steel moulds, shaped according to sanitary napkins, for preparation of absorbent layer. Moulds filled with the mixture of pulp and corn husk fibres were then compressed by a pressing machine which was operated manually. The pressing machine uses gravitational force to properly compact the fluffed pulp to ensure that liquid can be absorbed, the pad remains dry and breathable, and the absorbent layer is strong enough to keep its structure. After pressing, the absorbent layer was taken out of the mould and placed in a sealing machine with the bottom sheet below it. The top layer was then placed above, and it was sandwiched between top and bottom sheet (made of compostable material) and pressed by closing the lid with force, manually. The sealing machine makes pads through heat sealing, cutting and embossing technology. The temperature was maintained at 133–134°C as per the specifications. The thickness of the complete pads ranged from 8 to 10 mm.

After sealing the napkins, they were checked to ensure that none of the edges remained opened. If any napkin was found open from any side, it was sealed again. Napkins were then applied with an adhesive (water-soluble gum (CPW), using a screen, at the back and wings. This was followed by the pasting of the silicon release papers. Finally, the napkins were sterilized by keeping them in a UV-ray sterilization chamber for 30 min.

Evaluation of the branded and corn husk fibre napkins: Three branded napkins and two unbranded napkins manufactured at the same unit (Gulmeher Green, Ghazipur Dairy Farm, Delhi) were evaluated for various physical and hygiene properties. Both the branded and unbranded napkins were of regular variety.

Physical parameters: The manufactured napkins were assessed for following physical parameters:

pH of the sanitary napkins: The pH of sanitary napkins was tested as per the method given in IS: 1390-1961, using the aqueous extracts of the samples. 2 g of absorbent layer from the test napkins was taken and put into 100 mL of distilled water (pH-7) at room temperature. The sample was shaken in a mechanical shaker for 30 minutes, and the aqueous extract was checked for its pH. Three samples of each type were tested, and the mean of their readings was calculated.

Absorbency and ability to withstand pressure: One of the main requirements of sanitary napkins is to absorb body fluid and then retain it for long periods of time and also avoid its backflow under pressure [19].

Good absorbency prevents any leakage from taking place. The napkins were observed for any leakages from the sides or back after placing weight over them. This test was conducted in accordance with IS: 5405-1980. The napkins were laid on a level flat transparent surface, so that the underside of the sanitary napkin can be observed. Then 20 mL test fluid, prepared by the method mentioned in the standard, was poured at the rate of 10 mL per minute on to the centre of the sanitary napkin from a height of approximately 1–2 mm. The temperature was maintained at 27° ± 2°C. After the napkin had absorbed the full amount of fluid, a standard weight of 1 kg was kept for 1 minute on the portion where fluid was poured. After removing the weight, back and sides of the sanitary napkin were observed for any fluid showing up.

Water Retention: The water retention of sanitary napkins was measured in quantitative terms using the centrifuge method, ASTM: D 2402-2001. This test is intended to give a measure of the amount of water which cannot be removed from thoroughly wetted fibre solely by mechanical means as applied by the centrifugal force. In this method, water retained by the fibre mass includes water absorbed from the prevailing atmosphere, water imbibed during immersion and water adhering to the fibre surfaces after being centrifuged. Three samples weighing around 1 gm were cut out from different sections of each sanitary napkin. The extreme ends were not included where the absorbent core is the thinnest. These specimens were put in nylon bags and weighed again. Each prepared specimen was immersed in 250 mL distilled water at room temperature for 5 minutes to completely wet it out. The wetted-out specimens were put into centrifuge at an acceleration of 9800 m/s² and allowed to spin for 5 min. The average of three readings was calculated as below

$$R=100\left(M\mathrm{-}D\right)/\left(D\mathrm{-}\mathit{{\rm T}}\right)$$

where

• R = water retention %

• M = mass of moist specimen with its tare mass in grams

• D = mass of dried specimen with its tare mass in grams

• T = mass of the tare.

Disposability: The disposability of the napkins was tested in accordance to IS: 5405-1980. Three samples were drawn from each packet, and each napkin with the top and bottom coverings removed was immersed in 15 L of water at room temperature and stirred. Time taken for the absorbent layer to disintegrate in water was noted in terms of more or less than 5 minutes. The standard requires the fibre mass to disintegrate in water in 5 minutes to fulfil the standards of disposability.

Hygiene parameters: These were tested as per the requirements mentioned in IS-5405-1980 using standard tests prescribed for them. Microbiological testing was carried out at the Food microbiology and biotechnology laboratory, Amity Institute of Food Technology, Noida. It was done to evaluate the hygiene parameters of sanitary napkins and extracted corn husk fibres in terms of the level of micro-organisms in the product as well as the presence of common skin and uterine pathogens.

Bacterial and fungal bio burden: The determination of bacterial and fungal bio burden was carried out by the aerobic plate count method (APC) and the yeast and mould count (YMC) method, respectively, in accordance with the standard method, Bacteriological Analytical Manual, 2001. Five samples of 5 g each were cut from the centre portion of each napkin and were put into 50 mL of saline solution (0.85% sodium chloride). The sample was shaken vigorously in the solution and the liquid was extracted from the napkin. The extract was serially diluted and plated out on respective medium, that is, plate count agar for bacterial bio burden and sabouraud chloramphenicol agar for fungal bio burden. The plates were incubated at 37°C for 48 h for bacterial APC and at 22°C up to 120 h for YMC. All colony forming units (CFUs) were counted (including pinpoint size).

Presence of common skin pathogen ( Staphylococcus aureus ): The sanitary napkins were also tested for the presence of Staphylococcus aureus using the standard test method IS: 5887 (part II) – 2005. 5 g samples were cut from the centre portion of each napkin and were put into 50 mL of saline solution (0.85% sodium chloride). The sample was shaken vigorously in the solution, and the liquid was extracted from the napkin. The extract was inoculated on Baird Parker medium and the Baird Parker agar plates were incubated for 30 h at 37°C. From the incubated plates, the suspected colonies of the organism, if any, were counted [18].

Presence of common uterine pathogen (Candida albicans): Candida albicans is a common urinary tract pathogen known to cause urinary tract infections. To test for presence of this pathogen, five samples of 5 g each were cut from the centre portion of each napkin and were put into 50 mL of saline solution (0.85% sodium chloride). The sample was shaken vigorously in the solution, and the liquid was extracted from the napkin. The extract was inoculated on potato dextrose agar, and the agar plates were incubated for 48 h at 25°C. From the incubated plates, the suspected colonies of the organism, if any, were counted [18].

Results and discussion

Extraction and characterization of corn husk fibres

The fibres extracted from corn husk using alkali and enzyme were bleached and then characterized for their various properties. The composition of corn husk fibres was estimated as follows [15] (Table 1).

Table 1.

Composition of bleached corn husk fibres.

S.No	Component	Amount in %
1	Cellulose	76.00
2	Hemicelluloses	11.43
3	Lignin	7.50
4	Wax content	0.25
5	Ash content	0.34

Table 2 below gives the values of various physico-chemical properties of extracted corn husk fibres [15].

Table 2.

Some physical properties of the extracted corn husk fibres.

S. No	Parameter	Values for corn husk fibres
1	Fineness	86 denier
2	Bundle strength	1.33 g/denier
3	Elongation at break	18.5%
4	Moisture regain	11.4%
5	Absorbency (drop penetration time in seconds)	<1 s
6	Water retention	200%
7	pH	6.8

The drop penetration time of corn husk fibres was less than 1 s. Water retention of corn husk fibres was also found to be 200%, which is very high [15]. Sari et al. [20] studied the effect of water immersion and fibre content on properties of corn husk fibres–reinforced thermoset polyester composite and concluded that increase in corn husk fibre content lowered the mechanical strength but enhanced the swellability and amount of water absorbed by the composite. High water retention coupled with good water absorbency favoured the application of corn husk fibres in various absorbent materials.

Development of sanitary napkins using corn husk fibres: Sanitary napkins were manufactured using corn husk fibres mixed with wood pulp in the absorbent layer in 30% and 50% proportion (Figure 2).

Figure 2.

Sanitary napkins with (a) 30% corn husk fibres (b) 50% corn husk fibres in absorbent layer.

All the napkins were tested for various physical and hygiene characteristics, which are discussed below.

Comparative evaluation of physical parameters of corn husk sanitary napkins: The physical parameters of all the branded, locally made and developed corn husk napkins were evaluated in terms of pH, absorbency, flexibility, water retention and disposability.

pH: According to IS 5405-1980, a sanitary napkin should have a pH of 6–8.5. The pH of sanitary napkins was tested as per the method given in IS: 1390-1961. The pH of all the napkins varied from 6.25 to 7.45 (Table 3). Thus, all the sanitary napkins conformed to the acceptable pH range, that is, 6–8.5. Both the napkins, which were made by using 30% and 50% corn husk fibres in absorbent layer, also fell in the acceptable range and had almost similar pH, that is, 7.32 and 7.45, respectively. The pH impacts the adhesion of resident skin microflora; an acid skin pH is required to keep the resident bacterial flora attached to the skin, while an alkaline pH (8–9) might result in its dispersal from the skin [21]. In subsequent studies efforts could be made to lower the pH to a more desirable range of 5.5–6.5.

Table 3.

pH of sanitary napkins.

S. No	Napkin code	pH values			Average
1	A (branded)	6.27	6.38	6.29	6.31
2	B (branded)	6.33	6.35	6.32	6.33
3	C (branded)	6.23	6.28	6.24	6.25
4	D (local)	7.22	7.27	7.26	7.25
5	E (local)	7.29	7.18	7.21	7.19
6	F (50% corn husk fibres)	7.55	7.35	7.47	7.45
7	G (30% corn husk fibres)	7.33	7.35	7.29	7.32

Absorbency and ability to withstand pressure: The test is conducted under weight to simulate the real time conditions as the napkin incurs pressure to varying degrees during use, especially while sitting, which is when there are maximum chances of leakage and spotting. Table 4 shows the results of this test.

Table 4.

Absorbency and ability to withstand pressure of sanitary napkins.

S. No	Napkin code	Patch size after absorption (inches)		Time taken for absorption (seconds)	Leak through and remarks
		Initial patch size	Patch size after placing 1 kg weight
1	A (branded)	10.5 × 6	11× 6.5	01	No leak through
2	B (branded)	9.5 × 5	10 × 5.5	01	No leak through
3	C (branded)	10 × 5.5	11.5 × 5.5	01	No leak through
4	D (local)	9 × 5.5	9.5 × 6.0	20	No leak through
5	E (local)	10 × 5	10 × 5.5	20	No leak through
6	F (50% corn husk fibres)	8 × 4.5	9 × 5	15	No leak through
7	G (30% corn husk fibres)	8 × 4.5	8 × 5.5	17	No leak through

The time taken for absorption of fluid by different sanitary napkins ranged from 01 s to 20 s. Locally made napkin brands took a maximum of 20 s while branded napkins took the lowest time, that is, 01 s. Both the napkins which were made by using 30% and 50% corn husk fibres recorded water absorption time of 17 s and 15 s, respectively. The lesser time for absorption by napkins having 50% corn husk fibres implies that corn husk fibres might be having higher absorbency as compared to wood pulp used. The difference in quality of web due to variable thickness, compactness and adhesion affects the absorbency level of napkins [18]. Another important factor affecting the absorbency is the top sheet of the napkins. The top sheet of branded napkins was perforated which aids in wicking action, while all other napkins had non-woven top sheet. The wicking action of the top layer might have aided fast absorption of fluid in brand A, B and C napkins.

The spread (patch size after placing the weight) of the patch formed by the fluid absorbed varied from 8 × 4.5 inches square to 10.5 × 6 inches square for various napkins. Fluid retention is dependent on density of the absorbent layer. Most of the sanitary napkins available in market these days have super absorbent polymer (SAP) in compressed and uncompressed form which greatly enhances the absorbency and water retention properties of the napkins [22]. All the napkins showed an increase in patch size after placing of weight.

None of the napkins showed any kind of leakage at back or sides. Though, some of the napkins showed a narrow line of liquid flowing lengthwise, through capillary action, apart from the patch formed in centre (Figure 3). Corn husk fibre napkins had the smallest patch size before placing the weight, but it was highest after placing the weight. The ability to withstand pressure is not dependent solely on the type of fibres used in absorbent layer rather it gets affected by multiple factors. Density of the absorbent layer also influences the absorption and stability of the product to a large extent. A highly compressed fibre expands on absorption while lightly compressed fibre gets collapsed due to absorption [19].

Figure 3.

Napkins with corn husk fibres after absorption of fluid (a) front (b) back, branded napkin after absorption of fluid (c) front and (d) back.

Water Retention: Table 5 shows the water retention capacity of various sanitary napkins. Water retention of all the napkins ranged from 107.7% to 225.2%. Napkin brand A had the maximum water retention while napkin brand D showed the minimum retention of water. Napkin with 50% corn husk fibres showed better water retention, that is, 148.5% as compared to napkin with 30% corn husk fibres. The napkin having higher amount of corn husk fibres in absorbent layer showed better retention which implies that retention of corn husk fibres was higher than the wood pulp used. The difference in water retention of various fibres may be due to variety of pulp used in absorbent layer of the napkins [18]. All the three branded napkins’ higher water retention may be attributed to the presence of SAP in their absorbent layer while local napkins and corn husk napkins did not contain SAP. Super absorbent polymer is made up of sodium polyacrylate granules which transforms into a gel like on being wet and absorbs fluid, 30 times its weight. The fluid gets locked and stored even under applied pressure [22]. Though SAPs are added in the absorbent layer of sanitary napkins to improve their absorption capacity, they are found to have some adverse effects on the health and they are also not biodegradable. Sanitary napkins without SAP might not be equivalent in absorption capacity but will be safe for disposal and will not affect health of the user. Therefore, they can have a positive global impact in the near future [23].

Table 5.

Water retention of sanitary napkins by centrifuge method.

S. No	Napkin code		M (mass of moist specimen in grams)	D (mass of dry specimen in grams)	T (mass of tared specimen in grams)	R (retention %)	Average R (%)
1	A (branded)	(i)	56.15	51.65	49.93	261.6
		(ii)	43.29	38.32	35.18	232.2	225.2
		(iii)	32.65	30.34	29.07	181.8
2	B (branded)	(i)	37.49	34.80	33.62	227.9
		(ii)	52.45	50.35	49.24	189.1	200.0
		(iii)	39.98	36.10	33.98	183.0
3	C (branded)	(i)	54.65	51.50	49.79	184.2
		(ii)	44.61	43.18	42.39	181.0	174.5
		(iii)	52.15	49.47	47.78	158.5
4	D (local)	(i)	45.05	39.90	35.12	107.7
		(ii)	58.47	53.52	49.16	113.5	107.7
		(iii)	47.38	43.45	39.79	107.3
5	E (local)	(i)	48.60	47.26	45.87	96.4
		(ii)	45.93	40.80	37.01	135.3	114.6
		(iii)	44.12	40.34	36.97	112.1
6	F (50% corn husk fibres)	(i)	41.56	37.87	35.43	151.2
		(ii)	38.12	34.78	32.26	132.5	148.5
		(iii)	52.35	48.09	45.46	161.9
7	G (30% corn husk fibres)	(i)	43.42	40.74	38.58	124.0
		(ii)	49.85	47.34	45.05	109.6	115.7
		(iii)	51.23	49.13	47.28	113.5

Disposability: It was observed that all the napkins disintegrated in water in less than 5 min.

Evaluation of Hygiene Parameters of Branded and Corn husk Sanitary Napkins: Microbial testing of hygiene products like sanitary napkins holds significance because these are worn in close contact to the vagina. At puberty, the normal bacterial flora of the vagina maintains acidic pH by acid from carbohydrates, especially glycogen. This seems to be an important phenomenon for prevention of growth of other, possibly harmful, microorganisms. If the pH gets altered, yeasts or bacteria might increase in numbers and cause irritation and inflammation [18].

Bacterial and fungal bio burden: The level of bio-burden of a product gives an idea of the status of hygiene during processing, handling and packaging. The manufacturers of branded sanitary napkins (Johnson & Johnson Ltd.) consider a bio-burden of less than 1000 c.f.u/ml as acceptable for their products [18]. The bacterial and fungal bio-burden determined for various sanitary napkins is shown in Table 6.

Table 6.

Bacterial and fungal bio-burden of sanitary napkins.

S. No	Napkin code	Aerobic plate count (cfu/ml)	Mean yeast &mould count (cfu/ml)
1	A (branded)	2.1 × 102	2.3 × 102
2	B (branded)	1.5 × 102	2.0 × 102
3	C (branded)	4.8 × 103	4. 9 × 103
4	D (local)	9.5 × 102	9.7 × 102
5	E (local)	10.5 × 102	9.9 × 102
6	F (50% corn husk fibres)	1.2 × 102	1.1 × 102
7	G (30% corn husk fibres)	5.1 × 102	4.0 × 102

The bacterial bio-burden of all the sanitary napkins was found between 1.2 × 10² and 4.8 × 10³ c.f.u./ml while fungal bio-burden ranged from 1.1 × 10² to 4.9 × 10³ c.f.u./ml (Figure 4). The napkins made with 50% corn husk fibres had lowest bacterial and fungal bio-burden while napkins with 30% corn husk fibres were also found to have low bacterial (510 c.f.u./ml) and fungal (400 c.f.u./ml) bio-burden. Napkin brand C had much more bacterial and fungal bio-burden than the tolerance limit of 1000 c.f.u/ml. Thus, the bacterial and fungal bio-burden of the napkins made with corn husk fibres was found to be within permissible and acceptable limits.

Figure 4.

Typical colony characteristics of (a) and (b) bacterial bio-burden, (c) and (d) fungal bio-burden.

Presence of common skin pathogen ( Staphylococcus aureus ) and common uterine pathogen (Candida albicans): Many studies have shown earlier that diseases such as toxic shock syndrome and candidiasis might occur due to these [24]. The developed sanitary napkins were also tested for the presence of Staphylococcus aureus and Candida albicans . Both of these microorganisms were found to be absent in all the samples. Staphylococcus aureus is the causative agent for multiple human infections like bacteremia, infective endocarditis, skin and soft tissue infections [25].

Conclusion

The results of the study clearly indicate that corn husk fibres could prove to be a promising alternative in various hygiene products like sanitary napkins, diapers and absorbent sheets. The napkins developed with absorbent layer having corn husk fibres were found to be comparable to the napkins already available in the market. Various parameters like pH and bacterial and fungal bio-burden were within the range specified as per BIS standards and common skin and uterine pathogens were found to be absent. Though the absorbency and water retention of corn husk fibres are very high, the napkins having corn husk fibres in absorbent layer were less absorbent as compared to the branded napkins. This might have resulted due to factors such as the top sheet and SAP, used in the construction of sanitary napkins. As this was an exploratory study, only two proportions of corn husk fibres in absorbent layer were used. The study aimed to find out the feasibility of using corn husk fibres as a replacement of wood pulp in the absorbent layer of sanitary napkins/hygiene products. As consumption of hygiene products is on a continuous rise, alternative sources are required to replace wood pulp due to environmental concerns. Thus, an extensive study to standardize all the parameters for construction of sanitary napkins using corn husk fibres in absorbent layer shall be carried out so that application of corn husk fibres for various hygiene products could be undertaken successfully at the commercial level. As corn husk is considered a waste, its utilization as replacement of wood pulp will be a big leap in conservation of natural resources.