Hygroscopic Products Research Articles

Physicochemical stability, microbial growth and sensory quality of refined wheat flour as affected by packaging materials during storage

Wheat flour is a hygroscopic product requiring efficient packaging materials to maintain shelf stability and desired quality during long storage periods. This study aimed to assess the effectiveness of four packaging materials (Paper bag, Polypropylene, woven polypropylene bag + Low-density polyethylene, and Purdue Improved Crops Storage) in preserving the physicochemical, microbial, and sensory quality of refined wheat flour over 6 months at room temperature (14.8−26.80 °C). The experiment was conducted under laboratory conditions at the Postharvest Management and Animal Nutrition Laboratory of Jimma University College of Agriculture and Veterinary Medicine. Results revealed that hermetic packaging materials, specifically Purdue Improved Crop Storage (PICS) and Polypropylene bag + low-density Polyethylene (PP + LDPE), were the most effective in maintaining flour quality compared to non-hermetic options such as woven polypropylene bag (PP) and paper bag. As storage duration increased, there was a gradual decline in physicochemical quality, albeit to varying degrees depending on the packaging material. Nutritional losses were significantly lower in hermetic packaging materials. For instance, crude protein losses were 1.82% in PICS and 2.81% in PP + LDPE, compared to 4.64% in woven PP and 3.81% in paper bags. Moisture content increased by 4.43% with PP bags and 3.92% with paper bags, while the slightest changes, 1.99%, and 2.03%, were observed in PICS and PP + LDPE bags, respectively. Additionally, hermetic packaging materials reduced microbial growth. They maintained bulk density, water, and oil absorption capacity, as well as the odor and color of the stored flour compared to non-hermetic packaging materials evaluated. It is recommended that supply chain actors and consumers utilize PICS or PP + LDPE bags to ensure better physicochemical stability, microbial control, and sensory quality of refined wheat flour.

Study of the process of tea moisture sorption

The article presents studies of the sorption characteristics of green and black tea. The obtained experimental data indicate that tea is a hygroscopic product, so with an increase in the relative humidity of the environment, the sorption rate and the amount of moisture absorbed by tea increase. It was found that small-leaf black tea is more susceptible to intense moisture than large-leaf tea. At high values of relative humidity of the environment, molds of the species Aspergillus and Penicillium most often develop. When the moisture content of tea does not exceed the norms of the standard, the microflora does not have a significant impact on the quality indicators of the product. To preserve the quality of the product, it is necessary to use packaging materials with high barrier properties and maintain a relative humidity of less than 65% in warehouses.

Shelf‐life study of a Salicornia ramosissima vegetable salt: An alternative to kitchen salt

AbstractWaste of Salicornia ramosissima a halophyte plant used in gourmet cuisine, can be valorized after being dried and milled, becoming a vegetable salt, a healthier replacer of kitchen salt due to its lower sodium content (around 10‐fold less) but still maintaining an intense salty taste. To study the shelf life of this vegetable salt from S. ramosissima, packed in a cylindrical aluminum box, an accelerated shelf‐life testing (ASLT) was first carried out at 35, 40, 45, and 50°C by monitoring color, moisture, and water activity (aw) throughout the storage period. Moisture and aw decreased at increasing temperature, but the color was not affected. The moisture sorption isotherms (MSIs) were next produced at 15, 25, 35, and 45°C and relative humidity (RH: 6.5%–80%) using the static gravimetric method. Several mathematical models were tested to fit the MSI experimental data and finally the Oswin model was used to predict the moisture content. With this model, the isosteric heat was determined. A mass–balance model was used to predict shelf life and the equilibrium moisture content (Me) during storage based on predetermined MSI and water vapor rate transmission (WVTR) data. The predicted shelf life of the package with and without adhesive tape around the lid was 35 and 80 days (25°C, 75% RH) and 19 and 63 days (35°C, 90% RH), respectively.Practical ApplicationsBy understanding the moisture sorption phenomenon in hygroscopic powders, this study can provide valuable data to the food industry dealing with such products. Being a microbiologically safe product due to its low aw and having color stabilized through previous drying, its mode of failure during storage proved to be the loss of its free‐flowing capacity. A methodology to evaluate the shelf life of this hygroscopic product packed in a cylindrical aluminum box is described. There is a need to draw attention to the fact that, despite aluminum with a thickness of .23 mm is a very effective barrier to water vapor penetration, such package has an extremely small gap between the lid and body, which is hard to measure, yet allows water vapor to flow through the package at a rate that results in its shelf life being less than 3 months. Ways to overcome this issue are suggested.

Evaluation of the Vapor Hydrolysis of Lithium Aluminum Hydride for Mobile Fuel Cell Applications.

The controlled vapor hydrolysis of LiAlH4 has been investigated as a safe and predictable method to generate hydrogen for mobile fuel cell applications. A purpose-built vapor hydrolysis cell manufactured by Intelligent Energy Ltd. was used as the reaction vessel. Vapor was created by using saturated salt solutions to generate humidity in the range of 46–96% RH. The hydrolysis products were analyzed by thermogravimetric analysis (TGA) and powder X-ray diffraction and compared with possible hydroxide-based phases characterized using the same methods. Analysis of the products of the LiAlH4 vapor hydrolysis reaction at a relative humidity in excess of 56% indicated complete decomposition of the LiAlH4 phase and formation of the hydrated layered double hydroxide, [LiAl2(OH)6]2CO3·3H2O, rather than the simple salts, LiOH and Al(OH)3, previously suggested by the literature. The high level of hydration of the layered double hydroxide (LDH) (12% wt water) and the presence of carbonate indicated that the feed stream was contaminated with CO2 and that the highly hydrated and hygroscopic product would be detrimental to the mobile hydrogen production process, restricting recyclability of the water fuel cell byproduct and lowering the gravimetric density of LiAlH4. Carrying out the vapor hydrolysis reaction in a glovebox in the absence of CO2 indicated that the hydroxide derivative of the LDH, [LiAl2(OH)6]OH·2H2O, could be formed instead, but the water content was even more significant, equating to 17% of the carried weight. TGA showed that water was retained up to 300 and 320 °C in the two phases, making thermal recycling of the water retained impractical and casting doubt on whether generating hydrogen on the move by vapor hydrolysis of LiAlH4 is practical.

Sorption Behavior, Glass Transition and Flowability of Powdered Orange Co-product

The aim of this study was to contribute 100% to the circular economy models of the agri-food industry through the valorization of the whole orange juice co-product in order to offer it as a natural, versatile, high quality, and stable powdered food ingredient for human nutrition. Turning it into a cost-effective innovative product, with added value due to its high content of bioactive compounds, would lead to an increased competitiveness of the industrial sectors working with natural fibers. To ensure its efficient use for this purpose, co-product powder was characterized from a technological point of view in terms of the physicochemical aspects related to the presence of water and its ability to remain free-flowing and non-agglomerated, allowing for easy handling. The results of this study ensure the flowability of the freeze-dried orange co-product powder according to both the angle of repose (40°) and porosity (83%) values. However, it was also characterized as a hygroscopic product; therefore, specified conditions for a proper storage of the powdered co-product should be defined. In this case, both the refrigeration temperature and a relative humidity of under 35% should be established in order to avoid glass transition, thus remaining a free-flowing powder.

PEMODELAN PERSAMAAN ARRHENIUS UNTUK MEMPREDIKSI UMUR SIMPAN PENYEDAP RASA CANGKANG RAJUNGAN

The aim of this research is to determine the shelf life of seasoning of swimming crab shell in metalized packaging, which is stored at various temperatures using the Arrhenius modeling. Seasoning are packaged using metalized packaging with a thickness of 0.06 mm, which is stored at 25 ºC, 35ºC, and 45ºC for 8 weeks with 75% humudity. The parameters used for measuring shelf life are initial moisture content, critical water, and changes in water content during storage. In addition, analysis of hygroscopicity and water activities (aw) value of seasoning as supporting parameters were also carried out. The results showed that seasoning that the seasoning of the swimming crab shells was classified as a hygroscopic product, had moisture content, and aw values a low during storage. The longest shelf life of the swimming crab shell seasoning is storage at 25ºC, reaching 62 weeks based on moisture content parameters.

Isotherm moisture sorption of composite desiccant made from rice husk biomass

The behavior of isotherm moisture sorption form rice husk-CaCl2 composite desiccants was studied. The desiccant composite in various treatments was tested for its isotherm sorption using gravimetric method. Saturated solution of LiCl, CH3COOK, MgCl, K2CO3, NaBr, NaNO2, NaCl, KCl, and K2SO4 were used to obtain the moisture of 11 %, 22 %, 32 %, 44 %, 56 %, 64 %, 75 %, 84 % and 97 %. Water activity produced from these saturated salt solutions was measured using aw meter. The equilibrium moisture data was then fitted into several isothermal equation models that have been used and tested in several literature including the model of Courie, Oswin and Chen Clayton. This rice husk composite desiccant had exposed a J shape curve of equilibrium water content with a boundary zone A of aw 0.2 and zone B of aw 0.67. Based on the isothermic absorption curve, the Oswin equation model was able to predict the results of research with R2 of 0.96, 0.89 and 0.97, respectively for temperature of 30, 40 and 50°C. This rice husk desiccant was able to absorb water vapor at low RH. It means that this desiccant is promising to be used for low water content or hygroscopic product such as flour based product, food flavor powder, chili powder, palm sugar and other products.

HPMC Capsules for Moisture Sensitive and Hygroscopic Products

<i>Background</i>: Moisture content varies in capsules made from different materials. Gelatin capsules contain 13-16% moisture. HPMC (Hydroxypropyl methyl cellulose or Hypromellose) capsules may contain moisture 2- 8%. Usual HPMC capsules have inherently low moisture content which allows for the encapsulation of ingredients that are sensitive to moisture and are hygroscopic in nature. This has greatly broadened the scope of capsules in drug delivery. Moisture content of HPMC capsules can be reduced as low as 2%. HPMC capsules lower moisture content is better for moisture sensitive and hygroscopic products. <i>Objective</i>: Low moisture content of HPMC capsules help to improve stability of moisture sensitive active pharmaceutical and active nutraceutical active ingredients. This is illustrated with examples. Different properties of HPMC capsules helps targeted delivery. It offers some special advantages for nutraceutical products. It also helps to improve physical stability of capsules. Liquid filled hard capsules provide many options and are commonly used for nutraceutical products.

Determination of Absolute Purities of Hygroscopic Substances by Quantitative NMR Analysis for the Standardization of Quantitative Reagents in the Japanese Pharmacopoeia (Part 2).

As a new absolute quantitation method for low-molecular compounds, quantitative NMR (qNMR) has emerged. In the Japanese Pharmacopoeia (JP), 15 compounds evaluated by qNMR are listed as reagents used as the HPLC reference standards in the assay of crude drug section of the JP. In a previous study, we revealed that humidity affects purity values of hygroscopic reagents and that (i) humidity control before and during weighing is important for a reproducible preparation and (ii) indication of the absolute amount (not purity value), which is not affected by water content, is important for hygroscopic products determined by qNMR. In this study, typical and optimal conditions that affect the determination of the purity of ginsenoside Rb1 (GRB1), saikosaponin a (SSA), and barbaloin (BB) (i.e., hygroscopic reagents) by qNMR were examined. First, the effect of humidity before and during weighing on the purity of commercial GRB1, with a purity value determined by qNMR, was examined. The results showed the importance afore-mentioned. The results of SSA, which is relatively unstable in the dissolved state, suggested that the standardization of humidity control before and during weighing for a specific time provides a practical approach for hygroscopic products. In regard to BB, its humidity control for a specific time, only before weighing, is enough for a reproducible purity determination.

Shelf Life Determination of Pegagan (Centella asiatica) Chips Using Accelerated Shelf-Life Testing (ASLT) Method

Pegagan (Centella asiatica) is a wild plant with various kinds of efficacies for health and usually as herbal or traditional medicine. Pegagan has been processed into various new products including chips. Pegagan Chips are hygroscopic product that easy to absorb water from the environment. The objective of this study was to determine the shelf life of Pegagan Chips packed in different type of packaging materials. The shelf life of Pegagan Chips was determined using Accelerated Shelf-Life Testing (ASLT) method with a critical moisture content approach. Two different types of packaging used were polyethylene (PE) plastic and standing pouch aluminum foil. The samples were stored at 28°C and RH 75%. The results showed that the shelf life of Pegagan Chips with PE plastic and aluminum foil standing pouch were 83 and 139 days, respectively. Aluminum foil standing pouch possessed lower packaging permeability which was 0.0603 g/m2.day.mmHg compared to PE plastic.

Characterization of molybdenum and tungsten phosphates compounds prepared using ammonium phosphate salt as flux

Fusion of powdered molybdenum and tungsten oxide using ammonium phosphate salt as flux (ratio: 1:25 respectively) yielded soluble products which were unstable. The yellow (Mo) and purple-blue (W) solutions in deionized water, methanol and acetone decolorized within 3–5 hours. Infrared analysis of molybdenum and tungsten products revealed characteristic broad bands bearing two minor peaks in the region of 1040–1130 cm -1 which reflects the simultaneous existence of PO 2 and PO 3 groups. SEM-EDX quantitative analysis results showed percentage weight of the identified elements in the increasing order of Mo or W < P < O with molybdenum product having 7.1%wt (Mo), 37.2%wt (P) and 53.5%wt (O) whilst tungsten product had 10.3%wt (W), 24.7%wt (P) and 46.5%wt (O). The EDX results indicated the presence of polyphosphate products whilst the SEM images showed microscopic crystalline product of molybdenum and a hygroscopic product of tungsten. XRD patterns of both molybdenum and tungsten products corresponded to the standard (JCPDS) pattern of molybdenum oxide phosphate MoO 2 (PO 3 ) 2 and tungsten oxide phosphate (WO 2 (PO 3 ) 2 ), respectively. KEY WORDS : Molybdenum, Tungsten, Ammonium phosphate flux, Polyphosphates Bull. Chem. Soc. Ethiop. 2019 , 33(1), 103-112 DOI: https://dx.doi.org/10.4314/bcse.v33i1.10

Challenges in Transitioning Cocrystals from Bench to Bedside: Dissociation in Prototype Drug Product Environment.

Tablets containing a theophylline-glutaric acid (TG) cocrystal dissociated rapidly forming crystalline theophylline (20-30%), following storage at 40 °C/75% RH for 2 weeks. Control tablets of TG cocrystal containing no excipients were stable under the same conditions. The dissociation reaction was water-mediated, and the theophylline concentration (the dissociation product), monitored by synchrotron X-ray diffractometry, was strongly influenced by the formulation composition. Investigation of the binary compacts of the TG cocrystal with each excipient revealed the influence of excipient properties (hydrophilicity, ionizability) on cocrystal stability, providing mechanistic insights into a dissociation reaction. Ionizable excipients with a strong tendency to sorb water, for example, sodium starch glycolate and croscarmellose sodium, caused pronounced dissociation. Microcrystalline cellulose (MCC), while a neutral but hydrophilic excipient, also enabled solution-mediated cocrystal dissociation in intact tablets. Magnesium stearate, an ionizable but hydrophobic excipient, interacted with the cocrystal to form a hygroscopic product. The interaction is believed to be initiated in the disordered cocrystal-excipient particle interface. In contrast, the cocrystal was stable in the presence of lactose, a neutral excipient with no tendency to sorb water. The risk of unintended cocrystal dissociation can be mitigated by avoiding contact with water both during processing and storage.

Effect of Polyethylene on the Physical and Mechanical Properties of Particleboard

SummaryParticleboard is a common material used in furniture manufacturing. In the present study, it is made from natural rubber wood in the form of coarse and fine particles which is glued with urea formaldehyde adhesive. Because of the cellulosic structure containing many hydroxyl groups, the particleboard becomes a hygroscopic product. The objective of the present study was to increase the water resistance of the particleboard by adding polyethylene (PE). Four grades of PE were selected and mixed with the rubber wood particles before forming as a three‐layer particleboard. Water absorption and thickness swelling were determined. The mechanical properties of the particleboard were evaluated including modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength (IB) and screw holding force. It is found that the addition of 5 wt% PE decreased the thickness swelling at 2 h, e.g. from 19.27% to 13.18–17.16%, and at 24 h, e.g. from 23.81% to 16.88–21.04%. The presence of 5 wt% PE also decreased the water absorption at 2 h, e.g. from 56.17% to 42.01–52.98%, and at 24 h, e.g. from 70.89% to 58.63–66.76%. LDPE D209 and LDPE 2420T showed high potential in this application because they enhanced the water resistance and slightly increased the internal bond strength of the particleboard. MOR and MOE of particleboard could be ranked in the following order: D209 &gt; control &gt; 2420T.

Spray-Drying: An Emerging Technique for Pharmaceutical Product Development

Atomization of a solution of one or more solutes through a nozzle, spinning disk or other device followed by flash evaporation of the solvent from the droplets is termed as spray drying [1]. Spray-drying is a simple and robust continuous unit operation process which converts liquid to solid powder [2]. Thus, this process is based on drying of atomized liquid stream by contacting with high temperature gas stream by evaporation of liquid from the droplets, forming particles [3]. Being one of the oldest drying methods although it was known and used much before that, spray-drying gained much importance during the Second World War with the sudden need to reduce the transport weight of the foods and other materials [4]. Spray-drying is a versatile and one of the most emerging technologies for the pharmaceutical industry especially for novel pharmaceutical product development. This ideal technique is known to give up final product which complies with precise quality standards with respect to particle size and their distribution, residual solvent / moisture content, morphology and bulk density. Spray-drying offers multiple opportunities to provide very fine particles for pulmonary / nasal delivery, big agglomerated powers for oral administration, amorphous to crystalline products and is potential for one step formulation that no other technologies can offer. Apart from its ability to have high precision control over the particle size, bulk density, degree of crystallinity and residual solvent / moisture content in final product, this technique also holds good for typical applications in pre-formulated products, microencapsulation, solid solutions, improved bioavailability and stability through inclusion complex system and also provide opportunity to process the products with unusual or difficult characteristics such as sticky or hygroscopic products, slowly crystallizing products, products which are difficult to isolate and thermo sensitive materials.

A cause of water-sensitivity in modern oil paint films: The formation of magnesium sulphate

Unvarnished twentieth-century oil paintings are often sensitive to aqueous swabbing, a method routinely employed by conservators for surface cleaning. This study proposes a connection between sensitivity and the presence of magnesium sulphate heptahydrate which has been identified on the surface of some of water-sensitive paintings. The probable source of magnesium is magnesium carbonate, an additive in some twentieth-century oil paints, which has reacted with atmospheric sulphur dioxide (SO2). Films made using modern manufactured paints and formulations made in the laboratory were exposed to gaseous SO2 and raised relative humidity and examined using scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction to characterize the crystalline entities. Films containing magnesium carbonate formed magnesium sulphite and sulphate hydrates. Films containing zinc oxide were also investigated. These formed zinc and sulphur containing salts. Sensitivity to swabbing with water before and after exposure was evaluated. Films that developed salts, demonstrated increased sensitivity to aqueous swabbing after exposure to SO2. Findings suggest that increased water sensitivity may be due to a combination of the formation of hygroscopic degradation products and to weakening of the paint film due to salt-induced disruption of the surface.

Higroscopicidade de sementes de caju-de-árvore-do-cerrado

Estudos sobre a conservação e exploração de espécies nativas do Cerrado são fundamentais para tecnologias que visem à exploração racional destes produtos. Objetivou-se, neste trabalho, determinar as isotermas de dessorção de sementes de caju-de-árvore-do-cerrado, para diversas condições de temperatura e atividades de água, bem como ajustar diferentes modelos matemáticos aos dados experimentais, selecionando aquele que melhor representa o fenômeno. A higroscopicidade foi determinada pelo método estático-gravimétrico, para temperaturas de 25ºC, 30ºC, 35ºC e 40ºC e atividades de água entre 0,12 e 0,89 (decimal). Observou-se que o teor de água de equilíbrio decresceu com o aumento da temperatura, para uma mesma atividade de água, à semelhança dos produtos higroscópicos. O modelo de Chung-Pfost obteve o maior coeficiente de determinação e menores valores de erro médio relativo, erro médio estimado e Qui-quadrado, sendo selecionado para predição do equilíbrio higroscópico de sementes de caju-de-árvore-do-cerrado. O calor isostérico aumentou com a diminuição do teor de água, ou seja, aumentou a energia necessária para a remoção de água, com valores variando de 4.586,35 kJ kg-1 a 2.572,7 kJ kg-1, na faixa de teor de água de 1,76-6,56 (% b.s.).

Formulation and Evaluation of Melt-In-Mouth Tablets of Rizatriptan Benzoate

A B S T R A C T Over the past three decades, orodispersible tablets have gained considerable attention as a preferred alternative to conventional tablets and capsules due to better patient compliance. Rizatriptan Benzoate is potent anti migraine drug having agonist activity at the 5hydroxytryptamine (5-HT) 1B and (5-HT)1D receptor. It commonly used for relief of headaches in treatment of migraine. Conventional tablets of Rizatriptan Benzoate are not capable of rapid action, which is required for immediate relief from migraine pain. Marketed freeze dried tablet of Rizatriptan Benzoate is available. Freeze drying is cumbersome and it yields a fragile and hygroscopic product. Thus, the present investigation deals with development of Orodispersible tablets of Rizatriptan Benzoate to produce the intended benefits. Orodispersible tablets of Rizatriptan Benzoate were prepared using superdisintegrants viz; crospovidone, croscarmellose sodium and sodium starch glycolate using the direct compression method. The tablets prepared were evaluated for thickness, uniformity of weight, hardness, friability, wetting time, in vitro disintegration time and in vitro dissolution time. The tablets disintegrated within 21 to 75 s. Almost 95% of drug was released from all formulations within 15 min. The formulation containing 6% of croscarmellose sodium (F6) was found to give the best results. Apart from fulfilling all official and other specifications, the tablets exhibited higher rate of release. The stability studies were performed as per ICH guidelines. The Optimized formulation (F6) showed no significant variations for the tablets parameters and it was stable for the specified time period. It was concluded the Orodispersible tablets for Rizatriptan Benzoate can be formulated for emergency treatment of migraine.

Quality evaluation of Panax notoginseng extract dried by different drying methods

Quality control still remains a big issue, affecting herbs, formulations, and even the practice of Traditional Chinese Medicine. A promising solution to the problem is to take advantage of innovative process techniques including alternative drying methods within the pharmaceutical processing. Nowadays, vacuum belt drying (VBD) has gained more and more importance in food and pharmaceutical processing. In this work, Panax notoginseng extract was made into powder by the gentle VBD as well as by classical spray drying (SD), freeze drying (FD), and vacuum drying (VD). Certain chemical and physical properties of the dried powders such as moisture content, drying time, porosity, density, saponins content, pH value and hydroxyl radicals scavenging activity were evaluated. The results showed the qualities of dried products were influenced to different extent by drying methods certainly. Vacuum belt drying was suggested to dry P. notoginseng extract for its high quality assurance of hygroscopic products and suitable for sticky or high viscous products.

Umidade de equilíbrio de café cereja descascado baseadas em métodos estático e dinâmico

Construíram-se as isotermas de dessorção de grãos da espécie Café Arábica (Coffea arábica L.), da cultivar Novo Mundo-Acaiá, para as temperaturas de 50 e 73 °C e teores de mucilagem residual de 16,1 e 52,7%; posteriormente, oito modelos matemáticos de sorção de produtos higroscópicos foram ajustados aos dados experimentais (BET, BET Linear, GAB, Halsey, Halsey Modificado, Langmuir, Oswin e Peleg), com a finalidade de se obter seus coeficientes. A escolha do melhor ajuste se deu em função da avaliação do coeficiente de determinação (R²), do desvio relativo médio (DRM), da tendência de distribuição dos resíduos provenientes dos ajustes dos modelos e do desvio padrão da estimativa. As isotermas de dessorção para temperatura de 50°C e teores de mucilagem residual de 16,1 e 52,7% podem ser representadas pelos modelos Peleg, Halsey Modificado, GAB e Oswin. Para a temperatura de 73°C, o modelo GAB não representa bem os dados experimentais, sendo que os modelos Peleg e Halsey Modificado indicam o melhor desempenho. Com vistas à estimativa das umidades de equilíbrio dinâmicas, a equação proposta por Fioreze mostrou-se altamente satisfatória.

Changes of fatty acid aerosol hygroscopicity induced by ozonolysis under humid conditions

Abstract. Unsaturated fatty acids are important constituents of the organic fraction of atmospheric aerosols originating from biogenic or combustion sources. Oxidative processing of these may change their interaction with water and thus affect their effect on climate. The ozonolysis of oleic and arachidonic acid aerosol particles was studied under humid conditions in a flow reactor at ozone exposures close to atmospheric levels, at concentrations between 0.5 and 2 ppm. While oleic acid is a widely used proxy for such studies, arachidonic acid represents polyunsaturated fatty acids, which may decompose into hygroscopic products. The hygroscopic (diameter) growth factor at 93% relative humidity (RH) of the oxidized arachidonic particles increased up to 1.09 with increasing RH during the ozonolysis. In contrast, the growth factor of oleic acid was very low (1.03 at 93% RH) and was almost invariant to the ozonolysis conditions, so that oleic acid is not a good model to observe oxidation induced changes of hygroscopicity under atmospheric conditions. We show for arachidonic acid particles that the hygroscopic changes induced by humidity during ozonolysis are accompanied by about a doubling of the ratio of carboxylic acid protons to aliphatic protons. We suggest that, under humid conditions, the reaction of water with the Criegee intermediates might open a pathway for the formation of smaller acids that lead to more significant changes in hygroscopicity. Thus the effect of water to provide a competing pathway during ozonolysis observed in this study should be motivation to include water, which is ubiquitously present in and around atmospheric particles, in future studies related to aerosol particle aging.