Extraction of volatile and non-volatile components from custard apple seed powder using supercritical CO₂ extraction system and its inventory analysis

Highlights

• Volatile and non-volatile component recovery from custard apple seeds is assessed.

• Successful use of supercritical CO₂ as extraction fluid under optimized parameters.

• Custard apple seed extract showed antibacterial and anti-fungal properties.

• Inventory analysis for 1 kg extract production was executed.

Abstract

Custard apple (Annona Squamosa) seed is mainly an agricultural waste generated in many fruit and pulp industries. The seeds are an important source of value added products such as oil, polyphenols, and acetogenins, possessing medicinal properties and having excellent market potential. The current work aims at developing an intensified method to extract volatile and non-volatile components from custard apple seeds using supercritical CO₂ extraction (SC−CO₂) with detailed process optimization so as to establish conditions for maximum yield. The maximum extraction of non-volatile components was obtained at optimized conditions of 25 MPa pressure, 318 K temperature, and 2.5 mL/min flow rate. The extraction of volatile oils was maximum under conditions of 15 MPa pressure, 308 K temperature, and 1.5 mL/min. The extraction was observed to be complete within 1 h due to an increase in permeability based on the action of high pressure SC−CO_2, as also evident from the results of scanning electron microscopy (SEM) imaging. The antibacterial and antifungal properties of the obtained extract were also demonstrated in the work. The total number of energy units required for 1 kg extract production was calculated to be 40.69 kW h.

Introduction

Annona Squamosa, commonly known as sugar apple, has a huge demand in the fruit and pulp industry. The processing of fruits generates a large amount of waste in terms of seeds after the removal of pulp. These seeds consist of about 28–31 % oils, 15–18 % proteins, 3.2–17 % crude fiber and 10–12 % carbohydrates [[1], [2], [3], [4]]. Additionally, seeds also contain biomolecules such as terpenes, phenylpropanoids, acetogenins, α- and β-pinene, E-ocimene, germacrene-D, methyl butanoate, squamocins, ethyl butanoate, and methyl hexanoate [[5], [6], [7], [8]]. The seed extract has not only cytotoxic and phytotoxic effects but also has immense potential in the field of medicine. The extracted oils also find use in the flavoring and soap manufacturing industries [2]. Besides, the seed oil is also well known for anti-lice, insecticidal, bactericidal, antiviral, antifungal, and pesticide action [9,10]. Recent studies also show that the custard apple seed (CAS) oil can be used as a value added source for the production of biodiesel [11].

The extraction of oil and volatile components from the seeds can be performed using various conventional methods such as solvent extraction, but these have limitations such as a higher cost of operation and incomplete removal of valuable products. Thus it is very important to look for improved processing, especially considering the market potential. Recently the technological advancement and market demand have encouraged the use of green technologies. Supercritical fluid extraction (SFE) is one of the techniques that has emerged as an environmentally friendly, efficient, and scalable process in the field of extraction of oil and volatile components [12]. It can also be used for selective extraction of active compounds from natural resources using organic solvents in a single stage processing or an improved sequential extraction approach [[13], [14], [15]]. Compared to conventional methods such as steam distillation and Soxhlet extraction, SFE helps in reducing the processing problems such as solvent recovery, thermal degradation, and prolonged extraction time [16]. Carbon dioxide is the most commonly used supercritical solvent due to its non-toxic nature, low cost, easy separation, low critical temperature (304 K) and pressure (73 atm), as well as non-flammability. Supercritical extraction with CO₂ allows the application of mild operating conditions that ensures the stability and quality of the product. The efficacy of application of SFE is predominantly dependent on the parameters such as flow rate, time, temperature, and pressure that enhance the permeability of solvent (CO₂) and hence the obtained extraction yields.

The present work reports a detailed study into the extraction of volatile and non-volatile components from custard apple seeds using SC−CO₂ approach and also demonstrates process optimization for obtaining the best conditions for maximum yield. Also, the efficacy of the extracts was checked in terms of antibacterial as well as antifungal properties in order to check its applicability. Additionally, energy requirement analysis for obtaining 1 kg extract has been reported based on the mass and energy balances for the extraction system. Most of the literature reporting SC−CO₂ extraction does not report the yields of volatile and non-volatile components from the same sources separately. Considering these lacunae, the current work also reports selective extraction of essential components using SC−CO₂ extraction and establishes the effect of parameters such as flow rate and pressure on the yields of volatile and non-volatile components separately.