Techno-Economic Evaluation of the Production of Protein Hydrolysed from Quinoa (Chenopodium quinoa Willd.) Using Supercritical Fluids and Conventional Solvent Extraction ^†

Abstract

The production of quinoa protein hydrolysate (QPH) using two technologies to extract the oil and separate the phenolic compounds (PC) prior to enzymatic hydrolysis was evaluated: (1) Supercritical fluids extraction (SFE), and (2) Conventional solvent extraction (CSE). A economic evaluation and sensitivity study was performed using SuperPro Designer^® 9.0 software; quinoa grain batches of 1.5 kg (laboratory) and 2500 kg (industrial scale) were considered. The results revealed that SFE allows for higher yields and the separation of PC, however, both processes are economically promising, especially when the QPH and by-products are produced on a large scale and sold at the current market price.

1. Introduction

Peru is the world’s leading producer and exporter of quinoa (Chenopodium quinoa Willd.), however, around 91% of FOB value exported is in the form of grain, 3.6% in flakes, and 2.2% in flour [1]. The functional food market is constantly growing at a global level, which is projected to reach US$ 280 billion by 2025, with an annual growth rate of around 8% [2], which reaffirms the importance of focusing efforts on the industrialization of functional foods and nutraceuticals from Peruvian biodiversity. Peptides have drawn attention worldwide, due to their antioxidant capacity, which can be used as antioxidants in food, and to reduce the risk of chronic diseases related to oxidative stress, and additionally [3], recent research indicates that the peptides are important for the body’s immune system against viruses [4].

However, there is a lack of information on the operating costs of production on an industrial scale of QPH [5]. The aim of this study was to compare the oil extraction yield, remaining phenolic compounds, and quinoa protein hydrolysed (QPH) yield. Furthermore, an economic evaluation and sensitivity study was performed using SuperPro Designer^® 9.0 software; quinoa grain batches of 1.5 kg (laboratory) and 2500 kg (industrial scale) were considered.

2. Materials and Methods

2.1. Experimental Process

The input parameters and process conditions were obtained from previous works [6], used as input data for the model. The production of QPH begins with the first stage, which is the extraction of the saponins of the grains; the saponins yield for each process was 0.31 g saponin/100 g (db); the second stage consists of the extraction of oil and phenolic compounds of the quinoa flour, of which the bulk density was 450 kg/m³; for CSE, the parameters solid/solvent (petroleum ether) ratio was 1:3.33 for 19 h at 55 °C; the oil yield was 4.58 g fat/100 g (db); for SFE, the operating parameters used were P = 23 MPa, T_reactor = 55 °C, and ethanol 7–8 g of quinoa/100 mL, CO₂ mass flow = 35 g/min and extraction time for 4 h, the oil yield was 6.30 g fat/100 g (db). The third step consisted of the extraction of the protein, proteins were precipitated at acid pH for 2 h at 50 °C; for SFE, the protein yield was 11.94 g protein/100 g (db) and 11.74 g protein/100 g (db) for CSE, then the step consists of enzymatic hydrolysis; using endopeptidase COROLASE 7089, the enzyme concentration was 4.2 UHb/g protein for 2 h, and QPH yield for SFE was 197.12 g hydrolysed/100 g and 160.52 g hydrolysed/100 g for CSE. The remaining phenolic compounds in QPH were evaluated by the determination of rutin equivalent, expressed as μg rutin/mL, achieving a higher purification in the process with SCF (16.15 ± 2.05 μg rutin/mL), compared to CSE (113.22 μg rutin/mL ± 8.13).

2.2. Scale-Up and Economic Evaluation of QPH Production

It is possible to scale the cost of equipment with the required capacity of Equation (1), in which C₁ represents the cost of equipment with capacity Q₁, in the same way that C₂ is the cost of equipment with capacity Q₂ and n is the cost coefficient; the latter was obtained from literature, and varies according to the equipment used [7,8]. According to the above, the fixed capital investment (FCI) was calculated for both plants at a production scale of 2500 kg/batch, as shown in

Table 1. Input economic parameters used for COM simulation.

Type of Cost	Laboratory Scale (1.5 kg/Batch)	Industrial Scale (2500 kg/Batch)
Fixed Capital Investment (FCI)
Conventional extraction	US$ 94,562.61	US$ 490,165.00
Supercritical extraction	US$ 249,698.88	US$ 10,268,219.25
Depreciation rate	10%/year	10%/year
Annual maintenance rate	6%/year	6%/year
Cost of operational labor (COL)
Wage (US$/h)	US$2.34	US$2.34
347 Number of workers per shift	2	6
Cost of Raw Material (CRM)
Grains of quinoa	1567 US$/tonne	1567 US$/tonne
Industrial CO2	0.033 US$/kg	0.033 US$/kg
Absolute ethanol	0.53 US$/kg	0.53 US$/kg
Petroleum ether	859 US$//tonne	859 US$//tonne
NaOH 1 N	125 US$//tonne	125 US$//tonne
HCl 1 N	41.37 US$//tonne	41.37 US$//tonne
NaOH 0.1 N	120 US$//tonne	120 US$//tonne
Phosphate buffer	1160 US$//tonne	1160 US$//tonne
Endopeptidase COROLASE® 7089 AB Enzymes-Germany	US$ 27.73	US$ 27.73
Cost of utilities (COU)
Electricity	0.1183 US$/kw	0.1183 US$/kw
Water	1.63 US$//tonne	1.63 US$//tonne
Cost of Waste Treatment (CWT)	100 US$/tonne	100 US$/tonne

.

$$C_1=C_2 {\left(\frac{Q_1}{Q_2}\right)}^n,$$

(1)

The cost of manufacturing (COM) can be determined as the sum of the three main components: direct costs, fixed costs, and general expenses. COM was estimated according to the methodology proposed by Turton et al. [8], by using Equation (2). According to Equation (2), the three main components are estimated in terms of five operational major costs: Fixed capital investment (FCI), Cost of raw material (CRM), Cost of labour (COL), Cost of utilities (CUT), and Cost of waste treatment (CWT); the economic parameters to determine the COM are shown in Table 1.

COM = 0.304 × FCI + 2.73 × COL + 1.23 × (CUT + CWT + CRM)

(2)

The sensitivity study consisted of 16 scenarios, both for the industrial and laboratory scale, considering the sale of by-products such as saponins and oil, as shown in

Table 2. Cost of manufacture of QPH for both scales (laboratory = 1.5 kg/batch and industrial 2500 kg/batch) evaluated.

Process-Plant-Scenario	Sale of Saponins	Sale of Oil	Productivity (Tonne/Year)	COM (US$/kg)	CRM (%)	COL (%)	FCI (%)	CUT (%)	CWT (%)	GM (%)	ROI (%)	PBT (Year)	NPV (at 7% Interest) (US$)	Operating Cost (US$/Year)	Revenues (US$/Year)
SCF-L-1	Yes	Yes	162	2599.68	22.93	19.36	40.44	17.27	0.00	−1019.12	−33.86	NA	−3,470,000	421,000.00	37,000
SCF-L-2	Yes	No	162	2641.68	22.93	19.36	40.44	17.27	0.00	−1190.85	−34.40	NA	−3,512,000	421,000.00	32,000
SCF-L-3	No	Yes	162	2618.79	22.93	19.36	40.44	17.27	0.00	−1025.88	−33.88	NA	−3,472,000	421,000.00	37,000
SCF-L-4	No	No	162	2660.88	22.93	19.36	40.44	17.27	0.00	−1199.84	−34.43	NA	−3,514,000	421,000.00	32,000
SCE-L-5	Yes	Yes	35	4367.18	7.13	51.23	38.84	2.61	0.19	−1751.31	−36.63	NA	−1,305,000	151,000.00	7000
SCE-L-6	Yes	No	35	4409.26	7.13	51.23	38.84	2.61	0.19	−2065.05	−36.99	NA	−1,315,000	151,000.00	6000
SCE-L-7	No	Yes	35	4386.29	7.13	51.23	38.84	2.61	0.19	−1764.85	−36.64	NA	−1,305,000	151,000.00	7000
SCE-L-8	No	No	35	4428.38	7.13	51.23	38.84	2.61	0.19	2089.35	−37.01	NA	−1,315,000	151,000.00	6000
SCF-I-9	Yes	Yes	269,998	28.90	67.17	1.19	28.92	2.72	0.00	67.31	85.96	1.16	205,006,000	20,504,000	62,719,000
SCF-I-10	Yes	No	269,998	70.98	67.17	1.19	28.92	2.72	0.00	62.29	70.51	1.42	162,784,000	20,504,000	54,376,000
SCF-I-11	No	Yes	269,998	48.01	67.17	1.19	28.92	2.72	0.00	67.11	85.26	1.17	203.102.000	20,504,000	62,343,000
SCF-I-12	No	No	269,998	90.10	67.17	1.19	28.92	2.72	0.00	62.03	69.82	1.43	160,880,000	20,504,000	53,999,000
SCE-I-13	Yes	Yes	57,734	57.06	55.54	19.12	3.88	6.65	14.80	42.4	155.83	0.64	28,159,000	7,845,000	13,620,000
SCE-I-14	Yes	No	57,734	92.79	55.54	19.12	3.88	6.65	14.80	32.64	104.53	0.96	18,171,000	7,845,000	11,646,000
SCE-I-15	No	Yes	57,734	73.55	55.54	19.12	3.88	6.65	14.80	41.98	153.26	0.65	27,658,000	7,845,000	13,521,000
SCE-I-16	No	No	57,734	109.29	55.54	19.12	3.88	6.65	14.80	32.06	101.96	0.98	17,671,000	7,845,000	11,547,000

L: Laboratory; I = Industrial; SFE: Supercritical fluids extratction; CSE: Conventional solvent extraction; COM: Cost of manufacturing; CRM: Cost of raw material; FCI: Fixed cost of investment; CUT: Cost of utilities; CWT: Cost of Waste Treatment, GM: Gross margin; ROI: Return of investment; PBT = Payback time; NPV = Net present value.

. Additionally, a regression was carried out to evaluate the influence of two input variables (productivity and hydrolysate yield) on two economic indicators: Cost of manufacturing (CM), and Net present value (NPV). Finally, the statistical study consisted of evaluating the significance of COM and NPV, on both industrial and laboratory scales, considering scenarios 1–4 as group 1, scenarios 5–8 as group 2, scenarios 9–12 as group 3, and 13–16 as group 4. The COM was evaluated by one-way ANOVA followed by Tukey’s post hoc test (p < 0.05), and the NPV was evaluated by nonparametric Kruskal–Wallis analysis for independent samples (p < 0.05), analysed using SPSS for Windows version 24.0 (SPSS, Inc., Chicago, IL, USA).

3. Results and Discussion

3.1. Scale-Up Process

For the scale-up process, it was assumed that the yield and QPH composition obtained at the laboratory scale would be similar to those obtained at the industrial scale under the same processing shown in Table 1. Moreover, the financing of the scale-up process was not considered in this study. To perform the simulations was considered a process operation of three daily shifts for 330 days per year, corresponding to 7920 h per year. A laboratory scale of 1.5 kg/batch of quinoa grain and an industrial scale of 1500 kg/batch quinoa grain were considered. The mass of quinoa grain to be processed at each stage was calculated based on the volume of the extraction vessel and the bulk density of the material of 450 kg/m³, thus determining the volume of the vessel of the SFE unit, obtaining values of 4000 L and 15,000 L for the CSE in the defatted stage respectively; the flow diagrams obtained with the simulator for both processes are as follows in Scheme 1.

3.2. Economic Evaluation of QPH Production

The oil extraction yield with SCF is 37% higher than CSE; this is in agreement with other similar studies that report percentages higher than 89% of oil recovered using SCF [9,10], additionally, also confirming the feasibility of using SFE to obtain defatted quinoa as a raw material in food applications, free of solvent residues, and with a technological quality superior to that obtained by extraction with organic solvents [11]. The remaining phenolic compounds in QPH, with the SCF process, allow for a higher degree of purification of the quinoa flour, reducing it by 85.84%, which, to date, no similar work has been reported. The QPH yield with SCF was 22% higher than that obtained with CSE; this may be due to the higher protein yield content reported in the previous research [6], and authors also report similar values [12,13].

For both cases, the scale-up reduced the COM, the COM was lower in SFE compared to CSE, US$ 90.10/kg, and US$ 109.29/kg, respectively, and a higher net present value (NPV), US$ 205,006,000, and US$ 28,159,000, compared to CSE. The CRM is the most important at industrial scale for both processes, however, when using SCF, it is 20% higher than CSE, despite having constant raw material costs for both processes; with defatted quinoa flour by SCF, it increases from 6.06 to 85.23, considering CO₂ and absolute ethanol as important components in such a variation. The sensitivity study considered the sale of by-products such as saponins and oil; the market price for the QPH considered was US$ 200/kg. The best scenario is when the sale of both by-products is included; the COM is reduced to US$ 28.90/kg (SFE) and US$ 57.06/kg (SCE), and profitability also improves. In addition, the significance the COM and NPV was statistically evaluated; there are no significant differences (p < 0.05), on an industrial scale, between the two processes evaluated.

4. Conclusions

The type of pre-treatment with SFE and CSE applied to quinoa flour prior to enzymatic hydrolysis influences the oil yield, maintaining phenolic compounds and a hydrolysate yield. The significance analysis of the factors considered shows that there is no significant effect on the COM and NPV of the QPH production at an industrial scale between each technology; however, the pre-treatment with SFE allows obtaining a lower COM and higher NPV; the sensitivity study and the evaluated scenarios show an additional income generated by the sale of by-products such as saponins and oils.