Fatty Acids Composition of Apple and Pear Seed Oils

Abstract

In this study, oil content and fatty acid composition of apple and pear seeds were analyzed. Apple (cv. red Fuji) seeds and pear (cv. Dangshan Suli) seeds contained a large quantity of oils (apple seed oil, 291 g/kg seed; pear seed oil, 179 g/kg seed). Eleven types of fatty acids were identified in apple and pear seed oil; c16:0, c16:1, c18:0, c18:1, c18:2, c18:3, c20:0, c20:1, c20:2, c22:0, and c24:0. The dominant fatty acids in apple seed oil were c18:1 (43.03 g/100g oil), c18:0 (26.47 g/100g oil), and c16:0 (5.60 g/100g oil). The same three fatty acids were also dominant in pear oil (c18:1, 56.80 g/100g oil; c18:0, 20.28 g/100g oil; and c16:0, 6.39 g/100g oil). Compared with previous research, an additional six fatty acids were found in apple seed oil (c16:1, c18:3, c20:1, c20:2, c22:0, and c24:0). Unsaturated fatty acids comprised 70.598 g/100g oil of apple seed oil and 77.846 g/100g oil of pear seed oil. In conclusion, apple seeds and pear seeds contain a large quantity of oil comprised of many fatty acids, especially unsaturated fatty acids. These data suggest that apple and pear seeds could be new sources of edible oils.

Keywords:

• Apple
• Fatty acids
• Pear
• Seed oil

INTRODUCTION

In recent years, there has been considerable interest in finding new food resources that will meet the health and nutritional needs of the world's population.[1,2] In Japan, many of the new foods with health claims have been wild vegetables,[3] such as mustard leaf,[4] elm fruits,[5] etc. Such resources are limited, and more attention should be paid to existing waste resources such as pomace and seeds. Globally there are large quantities of fruit pomace produced by juice industries every year. For example, 2.8–3.0 million tons of apples are processed into juice each year in the Shandong Province of China, resulting in 10–12 thousand tons of seeds being discarded as waste.[6] There has been some research on apple pomace,[7] but pear pomace and seeds have received less attention. The content and composition of oils in apple seeds and pear seeds should be systematically analyzed before they are used as new sources of edible oils.

Yu's (2005)[7] research showed the rate of oil extraction was 209.4 g g/kg seeds apple seeds, and there were five kinds of fatty acid in the oil, among which over 89 g/100g oil are unsaturated. Li's[8] results showed the apple seed contains 277.0 g oil in 1 kg apple seeds, in which the content of unsaturated fatty acid was over 89.33 g/100 g oil. Lu[9] extracted the apple oil with hexane and analyzed the fatty acids composition by GC-MS and found that apple oil consisted mainly of fatty acids (80.9 g/100 g oil) with linoleic acid as the most dominant one (51.2 g/100 g oil), followed by palmitic, linolenic, stearic, and oleic acids (10.5 g/100 g oil, 5.6 g/100 g oil, 4.3 g/100 g oil, and 4.1 g/100 g oil, respectively). But all these researches only found five kinds of fatty acids in apple oil. The content and composition of oils in pear seeds were reported little. The objective of the study was to determine the fatty acid composition of apple and pear seed oils from China, and to compare them with other common edible plant oils. We also discuss their value as new food resources.

MATERIALS AND METHODS

Materials

The fully matured fruits were collected at the market in campus of China Agricultural University. Apples (Red fuji) were grown at Yantai city, Shandong province, the apple fruits were 70–80% area red, and 8.0–8.5 cm diameter. Pears (Dangshau Suli) were grown at Dangshan county, Anhui province, the pear fruits are yellow, and 8.5–9.0 cm diameter. Seeds were removed manually, air-dried, and stored at room temperature until used for extraction.

Fatty Acid Extraction

Five g seeds were ground into a powder with a High Speed Tissue Masher. The seed powder was mixed with petroleum ether, and extracted at 100–110°C for 5 h. The mixture was filtered through filter paper, and then petroleum ether was removed under vacuum at 40°C. The apple and pear seed oil was kept at 4°C until analysis.[10]

Fatty Acid Analysis

Fatty acid composition and concentration were analyzed using an Agilent 1222362 gas chromatograph, equipped with an FID detector and a wall-coated capillary column (65.0m × 249 μm id, 0.25 μm film thickness, SGE company). The GC conditions were as follows: injector and detector temperature, 240°C; injection volume, 1 μl. Oven temperature of the gas chromatograph was programmed at 180°C slowly for the best resolution of methyl esters. The temperatures of flame ionization detector (FID) and injector were maintained at 250°C. Nitrogen, the carrier gas used, was maintained at a flow rate of 30 ml/min.[11,12]

RESULTS

Fatty Acid Content

Oil content in pear seeds (179 g/kg seeds) was similar to that in soybeans, while oil content in apple seeds was significantly higher (291 g/kg oil). These results showed that apple and pear seeds are good sources of edible oils (Table 1). Compared with Yu's (2005),[7] Li's (2003),[8] and Lu's[9] research, this study obtained more oil, 291 g oil from 1 kg seeds—the reason could be the higher extracting temperature, 100–110°C in this study, 30°C in Yu's [9] paper and Li's [8] clod extraction.

Table 1 Oil content in seeds

Material	Oil content/kg seed
Apple seed oil	291 g
Pear seed oil	179 g
Soybean seed oil	180∼220 g[13]

Fatty Acid Composition

Figures 1 and 2 show that there are 11 kinds of fatty acids in apple seed oil and pear seed oil, i.e. c16:0, c16:1, c18:0, c18:1, c18:2, c18:3, c20:0, c20:1, c20:2, c22:0, and c24:0 with varied concentration. The concentrations of c16:0, c16:1, c18:0, c18:1, c18:2, c18:3, c20:0, c20:1, c20:2, c22:0, c24:0 in apple seed oil are 5.606 g/100g oil, 0.060 g/100g oil, 1.466 g/100g oil, 26.473 g/100g oil, 43.031 g/100g oil, 0.600 g/100g oil, 1.311 g/100g oil, 0.391 g/100g oil, 0.043 g/100g oil, 0.270 g/100g oil and 0.089 g/100g oil, respectively(Table 2), and those in pear seed oil are 6.388 g/100g oil, 0.119 g/100g oil, 1.746 g/100g oil, 20.281 g/100g oil, 56.801 g/100g oil, 0.320 g/100g oil, 1.251 g/100g oil, 0.275 g/100g oil, 0.050 g/100g oil, 0.238 g/100g oil and 0.109 g/100g oil, respectively (Table 2). Compared with Yu's (2005),[7] Li's (2003),[8] and Lu's (1998)[9] research, an additional six fatty acids from apple seed oil were found in this study, and the concentrations of C18:1 and C18:2 were much lower than their data, the higher extracting temperature and the source of the fruits may contribute to these changes.

Table 2 Fatty acid composition of apple and pear seed oil (n = 3)

Fatty acid type	Apple seeds oil (g/100g oil)	Pear seeds oil (g/100g oil)
c16:0	5.606	6.388
c16:1	0.060	0.119
c18:0	1.466	1.746
c18:1	26.473	20.281
c18:2	43.031	56.801
c18:3	0.600	0.320
c20:0	1.311	1.251
c20:1	0.391	0.275
c20:2	0.043	0.050
c22:0	0.270	0.238
c24:0	0.089	0.109
Total fatty acids	79.34	87.578

There were 11 types of fatty acids identified in apple and pear seed oils, as shown in Figures 1 and 2; c16:0, c16:1, c18:0, c18:1, c18:2, c18:3, c20:0, c20:1, c20:2, c22:0 and c24:0. Saturated fatty acids comprised 8.742 g/100g apple seed oil and 9.732 g/100g pear seed oil. Unsaturated fatty acids comprised 70.598 g/100g apple seed oil and 77.846 g/100g pear seed oil, and monounsaturated fatty acid comprised 26.924 g/100g apple seed oil and 20.675 g/100g pear seed oil (Table 3).

Figure 1 Composition and concentration of fatty acids in apple seed oil.

Figure 2 Composition and concentration of fatty acids in pear seed oil.

Table 3 Saturated, unsaturated, and monounsaturated fatty acids in apple and pear seed oil (n = 3)

Fatty acid type	Apple seed oil(g/100g oil)	Pear seed oil(g/100g oil)
Saturated fatty acid	8.742	9.732
Unsaturated fatty acid	70.598	77.846
Monounsaturated fatty acid	26.924	20.675

DISCUSSION

The annual apple yield in China is 19.241 million tons—one-third of the global annual yield. Apples are planted over 1.9383 million hectares, comprising 40% of the global planting area in 2002.[14] Since 2000, China has produced more than half of the global annual pear yield, and in 2004, 10.2265 million tons of pears were produced.[15] Apples and pears are mainly consumed fresh in China, followed by processed apple and pear products. However, apple and pear seeds are discarded both when fruit is eaten fresh and during processing. This waste stream contains a large quantity of edible fatty acids as shown previously,[7] and in this study (Table 1).

New resources must be systemically analyzed before they can be used. Our results showed that the total fatty acid content in apple seeds was much higher than that in soybean, a common source of edible plant oil (Table 1), and also higher than the previous research about apple seeds oil.[7] We detected 11 types of fatty acids in apple seed oil (Figure 1), with the dominant fatty acids being c18:1, c18:0, and c16:0. Our results differed from those reported previously; Yu et al.[7] found only 5 types of fatty acid in apple seed oil, whereas our results showed 11. Higher extracting rate of oil and the additional six fatty acids may be related to cultivation conditions, planting area (Shandong Province, China, in our study; Shanxi Province, on the northwest of China, Yu et al.[7]), may also be related to the higher extracting temperature, which should nevertheless contributed to the decrease of some volatile fatty acids (oleic acid and linen acid).

We determined the content and composition of fatty acids in pear seed oil from China. The total oil content in pear seeds was similar to that in soybeans. We detected the same 11 types of fatty acids that were found in apple seed oil (Table 2). There was a greater yield of oil from apple seeds than from pear seeds. Both oils had high levels of unsaturated fatty acids (70.598 g unsaturated fatty acids in 100 g apple seed oil, and 77.846g unsaturated fatty acids in 100g pear seed oil; Table 3). These data suggest that both apple and pear seeds could be new sources of edible oils.

ACKNOWLEDGMENTS

This research was supported by the program for Changjiang Scholars and Innovative Research Team in University (No. IRT0511), the Natural Science Foundation of China (No. 30671471), and the National Key Technology R&D Program (No.2006BAD25B02).