CHANGES IN VITAMIN C CONTENT IN SELECTED FRUITS AND VEGETABLES SUPPLIED FOR SALE IN THE AUTUMN-WINTER PERIOD

Tadeusz Wojdyła, Jarosław Pobereżny, Ilona Rogozińska
Department of Storage and Processing of Plant Products, University of Technology and Life Sciences in Bydgoszcz, Poland

ABSTRACT

Studies on vitamin C content were conducted on plant material (fruits, vegetables) from the producers who supplied the products to the network of retail trade in Bydgoszcz. The products were stored in storage rooms where vitamin C content was determined in 14-day-long intervals using Tillmans’ method according to PN-A-04019:1008. Differentiated content of vitamin C (ranging from 4.0 to 146.1 mg·100 g^-1 of fresh weight) depended on the analyzed cultivar and in case of apples, pears, cucumbers, Italian broccoli, yellow paprika, onion and white cabbage on the date of estimation. The daily demand of an adult organism for vitamin C, on average from November till February, is covered (with theoretical assumptions) by the consumption of 80 g of yellow paprika, 80 g of cauliflower and 100 g of white cabbage. The calculated variability coefficients for vitamin C content in fruits and vegetables pointed to the greatest stability for cauliflower (1.8%), and the lowest for onion (12.9%), apples (14.2%) and pears (30.4%).

Key words: fruits, vegetables, vitamin C, date of estimation, stability.

INTRODUCTION

From the point of view of nutrition, ascorbic acid contained in fruits and vegetables, which together with dexydroascorbic acid constitutes vitamin C, is an important element. Human organism is not able to produce vitamin C by itself as it does not have L-glutoniane and L-galactonian dehydrogenase [2]; therefore, it has to be supplied with food.

According to Drozdowski [5], the biological effect of vitamins in fruits and vegetables is much better than that of synthetic vitamins since the former occur together with the substances that activate them. Fruits and vegetables, which are the best in the fresh state, are a rich source of natural vitamin C [16,20]. In Poland cabbage vegetables, berry fruit and potatoes are most commonly consumed. The yellow and green edible parts of vegetable plants are especially rich in vitamin C [14,24].

Their optimum consumption was established at a fairly high level in relation to the average feeding habits – they are totally about 300 g of fruit and 500 g vegetables in 4-5 meals during the day. These products provide about 60-70% of daily needs for vitamin C [11]. The daily requirement of a human organism for vitamin C is 40-100 mg [18,20,23], and even – depending on the physical condition of the organism – up to 135 mg [2]. Contrary to others, vitamin C can be consumed in greater quantities exceeding the daily requirements, without any harmful effect on the human organism because its excess is eliminated by the organism with urine and sweat [7].

Vitamin C content in fruit and vegetables depends on a number of factors. The most important is the species (cultivar), place and methods of cultivation, climatic conditions of a given region, agricultural treatments, the degree of ripeness during the harvest and the storage conditions [10,15,16,24,25].

Considerable losses of vitamins, especially vitamin C, take place while storing the raw materials of plant origin, particularly when the conditions are inadequate. Vitamin C content changes as a result of oxidation of L-ascorbic acid to L-dehydroascorbic acid, which is subject to further oxidation and loses its biological activity [8,16,17]. The destruction of the cell wall and the process of overripeness also affect the decrease of vitamin C content. Low air temperature during storage, which later on delays metabolic processes, influences stabilization of vitamin C [8].

An indicator of the quality of fruit and vegetables in the period of long-term storage is the dynamics of the change of vitamin C quantity. The reduction of vitamin C content after storage in fruits and vegetables considerably lowers their nutritive value [26].

The purpose of the studies was to determine vitamin C content in selected fruits and vegetables supplied by producers to the retail trade in Bydgoszcz throughout the autumn-winter period.

MATERIAL AND METHODS

The object of the studies conducted for 3 years (2003-2005) were the edible parts of selected fruits: pears and apples, ad vegetables: broccoli, onion, garlic, cauliflower, white cabbage, yellow paprika, tomato, root celery. Vitamin C content was determined between the end of October and the end of February with 14-days’ intervals in the period adjusted to the storage durability of the fruit and vegetables selected for studies. The examined material came from the producers who supplied the material (fruit and vegetables) to the network of retail trade in Bydgoszcz. The fruit and vegetables were stored in storage rooms, where the thermal-humidity conditions were adjusted, depending on the material and its requirements [1,9]:

• durable fruit (pears and apples) at the air temperature of 0°C and relative air humidity of 95%, the storage time of 4 months;

• nondurable vegetables (cucumber and tomato) at the air temperature of +12°C and relative air humidity of 90%, the storage time of 1 month;

• vegetables of medium durability (Italian broccoli and cauliflower) at the air temperature of 0°C and yellow paprika at +7°C and relative air humidity of 95% for the whole group of vegetables, storage time of 2 months;

• durable vegetables (onion and garlic) at relative air humidity of 70% and white cabbage and root celery at 95% and the air temperature for the whole group of 0°C, storage time 4 months.

Vitamin C content was marked in the raw materials enumerated above according to Tillmans’ method in agreement with PN-A-04019:1998, using the colour reaction of the examined solutions with 2,6-dichlorofenoloidophenol.

Results of 3-year-long studies were submitted to statistical calculations using the method of variance analysis for one-factor experiments, making use of Tukey’s test to estimate the significance of differences. Variability coefficients were calculated to present the stability of the examined features [22]. Vitamin C daily intake by an adult was calculated on the basis of model calculation of fruits and vegetables, according to dieticians’ recommendations [21].

RESULTS AND DISSCUSION

Usually, a given plant material or its products is defined as having ‘good’ or ‘bad’ quality; however, not specifying the terms. The consumers generally makes the quality evaluation themselves on the basis of their own senses. The quality evaluation can be performed not only on the basis of the outside appearance of fruits and vegetables, but also analyzing their chemical composition [10,13]. Vitamin C is one of the more important nutritious elements provided by fruits and vegetables [5,11].

Fruit
Vitamin C content in the examined fruits significantly depended on the date of studies (Table 1). The greatest content of vitamin C in the examined material – on average for the whole period of studies – was characteristic of apples (13.4 mg·100 g^-1 in the fresh weight), then pears (4.0 mg·100 g^-1 in the fresh weight). According to Kiczorowska and Kiczorowski [10], the level of vitamin C in apples was related to the cultivar and place of cultivation, and it ranged from 2.7 to 4.6 mg·100 mg^-1 in the fresh weight. Other authors [3] report that apples contain 9.2 mg·100 g^-1 of vitamin C in the fresh weight on average, pears have 5.3 mg·100 g^-1, while according to Lange and Ostrowski [15], pears contain from 4.0 to 35.0 mg·100 g^-1 in the fresh weight.

Table 1. Daily consumption of vitamin C with the consumption of 300 g of fresh fruits depending on the content and different dates of estimation ( from 3 years of studies)

Estimation date [A]		Pears			Apples
		1**	2	3	1	2	3
October		6.1	18.3	30.5	16.2	48.6	81.0
November	I*	5.3	15.9	26.5	15.2	45.6	76.0
	II	4.6	13.8	23.0	14.8	44.4	74.0
		5.0	14.9	24.8	15.0	45.0	75.0
December	I	4.5	13.5	22.5	14.3	42.9	71.5
	II	4.0	12.0	20.0	13.5	40.5	67.5
		4.3	12.8	21.3	13.9	41.7	69.5
January	I	3.8	11.4	19.0	12.5	37.5	62.5
	II	3.1	9.3	15.5	11.8	35.4	59.0
		3.5	10.4	17.3	12.2	36.5	60.8
February	I	2.7	8.1	13.5	1.8	35.4	59.0
	II	2.3	6.9	11.5	10.4	31.2	52.0
		2.5	7.5	12.5	11.1	33.3	55.5
		4.0	12.1	20.2	13.4	40.2	66.9
LSD p = 0.05		A – 1.48*			A – 1.54*

I* – first term of determination II – second term of determination 1** – Vitamin C content, mg·100 g-1 fr. m. 2 – Consumption of vitamin C, mg·day-1 3 – Satisfaction of daily demand for vitamin C, % Daily demand of an organism for vitamin C – 60 mg·day-1 (an adult) [2]

During the autumn-winter storage the studies observed a decrease in vitamin C content in the examined fruits in relation to the initial material (October). The greatest decrease was found out in pears – on average (from November till February) – 34.4%, while in apples those losses in the same period were half as low and they were 17.3%. The studied pears showed the greatest dynamics of vitamin C losses in the initial period of storage, up to 11.5% (November), while in apples – in the final period up to 8.5% (Fig. 1). The authors’ own studies observed a significant decrease of vitamin C content in fruits after storing them for 4 months; this is a generally known opinion confirmed by other authors [8,17], who also found out the reduced content of this vitamin in the studied plant material.

Fig. 1. Decrease of vitamin C (%) content marked every 14 days in selected fruits in comparison with the moment of beginning the studies (October) – mean value from 3 years

Table 1 presents the percentage coverage of the demand for vitamin C with the consumption of 300 g of fresh fruits. According to a number of authors [18,20,23], it ranges from 40 to 100 mg·day^-1, depending on a lot of factors, such as the age and physical activity of human organism. Borek-Wojciechowska [2] reports that 60 mg·day^-1 of vitamin C satisfies the requirements of an adult organism for this vitamin. The studied apples could cover the demand (mean from three years of studies in October in 81.0% and at the end of February in 52.0%. On the other hand, pears in an analogous period could do it in 30.5% and 11.5%, respectively. The existing deficit of vitamin C can be supplemented with another group of plants, for example vegetables.

Table 3 presents variability coefficients concerning the content of vitamin C in fruits during the storage, and they indicate the range of the obtained results, pointing to the stability of the studied feature. Apples were characterized by far less variability of vitamin C (variability coefficient – 14.2%), and at the same time they had considerable stability of the studied feature as compared to pears (variability coefficient – 30.4%), where stability was clearly greater.

Vegetables
The data contained in Table 2 show that the highest content of vitamin C was characteristic of vegetables belonging to the group of medium storage durability – paprika (mean value from the studied period was 148.7 mg·100 g^-1 of dry weight). According to Dobrzańska and Dobrzański [4], who quote after Trajan and others, the content of vitamin C in paprika is 170.0 mg·100 g^-1 in the fresh weight. On the other hand, Adamicki and Czerko [1], report after Salunkhe that the mean quantity of vitamin C in paprika is 128.0 mg·100 g^-1 in the fresh weight, whereas according to Piekarska and Łoś-Kuczera [19] this content is at the level of 107.0 mg·100 g^-1 in the fresh weight. According to Kunachowicz et al. [14] and Wierzbicka and Kuskowska [28], the quantity of vitamin C in paprika is more than 100 mg·100 g^-1 of fresh weight. The smallest quantity of vitamin C in the examined vegetables was characteristic of cucumbers, which are included within the group of nondurable vegetables (mean – 5.6 mg·100 g^-1 of fresh weight). This is in accordance with the results obtained by Zadernowski and Oszmiański [27], where the quantity of this vitamin in cucumbers ranged between 2.0 and 12.0 mg·100 g^-1 of fresh weight. The lowest content of vitamin C (mean for the whole period of studies) was found in cucumber, belonging to nondurable vegetables, 5.6 mg·100 g^-1 in fresh weight. On the other hand, Wierzbicka and Kuskowska [25] obtained the mean content of vitamin C in the fresh weight of cucumbers at the level of 8.6 mg·100 g^-1 in the cucumber fresh weight.

Like in the studied fruits, vitamin C content in selected vegetables, namely: cucumber, Italian broccoli, yellow paprika, cabbage and white cabbage, during the period of autumn-winter storage decreased significantly (Table 2 and Fig. 2). The lowest losses of vitamin C at the end of the storage time, depending on the durability of vegetables, were observed in cauliflower (a vegetable of medium durability) – 3.4%, while the highest were found out in onion (a durable vegetable), mean 26.8%. A similar range of vitamin C decrease is reported by Adamicki and Czerko [1]. A drop in vitamin C content in cauliflower and onion during the storage time was also confirmed by Gajewski [6].

Table 2. Daily demand for vitamin C with the assumed consumption of fresh fruits depending on the content and various estimation dates ( from 3 years of studies)

Date of estimation [A]		Undurable vegetables						Vegetables of medium durability									Durable vegetables
		cucumber			tomato			Italian broccoli			cauliflower			yellow paprika			onion			garlic			white cabbage			root celery
		1**	2	3	1	2	3	1	2	3	1	2	3	1	2	3	1	2	3	1	2	3	1	2	3	1	2	3
October		6.1	4.9	8.2	23.7	19.0	31.7	32.1	25.7	42.8	69.9	55.9	93.2	160.7	128.6	214.3	29.5	17.7	29.5	10.1	1.0	1.7	41.1	41.1	68.5	8.8	5.3	8.8
November	I*	5.9	4.7	7.8	23.5	18.8	31.3	31.4	25.1	41.8	68.6	54.9	91.5	159.1	127.3	212.2	28.8	17.3	28.8	9.8	1.0	1.6	41.0	41.0	68.3	7.8	4.7	7.8
	II	4.9	3.9	6.5	21.6	17.3	28.8	29.0	23.2	38.7	68.5	54.8	91.3	157.5	126.0	210.0	28.5	17.1	28.5	9.6	1.0	1.6	39.9	39.9	66.5	7.6	4.6	7.6
		5.4	4.3	7.2	22.6	18.1	30.2	30.2	24.2	40.3	68.6	54.9	91.4	158.3	126.7	211.1	28.7	17.2	28.7	9.7	1.0	1.6	40.5	40.5	67.4	7.7	4.6	7.7
December	I							26.2	21.0	35.0	68.6	54.9	91.5	134.4	107.5	179.2	25.1	15.1	25.1	9.3	0.9	1.6	38.9	38.9	64.8	7.8	4.7	7.8
	II							25.6	20.5	34.2	66.4	53.1	88.5	131.6	105.3	175.5	24.2	14.5	24.2	9.1	0.9	1.5	38.3	38.3	63.8	7.5	4.5	7.5
								25.9	20.7	34.5	67.5	54.0	90.0	133.0	106.4	177.4	24.7	14.8	24.7	9.2	0.9	1.5	38.6	38.6	64.3	7.7	4.6	7.7
January	I																23.8	13.4	22.4	8.9	0.9	1.5	37.6	37.6	62.7	7.1	4.3	7.1
	II																22.8	13.7	22.8	8.8	0.9	1.5	35.9	35.9	59.8	6.9	4.1	6.9
																	23.3	13.6	22.6	8.9	0.9	1.5	36.8	36.8	61.3	7.0	4.2	7.0
February	I																21.8	12.8	21.4	8.7	0.9	1.5	34.9	34.9	58.2	6.8	4.1	6.8
	II																21.4	13.1	21.8	8.1	0.8	1.4	34.2	34.2	57.0	6.1	3.7	6.1
																	21.6	13.0	21.6	8.4	0.8	1.4	34.6	34.6	57.6	6.5	3.9	6.5
		5.6	4.6	7.7	22.9	18.4	30.7	28.9	23.1	38.5	68.4	54.7	91.2	148.7	118.9	198.2	24.9	15.0	24.9	9.2	0.9	1.5	38.0	38.0	63.3	7.4	4.4	7.4
LSD p = 0.05		A – 0.91*			A – n.i.			A – 2.64*			A – n.i.			A – 14.59*			A – 1.66*			A – n.i.			A – 4.34*			A – n.i.

I* – first term of determination II – second term of determination 1** – vitamin C content, mg·100 g-1 fresh weight 2 – vitamin C consumption, mg·day-1 3 – satisfaction of daily demand for vitamin C (%) with the consumption of: Italian broccoli – 80 g, onion – 60 g, garlic – 10 g, cauliflower – 80 g, white cabbage – 100 g, cucumber – 80 g, yellow paprika – 80 g, tomato – 80 g, root celery – 60 g Daily demand of an organism for vitamin C = 60 mg·day-1 (an adult) [2]

Fig. 2. Decrease of vitamin C (%) content marked every 14 days in selected vegetables in comparison with the moment of beginning the studies (October) – mean value from 3 years

In white cabbage (included in the group of durable vegetables), which is a common source of vitamin C, the decrease of this vitamin by 6.1% after 2 months was found out, whereas Wierzbicka and Kuskowska [25] obtained a decrease of vitamin C content after the same period of storage ranging from 12.9% to 52.8%. Such a big loss of vitamin C in the cabbage examined by the author was affected by the storage conditions (a cellar – temperature from 5 to 10°C). Besides, Grzesiuk and Górecki [8] obtained a decrease of vitamin C in cabbage after 6 moths’ storage at the temperature of -0.5°C reaching 18.0%, while Wieczorek and Traczyk [24] pointed to a significant decrease of vitamin C in cabbage in cool storage; after 4 months that decrease was 15.0%. Those reports are confirmed by the authors’ own studies, which point out that after the same time of storage the decrease of vitamin C was obtained at the level of 16.8%.

Yellow paprika (a vegetable of medium durability) is of interest since while consuming 80 g of this vegetable – from October to December, on average – we will cover the daily demand of an adult’s organism for vitamin C almost three times. On the other hand, if we consume, for example, 60 g of root celery daily – from October to February, on average – we will cover the demand of an adult’s organism for this vitamin only in 7.4% (Table 2). Besides, the daily demand of an adult’s organism for vitamin C in the period between October and February is covered (theoretically) by the consumption of 80 g of cauliflower and 100 g of white cabbage. With the assumed consumption the other vegetables satisfy the daily demand of the organism for vitamin C, but in much smaller quantities, mean 16.9% (Table 2).

Table 3. Variability coefficients (%) for witamin C content in selected vegetables and fruits (mean from 3 years)

Undurable vegetables		Vegetables of medium durability			Durable vegetables				Durable fruits
cucumber	tomato	Italia broccoli	cauliflower	yellow paprika	onion	garlic	white cabbage	root celery	apples	pears
11.4	5.1	10.2	1.8*	9.7	12.9	6.7	6.7	10.4	14.2	30.4**

* – least variability, ** – most variability

Vitamin C found in plant raw materials belong to organic compounds of little stability [6,12]. Among the examined vegetables, cauliflower showed the greatest stability (1.8%), while onion – the smallest (12.9%). Big stability of vitamin C in such vegetables as cauliflower, garlic, white cabbage, tomato and yellow paprika can point to a considerable relation of this property to genetic conditions, and not other external factors (Table 3).

CONCLUSIONS

1. Fruits and vegetables showed differentiated variability of vitamin C content. The least variability was obtained for cauliflower (1.8%), while the most for onion (12.9%), apples (14.2%) and pears (30.4%).

2. With the assumed amounts of consumption, only yellow paprika, cauliflower and white cabbage would completely satisfy the daily demand of the organism for vitamin C.

3. The greatest significant decrease of vitamin C content in the autumn-winter period as compared to the beginning of studies among the fruits was shown by pears (62%) and among the vegetables – onion (28%).

REFERENCES

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26. Wojdyła T., 2006. Rośliny przemysłowe wykorzystywane w przemyśle spożywczym oraz metody analiz stosowanych w ich przetwórstwie [Industrial plants used in food industry and the analytic methods used in processing industry]. AT-R Bydgoszcz [in Polish].

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Accepted for print: 1.04.2008

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Tadeusz Wojdyła
Department of Storage and Processing of Plant Products,
University of Technology and Life Sciences in Bydgoszcz, Poland
Ks. Kordeckiego 20, 85-225 Bydgoszcz, Poland
Phone: (+48 52) 374 93 20
email: wojdyla@atr.bydgoszcz.pl

Jarosław Pobereżny
Department of Storage and Processing of Plant Products,
University of Technology and Life Sciences in Bydgoszcz, Poland
Ks. Kordeckiego 20, 85-225 Bydgoszcz, Poland
Phone: (+48 52) 374 93 45
email: poberezny@atr.bydgoszcz.pl

Ilona Rogozińska
Department of Storage and Processing of Plant Products,
University of Technology and Life Sciences in Bydgoszcz, Poland
Ks. Kordeckiego 20, 85-225 Bydgoszcz, Poland
Phone: (+48 52) 374 93 88
email: ilonarog@utp.edu.pl

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