Nutritional and qualitative comparison of temperate fruits from conventional and organic orchards

Abstract

This research was conducted to compare the quality and nutritional profile of temperate fruits cultivated in conventional and organic orchards. Sampling was done in Iran from four orchards (two organic and two conventional). Ten fruits were sampled in three replicates in each of the organic and conventional orchards. Some traits such as the content of carotenoid, chlorophyll, ascorbic acid, phenolics, protein, soluble solids (TSS) and calcium (Ca), copper (Cu), zinc (Zn), iron (Fe), potassium (K), sulfur (S) and phosphorus elements were measured in the fruits and leaves. This study aims to evaluate the variability in chemical and nutritional quality parameters among various temperate fruit species sourced from both organic and conventional production methods. The research findings indicate that fruits cultivated in organic orchards exhibit superior quality and enhanced nutritional profiles compared to those grown conventionally. Specifically, the highest levels of carotenoids, chlorophyll, protein, and essential minerals were observed in the organic orchard. Notably, the interaction between orchard type and fruit variety revealed that organic mulberry displayed the highest concentrations of chlorophyll, protein, copper, and potassium. In contrast, organic grapes and figs presented elevated total soluble solids, copper, zinc, and iron levels. These results underscore the benefits of organic farming practices in producing nutritionally rich fruits.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-025-91768-5.

Introduction

Rapid population growth and increased demand for food in the last century caused a dramatic change in traditional agriculture. Therefore, the use of chemical fertilizers and pesticides and the planting of high-yielding cultivars of agricultural and horticultural species led to an increase in agricultural productions. This increase in production has been associated with numerous environmental problems such as soil and water pollution, and appearance of new plant pests and diseases, as well diseases caused by the decline in food quality. Among the various food pollutants, pesticides have the most shares. They not only kill the soil microorganisms and keep the poison residue on the food, but also cause the destruction of the natural ecosystem, disconnection of the food chains, weakening safety systems, and to hazard the health of farmers and consumers¹. Contrary to the rapid growth of organic crops in the developed countries of the world, the extension of organic agriculture in developing countries, including Iran, is very slow².

In organic agriculture, attentions are focused on biological processes and biodiversity in production instead of inputs with side effects such as toxins, chemical fertilizers, hormones and antibiotics³. Among the advantages of organic farming, we can mention the preservation of the environment, reduction of soil erosion, contribution to biodiversity, prevention of water pollution and increase of human health. Therefore, various policies were designed, formulated and implemented in different countries. So that during the past decades, it has witnessed the increase of organic crop farms and in 2009, around 37.5 million hectares of agricultural land was dedicated to organic cultivation⁴.

One of the important aspects of comparing organic and conventional agriculture is the type of fertilizer used in such a way that the amount of fruit antioxidant compounds decreases with the increase in the use of fertilizer⁵. In organic farming, organic fertilizers are used which have a beneficial effect on the physical, chemical and biological properties of the soil, in addition to their nutritional role. Organic fertilizers cause less pollution in the environment because their nutrients are released slowly and are available to the plant⁶. Some inorganic fertilizers are dangerous for the environment and human health due to the presence of heavy metals and radioactive particles⁷. Dangerous heavy metals in fertilizers include arsenic, cadmium, lead and to a lesser extent nickel and zinc, that are the main threat to human health⁸.

The antioxidant capacity of apple^9,10, grape¹¹ and strawberry¹² fruits produced through organic method was significantly higher than those of produced through traditionally method. Also, in blueberry, organic fruits had higher amount of sugars (fructose and glucose), malic acid, total phenol, total anthocyanin and antioxidant capacity compared to conventionally produced fruits¹². Strawberries produced in the organic method included higher vitamin C and flavonols than the conventional method¹³.

The reason for the smaller size of organic apple fruits was the formation of the smaller cells and less intercellular space, which increased the shelf life of the fruits¹⁴. It seems that the use of chemical fertilizers, especially high nitrogen causes increasing the cell size that makes the bigger fruits, in addition to accelerating the growth of shoots. Tangerines produced in the organic method had a higher concentration of vitamin C, minerals and carotenoids than the conventional method and showed better quality for the consumer¹⁵. This research was aimed to compare the quality and nutritional value of some temperate fruits in two conventional and organic orchards in Shahryar city, Tehran province, Iran.

Results

Analysis of variance (ANOVA) results showed that orchard type and fruit type had a significant interaction effect on all measured macroelements and microelement content in fruits (Table 1). Although all macro and micro elements of fruits were affected by the simple effect of the type of experimental fruits, the interaction effect of “orchard type × fruit type” was also significant on all elements (both micro and macro elements) except phosphorus. On the other hand, interaction effect of orchard type and fruit type was significant on the content of total soluble solids (TSS), protein, chlorophyll a, chlorophyll b, and total chlorophyll. There was no significant interaction effect of orchard type and fruit type on phenolics, ascorbic acid (vitamin C), and carotenoid content. Effect of fruit type on earlier parameters was significant (Table 2).

Table 1.

The analysis of variance (ANOVA) for the effect of experimental factors on the measured fruits’ mineral elements.

S.O.V	df	Means of squares (MS)
		Ca	Cu	Zn	Fe	K	S	P
Orchard type (A)	1	1,319,861*	26**	2912*	3003**	265,528ns	3386ns	1.35ns
Fruits (B)	9	4,494,880**	171**	3663**	1992**	12,371,940**	21,948**	170.06**
A × B	9	1,216,976**	18**	2389**	1294**	4,221,733**	6036*	14.11ns
Error	40	225,332	3	711	202	464,308	2280	8.32
C.V. (%)	–	16	26	144	29	6.62	20.88	26.84

*, **significant at the 0.05 and 0.01 probability levels, respectively; ns: not significant; S.O.V.: source of variances, C.V.: coefficient of variation; df: degrees of freedom.

Table 2.

The analysis of variance for the effect of experimental factors on the measured fruits’ physiological parameters.

S.O.V	df	Means of squares (MS)
		Carotenoid	Chlorophyll a	Chlorophyll b	Total Chlorophyll	Vitamin C	Phenolics	Protein	TSS
Orchard type (A)	1	20ns	38**	200**	433**	32ns	1.15ns	7*	7ns
Fruits (B)	9	140**	124**	108**	451**	2.58**	6.83**	13**	97.27**
A × B	9	4ns	27**	23**	90**	0.80ns	0.43ns	4*	18**
Error	40	5	4	5	10	0.41	0.35	1.6	2.36
CV (%)	–	18.28	16.58	22.24	14.51	13.58	8.13	75.00	9.99

*, **significant at the 0.05 and 0.01 probability levels, respectively; ns: not significant; S.O.V.: source of variances, C.V.: coefficient of variation; df: degrees of freedom.

Macro- and microelements content in fruits

Data presented in Table 3 (main effects of orchard type on mineral elements) obviously revealed that the content of all macro- and microelements in fruits produced in organic orchard was significantly higher than conventional orchard. Surprisingly, the content of Zn extracted from fruits produced in organic orchard was two- and five-fold than those of produced in conventional orchard, respectively. According to the mean comparison of the main effects of temperate fruits type on measured fruits’ mineral elements (Table 4), fig plants contained the highest amount of Zn (313 mg/kg), Fe (255 mg/kg), and S (546 mg/kg). The content of some of these elements like Zn in fig was 10-fold more than other plants. Grape produced the maximum amount of Cu (59 mg/kg), and P (36 mg/kg). The highest concentration of Ca (1084 mg/kg), and K (24,261 mg/kg) was extracted from mulberry and sour cherry, respectively (Table 4).

Table 3.

Mean comparison of the main effects of orchard type on measured characteristics.

Orchard type	Ca (mg/kg)	Cu (mg/kg)	Zn (mg/kg)	Fe (mg/kg)	Chlorophyll a (mg/ml)	Chlorophyll b (mg/ml)	Total Chlorophyll (mg/ml)	Protein (%)
Organic	6718a	25a	91a	176a	12a	12a	24a	2a
Conventional	6059b	21b	41b	132b	11b	8b	19b	1.32b

Means with different letters on the same column are significantly different (p < 0.05) based on LSD test.

Table 4.

Mean comparison of the main effects of temperate fruits on measured fruits’ elements.

Treatments	Concentration (mg/kg)
	Ca	Cu	Zn	Fe	K	S	P
Cherry	6577 bc	21 b	84 b	208 ab	23,783 a	482 ab	15 bc
Sour cherry	6635 bc	19 b	42 b	93 c	24,955 a	343 bc	15 bc
Apple	5079 cd	10 b	27b	112 c	16,403 b	305 c	22 b
Peach	4335 d	12 b	25b	127 bc	23,501 a	295 c	14 bc
Pear	5825 bcd	12 b	23b	81 c	16,750 a	279 c	16 b
Apricot	6664 bc	12 b	23b	137 bc	24,586 a	358 bc	15 b
Plum	5208 cd	13 b	37b	135 bc	23,132 a	391 abc	14 bc
Mulberry	11,084 a	13 b	29b	212 ab	24,261 a	544 a	5 c
Grape	4948 cd	59 a	57 b	167 bc	22,676 a	527 a	36 a
Fig	7523 b	56 a	313a	255 a	23,414 a	546 a	32 a

Means with different letters on the same column are significantly different (p < 0.05) based on LSD test.

Results of a farm survey which investigated the effects of production system (organic vs. conventional ) on fruits macro- and microelements content showed that maximum Ca (12,106 mg/kg), K (26,908 mg/kg), and S (614 mg/kg) was obtained from mulberry (Table 5). The mean comparison of the effect of orchard type (Table 3) showed that the highest amount of calcium was obtained by the organic method. The results showed that the highest amount of calcium was obtained from mulberry fruit obtained from organic cultivation. On the other hand, the production of mulberry by conventional cultivation method caused a 16.9% decrease in the amount of calcium compared to organic mulberry. The production of grapes by conventional method had the lowest calcium intake (Table 5). Results of this section also showed that the maximum Cu, Zn and Fe were extracted from fig fruits. The content of Zn and Cu extracted from fruits produced in organic orchard was about tenfold than those of produced in conventional orchard (Table 5).

Table 5.

Mean comparison of the interaction of temperate fruits and type of orchards on measured characteristics.

Treatments	Concentration (mg/kg)
	Ca	Cu	Zn	Fe	K	S
Organic orchards
Cherry	7228 bcde	30 de	80 b	313 ab	23,870 ab	523 abcd
Sour cherry	5439 cdef	17 ef	41 b	119 cd	24,586 ab	407 abcde
Apple	4986 cdef	9 f	25 b	122 cd	17,863 cd	316 bcde
Peach	3998 ef	8 f	21 b	100 cd	23,870 ab	251 e
Pear	4831 def	12 ef	18 b	97 cd	12,356 e	257 de
Apricot	8292 bc	12 ef	27 b	148 cd	25,324 ab	372abcde
Plum	6269 cdef	12 ef	40 b	100 cd	23,827 ab	294 bcde
Mulberry	12,106 a	13 ef	36 b	225 abc	26,908 a	614 a
Grape	6460 cdef	67 ab	84 b	173 cd	23,154 ab	615 a
Fig	7563 bcd	71.4 a	541 a	351 a	23,154 ab	555 ab
Conventional orchards
Cherry	5927 cdef	13 ef	88 b	103 cd	23,675 ab	441 abcde
Sour cherry	7834 bcd	22 ef	44 b	67 d	25,324 ab	278 cde
Apple	5170 cdef	12 ef	30 b	101 cd	14,943 de	294 bcde
Peach	4673 def	16 ef	30 b	155 cd	23,154 ab	337 bcde
Pear	6820 bcde	12 ef	28 b	66 d	21,147 bc	302 bcde
Apricot	5037 cdef	12 ef	19 b	126 cd	23,870 ab	345 bcde
Plum	4147 ef	15 ef	35 b	171 cd	22,416 abc	488 abcde
Mulberry	10,063 ab	12 ef	22 b	201 bcd	21,620 bc	475 abcde
Grape	3434 f	51 bc	29 b	162 cd	22,199 bc	439 abcde
Fig	7484 bcd	41 cd	86 b	159 cd	23,675 ab	537 abc

Means with different letters on the same column are significantly different (p < 0.05) based on LSD test.

The results of the lowest macro- and microelements content in fruits are as follows: Ca (3434 mg/kg in grape of conventional), Cu (8 and 9 mg/kg in peach and apple of organic), Zn (18 mg/kg in pear of organic), Fe (66 and 67 mg/kg in pear and sour cherry of conventional), K (12,356 mg/kg in pear of organic), and S (251 and 257 mg/kg in peach and pear of organic) (Table 5).

Physiological characteristics

Chlorophyll and carotenoid

The results of analysis of variance of the data showed that there were significant differences at the statistical level of 1% between the amount of chlorophyll a, b and total chlorophyll orchard type, fruit types and their interaction (Table 2). Mean comparison of data showed that the highest amount of chlorophyll a, b and total chlorophyll was obtained in the organic orchard (Table 3). Comparison of the simple effect of fruit type also showed that the highest amount of chlorophyll was related to mulberry fruit (Table 6). The reaction of fruits produced under organic and conventional gardening methods was different in terms of the amount of chlorophyll a in the interaction effect. In organic gardening, the amount of chlorophyll a (20 mg/ml) was high in mulberries. Grapes produced by the conventional method had the lowest amount of chlorophyll a (3 mg/ml) (Table 6).

Table 6.

Mean comparison of the main effects of temperate fruits type on measured fruits’ physiological parameters.

Treatments	Carotenoid (mg/g F.W.)	Chlorophyll a (mg/ml)	Chlorophyll b (mg/ml)	Total Chlorophyll (mg/ml)	Vitamin C (mg/100 g)	Phenolics (mg/100 g)	Protein (%)	TSS (%)
Cherry	14.84 abc	14.15 abc	12.78 ab	26.94 bc	4.62 bc	6.65 cd	0.87 b	15.25 bc
Sour cherry	16.95 ab	13.17 bcd	14.85 a	28.35 abc	6.01 a	9.24 a	0.57 b	20.00 a
Apple	12.63 bc	10.25 d	7.94 cd	18.19 d	4.53 bc	8.39 ab	2.04 b	12.50 cd
Peach	13.26 abc	12.69 cd	9.82 bc	22.51 cd	4.87 ab	6.85 c	2.60 b	10.00 d
Pear	16.57 abc	16.70 ab	13.33 ab	30.03 ab	4.19 bc	6.72 c	2.60 b	15.67 b
Apricot	14.15 abc	10.65 cd	9.51 bc	20.15 d	4.76 bc	6.77 c	0.87 b	11.08 d
Plum	12.22 c	11.37 cd	9.44 bc	20.77 d	5.38 ab	6.79 c	0.67 b	12.00 d
Mulberry	17.55 a	17.71 a	15.90 a	33.28 a	3.57 c	5.55 d	5.15 a	20.42 a
Grape	2.927 d	3.10 e	2.67 e	5.773 e	4.48 bc	8.11 ab	0.69 b	21.00 a
Fig	5.528 d	5.46 e	4.80 de	10.25 e	4.520 bc	7.58 bc	0.58 b	16.00 b

Means with different letters on the same column are significantly different (p < 0.05) based on LSD test.

The results of analysis of variance of the data (Table 2) showed that the effect of fruit type on carotenoid level was significant, but the effect of orchard type and the interaction effect of orchard type and fruit type on this trait were not significant. Based on mean comparison of the data (Table 6), the highest amount of carotenoids (17.55 mg/g fresh weight) was observed in mulberries. Also, the lowest amount of carotenoids (2.93 mg/g fresh weight) was observed in grapes, which were placed in the same statistical group with figs (5.53 mg/g fresh weight).

Mean comparison of the data of the interaction effect of orchard type and fruit type (Table 7) showed that the highest amount of chlorophyll b was obtained in cherry (18.97 mg/ml) and mulberry (19.14 mg/ml) produced in the organic method. Grape fruits produced by organic method (2.55 mg/ml) and grape fruits (2.79 mg/ml) and figs (2.73 mg/ml) produced by conventional horticulture method have the lowest amount of chlorophyll b and were placed in the same statistical group.

Table 7.

Mean comparison of the interaction effect of temperate fruits and type of orchards on measured fruits’ physiological parameters.

Treatments	Chlorophyll a (mg/ml)	Chlorophyll b (mg/ml)	Total Chlorophyll (mg/ml)	Protein (%)	TSS (%)
Organic orchards
Cherry	18.46 abc	17.24 ab	35.70 ab	0.40 c	13.17 defghi
Sour cherry	12.97 cdef	18.97 a	32.61 abc	0.38 c	21.67 a
Apple	8.65 efgh	7.03 cde	15.68 ef	2.69 abc	11.00 ghij
Peach	12.28 def	10.86 bcd	23.14 cde	3.82 abc	9.67 ij
Pear	13.97 bcde	13.35 abc	27.32 bcd	4.51 ab	17.00 abcde
Apricot	12.01 def	10.05 cd	22.06 de	0.62 bc	15.17 cdefgh
Plum	14.11 abcde	13.27 abc	27.30 bcd	0.25 c	11.67 fghij
Mulberry	20.09 a	19.14 a	39.24 a	6.20 a	20.50 ab
Grape	3.30 gh	2.55 e	5.850 fg	0.95 bc	21.33 a
Fig	7.36 fgh	6.86 cde	14.22 efg	0.26 c	16.17 b-f
Conventional orchards
Cherry	9.84 def	8.32 cde	18.17 de	1.34 bc	17.33 abcd
Sour cherry	13.36 cdef	10.72 bcd	24.08 cde	0.76 bc	18.33 abc
Apple	11.85 def	8.85 cde	20.70 de	1.39 bc	14.00 cdefghi
Peach	13.11 cdef	8.778 cde	21.88 de	1.38 bc	10.33 hij
Pear	19.43 ab	13.31 abc	32.75 abc	0.69 bc	14.33 cdefghi
Apricot	9.28 efg	8.97 cde	18.24 de	1.13 bc	7.00 j
Plum	8.62 efgh	5.62 de	14.24 efg	1.08 bc	12.33 efghi
Mulberry	15.33 abcd	12.67 abcd	27.33 bcd	4.09 abc	20.33 ab
Grape	2.90 h	2.79 e	5.69 g	0.43 c	20.67 ab
Fig	3.55 gh	2.73 e	6.28 fg	0.91 bc	15.83 bcdefg

Means with different letters on the same column are significantly different (p < 0.05) based on LSD test.

Based on the mean comparison results (Table 7), mulberry had the highest total chlorophyll (39.24 mg/ml) under organic gardening conditions. While, grapes had the lowest amount of total chlorophyll (5.70 mg/ml) under conventional conditions compared to other treatments.

Vitamin C (Ascorbic acid)

The amount of vitamin C in the fruit was significantly affected by the type of fruit (p< 1%) (Table 2). The comparative analysis of vitamin C content in various fruits, as presented in Table 6, reveals significant differences in the concentrations of this essential nutrient. Notably, cherries exhibited the highest vitamin C level, quantified at 6.01 mg per 100 grams, while mulberries recorded the lowest at 3.57 mg/100 g. This stark contrast underscores a remarkable variation, with the vitamin C content in cherries exceeding that of mulberries by approximately 68%. In terms of the amount of vitamin C, peach and plum were significantly superior to the other tested fruits and were in the same statistical group as cherry.

The content of phenolics in fruits

The analysis revealed a statistically significant effect of fruit type on the total phenolic content (p< 1%). Conversely, the type of orchard and the interaction between orchard type and fruit type did not yield significant results (Table 2). Mean comparisons indicated that sour cherries had the highest phenolic content at 9.24 mg/100 g, while mulberries recorded the lowest at 5.55 mg/100 g (Table 6). Notably, apples (8.39 mg/100 g) and grapes (8.11 mg/100 g) exhibited phenolic levels equivalent to those of cherries, thus categorizing them within the same statistical group. Overall, phenolic compounds were found to be more concentrated in certain fruits than in others.

Protein content

A significant difference was observed between different methods of orchard management in terms of protein amount, so the results of analysis of variance of the data showed that the effect of orchard type on protein amount was significant (p < 1%). Protein amount was significantly affected by fruit type and the interaction effect of orchard type and fruit type (Table 2). Based on the mean comparison of the data of the orchard type (Table 3), the highest amount of protein was obtained from the organic method. The mulberry fruit had the highest amount of protein (Table 6). Also, mean comparison of the interaction effect of type of orchard and type of fruit showed that the highest amount of protein was observed in mulberry fruit produced organically. The fruits of cherry, sour cherry, plum and fig produced by organic methods and grape produced by conventional methods had the lowest amount of protein and were placed in the same statistical group (Table 7).

Total Soluble Solids (TSS)

The investigation into the main effects of various fruit types and interaction of experimental factors on the total soluble solids (TSS) content has yielded noteworthy insights. A statistically significant difference (p < 1%) was observed, highlighting the influence that both the type of fruit and the conditions under which they are cultivated can have on their biochemical properties, as illustrated in Table 2. The mean comparison of different fruit types indicated that sour cherries, mulberries, and grapes exhibited the highest TSS levels. This finding underscores the potential of these fruits as sources of sugar, which is a critical factor in determining their sweetness and overall flavor profile, essential aspects for consumer preference and marketability (Table 6).

Furthermore, the interaction between orchard type and fruit type presented an intriguing dimension to the study. Notably, organic sour cherries and organic grapes demonstrated the highest TSS values, at 21.67% and 21.33%, respectively. This suggests that organic growing methods may enhance the sugar content in these fruits. Conversely, the study revealed that apricots grown through conventional methods had the lowest TSS content at 7%. In summary, the results of this study provide critical information regarding the influence of fruit type and cultivation method on TSS levels. The superior TSS content in organic sour cherries and grapes not only affirms the benefits of organic farming but also suggests a distinct advantage in producing sweeter, more flavorful fruits for both consumer enjoyment and health benefits.

Discussion

The importance of food quality and safety is progressively gaining attention within organic farming systems, which are anticipated to yield greater nutrient density and quality compared to conventional methods¹⁶. Practices associated with organic farming enhance food quality and promote human health, alongside ensuring food safety¹⁷. There is often a comparative analysis of foods produced through organic and conventional systems regarding their nutritional value, sensory attributes, and safety¹⁸. Most comparisons between these two farming systems emphasize aspects such as production efficiency, environmental impact, economic viability, welfare considerations, and sustainability¹⁶. The nutritional quality of plants is closely linked to the type of farming system employed. Our investigation revealed that fruits cultivated in organic orchards exhibited superior nutritional quality and phytochemical profiles compared to those from conventional orchards. Similar findings have been reported by various researchers^16,19. This aligns with the observation that management practices, particularly concerning pesticide and herbicide application, differ significantly between the two systems. A study examining 22 pesticides across four crops (lettuce, apple, grape, and tomato) indicated that pesticide levels in samples from conventional agriculture were markedly higher than those found in organic products²⁰. Regarding safety, there appears to be a general agreement that fruits grown organically contain lower levels of pesticide residues, HMs, and nitrates, highlighting distinct differences in quality and safety when compared to conventional options¹⁶. The reduced reliance on synthetic pesticides and fertilizers in organic systems may enhance plant defense mechanisms, resulting in an increased production of secondary metabolites such as antioxidants and phytoalexins²¹. Overall, the quality of a product encompasses its nutritional content as well as its sensory, mechanical, and functional characteristics. Comparison between the nutritional value and antioxidant compounds of kiwi fruit in organic, integrated and conventional farming methods showed that the amount of carotenoids and total chlorophyll in the organic treatment was significantly higher than the integrated and conventional method²². Amodio et al.²³ also revealed that kiwis produced in organic cultivation had a darker green color than conventional kiwis. In the present study, the highest amount of total chlorophyll was obtained in organic gardening conditions. It seems that the higher amount of chlorophyll in organic fruits is related to the higher amount of fruit acid²⁴.

Nutritional values can be understood in terms of vitamins, minerals, and proteins. Organic products serve as beneficial alternatives to nutritional supplements, often exhibiting slightly superior nutritional values compared to their conventional counterparts¹⁸. Navarro et al.²⁵ noted that organic mandarins displayed marginally enhanced nutritional and sensory attributes when compared to conventional mandarins. Similarly, Sreedevi and Divakar²⁶ found that organic ripe bananas contained higher levels of health-promoting nutrients, TSS, and sensory qualities than conventional varieties. Specifically, our observations indicated elevated concentrations of chlorophylls, carotenoids, vitamin C, total phenolics, proteins, and essential minerals in organically grown fruits. The highest levels of antioxidant compounds, particularly vitamin C, found in organic fruits may be attributed to enhanced plant stress responses and the activation of antioxidant enzymes. In contrast to our findings, Hasanaliyeva et al.²⁷ unexpectedly reported that the yields of grape varieties were comparable in both organic and conventional production systems. Furthermore, Seufert et al.²⁸ indicated that grape yields were generally higher in conventional production than in organic methods. This discrepancy may be attributed to factors such as variations in irrigation practices, disease severity, species or cultivar differences, production systems, nutrient inputs, responses to various stressors, soil management techniques, fertilization methods, microbial activity, maturation processes, and climatic conditions¹⁶. The selection of plant species or varieties and the production system employed are critical factors in evaluating both the quantity and quality of fruits. Ascorbic acid is one of the water-soluble antioxidants and plays an important role in the detoxification of reactive oxygen species (ROS), especially hydrogen peroxide. Also, it directly plays a role in neutralizing single oxygen radicals or superoxide and reproducing ɑ-tocopherol and other lipophilic antioxidants²⁹. In plants, this vitamin acts as a cofactor for many enzymes and enzyme metabolism. It is also necessary as a precursor for the synthesis of tartrate and oxalate. This vitamin is involved in many processes, including photosynthesis, cell wall growth, cell growth and division, resistance to environmental stress, synthesis of ethylene and gibberellin, anthocyanin and hydroxyproline³⁰. Vitamin C helps the proper hormonal balance in the body and increases the body’s immunity against diseases. Also, this vitamin helps to increase the strength of gums and teeth³¹. Levels of ascorbic acid in organically grown samples were reliably higher than the amounts for the conventionally grown crops. Sustainably grown strawberries contained higher levels of ascorbic acid as compared to conventionally grown fruits¹³.

The synthesis of phenolic compounds in plants is affected by living and non-living stresses, such as high levels of ultraviolet radiation, low temperature and food, attack by insects and pathogens, as well as orchard operations³². Although, the effect of orchard type and the interaction effect of orchard type and fruit type in the present study were not significant on the amount of phenol. Veberic et al.³³ reported that the higher amount of phenolic compounds in organic fruits at the time of harvest could be due to the encounter of these fruits to living and non-living stresses that strengthen the production of phenols. Abiotic and non-abiotic stresses increase the activity of phenylalanine ammonia-lyase (PAL) enzyme, which is one of the key enzymes in the production of phenolic compounds, so its activity can be directly related to the amount of phenolic compounds³². The difference and change in antioxidant activity and phenolic compounds during harvesting and storage depends on the size and fruit texture and management methods, in addition to the variety³⁴. In general, the increase in production should be accompanied by an increase in the quality of the product, or at least the decrease in its quality should be prevented. Research indicates that dry matter, a crucial metric for assessing organic matter accumulation and nutritional content, is present in greater quantities in organic fruits and vegetables compared to their conventional counterparts^16,35. Typically, organic berries and fruits are characterized by elevated levels of dry matter, vitamin C, and antioxidant activity¹⁶. Studies have shown that fruits cultivated in organic orchard systems exhibit enhanced polyphenol content and antioxidant capacity³⁶. Furthermore, organic pumpkins have been found to possess higher levels of dry matter, total carotenoids, phenolic acids, flavonoids, and polyphenols when compared to conventional varieties³⁷. Specifically, blueberries cultivated organically demonstrated significantly higher total phenolic and anthocyanin content³⁸. Koureh et al.³⁹ reported that organic white seedless grapes exhibited elevated levels of antioxidant activity, total phenolics, total flavonoids, and beneficial phenolic compounds. Additionally, organically grown raspberries showed greater antioxidant capacities along with higher levels of flavonoids, phenolics, and TSS compared to those produced conventionally⁴⁰.

The total phenolic content of conventionally grown Marion berries, strawberries, and corn were 412, 241, and 24.7 mg/100 g of fresh weight, respectively¹³. Their results revealed a statistically relevant trend of higher levels of total phenolic compound in organically and sustainably produced crops. More interestingly, their results indicated that total phenolic compound were highest in the crops grown by sustainable agricultural methods as compared to organic methods. Organic management in orchards has demonstrated effectiveness as a production system, yielding the highest amounts of blueberries while incurring the lowest production costs when compared to conventional orchards⁴¹.Research indicates that organic farming can boost the activity of ascorbate peroxidase, a crucial enzyme in vitamin C metabolism⁴². Additionally, the increased levels of total phenolics in organic fruits are linked to the upregulation of phenylpropanoid pathways, which play a significant role in the biosynthesis of these compounds. Studies have shown that strawberries grown in organic systems exhibit higher TSS contents than those from conventional systems⁴³. Oliveira et al. (2013) reported that the TSS content in organic fruits was approximately 56% greater than that in conventional fruits. This phenomenon can be attributed to the soil fertilization practices in organic systems, which utilize methods and tools that facilitate a gradual release of nutrients to plants, in contrast to conventional systems²⁸. The maximum ascorbic acid (vitamin C) levels recorded in strawberries were 92.6 mg/100 g for organic varieties and 68.9 mg/100 g for conventional varieties at the conclusion of storage⁴³. The vitamin C content is influenced by various factors, including the variety, stage of maturity, cultivation conditions, and timing of harvest. Comparable findings were observed regarding anthocyanin content, with no significant differences between the two production systems⁴³.

Proteins are one of the main and essential food groups for the body’s health, which are broken down into amino acids in the body and help to improve cell growth. Fresh fruits and vegetables are very important as a source of protein. The source of protein in fresh fruits is about 1%. According to the results obtained from this experiment, the used mulberry fruits can be a relatively suitable source for fruit protein. Tangerines produced in the organic method had a higher concentration of vitamin C and minerals than the conventional method and show better quality for the consumer¹⁵. Fruit may not be the first thing for sources of protein. The antioxidants present in fruits have been associated with various health benefits for humans; however, these benefits may be influenced by factors such as farming systems, agronomic practices, specific types or varieties, and processing methods²⁷. Research indicates that the total antioxidant activity or capacity in organic grapes is significantly higher—by 57%—compared to conventional grapes, although the differences were not statistically significant²⁷. The reasons behind the inconsistent and sometimes opposing effects of different production systems on antioxidant activity, as well as the total concentrations of phenolics and anthocyanins, remain inadequately understood²⁷. Potential factors contributing to these variations may include the availability of mineral elements and the use of pesticides (including herbicides, fungicides, and growth regulators) particularly in conventional farming practices²⁷. Additionally, the enhanced expression of phenolic compounds and other secondary metabolites with antioxidant properties in plants may be triggered by biotic stresses (such as pest and disease attacks) and abiotic stressors (including drought, flooding, or heat stress)¹⁷. Veberic et al.³³ noted that exposure to both biotic and abiotic stressors increase the production of phenolic compounds, a process mediated by the enzyme phenylalanine ammonia-lyase (PAL). There exists a direct correlation between PAL activity and the concentration of phenolic compounds. Studies on carrots (Daucus carota L.)⁴⁴ and various organically and traditionally cultivated plants³⁸ have demonstrated that organic products tend to have higher levels of dry matter, sugars, ascorbic acid, total phenolic compounds, and mineral nutrients. Furthermore, organically grown apples exhibited greater antioxidant capacity compared to their conventional counterparts³⁶. Numerous studies have indicated that the phenolic compound content is elevated in organic products, including apples, orange juice, pomegranate juice, apricots, raspberries, and strawberries¹⁶.

Sugars and organic acids are the main determinants of the taste of fruits. It has been reported that in organic blueberry fruits, the amount of sugar (fructose and glucose), malic acid, total phenol, total anthocyanin and antioxidant capacity were higher compared to the fruits produced by the conventional method¹². The amount of TSS is widely used to determine the quality of fruits after harvest and is closely related to other traits⁴⁵. It has been reported that the reason for the increase in TSS during fruit ripening is the increase in the activity of sucrose phosphate synthase (SPS), which is a key enzyme in sucrose biosynthesis. This enzyme is activated by ethylene during the ripening process⁴⁶. Organic farming practices have been linked to elevated levels of TSS in fruits. TSS is an essential indicator of fruit quality, as it indicates sugar concentration and plays a significant role in the flavor and overall appeal of the fruit. Additionally, TSS is interconnected with various other quality factors that influence consumer preferences and satisfaction⁴⁵. Research conducted by Wang et al.¹² revealed that blueberries cultivated through organic methods contained notably higher concentrations of sugars (fructose and glucose), malic acid, total phenolics, and total anthocyanins in comparison to those grown using conventional techniques. A comparative analysis of the nutritional value and antioxidant properties of kiwi fruit across organic, integrated, and conventional farming systems indicated that the organic approach resulted in significantly greater levels of carotenoids and total chlorophyll than the integrated and conventional methods²². Furthermore, a recent investigation showed that grape berries sourced from organic orchards exhibited superior edible quality, and increased antioxidant capacity and phytochemical content when compared to those harvested from conventional orchards⁴⁷.

According to the results of the present study, the highest amount of Ca and K was obtained from mulberry fruit obtained from organic gardening, the highest amount of Cu, Zn and Fe was obtained from fig fruit under organic gardening. Also, the highest amount of S was observed in organic grapes and the highest amount of fruit P was observed in grapes and figs. Since, the amount of absorption and type of elements are not the same in all fruits, therefore, the amount of elements present in the texture of different fruits cannot be considered as a result of industrial factors or gardener’s management policies, such as the use of chemical fertilizers and pesticides, and the only justifying reason is the difference in the type of fruits and natural factors due to the heterogeneity of horticultural conditions and gardener’s decisions in using inputs. In this research, the highest amount of elements was found in fruits from organic gardening conditions. Of course, the type of orchard management (organic or conventional) in addition to the absorption of elements is also effective on the biochemical characteristics of the products, so that in the study conducted on apple fruit in two management systems of conventional and organic cultivation, there was a significant difference in the antioxidant capacity of the fruit. It indicates the higher quality value of organically produced fruits¹⁰.

Gerasopoulos and Drogoudi⁴⁸ found that the high Ca content in apple fruits produced in organic cultivation increased the shelf life of fruits during storage. Cu is one of the micronutrients that are necessary for plant metabolism, thus the lack of Cu will cause the leaves to remain small and burn on the young stems. In general, the young leaves and seeds are usually enriched with Cu and Zn. One of the main reasons for the increase of Cu in leaves is the absorption of this element through the aerial organs, simultaneously with the spraying of liquid fertilizers or chemical poisons containing Cu⁴⁹. Shi et al.⁵⁰ demonstrated that Cu has a strong spatial dependence on natural factors including parent material, topography and soil type.

The highest amount of Cu, Zn and Fe in the present study was observed in fig fruit. Zn is one of the elements that is necessary for the plant growth, but in some cases, the high concentration of Zn is due to the excessive use of phosphate fertilizers, pesticides and animal manure⁵¹. Studies also indicated that fig fruit is rich in sugar and mineral elements⁵² and its important mineral elements are K, Ca, Mg, Na and Zn⁵³. So that this fruit is nutritious for the industrial production of food⁵⁴. Comparison between the mineral elements of figs with other fruits showed that figs have more calcium (Ca) than apples, dates, and strawberries, and their K concentration is higher than apples and dates⁵⁵. Some factors affecting the absorption of metals and their accumulation in agricultural products are soil pH, cation exchange capacity, soil organic matter content, soil type and the mutual effects of elements in the target organ⁵⁶.

The existing literature indicates that organic fruits possess equal or greater concentrations of minerals, phytochemicals, and vitamins C and E compared to their conventional counterparts⁵⁷. Several prior investigations have demonstrated that food products derived from organic farming exhibit enhanced nutrient levels as well as increased aroma compounds⁵⁸. Generally, organically cultivated crops tend to have elevated levels of dry matter, sugar, titratable acidity, protective substances, antioxidant capacity, flavonoids, total phenols, and essential elements such as Ca, Mg, P, Zn, and Fe when compared to conventionally grown crops¹⁶. Research has shown that organic pomegranate juices contain higher concentrations of amino acids than those produced conventionally⁵⁹. Various comparative studies indicate that organic crop products exhibit significantly higher levels of vitamin C, Fe, Mg, Zn, copper (Cu), and P than conventional crops^60,61. Additionally, the vitamin C content in organic potatoes is reported to be equal to or greater than that found in conventional varieties⁶². Higher levels of vitamin C have also been observed in organically grown fruits such as peaches, guavas, kiwifruit, oranges, and strawberries¹⁶. Furthermore, organically cultivated plums, jujube fruits, oranges, mandarins, and strawberries have been found to contain greater carotenoid levels^16,25. Data collected over the past six decades regarding the nutrient content of conventionally grown fresh fruits and vegetables in the United States and the United Kingdom reveal a decline in mineral content, including Ca, Mg, sodium (Na), potassium (K), P, and Fe⁶³. In our research, organic mulberries were found to be rich in Ca and K, while organic figs contained notable amounts of Cu, Zn, and Fe. The highest S levels were recorded in organic grapes, and the greatest concentrations of P were observed in both grapes and figs. The findings suggest significant absorption levels of various minerals. The variations observed illustrate the intrinsic diversity and intricacy of biochemical processes present in each fruit, influenced by distinct management practices in horticulture, whether organic or conventional.

Materials and methods

Selection of orchard and sampling

Conventional orchards typically employ synthetic fertilizers and pesticides, while organic orchards adhere to stringent guidelines that promote the use of natural amendments and biological pest control or fertilizers and pesticides are not used in these organic gardens. Accordingly, the orchards were selected in a geographical area that was almost identical in terms of climate and edaphic conditions. However, the selected fruits were the dominant fruits of the region. A comprehensive sampling strategy was employed across four orchards, with five 10 × 10 m² plots selected from each (Fig. 1). Within each plot, plant samples were systematically collected, encompassing both fruit and leaf tissues. This approach ensured a representative and standardized data collection process, minimizing variability and enhancing the reliability of subsequent analyses. .

Fig. 1.

Location of the four research orchards in Tehran province, Iran (35.665463, 50.947575), 1150 m above sea level (A: organic orchard, B: conventional orchard, bar represents 100 m). Geographic coordinates were recorded with a GARMIN GPSMAP 64 from Taiwan, and a map was created using Google Earth Pro 7.3.2 and incorporated into a schematic map of Iran.

The samples related to each of the orchards were coded. The samples were collected in spring and early 2020. According to European regulations for the maximum amount of contaminants⁶⁴, plant samples were gently washed to remove surface contamination by first dipping in water and then twice in deionized water. The moisture content of plant samples was determined and then they were dried at 70 °C.

Measurement of elements

In the present study, the concentrations of 5 micro and macro nutrients — copper (Cu), iron (Fe), potassium (K), sulfur (S), and zinc (Zn) — were assessed in the fruit tissues of selected plant species. Each 5 g fruit sample underwent incineration at 500 °C for 8 h, resulting in ash formation. A subsequent extraction was performed using 0.2 g of the ash in 3 ml of 65% nitric acid at room temperature for 24 h. The mixture was then heated to 110 °C for 5 h to achieve complete acidic digestion. Following filtration with Whatman 42 filter paper, the solution was adjusted to volumetric standards using either 1% nitric acid or water, after which it was subjected to inductively coupled plasma mass spectrometry (ICP-MS) for heavy metal concentration analysis. Calibration was ensured through the use of certified reference materials and pre-verified standards, with results expressed in milligrams per liter. The total uncertainty associated with the measurements was calculated in accordance with the EURACHEM/CITAC Guide, yielding an expanded uncertainty of ± 0.2%⁶⁵. To control the quality of analytical methods, plant and soil samples were examined from the evaluation programs of Wageningen Analytical Laboratories⁶⁶ along with the samples.

Measurement of physiological traits

Sampling was done to measure the amount of chlorophyll from different treatments. The content of 0.5 g of the sample was weighed and pounded in a Chinese mortar with 50 ml of 80% acetone (80 ml of acetone and 20 ml of distilled water). Then, the resulting extract was passed through a filter and brought to a volume of 50 ml and poured into small containers (covet). The amount of chlorophyll A was measured by a spectrophotometer. Chlorophyll was read at 2 wavelengths of 643 and 660 nm. Then, the read numbers were put in the following formula and the values ​​of chlorophyll a, chlorophyll b and total chlorophyll were obtained⁶⁷.

To measure the amount of carotenoid, sampling was taken from different treatments. The content of 0.5 g of the sample was weighed and pounded in a Chinese mortar with 50 ml of 80% acetone (80 ml of acetone and 20 ml of distilled water). Then, the resulting extract was passed through a filter and brought to a volume of 50 ml and poured into small containers (covet). The extracts were read at 3 wavelengths of 645, 663 and 660 nm. Then, the read numbers were put in the following formula and the carotenoid values of the treatments were determined⁶⁷.

The concentration of ascorbic acid in fruit extracts is determined based on the regeneration of the color reagent 2,6-dichlorophenol indophenol (DCIP) by ascorbic acid. The content of 1 g of the fruit extract was mixed with 5 ml of Meta phosphoric acid. After 0.5 h, 3 ml of the mixture with color reagent (DCPIP) containing sodium bicarbonate was titrated until the appearance of a pale pink color that persisted for 15 s. Then, the content of ascorbic acid (vitamin C) was calculated using resulted number and the following formula⁶⁸.

In which; a: sample weight, b: volume made by adding Meta phosphoric acid, c: volume removed from extract solution and Meta phosphoric acid for measurement, d: dye factor, and e: the content of consumed color solution for each sample.

The amount of total phenol compounds was determined with Folin-Ciocalteu reagent. To measure the amount of total phenol compounds, about 1 g of fresh leaves was ground in 10 ml of methanol for 2 min. and the obtained solution was filtered with filter paper. The content of 5 ml of diluted Folin-Ciocalteu (1:10 diluted with distilled water) and then 4 ml sodium carbonate solution (7.5% by volume) was added to 0.5 ml of the diluted extract (1:10 g/ml). Samples were left at room temperature for 15 min and their absorbance was read at 765 nm with a spectrophotometer⁶⁹. The standard curve was obtained using different concentrations of Gallic acid (0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 and 0.4 mg/ml) and the amount of total phenol was calculated for each sample from the standard curve and the obtained line equation.

In order to measure protein by Bradford method, 2 g sodium dodecyl sulfate (SDS) was added and dissolved in 100 ml of 0.5 M Tris buffer with a pH 6.8. The 200 ml of extraction buffer was added to the plant sample and mixed. All these steps were done at 4 °C. Then, the solutions were centrifuged at 13,000 rpm for 20 min. The 100 μl of the above extract was added to 5 ml of Bradford solution (Coomassie Brilliant Blue G-250) and after 30 min., the absorbance of the above extract was measured at a wavelength of 595 nm and the amount of protein was calculated using the standard curve in laboratory conditions. Protein standard solution was prepared by dissolving 1 mg of bovine serum albumin (BSA) powder in 5 ml of double distilled water. The 5 ml of Bradford solution and determined volumes from 20 to 200 μl of standard BSA solution were poured into the test tubes and made up to 500 μl with distilled water. After that, the absorbance of each standard color solution was read by spectrophotometer (SHIMADZ 160 UV, Japan) at a wavelength of 595 nm⁷⁰. To measure the TSS (total soluble solids), an optical refractometer model E 20 ATC Atago (Japan), with a range of 0–20% was used. The fruits were cut transversely, then one or two drops of the extract were placed on the refractometer and the TSS level was read.

Data analysis

This experiment was analyzed as a factorial design with two factors (Completely randomized design). The first factor included the type of orchard (traditional or conventional orchard and organic orchard) and the second factor included ten types of fruits (cherry, sure cherry, European plum, peach, apple, pear, apricot, berry, grape and fig). Each sample was evaluated statistically with at least three replicates. Comparison of treatment means was done using Tukey’s test depending on the normality of the data after one-way ANOVA using MSTATC software.

Conclusions

This study compared organic and traditional (conventional) production systems in terms of quality and nutritional parameters. Results reported here suggest the use of organic production system without the use of pesticides for broadly-produced yields and nutritional composition in fruits. Mulberry fruits produced with organic production system exhibited the highest Ca, K, S, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, protein, and TSS. The content of other measured parameters in mulberry was also high as acceptable range. Antioxidant activity (the content of vitamin C and phenol) was highest in sour cherry fruit. In total, our findings indicate a significant improvement in the quality of fruits in organic orchard, which can be used as an effective strategy to improve the quality of agricultural products. Although the literatures have shown differences between organic and conventional foods in a preference for organic ones, the existing information remains insufficient, necessitating further research to establish definitive conclusions. Organic system is recognized for its profitability and environmentally friendly, as well as its contributions to ecosystem and social benefits, while also being equally or more nutritious. Nevertheless, it is likely to remain a secondary option compared to conventional system due to its lower yields and higher costs. To address the need for increased food quantity and quality in a sustainable manner, research should focus on the management of organic agriculture and food-processing practices that utilize natural resources effectively, enhance the capacity to mitigate climate change through organic methods, and improve the nutritional and sensory qualities of agricultural products.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Author contributions

M. R., B. K., S. S. and A. E. were responsible for the experiment and contributed to the study’s conception and design. Data collection was performed by B. K., S. S. and A. E. Methodology and results were performed by M. R., B. K. and S. S.. Introduction and discussion were performed by M. R. and B. K. The manuscript was revised by B. K., S.S. and A. E. All authors read and approved the final manuscript.

Funding

This research received no external funding.

Data availability

Data is provided within the manuscript or supplementary information file.

Declarations

Competing interests

The authors declare no competing interests.