Quantitative assessment of biochemical traits in cashew (Anacardium occidentale L.) genotypes

Introduction

Cashew (Anacardium occidentale L.) is a tropical evergreen tree in the family Anacardiaceae. It is cultivated for its edible kernel and the juicy pseudo fruit called the cashew apple. In 2023-24 the crop covered 11.99 lakh hectares and produced 7.95 lakh tonnes of raw nuts (DCCD, 2023) [4] . The nut dominates commercial value but the cashew apple, which is 8-10 times heavier than the nut remains underutilized and is often wasted at the farm level despite its biochemical richness. The cashew apple is highly perishable but nutritionally valuable. It contains large amounts of ascorbic acid, Total Soluble Solids (TSS) and organic acids. Ascorbic acid levels range from 100 to 314 mg/100 g, far higher than in orange or guava (Assunção and Mercadante, 2003) [11] . TSS, which reflects sweetness and suitability for processing, usually falls between 10.2 and 14.0 °Brix depending on genotype and environment (Assunção and Mercadante, 2003) [11] . Titratable acidity corresponds to a pH of 3.5-4.6 and provides tartness while improving microbial stability. Besides these nutrients, the fruit contains tannins and phenolic compounds. These are not essential nutrients but they influence astringency, colour stability and antioxidant activity. Their high levels often require clarification or other processing methods to improve consumer acceptability. Tannins generally range from 0.4% to 1.0% and cause the characteristic astringency that limits consumer preference in spite of the nutritional richness of the fruit. Traits such as TSS, ascorbic acid, acidity and tannins vary with genotype, maturity, environment and storage conditions. They need systematic evaluation to identify promising material. Research on cashew has largely focused on nut yield and kernel traits, with relatively few studies on the biochemical properties of the cashew apple under uniform agronomic conditions. Evaluating variation in these parameters is essential for better utilization of cashew apple and for expanding its potential in functional foods and beverages. The present study was therefore carried out to assess TSS, ascorbic acid, titratable acidity and tannins in cashew genotypes to identify varieties with superior nutritional and processing potential.

Materials and Methods

A perennial genetic evaluation trial of cashew genotypes was established at this station during 2009-2012 by planting 65 genotypes consisting of 45 F₁ hybrids, 17 parents and 3 standard checks. The present investigation was carried out at the Cashew Research Station, Bapatla, Andhra Pradesh, India, during the 2024-25 season. By the time of the present study, the trees were in the regular bearing stage under uniform management. Fully bearing trees of all 65 genotypes in this trial served as the source material for the biochemical evaluation of cashew apples.

Experimental design

The genotypes were laid out in an augmented block design at the time of establishment, with the standard checks replicated in each block and the hybrids and parents treated as unreplicated test entries. Recommended agronomic and management practices for cashew in the region have been followed uniformly since planting .Biochemical characterization of the cashew apples was undertaken during the 2024-25 season using fruits harvested from these bearing trees.

Collection of Samples for Analysis

Fully matured and physiologically ripe cashew apples were harvested during the peak harvesting season. Uniformly sized, healthy and undamaged fruits were randomly collected from each genotype. The samples were immediately transported to the laboratory in clean, foodgrade containers and processed fresh on the same day to avoid biochemical deterioration and enzymatic changes. For the biochemical analysis, the cashew apples were washed thoroughly with distilled water and juice was extracted by gently pressing the apples under hygienic conditions. The extracted juice was filtered through muslin cloth to remove coarse particles and then subjected to analysis.

Analysis of Samples

The Total Soluble Solids (TSS) of the juice were measured using a hand refractometer and expressed in °Brix following the method of Ranganna (1986) [10] . Titratable acidity was determined by titrating a 10 ml aliquot of diluted juice against 0.1 N sodium hydroxide using phenolphthalein as the indicator until a faint pink endpoint was obtained and expressed as percent malic acid equivalent on a fresh weight basis (Ranganna, 1986) [10] . Ascorbic acid content was estimated by the 2,6-dichlorophenol indophenol (DCPIP) dye titration method employing 3% metaphosphoric acid as the extraction medium and expressed as mg 100 ml⁻¹ of juice (Ranganna, 1986) [10] . Tannin concentration was determined using the Folin-Denis colorimetric method (AOAC, 1975) [2] in which clarified juice was reacted with Folin-Denis's reagent and sodium carbonate incubated for 30 minutes and the absorbance was read at 760 nm. Tannin content was calculated against a standard tannic acid curve and expressed as mg 100 ml⁻¹.

Results and Discussions

The biochemical characterization of cashew apple juice across 65 genotypes revealed appreciable diversity in Total Soluble Solids, ascorbic acid, titratable acidity and tannin content. Detailed results and their discussions are provided in the subsequent sections.

Total soluble solids (TSS)

Total soluble solids (TSS) are a key index of fruit quality, indicating suitability for fresh consumption and for the preparation of juices, beverages and other processed products. As presented in Table 1, TSS in 2024 ranged from 8.91 to 13.20 °Brix with a mean of 10.92 °Brix. The best check was Vengurla 4 (11.54 °Brix) and 14 test entries exceeded this value. The maximum TSS was recorded in H-491 (13.20 °Brix) which was statistically on par with H-706 (12.68 °Brix), H-705 (12.54 °Brix), H-710 (12.54 °Brix) and H-715 (12.46 °Brix). The lowest value was observed in H-698 (8.91 °Brix). As shown in Table 1, TSS in 2025 ranged from 8.34 to 12.62 °Brix with a mean of 10.22 °Brix. The best check was again Vengurla 4 (11.47 °Brix) with five test entries surpassing this standard. The highest TSS was observed in H-491 (12.62 °Brix), which was statistically on par with H-715 (11.85 °Brix), H-710 (11.83 °Brix), H-705 (11.62 °Brix) and H-467 (11.53 °Brix). The lowest value was recorded in H-698 (8.34 °Brix). When the results of both years were combined, pooled data (Table 1) showed TSS ranging from 8.63 to 12.91 °Brix with a mean of 10.57 °Brix. The best check remained Vengurla 4 (11.51 °Brix) and seven genotypes exceeded this benchmark. The highest pooled value was noted in H-491 (12.91 °Brix), which was statistically on par with H-706 (10.67 °Brix), H-705 (12.08 °Brix), H-710 (12.18 °Brix) and H-715 (12.15 °Brix). The lowest pooled value was found in H-698 (8.63 °Brix).

Samples for Analysis

Digital Refractometer

Using Digital Refractrometer Analysis for Titratable Acidity Analysis for Ascorbic Acid

Spectrophotometer for Tannins Analysis

The present study revealed significant variability in TSS among cashew hybrids, ranging from 8.63 to 12.91 °Brix. Such variation is consistent with earlier reports, where values between 10-15 °Brix have been observed across genotypes (Mridha et al., 2019) [6] . Naidu et al. (2016) [7] also reported varietal differences in TSS, with Priyanka and BPP-8 recording higher levels, supporting the role of genetic background in influencing sweetness. Similarly, Chandrasekhar et al. (2018) [3] noted that Bhubaneswar-1 had the highest TSS among released varieties. These results are also in accordance with Kabita Sethi et al. (2015) [13] and M. Sreenivas et al. (2014) [15] who emphasized the potential of hybrids combining high sweetness and yield attributes. The present findings are in line with these studies, confirming the potential of certain genotypes for both fresh consumption and processing.

Titratable acidity

As presented in Table 1, titratable acidity in 2024 ranged from 0.23 to 0.87% with a mean of 0.53%. Because lower acidity is preferred for consumers, the best check was Vengurla 4 (0.57%) and 36 test entries recorded lower values. The minimum was in H-491 (0.23%), statistically on par with H-496 (0.23%), H-474 (0.24%), H-461 (0.25%) and H-656 (0.31%). The highest value in H464 (0.87%) is undesirable for fresh consumption. As shown in Table 1, titratable acidity in 2025 ranged from 0.17 to 0.82% with a mean of 0.48%. The best check was Vengurla 4 (0.53%) with 37 test entries below this benchmark. The lowest value was in H-491 (0.17%), on par with H-496 (0.18%), H-474 (0.19%), H-461 (0.20%) and H-656 (0.27%). The upper extreme in H-685 (0.82%) is less desirable for fresh use.

When both years were combined, pooled data (Table 1) showed titratable acidity ranging from 0.20 to 0.84% with a mean of 0.50%. The best check remained Vengurla 4 (0.55%) and 36 genotypes recorded lower values. The minimum pooled value was in H-491 (0.20%) on par with H-496 (0.20%), H-474 (0.21%), H-461 (0.22%) and H-656 (0.29%). The highest pooled value in H-685 (0.84%) is not preferred. Titratable acidity among hybrids ranged from 0.20% to 0.84%, with lower values being desirable for fresh consumption. Comparable variation was reported by Kabita Sethi et al. (2015) [13] and Mridha et al. (2019) [6] , who recorded acidity ranging from 0.23-0.86% among diverse cashew genotypes. Naidu et al. (2016) [7] observed varietal differences where acidity values varied between 0.60-1.20% depending on the cultivar. Abdullah et al. (2021) [1] also demonstrated that enzymatic treatments such as tannase can reduce acidity, thereby improving juice acceptability. The present investigation also identified hybrids with low acidity, supporting earlier observations (Sreenivas et al. 2014 and Paikra et al. 2016) [15,8] that acidity is negatively associated with TSS and consumer preference. Thus, our results corroborate previous work and indicate scope for selecting genotypes suitable for beverage development.

Ascorbic acid

Cashew apple juice is recognized as an excellent source of ascorbic acid (vitamin C). The elevated vitamin C levels justify expanded utilization in ready-to-drink formulations and value-added processing. As presented in [11] reported varietal and geographical effects on vitamin C, with yellow cashew apples generally containing higher ascorbic acid (up to 260 mg 100 g⁻¹). [6] also recorded genotypic variation from 180-254 mg 100 g⁻¹, while Abdullah et al. (2021) [1] reported values up to 269 mg 100 mL⁻¹ under optimized juice processing. Naidu et al. (2016) [7] documented high ascorbic acid in Priyanka and BPP-8, while Kabita Sethi et al. (2015) [13] and Sreenivas et al. (2014) [15] observed rich vitamin C content in selected hybrids. The present results are in line with these reports, reaffirming the nutritional superiority of certain genotypes and their potential use in functional food development. [13] reported variation from 2.5-4.0%, with lower tannin genotypes preferred for juice extraction and fresh consumption. According to Sreenivas et al. (2014) [15] , hybrids with reduced tannin levels not only improve palatability but also widen the scope for industrial utilization. Paikra et al. (2016) [8] also highlighted tannin content as a key factor influencing apple acceptability and stressed the importance of breeding programs that reduce astringency without compromising nutritional value. The present findings are in line with these reports, as hybrids with comparatively low tannin levels were also identified in this study, underscoring their potential for processing and table purposes.

Mridha et al. (2019)

Tannins

As presented in

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