What Are Tomato Harvest Maturity Indices and Are They Crucial?

• Tomatoes are harvested in five maturity or ripening stages, based on use and end-market.
• Different harvest indices are suitable for the varying ripening stages.
• Chemical, physical, and chronological harvest maturity indices are commonly used around the globe.

Tomato has various uses and is grown for local and long-distance markets. The vegetable is harvested at different times. So, varying harvest maturity indices, which measure dominant properties at that particular stage, are used. Find out what indices are helpful for the various stages, some of which are unique to the vegetable.

Tomato Harvesting Stages

Tomato (Solanum lycopersicum L.) is an important vegetable crop grown for the fresh market and processing. The part consumed is a fruit. Since tomatoes have climacteric ripening, they can be harvested when fully mature and ripened postharvest. However, tomatoes for the fresh market are harvested in various stages of ripening based on the distance to the market and end-use.

Figure 1: “Ripening stages of mature tomato fruit; from left to right: green, breaker, turning, pink, light red, red.” (Image credits: https://pdf.usaid.gov/pdf_docs/PNACY825.pdf)

 Hence, tomatoes have five harvesting stages after the fruits have attained full maturity (See Figure 1):

• Mature green: The fruit harvested at this stage is suited for long-distance markets to reduce postharvest losses. Artificial ripening is undertaken when required to produce targeted quality.
• Breakers
• Turning/half-ripe: At this stage, tomatoes are harvested for fresh consumption in local markets. The fruit continues to ripen postharvest.
• Pink
• Light-red
• Red: Ideal for seed production and processing (canning, juice extraction, and drying) and consumption as a vegetable.

The size, weight, and internal properties change at every stage. The internal attributes of interest during ripening are soluble sugar content, titrable acidity, firmness, and phenols. Size, weight, and sweetness increase while firmness and titrable acidity decrease during ripening.

Harvest Maturity Indices

Harvest maturity indices help determine tomato picking time. By evaluating randomly selected fruits, the internal and external attributes of tomatoes can indicate harvest maturity. The different categories of harvest maturity indices for tomatoes are:

• Internal chemical quality parameters
• External and physical/morphological quality attributes
• Chronological methods

Recommended harvest indices can be for specific varieties or general guidelines for a country that apply to all cultivars. Development of maturity and quality parameters is influenced by cultivars and soil, weather, year, and cultivation practices. Most simpler physical harvest indices and chronological methods will not incorporate these micro-differences. Modern tools for measuring internal chemical properties, such as near-infrared (NIR) spectroscopy, can cover all factors, depending on the chemometrics used.

Estimating internal and external parameters used as harvest maturity indices is possible through destructive and non-destructive sampling.

Internal Chemical Parameters

The biochemical parameters of harvest maturity indices are dry matter content, total soluble solids (TSS), titratable acidity (TA), and taste. NIR spectroscopy devices are used to measure dry matter and TSS. NIR measurements are non-destructive, precise, and can be obtained in real-time in the field. It is also easy to use and gives actionable insights. NIR is not accurate for measuring TA. Felix Instruments Applied Food Science offers the F-750 Produce Quality Meter, which has been used for decades in the markets for estimating dry matter and SSC.

Dry Matter

Dry matter (DM) content is all the solids minus water content and is a reliable harvest maturity index for tomatoes. The solids are starch, sugars, acids, pigments, vitamins, oils, fat, etc. Tomatoes meant for processing need more DM and SSC than ones intended for fresh consumption. DM accumulation increases the longer it is on the plants; tomatoes for processing are harvested in the red ripe stage. DM is highest in ripe stages, see Figure 2.

Figure 2. :” Amount of dry matter at different ripeness stages measured using near-infrared (NIR) spectroscopy and reference analyses,” Radzevičius et al. (2016). (Image credits: DOI 10.13080/z-a.2016.103.012)

DM content can vary between 4 to 7.5% depending on the cultivar.

• The highest DM in ‘Rutuliai’ for red ripe tomatoes is 6.680% in Lithuania.
• The characteristics DM content for 12 cultivars grown in France– Ferum, Levovil, Stupicke Polni Rane, LA0147, Cervil, Criollo, Plovdiv24A, LA1420, and four hybrids (Ferum×LA1420), (Levovil×Cevil), (LA0147×Plovdiv24A), and (Stupicke Polni Rane×Criollo) are shown in Figure 3. The DM ranges from 5 to 9%.

Figure 3.: Dry matter (DM) and fruit size (FD) at harvest for different varieties and their hybrids, Pascaul et al. 2013. (Image credits: DOI: 10.1093/jxb/ert349)

Around 50% of DM are soluble solids, and 25% are insoluble. The rest of DM comprises 13% organic acids, 8% minerals, and 4% other compounds.

Soluble solids contents

Sugar content is measured as soluble solids contents (SSC) or total soluble sugars (TSS). SSC increases as tomatoes ripen. A higher SSC is preferred for processing red ripe tomatoes.

In Rwanda, tomatoes at various maturity stages are harvested when they reach specific SSC, as listed below:

• Breaker- 4^oBrix
• Turning-4.5^oBrix
• Pink- 5^oBrix
• Light red-5.5^oBrix
• Red-5.5^oBrix

Bangladesh uses a TSS of 4.5% as a harvest maturity index for turning red tomatoes.

In Romania, five hybrids, Antalya, Cemil, Lorely, Tiger, and Sacher, have characteristic total soluble solids, as shown in Table 1.

Table 1. “The content variation in the TSS and titratable acidity in the tomato fruit during the harvesting phases,” Soare et al. (2019). (Image credits: doi: 10.17221/222/2017-HORTSCI)

Taste

The ideal harvest maturity index for ripe tomatoes is taste, a ratio of total soluble sugars (TSS)  to titrable acidity (TA).

In Romania, an additional harvest index is used. It is the ratio of taste and flavor index. The flavor index equals [(TSS/20 × titratable acidity) + titratable acidity]. The taste and harvest index for three stages (green, half-ripe/turning, and red ripe) are given in Table 2.

Table 2: “The variation in the taste and maturity index of the tomato fruit on the harvesting phases,” Soare et al. (2019). (Image credits: doi: 10.17221/222/2017-HORTSCI)

Physical Attributes

The most commonly used harvest maturity indices for tomatoes are physical attributes: color, firmness, size/ diameter, weight, seed formation, and jelly formation.

Color

External peel color is the most widely used harvest maturity index. The color development scheme of the five stages is standard for all varieties of tomatoes globally and must meet the following conditions:

1. Mature green: The fruit is entirely green and firm.
2. Breakers: Yellow is breaking through over less than 10% of the peel.
3. Turning/half-ripe: Tomatoes turn pinkish-yellow over 10 to 30% of the peel.
4. Pink: Tomatoes are pink over 30% of the peel
5. Light-red: The tomatoes are pinkish-red over 90% of the peel.
6. Red: Over 90% of the tomato peel is red, and the vegetable is firm.

Some countries, like India, harvest tomatoes from the dark green stages for cold storage to extend transport time and ensure better flavor and quality development. However, harvesting starts only from the breaker stages in many other countries, like Sri Lanka and the US.

While peel color can be judged from charts, objective and non-quantitative measurements of external and internal color through NIR devices, in this case, the Felix F-750 Quality Meter, as shown in Figure 4, are also possible. These results are more accurate than the classification of tomatoes by personnel. Both manual and NIR evaluation of peel are non-destructive.

Figure 4.: “Raw spectra curves of all tomato samples at various stages of fruit maturity (a), NIR measurements of tomatoes (b), and the five stages of fruit maturity in vertical rows (c): Vertical rows from left to right; (1) Breaker, (2) Turning, (3) Pink, (4) Light-red, (5) Red. Fresh tomato fruits were labeled and scanned using the handheld near infra-red enhanced spectrometer (F-750, Produce Quality Mater, Felix Instruments, Camas WA, USA), at wavelength range (285–1200 nm),” Alenazi et al. 2020. ( Image credits: https://doi.org/10.1016/j.sjbs.2020.07.004)

Firmness

Firmness is usually measured using a destructive penetrometer and applying force. Firmness decreases as the fruit ripens on the plant or after harvest.

Rwanda tomatoes have the same firmness harvest maturity indices for all cultivars. The following firmness is used to distinguish tomatoes at various maturity stages:

• Breaker- 1.5 Kgf
• Turning- 1.2 Kgf
• Pink- 1.3 Kgf
• Light red- 1 Kgf
• Red-1 Kgf

Size and Weight

While size measurements can be made on the plant, the weight harvest maturity index requires picking and destructive sampling. However, both are easy to use and give objective and quantitative data.

• Rwanda has the following general recommendations for weight and size harvest maturity indices for tomatoes:
• Breaker- 153 g and 13.7″
• Turning-155 g and 14″
• Pink- 157 g and 14″
• Light red-161 g and 14.9″
• Red-165 g and 17.2″

 

• India requires harvest of green or stage 1 fruit when 45 to 75 mm in diameter.

 

• Bangladesh‘s harvest maturity index for red ripe stages is a size of 6.5 cm in length and 6.2 cm in diameter, and a weight of 84 g.

Figure 5: “The fruit ripening stages of tomato cv. Micro Tom. The six stages included immature green (I), mature green (M), breaker (B), turning (T), red ripe (R) and overripe (O). The immature fruits (I) have jelly formation only in the right locule, while mature tomatoes (M) have both locules filled with jelly.” Hyodo et al. 2013. (Image credits: https://doi.org/10.1371/journal.pone.0078949)

Seed and jelly formation

Internal stages of fruit development can also be used as harvest indices. These can be seed and jelly development and are used to identify the green and firm stage (maturity 1) from immature green tomatoes.

Seed development: In Guyana, mature green fruits have tan-colored fully developed seeds, whereas immature green tomatoes have white seeds that are not their final size. Growers check seed development through destructive sampling by cutting tomatoes open.

Jelly formation: Mature green tomatoes have all locules filled with jelly or pulp, whereas immature green fruits have one or more locules without jelly, see Figure 5. Farmers from Guyana and India use this harvest index.

Chronological Harvest Maturity Indices

Chronological dates are some of the oldest harvest maturity indices. These are general recommendations for the cultivar and don’t consider differences due to soil, weather, or cultivation practices. However, they are in use as they are simple and help plan harvest operations. Examples of chronological harvest maturity indices are as follows:

• The approximate harvesting date is 73-75 days after planting, depending on the cultivar in India.
• Five weeks from anthesis is also used to determine turning red or half-ripe tomatoes in Bangladesh.

Importance of Tomato Harvest Stage

The tomato harvest stage will determine the storage temperature and period of the vegetable. Other postharvest handling methods, such as packaging, depend on maturity and firmness. While harvest maturity is more complex in the case of tomatoes, they are fine-tuned to meet market demands and increase the ROI of a farm. Like other fruits, simple physical harvest maturity indices are more common in developing countries, and internal chemical indices are used in more affluent countries and farms. All harvest indices can optimize the postharvest quality of tomatoes to meet consumer expectations, reduce food loss, and increase food sustainability.

Sources

Acharya, U. K., Subedi, P. P., & Walsh, K. B. (2017). Robustness of Tomato Quality Evaluation Using a Portable Vis-SWNIRS for Dry Matter and Colour. International journal of analytical chemistry, 2863454. doi:10.1155/2017/2863454

Alenazi, M. M., Shafiq, M., Alsadon, A. A., Alhelal, I. M., Alhamdan, A. M., Solieman, T. H., … & Saad, M. A. (2020). Non-destructive assessment of flesh firmness and dietary antioxidants of greenhouse-grown tomato (Solanum lycopersicum L.) at different fruit maturity stages. Saudi Journal of Biological Sciences, 27(10), 2839-2846.

Chaudhary, P. S., & Mishra, K. (2022). Maturity indices in vegetable crops. A Monthly Peer Reviewed Magazine for Agriculture and Allied Sciences, 26.

Face-CII.in (n.d.). Post-Harvest Management Protocols. Retrieved from https://www.face-cii.in/cclrc/fruits-vegetables/29/Vegetables/Tomato.pdf

Hyodo H, Terao A, Furukawa J, Sakamoto N, Yurimoto H, Satoh S, et al. (2013) Tissue Specific Localization of Pectin–Ca²⁺ Cross-Linkages and Pectin Methyl-Esterification during Fruit Ripening in Tomato (Solanum lycopersicum). PLoS ONE 8(11): e78949. https://doi.org/10.1371/journal.pone.0078949

New Guyana Marketing Corporation and the National Agricultural Research Institute. (2003). Tomato Postharvest Care and Market Preparation. Technical Bulletin No.9. Retrieved from https://pdf.usaid.gov/pdf_docs/PNACY825.pdf

Pascual, L., Xu, J., Biais, B., et al. …. & Causse, M. (2013). Deciphering genetic diversity and inheritance of tomato fruit weight and composition through a systems biology approach. Journal of Experimental Botany. 64. doi: 10.1093/jxb/ert349

Quamruzzaman, A. K. M., Islam, F., Akter, L., & Mallick, S. R. (2022). Effect of maturity indices on growth and quality of high value vegetables. American Journal of Plant Sciences, 13(7), 1042-1062.

Radzevičius, A., Viškelis, J., Karklelienė, R., Juskeviciene, D., & Viskelis, P. (2016). Determination of tomato quality attributes using near infrared spectroscopy and reference analysis. Zemdirbyste-Agriculture. 103. 443-448. 10.13080/z-a.2016.103.012.

Soare, R., Dinu, M., Apahidean, A., & Soare, M. (2019). The evolution of some nutritional parameters of the tomato fruit during the harvesting stages. Horticultural Science, 46(3), 132-137. doi:10.17221/222/2017-HORTSCI

TNAU. (2014, Dec). HARVESTING. Retrieved from https://agritech.tnau.ac.in/org_farm/orgfarm_tomato_harvest.html

UCDavis. (n.d.). Tomato Maturity Indices and Quality. Retrieved from https://horticulture.ucdavis.edu/ sites/g/files/dgvnsk1816/files/extension_material_files/Tomato-maturity-indices-and-quality-190404.pdf