January 23, 2023 at 4:20 pm | Updated January 23, 2023 at 4:20 pm | 7 min read
- Producing fruits whose quality meets consumer satisfaction is the new standard in the food industry.
- Effects of seasonal growing conditions on mango dry matter accumulation were monitored in two cultivars since most harvest indices are based only on summer data.
- Dry matter content was closely related to soluble sugars and consumer satisfaction but was not significantly different in Brazil.
Possible Seasonal Impact
Growers need accurate harvest indices for each cultivar and region to deliver fruits that meet consumer satisfaction. Dry matter content is emerging as a reliable index as it is closely related to consumer satisfaction. However, many factors can influence dry matter, and a study tried to find how seasonal variations in growing conditions could affect the harvest index.
Information Available About Dry Matter
Mango (Mangifera indica) grown in the tropics and sub-tropics is exported globally and is one of the most consumed fruits in the world. However, the mango flavor can depend on the genotype, harvest fruit quality, and environmental conditions.
In many regions, growers still judge harvest quality by fruit skin and flesh color. However, since color depends on environmental factors, season, and location, standard recommended color codes can’t account for the variations and therefore fail to determine harvest quality accurately.
Subscribe to the Felix instruments Weekly article series.
Fruit dry matter (DM) content at harvest has been strongly correlated with consumer satisfaction and can be a more reliable metric to use as a harvest index.
DM content is the total of all solids in the fruit minus water. DM consists mainly of storage and structural carbohydrates in mangoes, which accumulate during the fruit development stages. As the fruit reaches maturity, it is starch that’s primarily accumulated by the fruits. Post-harvest, during ripening, the carbohydrates and starch are broken down and converted to sugars, making fruit softer and sweeter.
The physiological differences in photosynthesis and sink competition for carbohydrates, arising due to genotype, result in varying rates of DM accumulation in the mango cultivars. Therefore, fruits from different cultivars at the same maturity stage can have other DM content and eating quality.
Environmental conditions like light, temperature, water, and nutrients that control photosynthesis and biomass production will also affect DM content at maturity.
Testing Dry Matter, Sweetness, and Consumer Acceptance
An international team of agricultural scientists decided to experiment in Brazil, which produces mangoes year-round due to its favorable warm climate, to find how environmental conditions and seasons affect minimum DM content at harvest.
The scientists de Freitas, Guimarães, Vilvert, do Amaral, Brecht, and Marques, also wanted to evaluate the stability of the relationship between DM content, sweetness/soluble solids content (SSC), and consumer acceptance for two mango varieties’ Palmer’ and ‘Tommy Atkins.’
Fruits of the two varieties were monitored during summer and winter in commercial orchards that followed the same cultivation practices in the two growing seasons.
For one month before harvest, researchers studied the dry matter (DM) content of 300 fruits from each cultivar weekly using a non-destructive method. The F-750 Produce Quality Meter, a spectrometer that uses light in the visible and near-infrared spectrum, was used for this purpose. In addition, the researchers used the F-750 Model Builder Software, provided by the instrument manufacturer Felix Instruments Applied Food Science, to develop models for each variety and calibrated the models using data from 200 fruits of the two genotypes from the same region in Brazil.
The monitored fruits from both varieties were harvested on the same day, in April and October, using industry standards of color and shape. April was the summer harvest, and October was the winter harvest. The fruits were classified into three different ranges based on the DM content.
- For ‘Palmer’ mangoes, the DM ranges were 100-120 g/kg, 130-150 g/kg, and 160-180 g/ kg for the summer harvest and 120-130 g/kg, 140-150 g/kg, and 160-170 g/kg for the winter harvest.
- For ‘Tommy Atkins,’ the DM ranges were 100-110 g/kg, 120-130 g/kg, and 140-150 g/ kg in summer and 110-120 g/kg, 130-140 g/kg, and 150-160 g/kg for the winter harvest.
Twenty fruits from each DM range were used for physicochemical analyses, and 100 fruits from each of the three ranges were stored in simulated standard shipping conditions of 12oC and 90-95% relative humidity. After the 100 fruits had reached 15N firmness, they were also physicochemically analyzed by laboratory methods for SSC, Titrable acidity, skin color, flesh color, and texture.
After the physicochemical analyses, sensory research was conducted to test consumer satisfaction. Fruits from each DM range were peeled, cut into uniform cubes, and placed in cups labeled with a three-digit code. Each cup had fruit pieces from a single DM range and variety. Consumers (100 women and 105 men) tasted and graded the fruits for appearance, texture, flavor, and overall satisfaction using a 9-point scale, with “1” indicating the least-liked and “9” indicating the most-liked samples.
Figure 1: “Dry matter accumulation in (A) ‘Palmer’ and (B) ‘Tommy Atkins’ mangoes before harvest each week. Fruits were produced in the summer and winter and harvested in April and October, respectively.” de Freitas et al. 2022. (Image credits: https://doi.org/10.1016/j.postharvbio.2022.111917)
DM is not Affected by Genotype and Season.
Previous studies concentrated only on summer mangoes to predict post-harvest fruit quality.
The average DM content for both seasons in both cultivars was the same. The scientists reasoned that the similarity in the two seasons is because essential factors such as temperature and relative humidity are similar in Brazil. Shortfalls of rain in winter were compensated by irrigation, so growing conditions were similar.
There was also a similar DM content observed at harvest in the two varieties due to the combination of DM accumulation rate and fruit development times, see Figure 1. ‘Palmer’ mangoes had a lower DM content accumulation rate of 4.4 and 5.7 g/kg per week, but a more extended fruit development period of 130 and 150 days in summer and winter, respectively. Therefore, their DM content was similar to ‘Tommy Atkins’, with a faster DM accumulation rate but shorter fruit growth time. ‘Tommy Atkins’ accumulated DM at the rate of 8.1 and 8.8 g/kg per week for 90 and 110 days in summer and winter, respectively.
Figure 2: “Relationship between dry fruit matter at harvest and soluble solids content in ripe ready-to-eat ‘Tommy Atkins’ and ‘Palmer’ mangoes,” de Freitas et al. 2022. (Image credits: https://doi.org/10.1016/j.postharvbio.2022.111917)
Though averages were similar, there was a significant variation in DM content between fruits within a variety. Since the fruits were harvested at the same physiological maturity based on color and shape, the scientists suggest that the variability was due to a difference in carbohydrate uptake by fruits. Fruits compete with each other even within a tree for phloem sap. To get a more even DM content in fruits, orchard management practices like crop load reduction or finding means to increase photosynthetic rate could provide more carbohydrates to each fruit. Growers should also ensure a homogeneous flowering time so that all fruits are of the same age and DM content at harvest.
More DM is Better
Fruits that had higher DM content at harvest had better SSC, see Figure 2. These fruits also had better color, texture, and juiciness. As a result, fruits with higher DM content had better consumer satisfaction scores. For example, ‘Palmer’ mangoes in April with 130-180 g/kg DM content and October harvests with 140-170 g/kg were the sweetest, had less acidity, and had the best satisfaction scores. In the case of ‘Tommy Atkins,’ the DM range of 140-150 g/kg in April and 150-160 g/kg in October had the highest sweetness, juiciness, and consumer satisfaction.
Figure 3: “Recommended dry matter content to harvest (A) ‘Palmer’ mangoes and (B) ‘Tommy Atkins’ in April and October to guarantee high fruit quality and consumer acceptance, based on consumer’s overall satisfaction (7=liked moderately in the nine-point hedonic scale).” de Freitas et al. 2022. (Image credits: https://doi.org/10.1016/j.postharvbio.2022.111917)
Minimum DM Content at Harvest
The scientists used the consumer satisfaction scores to find the minimum DM content at harvest suitable for use as the harvest index. For example, the scientists used a score of 7, equal to liked moderately, to find the minimum DM content at harvest. In the case of ‘Palmer’ and ‘Tommy Atkins,’ summer fruits with a score of 7 had lesser DM than winter fruits (see Figure 3).
‘Palmer’ fruits should be harvested with a minimum DM content of 137 g/kg and 145 g/kg, and ‘Tommy Atkins’ must be gathered when they have 144 g/kg and 153 g/kg in summer and winter, respectively.
However, the difference in DM content in the two seasons is slight. For example, the difference in DM content for ‘Palmer’ between the seasons is 8 g/kg and only 9 g/kg for ‘Tommy Atkins’ mangoes. However small, this seasonal difference shows that DM content alone can’t explain the fruit quality. Post-harvest environmental conditions mangoes experience in the supply chain could also be crucial to the growing environment. Therefore, the relationship between DM content to consumer satisfaction was higher for freshly harvested fruits than stored mangoes.
Making the Most of the Harvest
Tools like the F-751 Mango Quality Meter, customized for mango cultivars, provide rapid, accurate, and non-destructive estimations of mango DM content, SSC, titrable acidity, and internal and external color and can help growers monitor the DM accumulation on the farm. It can help them change orchard management since there are best practices to improve DM content and fruit quality for each fruit. Being able to fine-tune harvest time can increase transportation and storage time and deliver fresh produce that meets the highest quality standards set by importers and retailers, reducing food rejection and loss.
Read the original article for more details:
de Freitas, S. T., Guimarães, Í. T., Vilvert, J. C., do Amaral, M. H., Brecht, J. K., & Marques, A. T. (2022). Mango dry matter content at harvest to achieve high consumer quality of different cultivars in different growing seasons. Postharvest Biology and Technology, 189, 111917. https://doi.org/10.1016/j.postharvbio.2022.111917
- Spectrophotometry in 2023
- The Importance of Food Quality Testing
- NIR Applications in Agriculture – Everything…
- The 5 Most Important Parameters in Produce Quality Control
- Active Packaging: What it is and why it’s important
- Liquid Spectrophotometry & Food Industry Applications
- Ethylene (C2H4) – Ripening, Crops & Agriculture
- Guide to Fresh Fruit Quality Control
- Melon Fruit: Quality, Production & Physiology
- Understanding Chemometrics for NIR Spectroscopy