March 27, 2020
March 19, 2020
There are many methods to determine the maturity of fruits. Some methods need an external examination of fruits, while others require a more detailed analysis of the internal composition of fruits. Brix is a measure of internal components. Though it is not universally applicable as some other measures of maturity, Brix provides vital information of interest for the fruit industry and associated processing factories. Therefore, it is important to find out its strengths and limitations.
Degrees Brix or °Brix (Brix) is a measure of the total soluble solids (TSS) present in the fruit. TSS is mainly made up of sugars but also includes other compounds. The total soluble solids are made up of
Sugar content is maximum and can be around 80%, and the portion of other solids is little; Brix is taken as a measure of sugar or sweetness of fruits or fruit juices. The other components of TSS can, however, influence Brix if their proportion increases.
Brix doesn’t differentiate between the different sugars but indicates the total content of all sugars. The °Brix, measured at 200C, is said to be the amount of total sugar in fruit. So, 50 Brix means the fruit has 50% of sugar (or TSS).
Brix can be used as a measure of maturity, flavour, and level of sweetness in fruits and vegetables to help in fixing the time of harvest, sales, and processing.
To understand how Brix is used, it is necessary to know how fruits mature. There are many stages of maturity (See Figure 1):
Stages of fruit maturity in climacteric fruits. ( Image credits: http://www.fao.org/3/y4893e/y4893e04.htm)
In the case of climacteric fruits, harvesting is possible when they have accumulated enough starch to be physiologically mature. They can ripen post-harvest, and the starch is converted to sugars to reach commercial maturity.
In non-climacteric fruits, the fruits have to ripen on the tree, as they accumulate only sugars and no starch. So after harvest, this type can’t ripen further, and thus, physiological and commercial maturity is nearly the same point.
As a measure of maturity, Brix is not as useful as other indicators, such as dry matter (DM) which is currently the most preferred index.
One of the disadvantages of using Brix as a measure of maturity is that TSS at harvest is not a good indicator of TSS after a long period of storage in the case of climacteric fruits. Dry matter content at harvest is a much better indicator of TSS after storage. Dry matter is made of all solids - soluble sugars and insoluble starch among other things. So, the starch, which will later change to sugar, is taken into consideration, making DM a good indicator of taste as well in all fruits.
Brix is used to evaluate the flavour and quality of many fruits at different stages of fruit production, such as harvest and processing. In this case, Brix is used in combination with other maturity indices, such as firmness. The value of Brix and firmness and their combination will vary not only based on the type of fruits but also varieties. For example, consumers like Brix values of
As an indicator of sweetness Brix has many uses. Brix is used by:
It should be remembered that the Brix values of fruit are not constant. TSS and Brix increase as the fruit develops. During senescence, when the fruit is over-mature, the amount of sugar content falls.
Moreover, the rigour of Brix depends on samples and sampling procedure. Inconsistent sampling methods and choice of fruits can influence Brix readings.
DM, which indicates sweetness as it includes sugars and also sourness as it includes acids, is a better indicator of flavour and ultimate consumer preference. People like a combination of tartness and sweetness in their fruits, which Brix alone cannot reflect.
Besides the different stages of maturity, Brix values can be affected by several environmental, genetic, and management factors:
Since TSS levels are sensitive to the growing conditions of crops, it is one of the indicators used to judge the quality of fields.
Dry matter accumulation and total soluble solids (TSS) in fruits of Brazilian C. chinense accessions. From Lannes et al. 2007, Image credits: https://doi.org/10.1016/j.scienta.2006.12.029)
Any factor that improves dry matter content will also increase Brix as the two are co-related. As the dry matter increases, so does the total soluble solids. For example, in Capsicum chinense, a 1% increase in dry weight goes with a 0.28% increase in TSS content, until the TSS reaches 10.25%.
Brix can be measured by refractometer, hydrometer, or density meter, but none of these methods are non-destructive or suitable for the field. Near Infrared (NIR) spectroscopy, which can be incorporated in small handheld field devices to estimate TSS in the fields, as in the Felix Instruments F-750, is ideal for measuring Brix in the field. NIR spectroscopy, which measures Brix, DM, and Titratable acidity, provides all the maturity indicators needed by growers and producers of fruits and processed products.
Science Writer, CID Bio-Science
Ph.D. Ecology and Environmental Science, B.Sc Agriculture
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