To determine the effect of sugar/acid ratio and other maturity indices on the eating quality of Forelle pears destined for the FEMA programme, as a means of improving the FEMA release criteria

One of the major challenges with FEMA Forelle pears is that in many instances the two major release parameters, flesh firmness and sugar levels may remain constant and not change over 2 or 3 weeks. This has led to scrutiny of other parameters, and in particular the sugar/acid ratio as a possible means of an alternative and more accurate means of releasing an orchard under these circumstances.

The aim of this study is therefore to assess sugar and acid levels and their ratio, on the eating quality of FEMA fruit, and to determine if this could be used as an additional means of releasing an orchard in years when flesh firmness does not drop as quickly as expected.

Forelle pears harvested at different maturities from major growing areas were treated with SmartFresh^SM within 7 days after harvest and stored for 5 weeks at -0.5°C. Evaluations conducted were maturity at harvest, SmartFresh^SM efficacy testing, start of shelf life after cold storage as well as end of shelf life after a simulated shelf life at 20°C for 7 days after cold storage. Fruit were also subjected to a basic sensory evaluation.

2015

Generally, the sugar/acid ratio at time of harvest increased with delay in harvest time. SmartFresh^SM treated fruit were of acceptable quality after cold storage and shelf life, regardless of time of harvest or population.

2016

Population 1 fruit, which also had the best eating quality, was harvested at firmness’ lower than 6.0 kg for Harvests 2-4. TSS levels were lower than 14% and acidity was lower than 0.10%. Fruit from the other two populations had firmness’ higher than 6.0 kg for the first three harvests with TSS levels higher than 14%. Acidity at harvest was higher than 0.15% for Population 2 and higher than 0.24% for Population 3. 2017

Population 1 fruit had firmness’ at harvest below 6.0 kg and TSS levels lower than FEMA standards of 14%. Populations 2 to 4 had flesh firmness that was above 6.0 kg and TSS levels that were above 14% for all of the harvests. Population 1 and 2 had lower acidity levels compared to those of Population 3 and 4 fruit. This could contribute to the higher overall taste ratings for Populations 1 and 2. Population 3 had the highest acidity of the four populations, with Harvest 1 fruit reaching 0.31%. The sugar/acid ratio for Populations 3 and 4 was lower than Populations 1 and 2.

2015

2015 results indicated acceptable eating quality of FEMA fruit regardless of sugar/acid ratio. However, later harvests generally exhibited higher sugar/acid ratio values. The parameter’s usefulness of this index as an additional release parameter can only be determined over several seasons, especially in instances when TSS levels are below 14%, and flesh firmness is above the FEMA release criteria, or alternatively there is marked firmness loss without a corresponding increase in TSS levels.

2016

From the 2016 results it is evident that acidity might have a greater influence on taste than TSS. At low acidity levels TSS might have a greater influence on taste than at high acid levels. It is thus recommended that different acidity classes should be established where each class has its own sugar/acid ratio boundary values.

2017

From 2017 results, TSS is not the only factor influencing taste. It is expected that fruit with high TSS levels will have a better taste. However, fruit with the lowest TSS level at harvest (Population 1) had the best overall taste rating.

Fruit with low acidity levels (±0.20%) had better taste even with low TSS levels (≤ 14%) as was observed with fruit from Population 1 and to some extent Population 2. Fruit from Population 3 and 4 had the highest TSS and acidity levels after shelf life, but still had the worst eating experience. Fruit with low acidity levels and low TSS levels had a better overall taste rating. A higher sugar/acid ratio correlated with a higher overall taste rating.

Fruit from different areas had different TSS and acidity levels. No clear cut-off values could be established regarding the sugar/acid ratio as an additional maturity parameter for orchards destined for the FEMA program, even though a higher sugar/acid ratio resulted in higher overall taste ratings by consumers. Differences in taste after shelf life were more correlated with acidity than TSS levels, where lower acidity resulted in a higher sugar/acid ratio.

Even though a higher sugar/acid ratio correlated with a higher overall taste rating, the effect of acidity on the taste was greater than that of TSS. However, from results in 2016, at low acidity levels, high TSS levels seemed to influence taste more than high acidity levels.