Oregon Strawberry Commission
Research Progress Report

1994 - 1995


Evaluation of Processing Quality of Advanced
Strawberry Breeding Selections


Principal Investigators:
Brian Yorgey, Sr. Faculty Research Assistant
Food Science & Technology, Oregon State University

Daniel Farkas, Department Head
Food Science & Technology, Oregon State University

Instigator/Cooperator:
Chad Finn, Breeder/Scientist, Center for Small Fruit Research, USDA


Objectives:

  1. Assist Chad Finn, Pat Moore (berry breeder at WSU) and strawberry growers and processors in evaluating advanced selections from NWREC, WSU, USDA and grower plots by providing data related to processing quality
  2. Process samples of advanced selections, selected field crosses, and standard varieties for display to breeders and the industry

Project Duration: July 1, 1994, through June 30, 1995

Results:

In 1994 the first strawberries for processing arrived from the North Willamette Research and Extension Center plots on June 1. Samples for processing were picked on a weekly schedule (mostly) that continued through the end of the month. The weather was favorable for maturation and picking and quality was good. Four named varieties and thirteen selections, including three advanced selections and four highly pigmented selections, made the trip to Corvallis this year. There was also a stowaway flat attempting to masquerade as BC 84-16-10. It was definitely not. pH, TA, oBrix, Hunter L.a.b. color, relative firmness (penetrometer) and berry size distribution are reported in Table 1.

Totem and Redcrest were the standards in this years processing trials. Two selections that we have worked with over the past several seasons were named and released during the past year. WSU 1988, a high yielding selection from (duh) WSU that produces very large fruit throughout the season, was released as Puget Reliance. A British Columbia selection, BC 86-33-2, was released as Nanaimo. Nanaimo produces dark, very flavorful fruit that generally tends to be somewhat soft for processing. However, if you look at the results of the berry tasting held at last year's OSC Research Day, you will see that it was rated very highly. Three other advanced selections were also processed, British Columbia selection BC 84-16-10, and two litter-mates from the USDA breeding program here, ORUS 1267-236 and 1267-250.

Ten additional selections that are being evaluated for possible inclusion in replicated plots were also processed. Four of these have very dark, purple to almost black colored fruit: ORUS 1376-16, NW 9054-36, W87009-20, and W88001-48. Juice processors have expressed interest in inclusion of highly pigmented strawberries in the breeding program. We have processed and evaluated dark selections (and one variety, Black Beauty) over the last four years. None of these has had acceptable flavor, not even close. (The closest was no flavor.) This year we finally have four dark-fruited selections that also taste good. However, poor capping remains a problem with all four of these selections. Two of the remaining six selections, ORUS 1369-8 and NW 9055-35, showed some potential and will be grown and processed again in the coming year.

A blind tasting of six strawberry varieties and advanced selections was held last year during the Strawberry Commission's Research Day meeting in February at NWREC. Sixty-five people filled out ballots, rating sugared and sliced samples of Totem, Redcrest, Bountiful, Nanaimo (BC 86-33-2), ORUS 1267-236, and ORUS 1267-250. Color, appearance, flavor, sweetness, sourness, firmness, and overall acceptability were rated on a 1 to 9 preference scale (1 = dislike extremely, 5 = neither like nor dislike, 9 = like extremely). There was good agreement in ratings for almost all samples. Combined with the large number of participants, this produced

The large number of participants were in good agreement about almost all the samples and produced results that were in most cases even statistically significant. The results are organized by attribute. Histograms show the of total number of responses at each preference level for each varietal attribute. Many of these are classic normal distributions (bell curves). This indicates generally that the tasting went well and that people were attentive and not confused by the ballots and samples. The average rating for each variety is shown at the top of the second page for each attribute. Though the means do not appear to be radically different from one another, they are different enough so that we are able to say that, yes, these berries appear to be different from one another - at least that the testers were able to distinguish differences between some of the samples for color, appearance, flavor, sweetness, and overall. The sourness histograms, though they are mostly nice smooth curves, are all humped around the same average rating which is reflected in the statistics that say that from this sampling you can't reliably say that there is or is not a difference between the samples. (I also think sourness is a confusing concept for a preference test.) Some difference in the means is shown for firmness but the histograms, though nicely curved, are flatter, indicating a wider range of responses. One of the statistical tests says that there is just barely a measurable difference between some of the samples and the other says that it can't tell.

The second test, the Kruskal-Wallis Analysis of Variance by Rank, is more conservative but may be better suited to our conditions than is the Single-Factor ANOVA. We were not trying to rate the samples against any known standards and everyone's idea of like and dislike varies. But everyone would be consistent in how they themselves ranked the sample relative to the other samples they scored. That makes it harder to distinguish differences. And that's why it's called Analysis by Rank.

It became very apparent to me this year that measuring firmness by hand with a penetrometer is only relatively reliable if the same person performs the testing all the time. This person must also be aware of how she or he conducts the test and must try to be consistent in every aspect. I have recently seen a texture analyzer demonstrated that clearly belongs to the post-Instron (The Instron has been the standard.) generation of texture measuring devices. The new device basically consists of a computer driven robotic arm connected to a very sensitive load cell. Not only can the instrument detect forces in three dimensions, it also can calculate where the probe tip is at any moment. Self calibration is built in so that testing conditions can be reproduced and results compared over a span of years. The most impressive feature was its versatility. It has been designed to be used for a wide variety of applications and is set up to handle ones that no one has thought of yet. It is a very good instrument and costs around $18,000.

The equipment presently available in the Food Science Department consists of handheld penetrometer mounted on a benchtop drill press stand and an Allo-Kramer shear press that is part of the generation before the Instron. This is an instrument we really need and could be used by other research groups in our department. I've talked to several professors about sharing the joys and the cost of ownership. I'm asking the fruit and vegetable commissions that I work with to help me pay for part of it. There are many obvious uses for me and my work.

I'm not expecting or asking anyone to hand me with the whole $18K. But I would like you to consider helping to fund this purchase. The breeding program would certainly benefit. Equipment and instrumentation purchases have not been easy at the University and, as you can imagine, it's even harder now. I'd be happy to get more details for you. Thank you for considering this.


To view tables and charts related to the 1994-95 Strawberry Tasting Preference Evaluations, see the list below.


Strawberry Varieties and Advanced Selections
Strawberry Selections
Strawberry Selections and Varieties
Strawberry Selections and Varieties (continued)
Preference Scores: Color
Histogram: Color
Preference Scores: Appearance
Histogram: Appearance
Preference Scores: Flavor
Histogram: Flavor
Preference Scores: Sweetness
Histogram: Sweetness
Preference Scores: Sourness
Histogram: Sourness
Preference Scores: Firmness
Histogram: Firmness
Preference Scores: Overall Scores
Histogram: Overall Scores