Ripe Titratable Acidity Research Articles

Determining the Primary Drivers of Liking to Predict Consumers' Acceptance of Fresh Nectarines and Peaches

A generic descriptive analysis using 11 judges provided 16 sensory attributes that described the aroma, flavor, and texture characteristics of 7 nectarine and peach cultivars selected for their predominant sensory attributes. Simultaneously, the "in-store" acceptability of these cultivars was evaluated by 120 consumers from northern California. The relationships among instrumental measurements (flesh firmness, ripe soluble solids concentration (RSSC), and ripe titratable acidity (RTA), sensory panel descriptors, and consumer hedonic responses were studied. In these cultivars, RSSC was the only instrumental measurement significantly related to overall liking. Cultivars with medium acidity and/or flavor/aroma were liked "very much," and consumer willingness to pay more was correlated with overall liking without regard to cultivar. Cluster analysis revealed 3 segments that were associated with ethnicity and consumer preferences within each segment. Sweetness was the main driver of liking for 2 consumer clusters; however, for the 3rd cluster, the perception of fruit aromas described as grassy/green fruit and pit aromas were the main drivers of liking. There was a high correlation between instrumental measurements and their sensory perception; however, the sensory attribute measurements explained cultivar characteristics better than instrumental measurements alone. Sweetness correlated positively with overall liking and consumer acceptance.

New quality index based on dry matter and acidity proposed for Hayward kiwifruit

Researchers from various countries have proposed using dry matter at harvest as a worldwide quality index for Hay-ward kiwifruit, because it includes both soluble (sugars and acids) and insoluble (structural carbohydrates and starch) solids and doesn't change during post-harvest handling. Our consumer tests in 1999 and 2008 indicated that dry matter and ripe titratable acidity are related to in-store consumer acceptance of kiwifruit. In most California seasons, when ripe titratable acidity was less than 1.2%, only a dry matter greater than or equal to 15.1% was required for consumer acceptability. Our 6-year quality attribute survey of California kiwifruit at harvest and from cold storage demonstrated that dry matter and ripe soluble solids concentration were highly variable among vineyards and seasons, but ripe titratable acidity values varied more among seasons than between vineyards. Our results provide strong evidence that dry matter would be a reliable quality index candidate for California kiwifruit, especially if ripe titratable acidity were factored in.

IS DRY MATTER A RELIABLE QUALITY INDEX FOR 'HAYWARD' KIWIFRUIT?

Dry matter (DM) measurement at harvest is being proposed as a quality index for ‘Hayward’ kiwifruit because it includes both soluble solids (mainly sugars) and insoluble solids (largely structural carbohydrates and starch). From two seasons’ data, in-store consumer acceptance was well related to DM. However, in a harvest season when kiwifruit exhibited high ripe titratable acidity (RTA), RTA also played an important role in consumer acceptance. In both seasons, regardless of RTA, consumers ‘liked’ kiwifruit that had DM ≥16.1%. In the 2008 growing season, when RTA was high (RTA ≥1.2%), a high DM (≥16.1) was needed to satisfy consumers. However, with RTA <1.2%, a lower DM (≥15.1%) was required allowing a large proportion of the kiwifruit to satisfy a high percentage of consumers. Many of the DM survey kiwifruit samples had a DM content exceeding 15.1%, but DM varied among vineyards and seasons. DM did not change during cold storage. Thus, DM is a reliable candidate for a quality index, but RTA should also be considered.

Segregation of plum and pluot cultivars according to their organoleptic characteristics

Cultivar segregation according to the sensory perception of their organoleptic characteristics was attempted by using trained panel data evaluated by principal component analysis of 12 plum and four pluot cultivars as a part of our program to understand plum minimum quality. The perception of the four sensory attributes (sweetness, sourness, plum flavor intensity, plum aroma intensity) was reduced to three principal components, which accounted for 98.6% of the variation in the sensory attributes of the tested cultivars. Using the Ward separation method and PCA analysis (PC1 = 49.8% and PC2 = 25.6%), plum and pluot cultivars were segregated into groups (tart, plum aroma, and sweet/plum flavor) with similar sensory attributes. Fruit source significantly affected cultivar ripe soluble solids concentration (RSSC) and ripe titratable acidity (RTA), but it did not significantly affect sensory perception of plum flavor intensity, sourness, sweetness, and plum aroma intensity by the trained panel on fruit harvested above their physiological maturity. Based on this information, we recommend that validation of these organoleptic groups should be conducted using “in store” consumer tests prior to development of a minimum quality index within each organoleptic group based on ripe soluble solids concentration (RSSC). This organoleptic cultivar classification will help to match consumer preferences and enhance current promotion and marketing programs.

Segregation of peach and nectarine ( Prunus persica (L.) Batsch) cultivars according to their organoleptic characteristics

Cultivar segregation according to the sensory perception of their organoleptic characteristics was attempted by using trained panel data evaluated by principal component analysis of four sources per cultivar of 23 peach and 26 nectarine cultivars as a part of our program to develop minimum quality indexes. Fruit source significantly affected cultivar ripe soluble solids concentration (RSSC) and ripe titratable acidity (RTA), but it did not significantly affect sensory perception of peach or nectarine flavor intensity, sourness or aroma by the trained panel. For five out of the 49 cultivars tested, source played a role in perception of sweetness. In all of these cases when a source of a specific cultivar was not classified in the proposed organoleptic group it could be explained by the fruit having been harvested outside of the commercial physiological maturity (immature or over-mature) for that cultivar. The perception of the four sensory attributes (sweetness, sourness, peach or nectarine flavor intensity, peach or nectarine aroma intensity) was analyzed by using the three principal components, which accounted for 92 and 94% of the variation in the sensory attributes of the tested cultivars for peach and nectarine, respectively. Season did not significantly affect the classification of one cultivar that was evaluated during these two seasons. By plotting organoleptic characteristics in PC1 and PC2 (∼76%) for peach and nectarine, cultivars were segregated into groups (balanced, tart, sweet, peach or nectarine aroma and/or peach or nectarine flavor intensity) with similar sensory attributes; nectarines were classified into five groups and peaches into four groups. Based on this information, we recommend that cultivars should be classified in organoleptic groups and development of a minimum quality index should be attempted within each organoleptic group rather than proposing a generic minimum quality index based on the ripe soluble solids concentration (RSSC). This organoleptic cultivar classification will help to match ethnic preferences and enhance current promotion and marketing programs.

Relationship between ripe soluble solids concentration (RSSC) and consumer acceptance of high and low acid melting flesh peach and nectarine ( Prunus persica (L.) Batsch) cultivars

The minimum RSSC needed to reach high consumer acceptance for peach and nectarine was determined by using ‘in-store’ consumer tests of low and high RTA melting flesh cultivars as a part of our program to develop minimum quality indexes. For ‘Ivory Princess’, a low acid, white flesh peach, ‘Honey Kist’, a low acid, yellow flesh nectarine, ‘Elegant Lady’, a high acid, yellow flesh peach, and ‘Spring Bright’, a high acid, yellow flesh nectarine, degree of liking and consumer acceptance were associated with ripe soluble solids concentration (RSSC) regardless of ripe titratable acidity (RTA). For the two high acid (0.70–0.90% RTA) cultivars tested, consumer acceptance increased rapidly as RSSC increased, reaching ∼90%. In these cultivars, consumer acceptance reached a plateau and above which, it became insensitive to any additional increase in RSSC. For ‘Elegant Lady’ and ‘Spring Bright’, the plateau was reached at 11–12%, and 10–11% RSSC with ∼90% consumer acceptance, respectively. For the low acid cultivars (0.30–0.50% RTA), ‘Ivory Princess’ and ‘Honey Kist’, consumer acceptance progressively increased as RSSC increased without reaching a plateau, and attained nearly 100% acceptance with RSSC of 16 and 15%, respectively. For these low acid and high acid cultivars, consumer acceptance was closely related to RSSC but maximum consumer acceptance was attained at different RSCC levels depending on the cultivar. The fact that these cultivars reached high consumer acceptance with different RSSC levels indicates that a single generic RSSC quality index would not be reliable to assure consumer satisfaction across all cultivars.

Developing a Tree Fruit Code [Prunus persica (Batch.)] for Cultivars According to Their Organoleptic Characteristics

Cultivar segregation according to their organoleptic perception was attempted by using trained panel data evaluated by principal component analysis in four sources of 24 peach and 27 nectarine cultivars as a part of our program to develop minimum quality indexes. Source significantly affected cultivar ripe soluble solids concentration (RSSC) and ripe titratable acidity (RTA), but it did not significantly affect sensory perception of flavor, sourness and aroma by the trained panel. On two out of 51 cultivars tested, source played a role on sweetness perception. In all of these cases, when source fell out of the proposed cultivar organoleptic group it could be explained by fruit being harvested outside the commercial physiological maturity (immature or overmature). The perception of the four sensory attributes was reduced to three principal components that explain 92% for peach and 94% for nectarine of the variation in the sensory characteristics of the cultivars tested. Season did not affect significantly the classification of three cultivars that were evaluated during these two seasons. By plotting organoleptic characteristics in PC1 and PC2 (∼76%), cultivars were segregated into groups (balanced, robust, sweet, peach or nectarine aroma, and/or peach or nectarine flavor) with similar sensory attributes; nectarines were classified into five groups and peaches into four groups. Based on this information, we recommend that cultivars should be clustered in organoleptic groups and a development of a minimum quality index should be attempted within each organoleptic group rather than proposing a generic minimum quality index based on RSSC. This organoleptic cultivar classification will help to match ethnic preferences and enhance the current promotion and marketing programs.

UNDERSTANDING TREE FRUIT CONSUMER ACCEPTANCE

The role of ripe soluble solids concentration (RSSC), and its relationship with ripe titratable acidity (RTA) in peach, plum, and nectarine consumer acceptance was studied as a part of our program to develop minimum quality indexes. Results of our adulterated peach juice sensory analysis indicated that liking is well related to the perception of sweetness, but titratable acidity (TA) plays an important role at low soluble solids concentration (SSC) levels (<10%). In cases where SSC and TA were low with a high sugar-to-acid ratio (SSC:TA), perception of sweetness was low. Thus, perception of fruit juice sweetness appears to be dependent on the absolute quality attribute levels. Similar responses were found on whole fruit using in-store consumer acceptance tests. We found three types of relationships between consumer acceptance and tree fruit cultivars. In one group of cultivars, the degree of liking and percentage consumer acceptance rapidly increased as RSSC increased, reaching 70-75% consumer acceptance. After that point, consumer acceptance reached a plateau and became insensitive to additional increases in RSSC. The saturation points ranged from 10-12% SSC according to cultivar. In another group of cultivars, the degree of liking and percentage consumer acceptance increased as RSSC increased, reaching very high levels (90-100% consumer acceptance). In a third group of cultivars, consumer acceptance was low (70%) and related to RTA within a given RSSC range. This data corroborates our trained panel results, and suggests that cultivars should be clustered in organoleptic groups prior to proposing a unique minimum quality index based on RSSC.

Increasing ‘Blackamber’ plum (Prunus salicina Lindell) consumer acceptance

‘Blackamber’ plum (Prunus salicina Lindell) consumer acceptance and market life were highly dependent on harvest date. For fruit within the most common industry ripe soluble solids concentration (RSSC) range (10.0–11.9%), ripe titratable acidity (RTA) played a significant role in consumer acceptance. Plums within this RSSC range combined with low RTA (≤0.60%) were disliked by 18% of consumers, while plums with RTA ≥1.00% were disliked by 60% of consumers. Plums with RSSC ≥12.0% had ∼ 75% consumer acceptance, regardless of RTA. Fruit harvested between 35.6 and 17.8 N had high consumer acceptance because of lower RTA and higher RSSC than earlier harvested fruit. Ripening plums before consumption decreased TA by approximately 30% from the TA measured at harvest. In some cases, this decrease in TA during ripening may increase the acceptability of plums that would otherwise be unacceptable. Development of chilling injury (CI) symptoms limited market life of fruit harvested early (44.5–35.6 N) and late (17.8–13.3 N). Late harvested fruit were more likely to develop flesh translucency (overripe or bladderiness) when stored at 5 ◦ C, whereas early harvested fruit had low consumer acceptance and were more prone to develop flesh bleeding/browning during storage at 0 or 5 ◦ C. Based on this work, ‘Blackamber’ plums are well adapted to late harvest but proper postharvest temperature management, including ripening, and marketing within its market life potential are necessary to avoid the onset of storage disorders and maintain flavor. © 2004 Elsevier B.V. All rights reserved.

UNDERSTANDING CONSUMER ACCEPTANCE OF PEACH, NECTARINE AND PLUM CULTIVARS

In-store’ consumer acceptance tests, as part of a four-step program to develop a minimum quality index, were performed to determine the relationship between ripe soluble solids concentration (RSSC) and/or ripe titratable acidity (RTA), and consumer acceptance of ‘Elegant Lady’ peach, ‘Spring Bright’ nectarine, and ‘Blackamber’ plum. For these peach and nectarine cultivars, consumer acceptance was significantly related to RSSC. For ‘Blackamber’, consumer acceptance was significantly related to RSSC and RTA. The results from our “in-store” consumer tests and our previous orchard surveys demonstrated that these RSSC levels could be exceeded by these cultivars if good production practices are used. INTRODUCTION The increase in production of stone fruit in recent years includes new cultivars with different flesh colors, flavors, soluble solids concentrations (SSC), and titratable acidities (TA). Studies have associated high consumer acceptance of fruit with high soluble solids concentration (SSC) in peaches (Parker et al., 1991; Robertson et al., 1988; Kader, 1994). The importance of TA and SSC-TA ratio in oranges (Pehrson and Ivans, 1988) and volatiles (Romani and Jennings, 1971) in other commodities have been pointed out. From our previous research working with ‘Brooks’ and ‘Bing’ sweet cherries (Crisosto et al., 2002, 2003), ‘Hayward’ kiwifruit (Crisosto and Crisosto, 2001), and ‘Redglobe’ table grapes (Crisosto and Crisosto, 2002) we concluded that consumer acceptance was more sensitive to the SSC-TA ratio than to the SSC, but it depends on the cultivar. Tree fruit acidity is determined by several factors such as cultivar, environmental conditions, canopy position, crop load, ripening, fruit maturity (Crisosto et al., 1995, 1997), and rootstock (DeJong et al., 2002). As fruit production is increasing, we believe that it is important to understand the role of fruit SSC and TA in consumer acceptance. MATERIALS AND METHODS ‘In-store’ consumer acceptance tests were carried out on ‘Elegant Lady’ peach, ‘Spring Bright’ nectarine, and ‘Blackamber’ plum during the 2002 season as previously described by Crisosto and Crisosto (2002). Approximately 100 consumers at a major supermarket were interviewed for each cultivar. For each cultivar, each consumer was presented four fruit samples of the four ripe SSC classes. These classes were selected to include the historical SSC levels from previous industry-wide fruit quality surveys. On the day of the consumer test in the morning, all ripened fruit of the cultivar to be tested were placed at room temperature (20oC). On each fruit to be used for the consumer test, a dime-size piece of skin was removed from one cheek and the flesh firmness measured with a UC firmness tester equipped with an 8 mm tip. If the fruit was ripe, i.e. 4.4-17.8 N flesh firmness, a number code was written on the tip of the fruit and the flesh firmness recorded. Then a longitudinal wedge was removed from the same area as the flesh firmness, placed between two layers of cheesecloth and the juice expressed for subsequent soluble solids concentration (SSC) and titratable acidity (TA) measurements. The coded fruit was placed in one of four boxes of the correct SSC class (A, B, C, D) based on the SSC measurement. This single fruit RSSC and RTA measurement technique reduced the fruit to fruit variability within each SSC class. For each fruit sample, the consumer was asked to taste it, then to indicate if he/she “likes”, “neither likes nor dislikes”, or “dislikes” the sample. Then, the consumer was asked to indicate his/her degree of liking/disliking: slightly, moderately, very much, or extremely. The consumer’s response was recorded using a 9-point hedonic scale (1-dislike extremely to 9-like extremely). Consumer acceptance was measured as both degree of liking (1-

Understanding consumer acceptance of early harvested ‘Hayward’ kiwifruit

During two seasons, ‘in-store’ consumer acceptance tests were performed to determine the relationship between ripe soluble solids concentration (RSSC) and/or ripe titratable acidity (RTA) on ‘Hayward’ kiwifruit consumer acceptance. For this, 252 consumers were presented kiwifruit slice samples with RSSC of 11.0, 12.0, 13.0, and 14.0% with a RTA ranging from 0.8 to 1.2%. Kiwifruit with RSSC that ranged from 11.6 to 13.5% were always liked by consumers but with different degrees of liking. A 12.5% RSSC is proposed as a minimum quality index for early-marketed kiwifruit. RTA played a significant role in consumer acceptance only on kiwifruit that had RSSC11.6% with RTA1.17% (‘sour’). This kiwifruit quality survey indicated that some vineyards had kiwifruit with RSSC higher than 12.5% before they met the recommended minimum maturity standard of 6.5% HSSC. Kiwifruit picked with SSC6.2% developed flesh breakdown. This work demonstrated that some California vineyards could produce high taste quality (12.5% RSSC) kiwifruit before they reach 6.5% SSC measured when kiwifruit are hanging on the vines. © 2001 Elsevier Science B.V. All rights reserved.