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Changes in composition and sensory quality of buttercup squash (Cucurbita maxima Duch. 'Delica') during fruit development and postharvest temperature and humidity conditions simulating shipment to Japan were studied at three representative growing sites in New Zealand. Fruit of a known setting date were harvested at 10-day intervals and data were collected on heat accumulation, days after flowering, flesh colour, seed development, soluble solids, dry matter (DM) content, skin hardness, glucose, fructose, sucrose and starch content, and sensory properties before and after simulated shipment. Physical properties at harvest were related to sensory quality at the point of sale to identify an optimal harvest time. As fruit H97-23 Received 16 June 1997; accepted 18 September 1997 was left for longer on the vine the skin hardened, the flesh became redder, DM increased then decreased, the soluble solids and sucrose content increased and the sensory properties improved. Once harvested the flesh continued to become redder, sucrose and soluble solids increased, and starch and DM levels decreased. Starch and DM did not accumulate significantly after 40 days from flowering at any sites. Temperature accumulation affected the rate of increase in the maturity indicators measured. Sucrose levels, °Brix, and flesh colour varied too much with site and season to be used to indicate optimum harvest dates. Skin hardness and heat accumulation levels were the most effective means of estimating the optimum harvest date. The earliest time to harvest fruit to ensure an acceptable level of sensory quality after the simulated refrigerated shipment conditions imposed was at a skin hardness penetrometer score of 7 kgf. This point occurred between 240 and 300 growing degree days (base temperature 8°C) from flowering. Fruit harvested at this early stage required a postharvest ripening period to enhance sweetness and texture and to optimise sensory quality.

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Survival analysis and accelerated storage techniques were used to evaluate the shelf life of fruit-filled snack bars. Survival analysis of the consumer data gave estimated shelf lives of 37, 16 and 8 weeks for bars stored at 20, 25 and 30C, respectively. Reanalyzing the data with the first sample assessed excluded, greatly improved the shelf life confidence intervals indicating the value of including a warm-up sample in the consumer sample set. Storage at 25 and 30C reduced the shelf life by a factor of approximately 2 for every 5-C increase in storage temperature, as judged by consumer acceptability, and accelerated the rate of change of key sensory attributes evaluated by a trained sensory panel. The sensory attributes of fruit odor intensity, color development, sourness, freshness, uncharacteristic odors and uncharacteristic flavors were highly correlated with consumer rejection data and could be used as predictors of end of shelf life. PRACTICAL APPLICATIONSThis article supports survival analysis as a relatively simple methodology for use by the industry for the estimation of end of shelf life of shelf-stable foods such as fruit-filled snack bars, which can be slow and difficult to determine, driven by relatively small quality changes, rather than microbiological safety. Increased storage temperatures can be used to facilitate the process, accelerating the rate of change of key sensory attributes associated with consumer rejection. The data set can be modeled, allowing the estimation of such product rejection at any point in the product's shelf life and the level of risk selected accordingly. Shelf life confidence intervals are often wide when using this technique, but our findings indicate that including a warm-up sample in the product sample set increases the precision of shelf life estimates. This has not been done previously, but we recommend that it be considered for future testing. bs_bs_banner Journal of Sensory Studies