Postharvest Water Loss and Storage Quality of Nine Pepper (Capsicum) Cultivars

Nine pepper cultivars (Capsicum annuum L.) representing five pepper types were studied to determine water-loss rates, flaccidity, color, and disease development when stored at 8,14, or 20C for 14 days. Water-loss rate was markedly higher at 14C than at 8C, and was somewhat lower at 20C than at 14C. There were significant differences in waterloss rates between pepper cultivar with ‘NuMex R Naky’, ‘NuMex Conquistador’, and ‘New Mexico 6-4’ (New Mexican-type peppers) having the highest water-loss rates. Flaccidity followed a pattern similar to water loss at each storage temperature, suggesting a direct relationship. Color development was cultivarand package-dependent, and ratings increased with temperature. Placing pepper fruit in perforated polyethylene packages reduced water-loss rates 20 times or more, so that water loss no longer limited postharvest storage. Packaging also eliminated flaccidity and reduced color development across cultivars at 14 and 20C. Packaged fruit, however, developed diseases that limited postharvest longevity. Table 1. Effect of storage temperature and packaging on weight loss (percent weight loss/day per kiloPascal) for nine pepper cultivars stored for 14 days at 8, 14, or 20C. Demand for fresh pungent peppers has greatly increased as southwestern foods have become the most popular ethnic food in the United States (DeWitt, personal communication). However, fresh New Mexican-type peppers, a major ingredient in southwestern foods, have a shelf-life of only a few days. Extending postharvest longevity to meet the demand for fresh peppers requires an understanding of storage characteristics and factors affecting storage. Peppers rapidly lose water after harvest, limiting longevity (Anandaswamy et al., 1959; Ryan and Lipton, 1972; Showalter, 1973; Watada et al., 1987). New Mexican-type peppers become flaccid in 3 to 5 days at 20C (7% to 10% weight loss) and lose water twice as fast as bell or jalapeño types (Lownds and Bosland, 1988). To our knowledge, no work examines the effects of postharvest storage temperature and packaging on New Mexican-type peppers. Using a polyethylene shrink wrap to produce a water-saturated atmosphere and decrease transpirational water loss has been an effective method of increasing postharvest life of some tree fruit (Ben-Yehoshua, 1985). Polyethylene packages also produce a modified gaseous atmosphere around the fruit, which can further increase storage longevity (Cameron et al., 1989; Forney et al., 1989). Seal-packaged fruit stored at 20C lost less weight and were more turgid than nonsealed fruit at the optimal storReceived for publication 10 Apr. 1993. Accepted for publication 6 Aug. 1993. This research was supported by the New Mexico Agricultural Experiment Station. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. HORTSCIENCE, VOL. 29(3), MARCH 1994 age temperature and 85% relative humidity (RH) (Ben-Yehoshua et al., 1982). Several postharvest storage techniques should be applicable to New Mexican-type peppers, but their use and optimization requires an understanding of postharvest changes influencing longevity of these peppers. Therefore, studies were initiated to characterize postharvest water loss and storage quality of pungent pepper types, as well as bell peppers, in relation to storage temperature and packaging. Materials and Methods Fresh, green, mature bell (‘Keystone’ and ‘Mexibell’); New Mexican (’NuMexRNaky’, ‘NuMex Conquistador’, and ‘New Mexico 64’); yellow wax (‘Santa Fe Grande’ and ‘Cascabella’); jalapeño(‘TAM Jalapeño’); and serrano (‘TAM Hidalgo’ ) peppers were harvested from plants grown under standard cultural practices (Bosland et al., 1991) at the Leyendecker Plant Science Research Center (Las Cruces, N.M.). Fresh, mature fruit without visible defects were hand-picked, placed in plastic bags, and taken to the laboratory. zDifferent values within columns differ significantly Fruit were washed with distilled water, airdried, and randomized for each treatment. Each replication consisted of two bell-type and New Mexican-type fruit, five yellow waxtype fruit, and seven jalapeñoand serranotype fruit (similar total fruit weight). The fruit were stored either nonpackaged or packaged (low-density polyethylene, 17.5 × 20 × 0.0044 cm) at 8, 14, or 20C for 14 days. Each package contained eight 26-gauge needle holes (≈ 1 mm in diameter), adequate to maintain a 20% O2 atmosphere (A. Cameron, Michigan State Univ., personal communication). Ambient RH was 75% at each temperature, resulting in vapor pressure deficits of 0.21, 0.32, and 0.47 kPa at 8, 14, and 20C, respectively. Each treatment was replicated three times. Fruit were weighed before storage and again every 24 h for 14 days. Percent weight loss and rate of weight loss were calculated. Flaccidity (firmness decrease), color development, and disease were rated daily. Flaccidity was determined by subjectively measuring surface depression to applied finger pressure and assigning this a quantitative score, ranging from 0 to 9:0 = hard, 1 = isolated softness, <10% of fruit; 3 = isolated soft areas, < 25% of fruit 5=50% of fruit soft 7 = 75% of fruit soft; and 9 = completely soft (Risse and Miller, 1986). Packaged fruit were not removed from the package, and care was taken to avoid damaging the fruit. Color development was subjectively scored on a scale of O to 9:0 = 100% green; 1 = slight coloration; 3 = 25% red; 5 =50% red; 7 = 7570 red; and 9 = 100% red. Disease rating was scored on a scale of 0 to 9:0 = none; 1 = slight on stern, 3 = moderate on stem; 5 = severe on stem plus calyx; 7 = slight on fruit; and 9 = severe on fruit. Even numbers represented intermediate responses. Water-loss data were subjected to stepwise linear regression analysis using Statistical Analysis System (SAS Institute, 1982). Flaccidity, color, and disease ratings were analyzed as a split plot, assigning cultivars to main plots and packaging to subplots for each temperature. Treatments were compared using Fisher’s LSD test. Results and Discussion Water-loss rates of nonpackaged fruit varied from 1.4% to 13.9% per day per kpa depending on storage temperature and cultivar (Table 1). Cultivar differences were apparent