Journal of Horticulture and Forestry Vol. 1(3) pp. 052-056 May, 2009 Available online http://www.academicjournals.org/jhf ©2009 Academic Journals Full Length Research Paper Optimum timing for commercializing grapefruit based on fruit internal quality and weight Jesus Martinez de la Cerda 1 *, Adriana Gutierrez Diez 1 , Juan C. Rodríguez Ortiz 2 and Eduardo A. Garcia Zambrano 1 1 Faculty of Agronomy, Universidad Autonoma de Nuevo León. Carr. Zuazua-Marin km. 17.5, Marin, N.L. Mexico. 2 Facultad of Agronomy, Universidad Autonoma de San Luis Potosi, Mexico. Accepted 25 May, 2009 This study was conducted during the 2004 - 2005 production year on an 8 year grapefruit (Citrus paradasi Macf.) grove in the locality of “Las Anacuas” of the municipality of general Teran, N. L. Mexico. The objective of the study was to obtain elements based on fruit weight, internal and external quality of grapefruit and its interaction with prices, so that producers can determine the best time to sell their fruit. Results indicated that the best time for harvest, based on fruit weight was in April. It was also determined that if grapefruit is sold in November, producers lose 28% of the yield compared with April, because of the difference in fruit weight. After May, fruit begin to lose weight and internal and external quality deteriorates. With the information obtained, producers can select the optimum time to commercialize their grapefruit. Regarding internal fruit quality for fresh market, grapefruit reaches good quality by November. Key words: Citrus paradasi, grapefruit, fruit, weight, yield. INTRODUCTION Citrus is considered the most important fruit in the world and grapefruit has a great value in human diet (Ali, 2005). Double-red flesh grapefruit varieties are popular in the USA, Israel, Europe, Mexico and are increasing in Asia (Isgro et al., 2001). According to FAO in 2002 there was a production of 5 million tons of grapefruit in 74 countries having approximately 290,000 ha. Mean yields have been reported from 18.5 tons ha -1 to 40 tons ha -1 in Flori- da and Turkey (Sauls, 1998), Texas reported mean yields of 44 tons ha -1 with a high of 60 tons ha -1 (USDA, 2005). In Nuevo Leon, Mexico, mean productions are 30 tons ha -1 even though low technology is applied. Most of the citrus production is located between 24 and 40 o north- south latitude where minimum temperatures are greater than -6.6 o C. Between these latitudes there are several factors that benefit growth, development, yield and fruit quality. These latitudes include humid-tropical, humid- subtropical, arid and semi-arid regions. Generally in the tropics, fruit will not mature adequately with colorless juice, low soluble solids and low soluble solid/acid ratios. *Corresponding author. E-mail: jemarcer@yahoo.com.mx. Tel.: 81 2020-6946. Fax: 81 2020-6945. Therefore, the fruit does not satisfy fresh market re- quirements. The optimum latitude for citrus production is considered subtropical and semi-arid, where countries such as Spain, Italy, Morocco, Turkey, north Mexico, USA (Florida and California) and Israel are located have been producing fresh market citrus with good external and internal quality. Grapefruit obtains the best quality in the winter and spring with hot days and cool nights, resul- ting in high soluble solids, low acidity and good external color. High temperatures during the day and night pro- mote external green fruits with low sugars and high aci- dity that will only be good for processing. Low tempera- tures (< - 3°C) depending on exposure time and local conditions can cause freeze damage. High intensity of light and temperatures can affect internal and external fruit quality, which happens in Nuevo León and south Te- xas normally after May (Davies, 1996; Sauls, 1998). In- ternal maturity of grapefruit in the Nuevo Leon and south Texas area begins in October or November, but flavedo is still green. After November, the flavedo color changes slowly until the fruit is fully mature, normally by December (Sauls, 1998). Regarding internal maturity, the best index is the relationship between soluble solids and acidity. So- luble solids increase as maturity progresses with a range between 8 and 10% in grape fruits for fresh market. Aci-