The Effects of different gamma irradiation doses and storage on some chemical microbiological and sensory qualities of paprika (Capsicum annuum L. )

ABSTRACT THE EFFECTS OF DIFFERENT GAMMA IRRADIATION DOSES AND STORAGE ON SOME CHEMICAL, MICROBIOLOGICAL AND SENSORY QUALITBES OF PAPRHCA {Capsicum annuum L.) Ayhan TOPUZ Ph.D in Food Engineering Adviser: Assoc. Prof. Dr. Feramuz ÖZDEMİR November, 2002, 149 pages In this research, the effects of drying methods, irradiation doses and storage period were investigated on microbiological, chemical and sensory qualities of paprika which contribute our economy. In order to determine the effect of each treatment on quality parameters of both the sun dried and dehydrated samples, irradiated at five different doses (0, 2.5, 5, 7.5 and 10 kGy ) and stored for 10 months were analyzed. The experimental methods were applied to the samples in every two months period. Each sample was subjected to the total aerobic mesophilic bacteria, mold and yeast count for microbiological evaluation; moisture, ASTA extractable colour, carotenoids and capsaicinoids analysis for chemical evaluation and Scoville heat unit organoleptic test for sensory evaluation, respectively. HPLC technique was used to analyze the carotenoids and capsaicinoids of samples. Furthermore, anatoxins contents of paprika, obtained by sun drying and dehydration process, and the samples, irradiated at the highest dose (10 kGy), were determined by HPLC. Sun dried paprika was found highly contaminated with total aerobic mesophilic bacteria. Dehydrated paprika was also found moderately contaminated. The number of total aerobic mesophilic bacteria of both paprikas had a logarithmic decrease, whereas the same count had not changed by storing. The Dio value of these bacteria was determined as 0.67 kGy. Actually 7.5 kGy and 10 kGy irradiation doses were sufficient to sterilize the sample of dehydrated and sun dried paprika, respectively. Low level of mold and yeast were able to determine only in sun-dried paprika. However these microorganisms could not be detected in the other product. The mold and yeast of sun-dried paprika were eliminated by 2.5 kGy irradiation dose or two months storage in HDPE bag. Concerning in the low level of mold and yeast, there was no detectable anatoxins in both samples. The colour of paprika, produced by sun drying, was intensified owing to biochemical reactions, accompanied by drying period. However, it was seen that irradiation and storage negatively affected the colour quality of the samples. Each constituent of paprika pigment was affected more or less in every treatment. Losing of paprika pigments due to the storage was higher than irradiation effect. According to the results, the oxidation of paprika pigment depends on time. Additionally, the moisture incontent of paprika and ambient temperature also made pigment sensitive to oxidative reaction. The capsaicinoids content of sun dried paprika, analyzed by HPLC, was found to be higher than dehydrated paprika's. The amount of these compounds was increased by irradiation doses. On the other hand, capsaicinoids were decreased by the way of storage. Each constituent of capsaicinoid was similarly affected by drying method, irradiation process and duration of storage, but isodihydrocapsaicin was not similar. At the beginning of the storage period the compound was detected neither in sun dried nor in dehydrated paprika however, it could be determined as rising amount in each samples after 6 months storage. It is concluded that the HPLC method was more sensitive than Scoville heat unit test to evaluate the pungency components of paprika. In conclusion, after harvesting the red pepper in fully mature, it should be dried under hygienic condition in a long period of time, then process into the paprika and decontaminate by irradiation application at 10 kGy dose give the best quality product. In case of storage under controlled condition, the initial quality of paprika can be preserved in a certain extend. KEYWORDS: Drying method, Gamma irradiation, Storage, Paprika, Carotenoids, Capsaicinoids COMMITTEE: Assoc. Prof. Dr. Feramuz ÖZDEMİR Prof. Dr. Muharrem CERTEL Prof. Dr. Nevzat ARTIK Prof. Dr. Nalan GOKO?LU Assoc. Prof. Dr. Hüseyin BASIM iv