Influence of Apple Variety on the Total Aerobic Microbial Populations Found in Fresh Apple Juice/Cider

Apple variety

Aerobic microflora in fresh cider/juice from tree-harvested unsorted fruit

Total aerobic plate count (log CFU/ml)a

Yeast and mold count (log CFU/ml)a

Fuji Gala

Golden Delicious Granny Smith Mcintosh Red Delicious Red Rome

3.93 ± 0.36 2.65 ± 0.04 3.57 ± 0.57 3.32 ± 0.56 2.47 ±0.52 3.77 ± 0.60 3.85 ± 0.51

a Values are means ± standard deviation of 6 replicate composite samples. Adapted from Keller, S.E., Chirtel, S.J., Merker, R.I., Taylor, K.T., Tan, H.L., J. FoodProt, 67, 2240, 2004.

Although cider/juice physiochemical parameters such as °Brix, pH, and % TA are influenced by variety, there is large overlap in the range of values obtained for each apple variety. In addition, the range of any given parameter can be large. For example, the pH of cider/juice from over 32 batches of Fuji apples averaged 4.02 ± 0.30 (FDA, unreported data) [26]. However, individual batches from Fuji apples ranged from a low pH of 3.80 to a high pH of 4.65. Damaged and dropped fruit also have higher pH values. In a study by Dingman, fresh, undamaged tree-picked variety Red Delicious apples had a mean pH value of 3.98 ± 0.05, whereas bruised tree-picked, undamaged dropped fruit, and bruised dropped fruit had mean pH values of 4.57 ± 0.11, 4.15 ± 0.07, and 4.90 ± 0.09, respectively [27]. The range of physiochemical parameters such as pH of different apple varieties, as well as the influence of unsound fruit can be significant when compared to minimum levels required for growth of many foodborne pathogens.

Natural microflora found in fresh apple juice/cider also varies with apple variety and is significantly influenced by pH, % TA, and Brix (Table 9.2) [26]. Tree-harvested fruit that were culled to remove damaged fruit had total aerobic microbial populations in juice that ranged from 1.90 to 3.40 log CFU/ml. Yeast and mold populations in the same juice/cider ranged from 1.99 to 3.32 log CFU/ml. Total aerobic microbial and yeast and mold populations were also measured in poorer quality, ground harvest fruit. For this group, juice/ cider microbial populations were substantially higher, ranging from 4.19 to 5.43 log CFU/ml for total aerobic populations and from 3.84 to 5.23 log CFU/ ml for yeast and mold populations. Other studies reported similar population density ranges, particularly when ground harvested apples were included in cider production [28-30].

The types of organisms normally associated with fresh apple juice/cider are typically aciduric microorganisms, due to the pH, acid, and sugar content normally associated with this product. As with orange juice, human pathogenic microorganisms such as salmonella and enterohemorrhagic Escherichia coli are not considered endogenous microflora of the fruit or juice. Rather they are environmental contaminants originating from animal sources. However, unlike fresh citrus juice, populations of microorganisms in fresh apple juice/cider are generally higher than populations found on apples [28,29,31,32].

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